M 37 Chandra X-Ray Point Source Catalog

M 37 Chandra X-Ray Point Source Catalog M37CXO ivo://nasa.heasarc/m37cxo NASA/GSFC HEASARC Nunez et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source Empirical calibrations of the stellar age-rotation-activity relation (ARAR) rely on observations of the co-eval populations of stars in open clusters. The authors used the Chandra X-ray Observatory to study M 37 (NGC 2099), a 500-Myr-old open cluster that has been extensively surveyed for rotation periods (Prot). M 37 was observed almost continuously for five days, for a total of 440.5 ks, to measure stellar X-ray luminosities (LX), a proxy for coronal activity, across a wide range of masses. The cluster's membership catalog was revisited to calculate updated membership probabilities from photometric data and each star's distance to the cluster center. The result is a comprehensive sample of 1699 M 37 members: 426 with Prot, 278 with X-ray detections, and 76 with both. The authors calculate Rossby numbers, Ro= Prot/tau , where tau is the convective turnover time, and ratios of the X-ray-to-bolometric luminosity, LX/Lbol, to minimize mass dependencies in their characterization of the rotation-coronal activity relation at 500 Myr. They find that fast rotators, for which Ro < 0.09 +/- 0.01, show saturated levels of activity, with log(LX/Lbol) = -3.06 +/- 0.04. For Ro >= 0.09 +/- 0.01, activity is unsaturated and follows a power law of the form Rbetao , where beta = -2.03 (-0.14, +0.17). This is the largest sample available for analyzing the dependence of coronal emission on rotation for a single-aged population, covering stellar masses in the range 0.4 - 1.3 solar masses, Prot in the range 0.4 - 12.8 days, and LX in the range 1028.4 - 1030.5 erg s-1. These results make M 37 a new benchmark open cluster for calibrating the ARAR at ages of ~ 500 Myr. The central field of M 37 was observed five separate times between 2011 November 14 20:58 and 2011 November 1915:31 UTC for a total of 440.5 ks with the Advanced CCD Imaging Spectrometer (ACIS). The four ACIS-I chips and the ACIS-S3 chip were used in Very Faint telemetry mode to improve the screening of background events and thus increase the sensitivity of ACIS to faint sources. The exposure-weighted average aimpoint of the 16.9 x 16.9 arcmin2 ACIS-I field of view is RA = 05h 52m 17.86s,Dec = +32o 33' 48.23" (J2000). The pitch angle for four observations was 103 degrees; due to scheduling constraints, it was 253 degrees for the fifth. Table 1 in the reference paper provides the basic information for the 5 Chandra observations and Figure 1 in that paper shows their footprints superimposed on a 40' x 40' i' image centered on M 37 obtained by Hartman et al. (2008, ApJ, 675, 1233, hereafter HA08) with the Megacam on the MMT telescope. This HEASARC table contains all of the data from Table 3 of the reference paper, the M 37 Chandra catalog of 774 X-ray sources, and the data from Table 5, the catalog of optical objects, for those objects which have been identified as optical counterparts to the X-ray sources. It does not contain entries for those optical objects in Table 5 which lack X-ray counterparts. This online catalog was created by the HEASARC in December 2015 based on machine-readable versions of tables 3 and 5 from the paper which were obtained from the ApJ website. This is a service provided by NASA HEASARC . 2015ApJ...809..161N https://heasarc.gsfc.nasa.gov/W3Browse/all/m37cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=m37cxo& GET text/xml 180 99999 true 88.131745 32.393678 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=m37cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_m37cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public m37cxo M 37 Chandra X-Ray Point Source Catalog source_number Sequential Identification Number for Each Source in the Catalog meta.id;src short nullable name IAU-Style Source Designation meta.id;meta.main char nullable off_axis Off-Axis Angle of X-Ray Source arcmin instr.offset double nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius 80%-Confidence Level X-Ray Positional Uncertainty arcsec stat.error;pos double nullable fb_counts Net Source