- ID:
- ivo://CDS.VizieR/J/ApJS/91/625
- Title:
- ROSAT survey of the Pleiades
- Short Name:
- J/ApJS/91/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT PSPC images, 171 of which we associate with certain or probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, and M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of the Pleiades.
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- ID:
- ivo://CDS.VizieR/J/A+A/371/833
- Title:
- ROSAT Ultra Deep Survey
- Short Name:
- J/A+A/371/833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT Ultra Deep Survey in the Lockman Hole consists of a sample of 94 X-ray sources reaching a limiting flux of 1.2x10-15erg/s/cm^2^ in the 0.5-2.0keV energy band. About 90% of the X-ray sources have been spectroscopically identified using low-resolution Keck spectra.
- ID:
- ivo://CDS.VizieR/J/AJ/110/1229
- Title:
- ROSAT X-ray survey in NGC 6475
- Short Name:
- J/AJ/110/1229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A ROSAT X-ray survey, with complementary optical photometry, of the open cluster NGC 6475 has enabled the detection of ~50 late-F to K0 and ~70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low galactic latitude, 220Myr old cluster. The X-ray observations reported here have a typical limiting sensitivity of L_X_ ~ 10^29^erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the X-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the X-rays. The ratio between X-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of X-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in X-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of X-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.
- ID:
- ivo://nasa.heasarc/rosatxuv
- Title:
- ROSAT XUV Pointed Phase
- Short Name:
- ROSAT/REP
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- We present a catalogue of XUV sources from observations by the Wide Field Camera (WFC) on ROSAT during the pointed phase. The ROSAT WFC is a telescope sensitive in the extreme UV range (17-210eV) which observes in parallel with the ROSAT X-Ray Telescope (XRT). The 5916 pointed observations processed are from the calibration and verification phase in June 1990 and from the period 9 Feb. 1991 to 15 July 1994. The catalogue contains 1022 independent source detections which correspond to 328 individual sources, many of which have been observed repeatedly. Each observation was done with one of four filters S1, S2, P1 and P2. Of the 328 sources 113 are new sources (they are not listed in the "2RE" catalogue) and 274 have been identified with optical counterparts. The catalogue contains coordinates, observed count rates, normalized source count rates and the proposed optical counterpart with its spectral class. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/roxa
- Title:
- ROXA (Radio-Optical-X-ray at ASDC) Blazars Catalog
- Short Name:
- ROXA
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Although blazars are a small fraction of the overall AGN population, they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect several thousand of objects of this type. In preparation for these missions it is necessary to identify new samples of blazars to study their multi-frequency characteristics and statistical properties. The authors have compiled a sample of objects with blazar-like properties via a cross-correlation between large radio (NVSS, ATCAPMN) and X-ray surveys (RASS) using the SDSS-DR4 and 2dF survey data to spectroscopically identify their candidates and test the validity of the selection method. They present the Radio-Optical-X-ray catalog built at ASDC (ROXA), a list of 816 objects among which 510 are confirmed blazars. Only 19% of the candidates turned out to be certainly non-blazars, demonstrating the high efficiency of our selection method. This catalog includes 173 new blazar identifications, or about 10% of all presently known blazars. The relatively high flux threshold in the X-ray energy band (given by the RASS survey) preferentially selects objects with high F_X/F_r ratio, leading to the discovery of new High Energy Peaked BL Lac (HBLs). This catalog therefore includes many new potential targets for GeV-TeV observations. The selection method consisted of three steps: 1) a first cross-correlation between radio and X-ray surveys (the NRAO VLA Sky Survey, ATCAPMN (ATCA catalogue of compact PMN sources) and ROSAT All Sky Survey; 2) for each radio/X-ray match, optical magnitudes were retrieved from the Guide Star Catalog; 3) for all radio/optical/X-ray matches the authors calculated the X-ray to optical (alpha_ox) and radio to optical (alpha_ro) spectral slopes and took only sources with alpha_ox and alpha_ro values within the blazar area. For each object, redshift, B and G magnitudes, radio fluxes at 1.4 GHz and at 5 GHz, X-ray flux, F_X/F_r ratio, X-ray luminosity, radio luminosity, Ca H&K break and classification are given. This table was created by the HEASARC in November 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/472/699">CDS catalog J/A+A/472/699</a> file catalog.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sacy
