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2SXPS Catalogue: On-line Documentation

Search catalogue | Catalogue paper | Table descriptions | Download catalogue files | Upper limit server.

On this page:

  1. Summary / Quick-start information.
  2. Access & Usage.
  3. Catalogue completeness and purity.
  4. Notes on terminology.
  5. Catalogue contents.
  6. Known issues / warnings.

Other documentation:

Summary / Quick-start information

Data included2005 Jan 01 — 2018 August 01
Sky coverage3,790 square degrees
Typical Sensitivity
(0.3—10 keV)		 2×10-13 erg cm-2 s-1 (observations)
4×10-14 erg cm-2 s-1 (stacked images)
Typical position error5.6′′ (90% confidence radius, including systematics)
Detections1,091,058
Unique sources206,335
Variable sources82,324
Uncatalogued sources178,100
False positive rateFlag=Good0.3%
Flag=Good/Reasonable1%
Flag=Good/Reasonable/Poor<10%

Table 1. Summary details of the 2SXPS catalogue.
1Sources counted as ‘Uncatalogued’ here may have matches USNO-B1, 2MASS or ALLWISE, as the rate of spurious matches to those catalogues is very high.

The 2SXPS catalogue covers 3,790 square degrees on the sky and contains position, fluxes, spectral details and variability information for 206,335 X-ray point sources detected in observations with the Swift X-ray Telescope between 2005 Jan 01 and 2018 August 01. Each source has a detection flag which indicates how likely it is to be a real astrophysical object. Table 1 shows the false positive rate as a function of flag and other summary information.

Full details of how the catalogue was constructed are given in Evans et al (2020). The underlying process was similar to 1SXPS, however with several key improvements. Most noteworthy of these were better modelling of pile up, improved background modelling, especially in the presence of stray light, and a refined PSF. Additionally, larger stacked images were permitted than was possible in 1SXPS.

On this web page we give some summary details of the catalogue; how to access, use and cite it; a demonstration of its quality and performance; and finally details of the catalogue contents. Other pages provide details about the 2SXPS website and the upper-limit tool.

When Searching the catalogue you can select a pre-defined subset of the full catalogue to search, for greater purity (but reduced completeness). There are two such samples, as defined in Table 2.

SampleSourcesDatasets
All All sources. All datasets.
Clean Sources with a detection flag of 0 or 1, a field flag of 0 or 1, and none of the ‘OpticalLoadingWarning,’ ‘StrayLightWarning’ and ‘NearBrightSourceWarning’ warnings set. Datasets with a field flag of 0 or 1.
Ultra-clean A subset of clean sources with detection and field flags of 0. Datasets with detection flag of 0.

Table 2. Definitions of the pre-defined subsets that can be selected.

[Back to top | 2SXPS index]

Data Access and Usage

The catalogue can be queried through the search interface, or downloaded as a FITS file, CSV file or SQL dump.

Not all columns contain values for each entry in the tables, for example, in the Sources table, only sources for which a spectral fit exists have entries in the Fitted* fields. In the CSV files, such empty entries are literally empty; in the FITS and SQL files these entries are NULL.

If you use data from this catalogue in your work, please cite Evans et al. (2020) and in the acknowledgements section of your publication, please state:

This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.

[Back to top | 2SXPS index]

Completeness and purity

In order to evaluate the performance of the 2SXPS source detection system we made use of an extensive set of simulations. This is described in detail in Section 7 of Evans et al. (2020). We simulated fields for a range of exposure times and background levels, chosen to reflect the range of such values in 2SXPS. Simulations did not include artifacts such as stray light, hot pixels, bright Earth or diffuse sources; however, our screening process is designed to identify and flag 2SXPS sources affected by such phenomena. We ran the 2SXPS source detection algorithm on the simulated images, and so by comparing the set of detected sources with the input list of simulated sources, we can measure both the completeness of our detection system and its purity.

Each detection is assigned a flag based on various statistical tests. These flags were calibrated (via the simulations) such that the fraction of spurious sources was 0.3% (i.e. equivalent to a Gaussian 3-σ significance) for Good, 1% when Good and Reasonable sources are considered, and up to 10% when the Poor sources are also included. Fig. 1 shows the false positive rate obtained from the simulations as a function of exposure time, validating the purity claims made here.

False alarm rate as a function of exposure time and flag

Fig. 1 False positive rate as a function of exposure time and flag. The green points refer to Good sources, blue points are Good and Reasonable and red shows all sources.

False alarm rate as a function of exposure time and flag

Fig. 2 The completeness of 2SXPS. The dotted, solid and dash-dot lines show the flux at which 10%, 50% and 90% of the simulated sources were recovered, respectively. Colours are as in Fig. 1.

[Back to top | 2SXPS index]

Notes on terminology

There are various phrases and labels used within the 2SXPS catalogue which it is important users properly understand, especially since the meanings of these labels may differ from those used in other catalogues. Several key pairs of labels are described here.

Datasets: observations and stacked images (and snapshots)

Swift data are organised into observations, each of which has a unique 11-digit obsID. An observation generally contains all observations of a given location within a UT day, and may consist of multiple snapshots, taken on different spacecraft orbits, as described on this page. The basic datasets from which 2SXPS was created are the observations.

Many locations on the sky are observed repeatedly by Swift, for example, to monitor the evolution of a specific source, and so we also combined overlapping observations to give a single dataset of greater exposure, allowing fainter sources to be detected. We call these datasets stacked images. Some observations have only partial overlap, and one can make long ‘chains’ of overlapping observations covering large spatial areas. We defined a maximum stacked image size of 2,300 pixels (~90′) to a side and then created stacked images such that every overlap of observations is in at least one stack. Thus, multiple stacked images can overlap, and an observation can contribute to multiple stacked images; but the maximum exposure at any given sky is reached for every location Swift has observed.

Within each dataset (observation or stacked image), source detection and PSF fitting is carried out on each of the four bands independently of each other. Note that this is not the same approach as the XMM catalogues, in which the energy bands are handled simultaneously.

There is a third natural timescale to consider for Swift data. The satellite is in a low-Earth orbit and due to its Earth-limb avoidance constraints, the longest window of continuous visibility for any point on the sky is around 2.7 ks. Thus if an observation is required which is longer than this (or in which multiple exposures are desired within a UT day, for science reasons) the observation will comprise a number of separate exposures, known as ‘snapshots’. Each snapshot is a continuous exposure in a single pointing direction. We do not carry out source datection on individual snapshots, however light curves are built with per-snapshot binning (as well as per-observation binning) and variability calculations are also carried out on this timescale.

Detections and sources; and aliases

In the creation of 2SXPS source detection was carried out on every dataset, and every energy band independently (as noted above, this differs from the XMM approach). Thus for many sources there are multiple detections, in the different energy bands and in different datasets covering the source location. Details of these are all listed in the ‘Detections’ table available for download, and are given in the relevant parts of the different web pages.

