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About the 1SXPS Web Pages

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

Contents

Other documentation:

Important note about javascript

This website makes extensive use of javascript, in order to allow for the large volume of information to be available without making the pages unreadable. The critical functionality: catalogue searches, upper limit calculation and downloading the tables, are available without javascript, however the source and dataset web pages will not render properly without javascript. Since this website is aimed at professional astronomers, of whom we expect ~all to be using javascript-enabled tools, we have not make the (significant) investment of time to provide non-javascript alternatives. However, if you require a non-javascript interface, please email the help-desk to explain why. If a body of need emerges we may reconsider this decision.

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Inline help

On most web pages, any heading, control or table column whose meaning may not be instantly obvious has an associated glossary link. When you move the cursor over such an item, it will change to your browser's ‘help’ cursor style, and a click will open a pane giving an explanation of the item clicked on. This pane can be closed by pressing escape, clicking on the close link, or clicking anywhere outside the pane.

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Simple Query

The simple query interface allows you to perform a cone search around a given location. This can be either a catalogued object or a position on the sky. The coordinates can be entered in decimal or sexagesimal format, which all common sexagesimal delimiters supported. If an object name is entered it is resolved, if possible, using SIMBAD. The controls for the simple search are very limited: you can select whether to retrieve a pre-selected set of columns or the entire set of columns, whether the columns containing parameter uncertainties should be included in those returned, and whether to search the entire catalogue or just the ‘clean’ sub-sample. This latter sample comprises only Good or Reasonable sources from fields which are either unflagged or contain artefacts, but not diffuse emission. You can also select whether the co-ordinates of any objects found should be given in sexagesimal or decimal format, and whether you want an HTML table or ASCII list of objects.

For users with javascript enabled, the results of the search will appear beneath the search form: for non-javascript users they will be taken to a new page for the results. In either case a link is given which will reproduce the search, so that the search results can be bookmarked or shared.

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Advanced Query

The advanced query interface allows for detailed control over the search performed, and the results retrieved. There are controls for each field in the Sources table to determine whether the field is retrieved, or used in filtering or sorting the data. By default these controls are only shown for a subset of the catalogue fields, to keep the page manageable. The drop-down select box entitled, Show filters for which columns, allows you to change which fields are shown. The option ‘Custom’ when selected presents a list of the field categories with checkmarks so that you can select precisely which filters are shown.

For each field in the sources table there is a checkbox which can be set to retrieve that field with the results. The controls Columns to retrieve and Retrieve error columns work by changing which of these boxes are checked: thus, for example, if you set Columns to retrieve to Basic, the checkboxes for all of the ‘basic’ fields will be set, and the rest unset. But if you then check/uncheck other boxes if it this which will determine what fields are retrieved by the query. If the Retrieve error columns control is checked then checking/unchecking a field with accompanying errors, such as ‘HR1’ will result in the related error fields (e.g. ‘HR1_pos’ and ‘HR1_neg’) also being checked/unchecked.

Unlike for the simple query the Name or position box can be left blank. If it is filled in then a cone search is performed and then any filters selected below are then applied; otherwise the filters are applied to the entire catalogue. Note that complex queries or those which retrieve large numbers of rows may take some time to process and some browsers warn that the script has become unresponsive. In such cases tell your browser to wait: the script is still running but it waiting on the database query, and when that is complete (which should be less than 2 minutes even for complex searches) the script will continue.

As for the simple search, there are options to select between sexagesimal and decimal co-ordinates, and HTML vs ASCII output. There is also an option to select whether the data should be sorted in ascending or descending order. Finally the filter controls appear. The same set of controls appears for each field in the database, and the fields are grouped into categories: which categories appear on the page can be controlled as described above. For each field there is a checkbox which must be checked if that field is to be retrieved by the query, a radio box to select if the results are to be sorted by that field, and then a drop-down box to select an SQL operator (e.g. <, ==, etc.) to be applied to that field and a text box where the corresponding value can be given. (e.g. to select only southern hemisphere sources, one would set the Decl filter to ‘<=’ and put a value of ‘0’ in the text box). If a compound query is desired a click on the ‘More’ link will expand the page to show a second drop-down list of filter types and a related text box, as well as a control as to whether the two filters should be combined with a logical OR or AND. (e.g. to select only objects away from the Galactic plane would could set the filters on the ‘b’ field to be <-3 OR >3; to select objects in the plane this would be >=-3 AND <=3).