- Title:
- SACY (Search for Associations Containing Young Stars) Catalog
- Short Name:
- SACY
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The SACY (Search for Associations Containing Young Stars) Catalog contains the results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and young stars among optical counterparts of ROSAT All-Sky Survey X-ray sources in the Southern Hemisphere. 1953 late-type (B-V>=0.6), potentially young, optical counterparts were selected out of a total of 9574 1RXS sources for follow-up observations. At least one high-resolution spectrum was obtained for each of 1511 targets. This paper is the first in a series presenting the results of the SACY survey in which the sample of X-ray selected stars and the supporting optical observations are described. The SACY sample is defined by Hipparcos (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/I/239">CDS Cat. <I/239></a>) and Tycho-2 (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/I/259">CDS Cat. <I/259></a>) stars within an error radius of 2.6 times the positional error of the ROSAT All-Sky Bright Source Catalogue (1RXS, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/IX/10">CDS Cat. <IX/10></a>). The used cut-off (B-V=0.6), corresponding approximately to a G0 dwarf, is near the hottest stars where the strength of the LiI line can be used as an youth indicator. All Hipparcos stars having M_v < 2.0 have been excluded. The northern boundary limits of the survey are given in Table 1 of the reference paper. In addition to the 1511 stars observed at least once, 115 stars with data taken from the literature have been added in order to complement the sample. In addition to these 1626 stars in the SACY sample (sources with source number prefixes of 'S'), entries for 165 other observed stars (sources with source number prefixes of 'O') are also included in this table. Most of the spectroscopic observations (~70%) were performed with the FEROS spectrograph at the 1.5m/ESO telescope at La Silla between January 1999 and September 2002 (ON-ESO agreement and ESO program identification 67.C-0123). Two more runs (ESO program identifications 072.C-0393 and 077.C-0138) were carried out at the 2.2m/ESO telescope. Another set of data (~30%) was collected at the coude spectrograph attached to 1.60m telescope at the Observatorio rio do Pico dos Dias (OPD), LNA, Brazil. Some spectra are a re-analysis of the ones taken for the PDS program. A few observations were collected using the CORALIE attached to the Swiss Euler Telescope at La Silla. UBV(RI)c photometry for part of the sample was obtained using FOTRAP at the 0.60m Zeiss telescope of the OPD. When a star was not observed photometrically by the authors, they tried to obtain some useful photometric data from the Hipparcos and Tycho Catalogues or in the available literature in the SIMBAD. For multiple stars, magnitudes and colors were corrected in order to take into account the presence of the companion(s). This table was created by the HEASARC in March 2007 based on the CDS table J/A+A/460/695, files table3.dat and table4.dat This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/spidersros
- Title:
- SDSS-IV/SPIDERS ROSAT-Based X-Ray Point Source Spectroscopic Catalog
- Short Name:
- SPIDERSROS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog aims to provide a detailed description of the SPectroscopic IDentification of ERosita Sources (SPIDERS) survey, an SDSS-IV program aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. The authors describe the SPIDERS X-Ray Point Source Spectroscopic Catalog, considering its store of 11,092 observed spectra drawn from a parent sample of 14,759 ROSAT and XMM sources over an area of 5,129 deg<sup>2</sup> covered in SDSS-IV by the eBOSS survey. This catalog presents the SPIDERS ROSAT subsample of 21,288 sources which were drawn from the Second ROSAT All-Sky Survey (2RXS), provided by the HEASARC in <a href="/W3Browse/rosat/rass2rxs.html">RASS2RXS</a>. The accompanying <a href="/W3Browse/xmm-newton/spidersxmm.html">SPIDERSXMM</a> table contains the 3,196 sources drawn from the XMM Slew Survey Source Catalog, version 2 (XMMSL2), provided by the HEASARC in <a href="/W3Browse/xmm-newton/xmmslewful.html">XMMSLEWFUL</a>. This program represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10,970 (98.9%) of the observed objects are classified and 10,849 (97.8%) have secure redshifts. The majority of the spectra (10,070 objects) are active galactic nuclei (AGN), 522 are cluster galaxies, and 294 are stars. The SDSS-IV/BOSS spectrographic observations are taken between 2014 and 2019. This table was created by the HEASARC in May 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/636/A97">CDS Catalog J/A+A/636/A97</a> file vc2rxs.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/rass2rxs