These separate detections were then rationalised into a single list of unique source in two steps. First, detections across different bands but within the same dataset were combined. For this stage, only the statistical errors on the source positions, as deduced from the PSF fit, were used to determine whether two detections corresponded to the same underlying source. This is because, since all detections at this point are from the same dataset, the astrometric system is the same for all sources and so its uncertainty is irrelevant. Then the lists of unique soures per dataset were combined to create the final source list; at this stage the astrometric uncertainty associated with the datasets was taken into account.

The process of merging detections was not perfect. Occasionally the statistical uncertainties were underestimated and also the astrometric uncertainty appears to have a broad tail. As a result of this a small number of sources exist for which multiple detections were not correctly merged, and instead the catalogue contains two distinct sources which really are the same object. Based on an inspection of the distribution of source separations in the catalogue, we therefore identified any sources which lie within 20″ of each other and are not detected in the same dataset, and labelled these as possible aliases of each other. It is vital to note that not everything so labelled is really an alias; in some cases they are genuinely distinct sources which are close together. In other cases, particularly where one of the sources is very bright; the nearby sources are spurious detections in the PSF wings; this is not the same as an alias. In the case of genuine aliases, the available light curves of the sources will be incomplete and incorrect. That is, if a source is incorrectly identified as being two sources, called source A and source B, then the light curve of source A will not contain values derived from the blind detections that were assigned to source B, and furthermore the bins from those datasets where the source was called source B will have been deduced (for source A) based on the background map with the PSF model of source B present! Therefore, in the light curve section of the source pages, an option is given to consolidate across aliases of the source. Using this you can select which sources are genuine aliases, and the correct light curve will then be produced.

Blind and non-blind (retrospective) detections

The sources present in 2SXPS were detected via a blind search. That is, no a-priori knowledge of the possible existence of sources was used to deduce whether or not a given set of photons corresponded to the detection of a point source. However, once the list of sources had been produced, a retrospective check was carried out on those datasets in which the source was located, but had not been detected by the blind search. In this case the existence of a source at the specific location was assumed a-priori, and the count-rate of the source inferred based on the number of source and background events at the source's location. If this count-rate was above zero, with 99.7% confidence (i.e 3-σ), the source was deemed to have been present and thus detected in that dataset. The detections database table only lists the blind detections; sources identified as detected in this non-blind, retrospective analysis were not added to the table, however in the light curve analysis they are marked as being detected in those datasets. When viewing the light curves you have the option of whether non-detections should be shown as 3-σ upper limits, or datapoints with 1-σ error-bars, and you can specify this separately for bins in which the source was not detected in any way, and those in which there was no blind detetion, but in which the targeted analysis yields a non-zero count rate.

[Back to top | 2SXPS index]

Catalogue Contents

There are four tables available for download:

Sources
This is the main catalogue table. This contains the details of the unique sources in the catalogue.
Datasets
This contains details of the individual datasets (observations and stacked images) of which the catalogue is composed.
Detections
This contains details of the individual detections in each dataset and energy band, of the sources.
Cross correlations
This contains details of sources from external catalogues which are positionally coincident with 2SXPS sources.

[Back to top | 2SXPS index]

Sources Table

The Sources table is the main catalogue table, and gives details of each unique source identified in the catalogue. There are 230 columns in this table in total, so for ease of consideration we have grouped them into the following categories:

Identifiers

2SXPS ID
A unique numerical identifier for this source.
Name
The unique IAU format unique source name, of the form: 2SXPS JHHMMSS.S+ddmmss

[Hide identifier columns | Back to Sources table | Back to top | 2SXPS index]

Position information

RA
The Right Ascension (J2000) of the source, taken from the individual detection with the highest S/N and best detection flag.
Decl
The declination (J2000) of the source, taken from the individual detection with the highest S/N and best detection flag.
Err90
The 90% confidence radial position error on the source position, taken from the same individual detection as the position. This includes the astrometric systematic error.
AstromType
This relates the provenance of the astrometry used to derive the source position.
  • 0: Astrometry from the Swift star trackers.
  • 1: Astrometry from rectification with 2MASS.
l
The Galactic longitude in degrees of the best position of the source.
b
The Galactic latitude in degrees of the best position of the source.
MeanOffAxisAngle
The mean distance angle (in arc minutes) of the source from the centre of the XRT detector averaged over all observations in which the source was detected and inside the XRT field of view. There is a handful of sources for which this value is -1. This indicates that the source centre was never in the field of view, that is, the detection and centroid was based on the wings of the PSF that extended into the field of view while the source itself was outside.
OrigErr90
In the initial release of 2SXPS the statsitical component of the error was a factor of 1.5 too large, due to an error in the conversion from 1-σ to 90% confidence. This has now been corrected, however the value originally released (and used in cross correlation) is given in this field.
NearestNeighbour
The distance to the nearest 2SXPS source to this one, in arcsec.
NearestOKNeighbour
The distance to the nearest 2SXPS source to this one, with a flag of 0 or 1, i.e. Good or Reasonable with no other warning bit set; in arcsec.

[Hide position columns | Back to Sources table | Back to top | 2SXPS index]

Exposure information

Exposure
The total exposure at the location of the source in seconds, including datasets in which the source was not detected.
FirstObsDate
The UTC date and time of the start of the first observation in 2SXPS which covered the location of the source.
LastObsDate
The UTC date and time of the end of the last observation in 2SXPS which covered the location of the source.
FirstObsMET
The time of the start of the first observation in 2SXPS which covered the location of the source, in Swift MET.
LastObsMET
The time of the end of the last observation in 2SXPS which covered the location of the source, in Swift MET.
FirstDetDate
The UTC date and time of the start of the first observation in 2SXPS in which the source count-rate in any band is inconsistent with 0 at the 3-σ level; i.e. the first observation in which the source was detected by the blind search or retrospective count-rate determination.
LastDetDate
The UTC date and time of the end of the last observation in 2SXPS in which the source count-rate in any band is inconsistent with 0 at the 3-σ level; i.e. the first observation in which the source was detected by the blind search or retrospective count-rate determination.
FirstDetMET
The time, in Swift MET, of the start of the first observation in 2SXPS in which the source count-rate in any band is inconsistent with 0 at the 3-σ level; i.e. the first observation in which the source was detected by the blind search or retrospective count-rate determination.
LastDetMET
The time, in Swift MET, of the end of the last observation in 2SXPS in which the source count-rate in any band is inconsistent with 0 at the 3-σ level; i.e. the first observation in which the source was detected by the blind search or retrospective count-rate determination.
FirstBlindDetDate
The UTC date and time of the start of the first observation in 2SXPS in which the source was detected in the blind search.
LastBlindDetDate
The UTC date and time of the end of the last observation in 2SXPS in in which the source was detected in the blind search.
FirstBlindDetMET
The time, in Swift MET, of the start of the first observation in 2SXPS in which the source was detected in the blind search.
LastBlindDetMET
The time, in Swift MET, of the end of the last observation in 2SXPS in which the source was detected in the blind search.
NumObs
The total number of datasets (observations+stacked images) which cover the location of the source, including those in which the source was not detected.
NumBlindDetObs
The number of datasets (observations+stacked images) in which the source was detected in the blind search.
NumDetObs
The number of datasets (observations+stacked images) in which the source was detected with the retrospective analysis.
BestDetectionID
The ID value from the detections table corresponding to the detection of this source for which the position and error have been taken.
NonBlindDet_band0
Whether the mean count-rate in the total (0.3—10 keV) is non-zero with 3-σ significance.
NonBlindDet_band1
Whether the mean count-rate in the soft (0.3—1 keV) is non-zero with 3-σ significance.
NonBlindDet_band2
Whether the mean count-rate in the medium (1—2 keV) is non-zero with 3-σ significance.
NonBlindDet_band3
Whether the mean count-rate in the hard (3—10 keV) is non-zero with 3-σ significance.