Filters are only applied for fields where they is an entry in the text box for the filter, and the filters for different fields are combined with a logical AND. Therefore if the ‘DetFlag’ field has <2 set and the ‘Rate_band0’ field has <0.01 set, then only Good or Reasonable sources with 0.3—10 keV count-rates below 0.01 ct s-1 will be found. Additionally, if the ‘Name or position’ box contained GK Per and the radius was set to 200′′ then only the 3 sources meeting these criteria and lying within 200′′ of GK Persii would be returned.

As with the simple query, on submitting the form non-javascript users will be directed to a new page, whereas users with javascript will find the results of the search appearing on the query page. In the latter case, the search controls will disappear (otherwise the page becomes unwieldy), however clicking on ‘Modify query’ will bring them back with the last-submitted settings in place so the query can be easily tweaked. For most queries a permanent link to the query is also given, so that the search results can be bookmarked or shared. For complex queries however, the permanent link may exceed the server URL length limits, in which case it is not provided.

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Source pages

For each 1SXPS source there is a web page providing information related to the source, and access to the light curves and spectra (if available). These pages can be accessed either by entering the name into the URL thus: http://www.swift.ac.uk/1SXPS/SOURCEID (where SOURCEID is the 1SXPS name, with any + sign replaced with ‘%2B’), through the link returned by a catalogue query (click on the source name), or through the links on the per-dataset web pages. The per-source web pages contain the following elements:

Summary details and thumbnail image

At the top of the page the left-hand column gives basic details of the source: its detection flag, the on-source exposure time (including datasets in which the source was not detected), the position, brightness etc. A link is also given here to the user objects page. This allows custom products to be built for a source, and if reached through this link will automatically be completed with the details of this source.

To the right is a thumbnail image of the source location taken from the dataset with the best detection flag and the longest exposure time (selected in that order). The image is 6.3′×6.3′, North is up and the pixel intensities are logarithmically scaled. Yellow cross-hairs mark the location of the source: any other nearby sources are not marked. Above the image are links to each of the four energy bands, and the exposure map: hovering the mouse over one of these links causes the image to change to the selected band or map. Clicking on the image (or links) leads to a more complete version of the plot.

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Spectral and flux information

On this section of the website the spectral details are available. By default the flux values derived for both power-law and APEC spectra are shown, taken from the best available source: i.e. a spectral fit if possible, otherwise from hardness ratio interpolation, otherwise the fixed spectrum. Which of these was used is also displayed. Note that, if a spectral fit is available, the flux from that fit is always selected, even if the χν2 value is high. If a spectral fit was available, the thumbnail plot of the fit is given. Clicking on this plot takes you to a web page giving full details of the spectral fit, and the option to download the spectral files.

Which spectral details are shown can be manipulated using the, Show table controls link. This reveals a set of check boxes allowing you to decide which pieces of information are shown. The Spectral details option refers to whether the absorption and emission parameters should be shown (for the HR-interpolated and fitted spectra). Spectral plots only exist for the fitted spectra, so can only be shown when such a product exists, and is selected for display.

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Temporal information

This section consists of a table, and a pair of figures. The table shows, for each band, the mean count-rate and the details from which is was determined. Specifically this is the total number of events in the image in the source extraction region, and how many of those are expected to be background events (derived from the background map). The correction factor necessary to correct for bad columns on the CCD, pile up, vignetting etc is also given. The final column shows the probability that the source is constant, based on the Pearson's χ2 value. Two probabilities are given: first the probability that the source is constant between observations, and second the probability that it is constant within a single observation (i.e. between snapshots).

The two images beneath the table show the source light curves: on the left the light curve with one bin per observation and on the right with one bin per snapshot. Initially the total-band light curves are shown, but this can be changed by hovering the mouse over the name of the band desired. Clicking on the light curve (or band) takes you to a page showing all of the light curves (the raw data of which can be seen by clicking on the curve), complete with controls to rescale the axes of the plot.

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Details of external catalogue matches

The position of every 1SXPS source was cross correlated against various external catalogues. The results of that cross-correlation are given here: for each match the distance from the 1SXPS position to the external position is given, along with the catalogue in which the external match was found, and the name, position and (if available) position error of the object in that catalogue. Where available, the error has been converted to a 90% error and any appropriate systematics added, as described in Evans et al. (2014). Clicking on the table headers causes the table to be sorted on the column selected, a second click on the same column inverts the sort direction. A control above the table allows you to toggle between sexagesimal and decimal co-ordinates. If there are more than 15 matches then initially only the first 10 are shown: an option is then given to expand the table to reveal all matches (note that resorting takes place over the entire list, so which 10 are shown will change if you click to sort the data on a different property).

