ROSAT Status Report #107:
October 31, 1994
This bulletin describes the release of two ROSAT catalogs derived from archival data taken during the pointed phase. One is from the ROSAT data center and is derived from the results of the SAS processing. The other has been produced independently by White (HEASARC), Giommi (ESIS) and Angelini (HEASARC) as their own research effort. These catalogs have approximately 50,000 sources, by far the largest X-ray catalogs in existence and represent a major new resource for the astronomical community. Since the two catalogs have been produced independently from the same archival data, they can be used as a quality crosscheck.
ROSAT WGACAT Point Source Catalog
A ROSAT catalog of point sources called WGACAT is now available through the HEASARC online service. This catalog has been generated by N.E.White (HEASARC/GSFC), P. Giommi (ESIS/ESA) and L. Angelini (HEASARC/GSFC) using the ROSAT PSPC pointed data publicly available up to Sept 1994. This catalog, contains 50,000 detections and more than 45,600 individual sources. A total of 2624 fields were searched. This catalog is an independent research effort aimed at releasing as quickly as possible a list of sources detected by ROSAT in its pointed phase to: 1) identify the detected sources, 2) ensure their timely observation by currently active X-ray missions e.g. ASCA, and 3) to search for objects which show exceptional time variability and spectral properties. Papers on the WGACAT will be presented this week at the AAS/HEAD meeting, and also at the AAS meeting in Tucson in January. A preliminary paper was presented at the ADASS meeting in Baltimore several weeks ago.
WGACAT was generated using the optimized sliding cell detect in XIMAGE (first developed for the EXOSAT project). The inner and outer parts of the images were run separately, to maximize the source detection sensitivity. This method is an excellent approach for finding point sources, but can also find spurious sources where there is extended emission. A visual quality check on the detect output has been made and obvious problem fields and sources flagged. Users of this catalog should carefully check the QFLAG parameter for each source (values >5 are good and are the ones provided by default) and examine the gif images that have been provided. WGACAT has been cross-correlated against many other catalogs and the results written to the catalog. GIF and FITS format images of the image of each detected source, its lightcurve and spectrum will be made available (within the next week).
WGACAT can be accessed via the HEASARC online service by logging into heasarc.gsfc.nasa.gov with the username xray. Type "browse wgacat" to access the catalog. For information on the catalog contents type dbhelp from the Browse command line. The commands sc, simbad, sn, and sp can be used to search the catalog. Contact Feedback to receive a Browse users guide.
Alternately WGACAT can be accessed via the HEASARC W3Browse service by clicking on ROSAT and then selecting WGACAT.
Contact us via the Feedback form if you have any questions regarding this catalog.
N.E. White, P. Giommi and L. Angelini (30 Oct 1994)
ROSAT NEWS No. 32 - 1-Nov-1994
ROSAT Scientific Data Center at the
Max-Planck-Institut fuer Extraterrestrische Physik (MPE)
Postfach 1603, D-85740 Garching, Germany
- e-mail addresses (Uli Zimmermann):
- rosat_svc@mpe-garching.mpg.de (Internet) or MPE::ROSAT_SVC (SPAN)
- ROSAT Service Area (including ROSAT Data Archive):
- ftp rosat_svc.mpe-garching.mpg.de user: anonymous
- WWW address: http://www.mpe.mpg.de/xray/wave/rosat/mission/rosat/
- XUV Center: 29382::GXUVDC or GXUVDC@AIT.PHYSIK.UNI-TUEBINGEN.DE
- WFC Archive access via telnet/ftp ait.physik.uni-tuebingen.de user: xuv (password: xuv_archive)
- rosat_svc@mpe-garching.mpg.de (Internet) or MPE::ROSAT_SVC (SPAN)
- Contents: - SATELLITE STATUS
- - THIRD ROSAT WORKSHOP at MPE
- - THE FIRST ROSAT SOURCE CATALOG
- - INTERACTIVE ACCOUNT XRAY
- - EXSAS FOR LINUX
- - THIRD ROSAT WORKSHOP at MPE
SATELLITE STATUS
No major problems were encountered during the last month.
THIRD ROSAT WORKSHOP at MPE
More than 100 participants of 30 research institutions attended the workshop to discuss actual ROSAT results and data evaluation issues. The directory general/workshop in the ROSAT Service Area contains the final list of the participants (including email addresses) and the program.
THE FIRST ROSAT SOURCE CATALOG
During the ROSAT workshop at MPE on October 26, 1994 Wolfgang Voges announced on behalf of the ROSAT Consortium (MPE-Garching, GSFC/SAO-US, and WFC-Consortium-UK) the public release of "THE FIRST ROSAT SOURCE CATALOGUE OF POINTED OBSERVATIONS WITH THE PSPC". This catalogue contains 50,408 sources from 2876 pointed observations. For each source the following properties are provided: the observation number, the ROSAT name, the position in equatorial and in galactic co-ordinates, four positional errors (intrinsic, systematic, boresight, and total), the source count-rate and its error, the background countrate, exposure time, hardness-ratios HR1 and HR2 and their errors, extent and likelihood of extent, likelihoods of the map-detect algorithm and of the maximum-likelihood detection algorithm, flags to indicate in which energy band and by what algorithm the source was detected, the detection cell size, the off-axis radius, the distances to the nearest rib and source (before and after removal of ambiguous sources), and a source confusion flag (set if another source is within 2.1*FWHM of the point-spread function).
This catalogue contains observations which have been performed until the end of May 1993 and which are in the public archive. A visual inspection of all soft and hard images, and an automated screening process on the original so called master source lists (MASOL), have been used to remove confused sources and 124 observations with too crowded regions and regions of high surface brightness diffuse emission. The resulting 50,408 sources have a likelihood of at least 10, corresponding to a rate of accidental detections of about 1 percent. This data base contains 80% of all PSPC observations. Since the acceptance criteria were rather conservative a total number of about 70,000 X-ray sources detected during the pointed PSPC observation phase can be expected.
The new catalogue has been moved into the public area and can be accessed via the interactive account xray (see header).
INTERACTIVE ACCOUNT XRAY
In the ROSAT Service Area we have now installed a copy of the HEASARC database system (developed by GSFC) including the BROWSE interface. Via the telnet address (given in the header) users can interactively access a large number of astronomical catalogs, and with the help of BROWSE select, correlate, extract and display data on sources and observations from missions like ROSAT, EINSTEIN, EXOSAT, GRO etc..
The new ROSAT PSPC Source Catalog is available under the database name rosatsrc (ROSAT sources), database rosatseq contains information on the individual observation fields. The command dbhelp within BROWSE will display general info on the catalog including explanations of the applied source selection and completeness criteria (available within the next 2 weeks).
EXSAS FOR LINUX
It is now possible to run EXSAS/MIDAS also on your PC under LINUX. The disk space used by both MIDAS and EXSAS (only executables are distributed) is in the order of 30 MBytes only. On systems with 486 processors of 50 MHz or more it runs similarly fast as on normal workstations. At the time of writing the first tests with the system run successfully. A (compressed) tar file of the LINUX version will be made available in the ROSAT Service Area within the next days, if further tests indicate no major problems. Interested users that use already EXSAS (and therefore have the allowance to access the secured area) may then directly ftp the file named exsas/94JUL_EXP/94JUL_LINUX.tar.Z. Others users are asked to first fill in the EXSAS questionnaire that can be copied as exsas/questionnaire.form via the anonymous ftp account, and send it to us.
Status Report #106
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