[Hide exposure columns | Back to Sources table | Back to top | 2SXPS index]

Flag information

DetFlag
The best detection flag from all detections of the source. The basic values are 0, 1, or 2, meaning Good, Reasonable or Poor respectively. Higher values mean that an extra warning is associated with the source. This warning is bitwise, defined as follows:
BitValueDescription
2 4 The source position is consistent with that of a known extended source.
3 8 The source is likely an alias of a badly-fitted piled up source.
4 16 The source lies in a region marked as contaminated during the visual screening.
Fieldflag
The best field flag from all detections of the source. This is a bitwise flag with the following values:
BitValueDescription
0 1 Field contains stray light.
1 2 Field contains diffuse emission or artifacts.
2 4 Field contains stray light that could not be adequately modelled.
3 8 Field contains a bright, piled up source which was not properly fitted in some bands.
5 32 Screening of artifacts may contain an error. See explanation.
DetFlag_band0
The best total-band (0.3—10 keV) detection flag from all detections of the source.
DetFlag_band1
The best soft-band (0.3—1 keV) detection flag from all detections of the source.
DetFlag_band2
The best medium-band (1—2 keV) detection flag from all detections of the source.
DetFlag_band3
The best hard-band (2—10 keV) detection flag from all detections of the source.
OpticalLoadingWarning
This is the worst optical loading warning from any detection of the source. If an optical source exists near the 2SXPS source, and is bright enough to cause optical loading then this field indicates how many magnitudes brighter than the optical loading limit that source is, otherwise it is zero.
StrayLightWarning
This is set to one if any detections of the source occurred in a region affected by stray light, otherwise zero.
NearBrightSourceWarning
Whether any detection of this source occurred where the background level exceeded 10-3 ct s-1 pixel-1, i.e. was likely in the wings of a bright source. A value of zero indicates this did not occur. A value of one indicates that it did. A value of two means that the source was detected in a stacked image in which the background was not high (averaged over the whole stacked exposure), but where there was at least one observation in which the source was undetected, and the background at the source position was in excess of 10-3 ct s-1 pixel-1.

[Hide flag columns | Back to Sources table | Back to top | 2SXPS index]