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Individual detections of the source

Most sky locations in the 1SXPS catalogue have been observed more than once, and nearly 40% of the sources in the catalogue are detected in multiple datasets. This section of the page presents details of every individual detection, first from the stacked image(s) (if any) in which the source was found, then from individual observations. By default the dataset ID is given (which is also a link to the dataset page), along with various summary details for the detection in that dataset (the best flags, exposure, hardness ratios), as well as various band-specific details (flag, SNR and brightness/variability information). For each band displayed a link labelled details can be followed to expand the table row to give full details of the detection in the specific dataset and energy band that table row related to. Above the table a link Show table controls opens a control panel allowing you to select precisely which datasets, energy bands and detection details are shown in the table.

As with the cross-correlations table, if more than 15 datasets exist for this source, then only the first 10 are shown at first, but a link is provided to reveal them all.

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Non-detections of the source

Nearly 90% of the sources in the 1SXPS catalogue are observed but not detected at least once. This section of the page gives details of those datasets in which the sources was not detected. For each stacked the ID of the dataset (linking to the dataset page) and the exposure time of the image is also given. For the individual observations a 3-σ upper limit to the count-rate is given, along with the total number of counts in the image in a 12-pixel-radius circle at the source position, how many of these are expected to be background counts, the correction factor applied to convert this to an on-axis equivalent, and the exposure in the image. See the upper limit server documentation for details about how the upper limits were calculated.

Upper limits are not given for the stacked images because these images include both the observations during which the source was detected and those where it was not detected, thus have limited meaning. As with the other tables, if more than 15 datasets exist for this source, then only the first 10 are shown at first, but a link is provided to reveal them all.

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Dataset pages

For each dataset in the catalogue there is a page giving details of the observation or stacked image in question, a set of images to view or download, and details of the sources detected in that image. You can reach these pages either through the upper limit server, or following a link on the individual source pages. In the latter case, some text at the top of the page tells you which source you had been observing, and the number of that source in the current dataset. The details of the source in the table are also shown by default. These concepts are addressed below. The page comprises three main elements:

Summary details and thumbnail image

The summary details give an overview of the dataset as a whole: the flag assigned to the dataset (Good unless manual inspection revealed the presence of artefacts or diffuse emission), the centre of the image, the exposure time, number of snapshots etc. Note that the central position refers only to the centre in the XRT sky coordinates constructed for the image. For observations these will close to (within a few arc minutes) the boresight of the instrument but they should not be treated as the pointing direction of the XRT.

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Dataset images

For each of the four energy bands and the exposure map, the web page contains an image of the data, with the locations all of the sources detected in that specific energy band and dataset marked. Initially the total-band image is shown, but this can be changed by hovering the mouse over the labels above the image. Clicking on the image, or the labels, links to a FITS format version of the image: links are also provided to the background map for the image: both before and after the model PSFs of the detected sources have been added in. By default the image shown is scaled to fit the entire 1000×1000 pixel image in the web page: this naturally makes small details hard to see. There is a checkbox to toggle between this view, and a full-size view which can be dragged around for detailed exploration. A further option exists to show on the image 1SXPS sources which are within the field of view but not detected. When this option is selected magenta boxes are added which show sources not detected in this dataset, and white boxes show sources detected in this dataset, but not in the currently displayed band.

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Source list

To the left of the image is a list of the sources detected in the dataset; this list shows the objects detected in any of the 4 energy bands, after they have been merged into a unique list of objects found in this dataset. The source number in the table corresponds to the labels in the image. Initially only the position (the format of which can be set using the drop-down box above the table) is shown, along with the best detection flag are shown. This is the best flag of all detection of the source in this dataset, and the position is the position from the band in this dataset that yielded the smallest error.

By clicking on the source number in the table, a detailed pane will open, giving more details of the source. If you reached this page from a specific source page the pane for that source will be open when the page loads. This detailed pane gives a couple of source-specific details (again, relevant for this dataset only): the position uncertainty and distance of the source from the XRT boresight. The 1SXPS catalogue ID of the source is also given, and this serves as a link to the specific source page for the object. Beneath this some information is given about the detection in the specific band currently displayed in the dataset image: changing the selected image changes the details in this pane. A link is also provided to the light curves of this source as created purely from this dataset, binned at one bin per snapshot.