- Title:
- Second ROSAT All-Sky Survey Point Source Catalog (2RXS)
- Short Name:
- RASS2RXS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains the Second ROSAT All-Sky Survey Point Source Catalog (2RXS). This is the second publicly released ROSAT catalog of point-like sources obtained from the ROSAT All-Sky Survey (RASS) observations performed with the Position-Sensitive Proportional Counter (PSPC) between June 1990 and August 1991. It is an extended, revised, and combined version of the RASS <a href="/W3Browse/rosat/rassbsc.html">Bright</a> and <a href="/W3Browse/rosat/rassfsc.html">Faint Source Catalog</a>s. Utilizing the latest RASS processing, this catalog includes more than 135,000 X-ray detections in the 0.1-2.4 keV energy band down to a likelihood threshold of 6.5. Additional information can be found at <a href="http://www.mpe.mpg.de/ROSAT/2RXS/">http://www.mpe.mpg.de/ROSAT/2RXS/</a>. This table was created by the HEASARC in March, 2017, based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/588/A103">CDS Catalog J/A+A/588/A103</a> file cat2rxs.dat.gz. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+A/588/A103
- Title:
- Second ROSAT all-sky survey (2RXS) source catalog
- Short Name:
- J/A+A/588/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second ROSAT all-sky survey source catalogue, hereafter referred to as the 2RXS catalogue. This is the second publicly released ROSAT catalogue of point-like sources obtained from the ROSAT all-sky survey (RASS) observations performed with the position-sensitive proportional counter (PSPC) between June 1990 and August 1991, and is an extended and revised version of the bright and faint source catalogues. We used the latest version of the RASS processing to produce overlapping X-ray images of 6.4 by 6.4 degrees sky regions. To create a source catalogue, a likelihood-based detection algorithm was applied to these, which accounts for the variable point-spread function (PSF) across the PSPC field of view. Improvements in the background determination compared to 1RXS were also implemented. X-ray control images showing the source and background extraction regions were generated, which were visually inspected. Simulations were performed to assess the spurious source content of the 2RXS catalogue. X-ray spectra and light curves were extracted for the 2RXS sources, with spectral and variability parameters derived from these products. We obtained about 135,000 X-ray detections in the 0.1-2.4keV energy band down to a likelihood threshold of 6.5, as adopted in the 1RXS faint source catalogue. Our simulations show that the expected spurious content of the catalogue is a strong function of detection likelihood, and the full catalogue is expected to contain about 30 per cent spurious detections. A more conservative likelihood threshold of 9, on the other hand, yields about 71,000 detections with a 5 per cent spurious fraction. We recommend thresholds appropriate to the scientific application. X-ray images and overlaid X-ray contour lines provide an additional user product to evaluate the detections visually, and we performed our own visual inspections to flag uncertain detections. Intra-day variability in the X-ray light curves was quantified based on the normalised excess variance and a maximum amplitude variability analysis. X-ray spectral fits were performed using three basic models, a power law, a thermal plasma emission model, and black-body emission. Thirty-two large extended regions with diffuse emission and embedded point sources were identified and excluded from the present analysis. The 2RXS catalogue provides the deepest and cleanest X-ray all-sky survey catalogue in advance of eROSITA.
- ID:
- ivo://CDS.VizieR/IX/30
- Title:
- Second ROSAT PSPC Catalog
- Short Name:
- IX/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains sources from PSPC-ROSAT (Position-Sensitive Proportional Counter aboard the Roentgen Satellite), as provided by Max-Planck Institut fuer extraterrestrische Physik (MPE). It supersedes the 1994 version (Cat. <IX/11>) The current release of the catalog is comprised of results from 4093 sequences (sky coverage of 14.5%). The complete version contains entries for 95,331 detections whereas the short version has 43,156 detections. 2189 obvious sources were not detected by the automated Standard Analysis Software System (SASS), and are not yet contained in this catalogue. These data have been screened by ROSAT data centers in the US, Germany, and the UK as a step in the production of the ROSAT RESULTS ARCHIVE. The RRA contains extracted source and associated products with an indication of reliability for the primary parameters.