Count-rate information

Rate_band0
The time-averaged total-band (0.3—10 keV) count-rate of the source, in counts per second.
Rate_band0_pos
The 1-σ positive error on the time-averaged total-band (0.3—10 keV) count-rate of the source. If more than 100 net counts (i.e. after background subtraction) were detected, or the number of counts in the source or background exceeded 1000, this is the Poisson error, otherwise it is calculated from the Bayesian method of Kraft, Burrows & Nousek (1991).
Rate_band0_neg
The 1-σ negative error on the time-averaged total-band (0.3—10 keV) count-rate of the source. If more than 100 net counts (i.e. after background subtraction) were detected, or the number of counts in the source or background exceeded 1000, this is the Poisson error, otherwise it is calculated from the Bayesian method of Kraft, Burrows & Nousek (1991).
HR1
The HR1 hardness ratio = (M-S)/(M+S) where M and S are the medium (1—2 keV) and soft (0.3—1 keV) band count-rates. If both bands had more than 100 photons and an S/N ratio of at least 2 this was calculated simply from this equation, otherwise the Bayesian approach of Park et al. (2006) was employed.
HR1_pos
The 1-σ positive error on HR1. In a small number of cases where the Bayesian approach of Park et al. (2006) was used to derive HR1, the mean HR value lay outside the 1-σ confidence interval. In these cases the HR1_pos error may be negative.
HR1_neg
The 1-σ negative error on HR1. In a small number of cases where the Bayesian approach of Park et al. (2006) was used to derive HR1, the mean HR value lay outside the 1-σ confidence interval. In these cases the HR1_neg error may be positive.
HR2
The HR2 hardness ratio = (H-M)/(H+M) where H and M are the hard (2—10 keV) and medium (1—2 keV) band count-rates. If both bands had more than 100 photons and an SNR of at least 2 this was calculated simply from this equation, otherwise the Bayesian approach of Park et al. (2006) was employed.
HR2_pos
The 1-σ positive error on HR2. In a small number of cases where the Bayesian approach of Park et al. (2006) was used to derive HR2, the mean HR value lay outside the 1-σ confidence interval. In these cases the HR2_pos error may be negative.
HR2_neg
The 1-σ negative error on HR2. In a small number of cases where the Bayesian approach of Park et al. (2006) was used to derive HR2, the mean HR value lay outside the 1-σ confidence interval. In these cases the HR2_neg error may be positive.
Rate_band1
The time-averaged soft-band (0.3—1 keV) count-rate of the source, in counts per second.
Rate_band1_pos
The 1-σ positive error on the time-averaged soft-band (0.3—1 keV) count-rate of the source.
Rate_band1_neg
The 1-σ negative error on the time-averaged soft-band (0.3—1 keV) count-rate of the source.
Rate_band2
The time-averaged medium-band (1—2 keV) count-rate of the source, in counts per second.
Rate_band2_pos
The 1-σ positive error on the time-averaged medium-band (1—2 keV) count-rate of the source.
Rate_band2_neg
The 1-σ negative error on the time-averaged medium-band (1—2 keV) count-rate of the source.
Rate_band3
The time-averaged hard-band (2—10 keV) count-rate of the source, in counts per second.
Rate_band3_pos
The 1-σ positive error on the time-averaged hard-band (2—10 keV) count-rate of the source.
Rate_band3_neg
The 1-σ negative error on the time-averaged hard-band (2—10 keV) count-rate of the source.
Counts_band0
The total number of events (not background subtracted or exposure corrected) in the total-band (0.3—10 keV) image, in the source extraction region for this source. This is found by summing the counts in the individual observations of the location, not from the stacked image.
Counts_band1
The total number of events (not background subtracted or exposure corrected) in the soft-band (0.3—1 keV) image, in the source extraction region for this source.
Counts_band2
The total number of events (not background subtracted or exposure corrected) in the medium-band (1—2 keV) image, in the source extraction region for this source.
Counts_band3
The total number of events (not background subtracted or exposure corrected) in the hard-band (2—10 keV) image, in the source extraction region for this source.
BGCounts_band0
The sum of the background map in the total-band (0.3—10 keV) source extraction region for this source. This is found by summing the maps in the individual observations of the location, not from the stacked image.
BGCounts_band1
The sum of the background map in the soft-band (0.3—1 keV) image, in the source extraction region for this source.
BGCounts_band2
The sum of the background map in the medium-band (1—2 keV) image, in the source extraction region for this source.
BGCounts_band3
The sum of the background map in the hard-band (2—10 keV) image, in the source extraction region for this source.
RateCF_band0
The count-rate correction factor in the total band (0.3—10 keV). This corrects for vignetting, bad columns, pile-up and the finite radius within which counts were extracted.
RateCF_band1
The count-rate correction factor in the soft band (0.3—1 keV).
RateCF_band2
The count-rate correction factor in the medium band (1—2 keV).
RateCF_band3
The count-rate correction factor in the hard band (2—10 keV).
UL_band0
The overall 3-σ upper limit on the total-band (0.3—10 keV) count-rate from the source, derived from the Counts_band0, BGCounts_band0, RateCF_band0 and Exposure columns. If more than 100 net counts (i.e. after background subtraction) were detected, or the number of counts in the source or background exceeded 1000, this was determined using Poisson errors, otherwise it is calculated from the Bayesian method of Kraft, Burrows & Nousek (1991). Note that this upper limit value is supplied for all sources, regardless of the strength of the detection.
UL_band1
The overall 3-σ upper limit on the soft-band (0.3—1 keV) count-rate from the source.
UL_band2
The overall 3-σ upper limit on the medium-band (1—2 keV) count-rate from the source.
UL_band3
The overall 3-σ upper limit on the hard-band (2—10 keV) count-rate from the source.
PeakRate_band0
The peak count-rate of the source in the total band (0.3—10 keV). The peak rate is defined as the count-rate in the light curve bin (from per-snapshot or per-obsid binning) with the highest 1-σ lower limit.
PeakRate_band0_pos
The 1-σ positive error on the peak total-band (0.3—10 keV) count-rate of the source.
PeakRate_band0_neg
The 1-σ negative error on the peak total-band (0.3—10 keV) count-rate of the source.
PeakRate_band1
The peak count-rate of the source in the soft band (0.3—1 keV).
PeakRate_band1_pos
The 1-σ positive error on the peak total-band (0.3—1 keV) count-rate of the source.
PeakRate_band1_neg
The 1-σ negative error on the peak total-band (0.3—1 keV) count-rate of the source.
PeakRate_band2
The peak count-rate of the source in the soft band (1—2 keV).
PeakRate_band2_pos
The 1-σ positive error on the peak total-band (1—2 keV) count-rate of the source.
PeakRate_band2_neg
The 1-σ negative error on the peak total-band (1—3 keV) count-rate of the source.
PeakRate_band3
The peak count-rate of the source in the soft band (2—10 keV).
PeakRate_band3_pos
The 1-σ positive error on the peak total-band (2—10 keV) count-rate of the source.
PeakRate_band3_neg
The 1-σ negative error on the peak total-band (2—10 keV) count-rate of the source.

[Hide count-rate columns | Back to Sources table | Back to top | 2SXPS index]

Variability information

PvarPchiSnapshot_band0
The probability that the source is constant between snapshots in the total band (0.3—10 keV), as derived from the Pearson's χ2 test. The minimum recordable value for this is 1.1×10-16 so values of 0 mean <1.1×10-16.
PvarPchiSnapshot_band1
The probability that the source is constant between snapshots in the soft band (0.3—1 keV), as derived from the Pearson's χ2 test.
PvarPchiSnapshot_band2
The probability that the source is constant between snapshots in the medium band (1—2 keV), as derived from the Pearson's χ2 test.
PvarPchiSnapshot_band3
The probability that the source is constant between snapshots in the hard band (2—10 keV), as derived from the Pearson's χ2 test.
PvarPchiSnapshot_HR1
The probability that the source HR1 hardness ratio is constant between snapshots, as derived from the Pearson's χ2 test.
PvarPchiSnapshot_HR2
The probability that the source HR2 hardness ratio is constant between snapshots, as derived from the Pearson's χ2 test.
PvarPchiObsID_band0
The probability that the source is constant between observations in the total band (0.3—10 keV), as derived from the Pearson's χ2 test.
PvarPchiObsID_band1
The probability that the source is constant between observations in the soft band (0.3—1 keV), as derived from the Pearson's χ2 test.
PvarPchiObsID_band2
The probability that the source is constant between observations in the medium band (1—2 keV), as derived from the Pearson's χ2 test.
PvarPchiObsID_band3
The probability that the source is constant between observations in the hard band (2—10 keV), as derived from the Pearson's χ2 test.
PvarPchiObsID_HR1
The probability that the source HR1 hardness ratio is constant between observations, as derived from the Pearson's χ2 test.
PvarPchiObsID_HR2
The probability that the source HR2 hardness ratio is constant between observations, as derived from the Pearson's χ2 test.

[Hide variability columns | Back to Sources table | Back to top | 2SXPS index]