Counts in the 0.5-7 keV Band ct phot;em.X-ray double nullable fb_counts_neg_err 1-Sigma Negative Error of Net Source Counts in the 0.5-7 keV Band ct stat.error;phot;em.X-ray double nullable fb_counts_pos_err 1-Sigma Positive Error of Net Source Counts in the 0.5-7 keV Band ct stat.error;phot;em.X-ray double nullable fb_flux Absorbed Energy Flux in the 0.5-7 keV Band erg/s/cm^2 phot.flux;em.X-ray double nullable sb_lx X-Ray Luminosity in the 0.1-2.4 keV Band erg/s phys.luminosity;em.X-ray double nullable optical_cxo_offset Offset Between X-Ray Source and Optical Match arcsec pos.angDistance;em.opt;em.X-ray double nullable gmag g Magnitude mag phot.mag;em.opt double nullable gmag_error g Magnitude Standard Deviation mag stat.error;phot.mag;em.opt double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable lbol_error Standard Deviation of Bolometric Luminosity erg/s stat.error;phys.luminosity double nullable hb_flux Absorbed Energy Flux in the 2-7 keV Band erg/s/cm^2 phot.flux;em.X-ray.medium double nullable optical_ra Right Ascension of Optical Match degree pos.eq.ra;em.opt double nullable imag i Magnitude mag phot.mag;em.opt.I double nullable xray_notes Additional Notes meta.note;em.X-ray char nullable conv_turnover_time Convective Turnover Time d double nullable prob_no_source Probability That Extracted X-Ray Counts Are Solely from Background stat.probability;em.X-ray double nullable rmag r Magnitude mag phot.mag;em.opt.R double nullable hb_counts_pos_err 1-Sigma Positive Error of Net Source Counts in the 2-7 keV Band ct stat.error;phot;em.X-ray.medium double nullable me08_id Identification of ME08 Match meta.id.cross;em.opt short nullable rotation_period_flag Rotation Period Flag meta.code;time.period double nullable snr Signal-to-Noise Ratio stat.snr;em.X-ray double nullable me08_dec Declination of ME08 Match degree pos.eq.dec;em.opt double nullable optical_dec Declination of Optical Match degree pos.eq.dec;em.opt double nullable sb_counts_neg_err 1-Sigma Negative Error of Net Source Counts in the 0.5-2 keV Band ct stat.error;phot;em.X-ray.soft double nullable sb_counts Net Source Counts in the 0.5-2 keV Band ct phot;em.X-ray.soft double nullable hb_counts_neg_err 1-Sigma Negative Error of Net Source Counts in the 2-7 keV Band ct stat.error;phot;em.X-ray.medium double nullable prob_single_member Probability That Object Is Single Member stat.probability double nullable bii Galactic Latitude degree pos.galactic.lat double nullable hb_counts Net Source Counts in the 2-7 keV Band ct phot;em.X-ray.medium double nullable sb_lx_error Standard Deviation of X-Ray Luminosity erg/s stat.error;phys.luminosity;em.X-ray double nullable sb_flux Absorbed Energy Flux in the 0.5-2 keV Band erg/s/cm^2 phot.flux;em.X-ray.soft double nullable rotation_period Rotation Period d time.period double nullable median_energy Median Photon Energy in the 0.5-7 keV Band keV phys.energy double nullable me08_optical_offset Offset Between Optical Object and ME08 Match arcsec pos.angDistance;em.opt double nullable lii Galactic Longitude degree pos.galactic.lon double nullable source_anomaly_flags Flags Indicates Source Anomalies meta.code;src char nullable sb_counts_pos_err 1-Sigma Positive Error of Net Source Counts in the 0.5-2 keV Band ct stat.error;phot;em.X-ray.soft double nullable lbol Bolometric Luminosity erg/s phys.luminosity double nullable psf_fraction Fraction of the PSF Enclosed within Extraction Region instr.det.psf double nullable me08_ra Right Ascension of ME08 Match degree pos.eq.ra;em.opt double nullable rmag_error r Magnitude Standard Deviation mag stat.error;phot.mag;em.opt.R double nullable stellar_mass Stellar Mass Solar_Mass phys.mass double nullable ks_var_flag Variability Based on K-S Statistic meta.code;src.var char nullable optical_id Identification of Optical Match meta.id.cross;em.opt char nullable prob_binary_member Probability That Object Is Likely Binary Member stat.probability double nullable optical_notes Additional Notes Concerning Optical Match meta.note;em.opt char nullable imag_error i Magnitude Standard Deviation mag stat.error;phot.mag;em.opt.I double nullable prob_member Probability That Object Is Member stat.probability double nullable