RASSDSSTAR ivo://nasa.heasarc/rassdsstar NASA/GSFC HEASARC Agueros et al. 2026-04-03 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Star The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. Combining the RASS Bright and Faint Source Catalogs yields an average of about three X-ray sources per square degree. However, while X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient to determine the nature of an X-ray source. As a result, large-scale follow-up programs are required to construct samples of known X-ray emitters. The authors use optical data produced by the Sloan Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters cataloged in the RASS and falling within the SDSS Data Release 1 footprint. Most of these are bright stars with coronal X-ray emission unsuitable for SDSS spectroscopy, which is designed for fainter objects (g > 15<sup>mag</sup>). Instead, the authors use SDSS photometry, correlations with the Two Micron All Sky Survey (2MASS) and other catalogs, and spectroscopy from the Apache Point Observatory 3.5 m telescope to identify these stellar X-ray counterparts. Their sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest X-ray-selected samples of such stars. The authors derive distances to these stars using photometric parallax relations appropriate for dwarfs on the main sequence, and use these distances to calculate their X-ray luminosities L<sub>X</sub>. They also identify a previously unknown cataclysmic variable (CV) as a RASS counterpart. Much more information on the SDSS is available at the project's web site at <a href="https://www.sdss.org/">https://www.sdss.org/</a>. This table was created by the HEASARC in April 2009 based on the the machine-readable version of Table 4 from the reference paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC . 2009ApJS..181..444A https://heasarc.gsfc.nasa.gov/W3Browse/all/rassdsstar.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=rassdsstar& GET text/xml 180 99999 true 5.36583 -11.01625 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=rassdsstar GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_rassdsstar&Action=More+Options&Action=Parameter+Search&ConeAdd=1 STAR CATALOG 0.0166666666666667 Infrared Optical X-ray public rassdsstar ROSAT All-Sky Survey and SDSS Sample of X-Ray Emitting Stars twomass_dec 2MASS Declination degree pos.eq.dec;em.IR double nullable sdss_ra SDSS Right Ascension degree pos.eq.ra;em.opt double nullable source_extent Source Extent arcsec phys.angSize;em.X-ray.soft short nullable "__z_ra_dec" System unit vector column double nullable distance_error Uncertainty in Distance (pc) pc stat.error;pos.distance double nullable twomass_ra 2MASS Right Ascension degree pos.eq.ra;em.IR double nullable umag_error Uncertainty in umag mag stat.error;phot.mag;em.opt.U double nullable "__row" System index column char nullable umag SDSS u Band PSF Magnitude mag phot.mag;em.opt.U double nullable exposure RASS Exposure Time s time.duration;obs.exposure short nullable bii Galactic Latitude degree pos.galactic.lat double nullable lx_error Uncertainty in RASS X-Ray Luminosity (erg/s) erg/s stat.error;phys.luminosity;em.X-ray.soft double nullable bmag SIMBAD B Band Magnitude mag phot.mag;em.opt.B double nullable class Browse Object Classification src.class short nullable ks_mag_error Uncertainty in Kmag mag stat.error;phot.mag;em.IR.K double nullable lii Galactic Longitude degree pos.galactic.lon double nullable rmag SDSS r Band PSF Magnitude mag phot.mag;em.opt.R double nullable hr2_error Uncertainty in Second Hardness Ratio stat.error;phot.flux;arith.ratio;em.X-ray.soft double nullable abs_ks_mag Synthetic Absolute K_S_ Band Magnitude mag double nullable spect_type Source Spectral Type src.spType char nullable extent_likelihood Extent Likelihood; See Voges et al. 1999 stat.likelihood;phys.angSize;em.X-ray.soft short nullable jmag 2MASS J Band Magnitude mag phot.mag;em.IR.J double nullable count_rate_error Uncertainty in RASS Count Rate ct/s stat.error;phot.count;em.X-ray.soft double nullable name Source Designation meta.id;meta.main char nullable sdss_simbad_offset Offset Between SDSS and SIMBAD Positions arcsec pos.angDistance double nullable log_fx_over_fj Logarithm of Ratio of RASS X-Ray to 2MASS J Band Fluxes phot.flux;arith.ratio double nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable detect_likelihood Detection Likelihood; See Voges et al. 1999 stat.likelihood;em.X-ray.soft short nullable "__x_ra_dec" System unit vector column double nullable simbad_name SIMBAD Identification meta.id.cross char nullable gmag_error Uncertainty in gmag mag stat.error;phot.mag;em.opt.B double nullable ks_mag 2MASS K_S_ Band Magnitude mag phot.mag;em.IR.K double nullable sdss_name SDSS Source Identification meta.id.cross;em.opt char nullable hr2 Second Hardness Ratio phot.flux;arith.ratio;em.X-ray.soft double nullable abs_ks_mag_error Uncertainty in Synthetic Absolute K_S_ Band Magnitude mag double nullable hmag_error Uncertainty in Hmag mag stat.error;phot.mag;em.IR.H double nullable sdss_2mass_offset Offset Between SDSS and 2MASS Positions arcsec pos.angDistance;em.opt;em.IR double nullable rmag_error Uncertainty in rmag mag stat.error;phot.mag;em.opt.R double nullable twomass_flags Flags Indicate Photometry in the J/H/K Bands for the 2MASS Infrared Counterpart meta.code;em.IR char nullable sdss_flags SDSS Flags Indicate Photometry for the SDSS Optical Counterpart meta.code;em.opt char nullable hr1 First Hardness Ratio phot.flux;arith.ratio;em.X-ray.soft double nullable vmag SIMBAD V Band Magnitude mag phot.mag;em.opt.V double nullable simbad_dec SIMBAD Declination degree pos.eq.dec double nullable dec Declination degree pos.eq.dec;meta.main double nullable "__y_ra_dec" System unit vector column double nullable simbad_ra SIMBAD Right Ascension degree pos.eq.ra double nullable imag SDSS i Band PSF Magnitude mag phot.mag;em.opt.R double nullable hmag 2MASS H Band Magnitude mag phot.mag;em.IR.H double nullable jmag_error Uncertainty in Jmag mag stat.error;phot.mag;em.IR.J double nullable count_rate RASS Count Rate ct/s phot.count;em.X-ray.soft double nullable simbad_class SIMBAD Classification src.spType char nullable gmag SDSS g Band PSF Magnitude mag phot.mag;em.opt.B double nullable zmag_error Uncertainty in zmag mag stat.error;phot.mag;em.opt.I double nullable zmag SDSS z Band PSF Magnitude mag phot.mag;em.opt.I double nullable twomass_name 2MASS Source Identification meta.id.cross;em.IR char nullable imag_error Uncertainty in imag mag stat.error;phot.mag;em.opt.R double nullable sdss_rass_offset Offset Between SDSS and RASS Positions (arcsec) arcsec pos.angDistance;em.opt;em.X-ray.soft double nullable apo_obs_date APO Observation Date mjd time.epoch;obs int nullable log_fx_over_fv Logarithm of Ratio of RASS X-Ray to SIMBAD V Band Fluxes phot.flux;arith.ratio double nullable "distance" Distance (pc) pc pos.distance double nullable hr1_error Uncertainty in First Hardness Ratio stat.error;phot.flux;arith.ratio;em.X-ray.soft double nullable error_radius RASS Positional Uncertainty arcsec stat.error;pos short nullable source_notes Additional Note(s) Concerning Source meta.note;src char nullable lx RASS X-Ray Luminosity (erg/s) erg/s phys.luminosity;em.X-ray.soft double nullable sdss_dec SDSS Declination degree pos.eq.dec;em.opt double nullable