Spectral/Flux information

GalacticNH
The Galactic absorption column density (in cm-2) in the direction of the source, determined from Willingale et al. (2013).
WhichPow
Which of the available estimates of the power-law spectral ECF and fluxes is given in the summary fields:
ValueSource of spectral information
0 Fixed spectrum: power-law with Γ=1.7 and NH is GalacticNH.
1 Power-law spectral values derived from the hardness ratios.
2 Power-law spectral values taken from a fit to a custom-built spectrum.
WhichAPEC
Which of the available estimates of the APEC spectral ECF and fluxes is given in the summary fields:
ValueSource of spectral information
0 Fixed spectrum: APEC with kT=1 keV and NH is GalacticNH.
1 APEC spectral values derived from the hardness ratios.
2 APEC spectral values taken from a fit to a custom-built spectrum.
PowECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the power-law spectrum indicated by the WhichPow field.
PowECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the power-law spectrum indicated by the WhichPow field.
PowFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0*PowECFO.
PowFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0_pos*PowECFO, so does not include uncertainties in the spectral modelling.
PowFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0_neg*PowECFO, so does not include uncertainties in the spectral modelling.
PowUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1), derived from the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0*PowECFU.
PowUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0_pos*PowECFU, so does not include uncertainties in the spectral modelling.
PowUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by Rate_band0_neg*PowECFU, so does not include uncertainties in the spectral modelling.
APECECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived the APEC spectrum indicated by the WhichAPEC field.
APECECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the APEC spectrum indicated by the WhichAPEC field.
APECFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0*APECECFO.
APECFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0_pos*APECECFO, so does not include uncertainties in the spectral modelling.
APECFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0_neg*APECECFO, so does not include uncertainties in the spectral modelling.
APECUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1), derived from the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0*APECECFU.
APECUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0_pos*APECECFU, so does not include uncertainties in the spectral modelling.
APECUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by Rate_band0_neg*APECECFU, so does not include uncertainties in the spectral modelling.
PowPeakFlux
The peak observed 0.3—10 keV flux (in erg cm-2 s-1) for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0*PowECFO.
PowPeakFlux_pos
The 1-σ positive error on the peak observed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0_pos*PowECFO, so does not include uncertainties in the spectral modelling.
PowPeakFlux_neg
The 1-σ negative error on the peak observed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0_neg*PowECFO, so does not include uncertainties in the spectral modelling.
PowPeakUnabsFlux
The peak unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0*PowECFU.
PowPeakUnabsFlux_pos
The 1-σ positive error on the peak unabsorbed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0_pos*PowECFU, so does not include uncertainties in the spectral modelling.
PowPeakUnabsFlux_neg
The 1-σ negative error on the peak unabsorbed 0.3—10 keV flux for the power-law spectrum indicated by the WhichPow field. This is given by PeakRate_band0_neg*PowECFU, so does not include uncertainties in the spectral modelling.
APECPeakFlux
The peak observed 0.3—10 keV flux (in erg cm-2 s-1) for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0*APECECFO.
APECPeakFlux_pos
The 1-σ positive error on the peak observed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0_pos*APECECFO, so does not include uncertainties in the spectral modelling.
APECPeakFlux_neg
The 1-σ negative error on the peak observed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0_neg*APECECFO, so does not include uncertainties in the spectral modelling.
APECPeakUnabsFlux
The peak unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0*APECECFU.
APECPeakUnabsFlux_pos
The 1-σ positive error on the peak unabsorbed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0_pos*APECECFU, so does not include uncertainties in the spectral modelling.
APECPeakUnabsFlux_neg
The 1-σ negative error on the peak unabsorbed 0.3—10 keV flux for the APEC spectrum indicated by the WhichAPEC field. This is given by PeakRate_band0_neg*APECECFU, so does not include uncertainties in the spectral modelling.
FixedPowECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field).
FixedPowECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field).
FixedPowFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0*FixedPowECFO.
FixedPowFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux for a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_pos*FixedPowECFO, so does not include uncertainties in the spectral modelling.
FixedPowFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux for a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_neg*FixedPowECFO, so does not include uncertainties in the spectral modelling.
FixedPowUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) derived from a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0*FixedPowECFU.
FixedPowUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux for a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_pos*FixedPowECFU, so does not include uncertainties in the spectral modelling.
FixedPowUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux for a power-law spectrum with a photon index of 1.7 absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_neg*FixedPowECFU, so does not include uncertainties in the spectral modelling.
FixedAPECECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field).
FixedAPECECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field).
FixedAPECFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0*FixedAPEECECFO.
FixedAPECFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux for an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_pos*FixedAPECECFO, so does not include uncertainties in the spectral modelling.
FixedAPECFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux for an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_neg*FixedAPECECFO, so does not include uncertainties in the spectral modelling.
FixedAPECUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) derived from an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0*FixedAPECECFU.
FixedAPECUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux for an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_pos*FixedAPECECFU, so does not include uncertainties in the spectral modelling.
FixedAPECUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux for an APEC spectrum with a temperature of 1 keV absorbed by the Galactic column (from the GalacticNH field). This is given by Rate_band0_neg*FixedAPECECFU, so does not include uncertainties in the spectral modelling.
InterpPowECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra.
InterpPowECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra.
InterpPowNH
The absorption column (in cm-2) of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra.
InterpPowNH_pos
The 1-σ positive error absorption column of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra. A value of -1 indicates that this error could not be constrained.
InterpPowNH_neg
The 1-σ negative error absorption column of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra. A value of +1 indicates that this error could not be constrained.
InterpPowGamma
The power-law photon index of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra.
InterpPowGamma_pos
The 1-σ positive error on the power-law photon index of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra. A value of -1 indicates that this error could not be constrained.
InterpPowGamma_neg
The 1-σ negative error on the power-law photon index of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of power-law spectra. A value of +1 indicates that this error could not be constrained.
InterpPowFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) based on the HR-interpolated power-law spectrum. This is given by Rate_band0*InterpPowECFO.
InterpPowFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux derived based on the HR-interpolated power-law spectrum. This is given by Rate_band0_pos*InterpPowECFO, so does not include uncertainties in the spectral modelling.
InterpPowFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux derived based on the HR-interpolated power-law spectrum. This is given by Rate_band0_neg*InterpPowECFO, so does not include uncertainties in the spectral modelling.
InterpPowUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) based on the HR-interpolated power-law spectrum. This is given by Rate_band0*InterpPowECFU.
InterpPowUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux derived based on the HR-interpolated power-law spectrum. This is given by Rate_band0_pos*InterpPowECFU, so does not include uncertainties in the spectral modelling.
InterpPowUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux derived based on the HR-interpolated power-law spectrum. This is given by Rate_band0_neg*InterpPowECFU, so does not include uncertainties in the spectral modelling.
InterpAPECECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra.
InterpAPECECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra.
InterpAPECNH
The absorption column (in cm-2) of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra.
InterpAPECNH_pos
The 1-σ positive error absorption column of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra. A value of -1 indicates that this error could not be constrained.
InterpAPECNH_neg
The 1-σ negative error absorption column of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra. A value of +1 indicates that this error could not be constrained.
InterpAPECkT
The APEC plasma temperature (in keV) of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra.
InterpAPECkT_pos
The 1-σ positive error on the APEC plasma temperature of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra. A value of -1 indicates that this error could not be constrained.
InterpAPECkT_neg
The 1-σ negative error on the APEC plasma temperature of the spectrum of the source derived from the hardness ratios of the source interpolated on a look-up table of APEC spectra. A value of +1 indicates that this error could not be constrained.
InterpAPECFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) based on the HR-interpolated APEC spectrum. This is given by Rate_band0*InterpAPECECFO.
InterpAPECFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux derived based on the HR-interpolated APEC spectrum. This is given by Rate_band0_pos*InterpAPECECFO, so does not include uncertainties in the spectral modelling.
InterpAPECFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux derived based on the HR-interpolated APEC spectrum. This is given by Rate_band0_neg*InterpAPECECFO, so does not include uncertainties in the spectral modelling.
InterpAPECUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) based on the HR-interpolated APEC spectrum. This is given by Rate_band0*InterpAPECECFU.
InterpAPECUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux derived based on the HR-interpolated APEC spectrum. This is given by Rate_band0_pos*InterpAPECECFU, so does not include uncertainties in the spectral modelling.
InterpAPECUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux derived based on the HR-interpolated APEC spectrum. This is given by Rate_band0_neg*InterpAPECECFU, so does not include uncertainties in the spectral modelling.
P_pow
If the (HR1,HR2) values of the source lie inside the range allowed by the simple power-law spectrum, this field is 1. Otherwise it is the probability of obtaining the measured hardness ratios and errors if the true spectrum is that which gives (HR1,HR2) closest to the source's values.
P_APEC
If the (HR1,HR2) values of the source lie inside the range allowed by the simple APEC spectrum, this field is 1. Otherwise it is the probability of obtaining the measured hardness ratios and errors if the true spectrum is that which gives (HR1,HR2) closest to the source's values.
FittedPowECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowNH
The absorption column (in cm-2) of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowNH_pos
The 1-σ positive error absorption column of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowNH_neg
The 1-σ negative error absorption column of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowGamma
The power-law photon index of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowGamma_pos
The 1-σ positive error on the power-law photon index of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowGamma_neg
The 1-σ negative error on the power-law photon index of the spectrum of the source from an automated power-law spectral fit to an automatically-extracted spectrum of the source.
FittedPowFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0*FittedPowECFO.
FittedPowFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_pos*FittedPowECFO, so does not include uncertainties in the spectral modelling.
FittedPowFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_ne*FittedPowECFO, so does not include uncertainties in the spectral modelling.
FittedPowUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0*FittedPowECFO.
FittedPowUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_pos*FittedPowECFU, so does not include uncertainties in the spectral modelling.
FittedPowUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux derived from an automated power-law spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_neg*FittedPowECFU, so does not include uncertainties in the spectral modelling.
FittedPowCstat
The Cstatistic from the power-law spectral fit.
FittedPowDOF
The number of degrees of freedom in the power-law spectral fit.
FittedPowRedChi
The Churazov-weighted χν2 value of the best fitting power-law spectral model.
FittedAPECECFO
The counts-to-observed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1) derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECECFU
The counts-to-unabsorbed-flux (0.3—10 keV) conversion factor (in erg cm-2 ct-1), derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECNH
The absorption column (in cm-2) of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECNH_pos
The 1-σ positive error absorption column of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECNH_neg
The 1-σ negative error absorption column of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECkT
The APEC plasma temperature (in keV) of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECkT_pos
The 1-σ positive error on the APEC plasma temperature of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECkT_neg
The 1-σ negative error on the APEC plasma temperature of the spectrum of the source derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source.
FittedAPECFlux
The observed 0.3—10 keV flux (in erg cm-2 s-1) derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0*FittedAPECECFO.
FittedAPECFlux_pos
The 1-σ positive error on the observed 0.3—10 keV flux derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_pos*FittedAPECECFO, so does not include uncertainties in the spectral modelling.
FittedAPECFlux_neg
The 1-σ negative error on the observed 0.3—10 keV flux derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_ne*FittedAPECECFO, so does not include uncertainties in the spectral modelling.
FittedAPECUnabsFlux
The unabsorbed 0.3—10 keV flux (in erg cm-2 s-1) derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0*FittedAPECECFO.
FittedAPECUnabsFlux_pos
The 1-σ positive error on the unabsorbed 0.3—10 keV flux derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_pos*FittedAPECECFU, so does not include uncertainties in the spectral modelling.
FittedAPECUnabsFlux_neg
The 1-σ negative error on the unabsorbed 0.3—10 keV flux derived from an automated APEC spectral fit to an automatically-extracted spectrum of the source. This is given by Rate_band0_neg*FittedAPECECFU, so does not include uncertainties in the spectral modelling.
FittedAPECCstat
The Cstatistic from the APEC spectral fit.
FittedAPECDOF
The number of degrees of freedom in the APEC spectral fit.
FittedAPECRedChi
The Churazov-weighted χν2 value of the best fitting APEC spectral model.
HasSpec
Whether there is (1) or is not (0) an automatically-built spectrum for this source.

[Hide spectral/flux columns | Back to Sources table | Back to top | 2SXPS index]

Cross-correlation information

Numxcorr
The number of sources in the external catalogues against which we performed cross-correlation, which agree spatially at the 3-σ level.
Numxcorr_slim
The number of sources in the external catalogues against which we performed cross-correlation, which agree spatially at the 3-σ level, excluding the 2MASS, USNO-B1 and ALLWISE caltalogues.
MatchInROSHRI
Whether the object does (1) or does not (0) match an object in the Rosat HRI catalogue.
MatchIn2RXS
Whether the object does (1) or does not (0) match an object in the 2RXS catalogue.
MatchIn3XMMDR8
Whether the object does (1) or does not (0) match an object in the 3XMM-DR8 catalogue.
MatchIn3XMMDR8_Stack
Whether the object does (1) or does not (0) match an object in the 3XMM-DR7 catalogue.
MatchInXMMSL2
Whether the object does (1) or does not (0) match an object in the XMMSL2 catalogue.
MatchInSwiftFT
Whether the object does (1) or does not (0) match an object in the SwiftFT catalogue.
MatchIn1SWXRT
Whether the object does (1) or does not (0) match an object in the 1SWXRT catalogue.
MatchInXRTGRB
Whether the object does (1) or does not (0) match a catalogued XRT position of a Gamma Ray Burst.
MatchInSDSSQSO
Whether the object does (1) or does not (0) match an object in the SDSS QSO DR14 catalogue.
MatchIn2MASS
Whether the object does (1) or does not (0) match a 2MASS source.
MatchInUSNOB1
Whether the object does (1) or does not (0) match a USNO-B1 source.
MatchIn2CSC
Whether the object does (1) or does not (0) match an object in the 2CSC (Chandra) catalogue.
MatchIn1SXPS
Whether the object does (1) or does not (0) match an object in the 1SXPS catalogue.
MatchInALLWISE
Whether the object does (1) or does not (0) match an object in the ALLWISE catalogue.

[Hide cross-correlation columns | Back to Sources table | Back to top | 2SXPS index]

Datasets Table

The Datasets table contains information about individual datasets — observations and stacked images — which make up the 2SXPS catalogue.

ObsID
The Swift obsID of this dataset. Values >1010 are stacked images.
FieldFlag
The warning flag associated with this dataset. This is a bitwise flag with the following values:
BitValueDescription
0 1 Field contains stray light.
1 2 Field contains diffuse emission or artifacts.
2 4 Field contains stray light that could not be adequately modelled.
3 8 Field contains a bright, piled up source which was not properly fitted in some bands.
5 32 Screening of artifacts may contain an error. See explanation.
RA
The Right Ascension (J2000.0) of the image centre in degrees.
Decl
The Right Ascension (J2000.0) of the image centre in degrees.
l
The Galactic longitude of the image centre in degrees.
b
The Galactic latitude of the image centre in degrees.
ImageSize
The side length of the dataset image, in XRT pixels (1 pixel = 2.357″).
ExposureUsed
The total exposure time of the dataset, after filtering, in seconds.
OriginalExposure
The total exposure time of the dataset, before filtering, in seconds.
StartTime_MET
The start time of the dataset in Swift MET.
StopTime_MET
The end time of the dataset in Swift MET.
MidTime_MET
The mid-time of the dataset in Swift MET.
MidTime_TDB
The mid-time of the dataset in TDB.
MidTime_MJD
The mid-time of the dataset in MJD.
StartTime_UTC
The start time of the dataset as a UTC calendar date/time.
StopTime_UTC
The end time of the dataset as a UTC calendar date/time.
FieldBG_band0
The mean background value in the total (0.3—10 keV) band in ct s-1 pix-1. This is measured from the background map before the detected sources have been added to it.
Field BG_band1
The mean background value in the soft (0.3—1 keV) band in ct s-1 pix-1. This is measured from the background map before the detected sources have been added to it.
Field BG_band2
The mean background value in the medium (1—2 keV) band in ct s-1 pix-1. This is measured from the background map before the detected sources have been added to it.
Field BG_band3
The mean background value in the hard (2—10 keV) band in ct s-1 pix-1. This is measured from the background map before the detected sources have been added to it.
Numsrc_band0
The number of sources detected in the total (0.3—10 keV) band image of this dataset.
NumOK_band0
The number of Good and Reasonable sources detected in the total (0.3—10 keV) band image of this dataset.
MedianNNDist_band0
The median distance between sources detected in the total (0.3—10 keV) band image of this dataset, in arc seconds.
Numsrc_band1
The number of sources detected in the soft (0.3—1 keV) band image of this dataset.
NumOK_band1
The number of Good and Reasonable sources detected in the soft (0.3—1 keV) band image of this dataset.
MedianNNDist_band1
The median distance between sources detected in the soft (0.3—1 keV) band image of this dataset, in arc seconds.
Numsrc_band2
The number of sources detected in the medium (1—2 keV) band image of this dataset.
NumOK_band2
The number of Good and Reasonable sources detected in the medium (1—2 keV) band image of this dataset.
MedianNNDist_band2
The median distance between sources detected in the medium (1—2 keV) band image of this dataset, in arc seconds.
Numsrc_band3
The number of sources detected in the hard (1—10 keV) band image of this dataset.
NumOK_band3
The number of Good and Reasonable sources detected in the hard (1—10 keV) band image of this dataset.
MedianNNDist_band3
The median distance between sources detected in the hard (2—10 keV) band image of this dataset, in arc seconds.
NumberOfSnapshots
The number of snapshots in the dataset.
AstromErr
If the astrometry of this image could be determined by matching the XRT sources with the 2MASS catalogue, this gives the 90% confidence radial error associated with that astrometry.
CRVAL1_corr
The CRVAL1 WCS reference value for the dataset derived from the XRT-2MASS astrometric solution.
CRVAL2_corr
The CRVAL2 WCS reference value for the dataset derived from the XRT-2MASS astrometric solution.
CROTA_2_corr
The CROTA_2 WCS reference value for the dataset derived from the XRT-2MASS astrometric solution.

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Detections Table

The Detections table contains details of the specific detections that comprise the catalogue. Each source in the Sources table has at least one entry in this detections table; most sources have multiple entries as they were detected in more than one band or dataset. The information in the detections table relates to the specific detection, not to the unique source as a whole. The fields in this table, and their definitions are given below.

DetectionID
The unique identifier of this detection.
2SXPS_ID
The 2SXPS_ID value in the sources table of the unique source to which this detection relates.
SourceNo
The identifier of this detection within the specific dataset and energy band in which it occurred.
Band
The band in which this detection occurred, as an integer:
ValueBand nameEnergy range
0 Total 0.3— 10 keV
1 Soft 0.3— 1 keV
2 Medium 1— 2 keV
3 Hard 2— 10 keV
ObsID
The Swift obsID of this dataset. Values >1010 are stacked images. This corresponds to an entry in the ‘Datasets’ table.
CorrectedExposure
The actual exposure in this dataset at the position of this detection.
ExposureFraction
The fractional exposure at the position of this detection; that is, the CorrectedExposure value divided by the nominal exposure of the dataset.
OffAxisAngle
The mean angular distance of the detection from the XRT boresight, in arc minutes, in this specific dataset and energy band. This is calculated only from the snapshots during which source is inside the field of view. A value of -1 indicates that the source centre is never in the field of view (i.e. it was detected and localised via the PSF wings).
RA
The Right Ascension (J2000) of this detection, using the astrometry from the on-board star trackers, in decmial degrees.
RA_pos
The 1-σ positive uncertainty on the RA, in decimal degrees.
RA_neg
The 1-σ negative uncertainty on the RA, in decimal degrees.
Decl
The declination (J2000) of this detection, using the astrometry from the on-board star trackers, in decmial degrees.
Decl_pos
The 1-σ positive uncertainty on the declination, in decimal degrees.
Decl_neg
The 1-σ negative uncertainty on the declination, in decimal degrees.
Err90
The 90% confidence radial position error, including systematic error, using the astrometry from the on-board star trackers. This is derived from the RA and Decl errors above and has been converted to 90% confidence using Rayleigh statistics, with the 3.5′′ astrometric systematic error from the star trackers added in quadrature. For the sources where one of the individual RA/Dec pos/neg errors was unavailable, the statistical radial 90% confidence error was set to be 11.301′′/√N (where N is the number of events used in the PSF fit) and the systematic error was combined with this.
RA_corrected
The Right Ascension (J2000) of this detection, using the XRT-2MASS astrometry, in decimal degrees.
Decl_corrected
The declination (J2000) of this detection, using the XRT-2MASS astrometry, in decimal degrees.
Err90_corrected
The 90% confidence radial position error, derived as for the Err90 field above, but where the systematic error is taken from the X-ray/2MASS rectification process and not the on-board star trackers.
l
Galactic longitude of the detection, based on the star tracker astrometry, in decimal degrees.
b
Galactic latitude of the detection, based on the star tracker astrometry, in decimal degrees.
l_corrected
Galactic longitude of the detection, based on the XRT-2MASS astrometry, in decimal degrees.
b_corrected
Galactic latitude of the detection, based on the XRT-2MASS astrometry, in decimal degrees.
IMG_X
The sky x position of the source in the specific dataset and energy band shown.
IMG_Y
The sky y position of the source in the specific dataset and energy band shown.
NearestNeighbour
The distance in arc seconds to the nearest source also detected in this dataset and energy band. If no other sources are detected this is -1.
NearestOKNeighbour
The distance in arc seconds to the nearest source flagged as Good or Reasonable also detected in this dataset and energy band. If no such sources are detected this is -1.
DetFlag
The detection flag from this specific detections. The basic values are 0, 1, or 2, meaning Good, Reasonable or Poor respectively. Higher values mean that an extra warning is associated with the source. This warning is bitwise, defined as follows:
BitValueDescription
2 4 The source position is consistent with that of a known extended source.
3 8 The source is likely an alias of a badly-fitted piled up source.
4 16 The source lies in a region marked as contaminated during the visual screening.
OpticalLoadingWarning
If an optical source exists near the detection, and is bright enough to cause optical loading then this field indicates how many magnitudes brighter than the optical loading limit that source is, otherwise it is zero.
StrayLightWarning
This is set to one if the detections occured within 30 pixels of fitted stray light emission, otherwise zero.
NearBrightSourceWarning
This is set to one if the background level at the detection location exceeded 10-3 ct s-1 pixel-1, i.e. was likely in the wings of a bright source, otherwise zero.
MatchesKnownExtended
Whether the position of this detection matches that of a known extended source.
PileupFitted
Whether pile up was deemed necessary, and therefore the parameters reported come from the piled up fit.
SNR
The signal-to-noise ratio of the detection (from the cell-detect pass).
CtsInPSFFit
The number of counts in the image in the region over which the final PSF fit was performed. This will include counts from the source and background.
BGRateInPSFFit
The mean count-rate in the background map in the region over which the final PSF fit was performed.
Cstat
The Cstat from the final PSF, from which the detection parameters were taken.
Cstat_nosrc
The Cstat calculated assuming no source was present.
L_src
The likelihood value that this is a real source, not a background fluctuation.
Cstat_flat
The Cstat calculated assuming a spatially uniform increase above the background.
Lflag
The likelihood value associated with Cstat_flat
FracPix
The fraction of the pixels within the PSF fit region which were exposed.
Pileup_S
The best-fitting S value of the pile up model. This is reported even if the pile up fit was not deemed to be an improvement and was not used.
Pileup_l
The best-fitting l value of the pile up model. This is reported even if the pile up fit was not deemed to be an improvement and was not used.
Pileup_c
The best-fitting c value of the pile up model. This is reported even if the pile up fit was not deemed to be an improvement and was not used.
Pileup_tau
The best-fitting τ value of the pile up model. This is reported even if the pile up fit was not deemed to be an improvement and was not used.
Cstat_altPileup
The Cstat from the PSF fit which was not used. That is, if PileupFitted is 1 (the pile up fit was used) this column contains the Cstat obtained from the non-piled-up fit, and vice versa.
PSF_Fit_Radius
The radius of the circular region over which PSF fitting was carried out, in XRT pixels (1 pixel = 2.357″)
CellDetect_BoxWidth
The full width of the cell-detect box in which this object was detected, and for which the SNR value was computed, in XRT pixels.
Rate
The mean count rate of this detection (i.e. in this dataset and band), corrected for pile up, vignetting, bad columns etc.
Rate_pos
The 1-σ positive uncertainty on the count-rate.
Rate_neg
The 1-σ negative uncertainty on the count-rate.
CtsInRate
The total number of counts in the image in the region used to determine the count-rate.
BgCtsInRate
The total number of counts in the background map in the region used to determine the count-rate.
Rate_CF
The PSF correction factor used to correct the count rate for pile up, vignetting, bad columns etc.
BGRateinRate
The mean background count-rate at the position of the detection.
OrigErr90
In the initial release of 2SXPS the statsitical component of the error was a factor of 1.5 too large, due to an error in the conversion from 1-σ to 90% confidence. This has now been corrected, however the value originally released (and used in cross correlation) is given in this field.
OrigErr90_corrected
As OrigErr90, but the astrometrically corrected (using XRT and 2MASS) version.

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Cross Correlations Table

The Cross correlations table contains details of the cross correlation between the 1SXPS sources and other catalogues.

2SXPS_ID
The ID of the 2SXPS source.
ExtCat_ID
The name of the matched source in the external catalogue.
Catalogue
The name of the catalogue in which the match occurs.
Distance
The distance, in arc seconds, between the 2SXPS source and the external catalogue source.
RA
The Right Ascension (J2000), in decimal degrees, of the source in the external catalogue.
Decl
The declination (J2000), in decimal degrees, of the source in the external catalogue.
Err90
The 90% confidence radial error in the external catalogue position (if available). Where necessary, this has been converted from a 1-σ error using Rayleigh statistics, and has had any relevant systematic error added.

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Known issues and problems

While every attempt was made to guarantee the accuracy of all of the data in this catalogue, some issues have since been identified, and where possible, mitigated. These are detailed below.

Incorrect flagging of some sources affected by diffuse emission.
For fields in which areas of diffuse emission or artifacts were identified by human inspection and described by an elliptical region, the flagging of sources was incorrect. The elliptical region applied to identify affected sources was rotated by 90° compared to the correct orientation. Thus, some detections in those fields have a DetFlag value with bit 4 incorrectly (un)set. Affected fields have bit 5 (value 32) set in their FieldFlag. This issue has been fixed for future catalogues.
Poor pile-up correction in some light-curve bins.
In a small number of cases, the pile up fitting to the soft, medium or hard energy bands is unreliable, to a degree that the count-rate in a specific observation and band is unreliable. This is simply a result of the stochastic nature of fitting pile up and determining whether the piled-up or non-piled up fit is better. There are two problematic cases: when an object is found to be piled up in a sub-band but not the total band; or the pile-up correction factors in the total band and the sub-band differ by more than 50%. In these cases the light curve bin is flagged, and by default is excluded from the light curve displayed / downloaded; you have to specifically request to include these bins.
Source blending in crowded fields
The process of identifying unique sources is a two-step process. The first step merges detections across the different bands within the same dataset into a list of unique objects in that dataset. In the second step, these “obsSources” are merged across all datasets into a unique source list. An error has been identified in the first step, whereby distinct by nearby detections in the same band can associated with the same object: being distinct detections in the same band they must, in fact, be distinct objects. This means that the number of sources in the catalogue is slightly underestimated. This issue has been fixed for future catalogues.

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