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NGC6231CX2 - NGC 6231 Chandra X-Ray Point Source Catalog 2

HEASARC
Archive

Overview

NGC 6231 is a young cluster (age ~2-7 Myr) dominating the Sco OB1 association (distance ~1.59 kpc) with ~100 O and B stars and a large pre-main-sequence stellar population. The authors combine a reanalysis of archival Chandra X-ray data with multi-epoch near-infrared (NIR) photometry from the VISTA Variables in the Via Lactea (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, the authors identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, they estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 Msun (assuming a universal initial mass function) with a completeness limit at 0.5 Msun. A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars.

This work makes use of some basic cluster properties available from the literature. Summaries of older studies are provided by Sana et al. (2006, J/A+A/454/1047), available in NGC6231XMM, and Reipurth (2008hsf2.book.....R). Expanded catalogs of cluster members have been provided by Sung et al. (2013, J/AJ/145/37) and Damiani et al. 2016, J/A+A/596/A82 (DMS2016), available at NGC6231CXO.

Chandra X-ray observations were made using the imaging array on the Advanced CCD Imaging Spectrometer (ACIS-I; Garmire et al. 2003SPIE.4851...28G). This instrument is an array of four CCD detectors that subtends 17'x17'. The target was observed in 2005 July (Sequence 200307; PI: S. Murray) in two observations (ObsID 5372 and 6291), and the data were retrieved from the Chandra Data Archive.

The NIR ZYJHKs data were obtained from the VVV survey (Minniti et al. 2010NewA...15..433M; Saito et al. 2012, Cat. II/337). VVV is a multi-epoch NIR survey that covers both the Galactic bulge and an adjacent Galactic disk region and was carried out using the 4.1 m VISTA telescope on Cerro Paranal. The VVV data were taken with the VISTA Infrared CAMera (VIRCAM; Dalton et al. 2006SPIE.6269E..0XD), a 4x4 array of Raytheon VIRGO 2048x2048 20 micron pixel detectors with a pixel scale of 0.34".

In addition to the VVV photometry, public optical or infrared catalogs are available from surveys and publications. We have included VPHAS+ photometry (Drew et al. 2014, J/MNRAS/440/2036), UBVRI (Johnson-Cousins system) and H-alpha photometry from Sung et al. (2013, J/AJ/145/37), and Spitzer/IRAC photometry from the GLIMPSE survey (Benjamin et al. 2003, Cat. II/293).


Catalog Bibcode

2017AJ....154...87K

References

The structure of the young star cluster NGC 6231.
I. Stellar population.
    Kuhn M.A., Medina N., Getman K.V., Feigelson E.D., Gromadzki M.,
    Borissova J., Kurtev R.
    <Astron. J., 154, 87 (2017)>
    =2017AJ....154...87K

Provenance

This table was created by the HEASARC in October 2020 based upon the CDS Catalog J/AJ/154/87 file table1.dat, table3.dat, and table5.dat.

Parameters

Name
The IAU-style J2000 position-based source designation, e.g., 'CXO JHHMMSS.ss+DDMMSS.s'. Notice that these designations are non-standard according to the guidelines of the Dictionary of Nomenclature of Celestial Objects, which would suggest that they should be of the form 'CXOU JHHMMSS.s+DDMMSS', i.e., with the prefix CXOU for Chandra X-ray Observatory, Unregistered, and lower-precision coordinates.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates to an accuracy of 10-6 degrees (0.0036 arcseconds) in the original reference.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates to an accuracy of 10-6 degrees (0.0036 arcseconds) in the original reference.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The radius of the 1-sigma error circle around the X-ray source position, in arcseconds.

Pos_Algorithm
The particular algorithm that was used to estimate the position of the specified X-ray source ("AE correlation", "AE mean data", "AE reconstruction" or "eye").. The algorithms used are described in Section 7.1 of Broos et al. (2010, ApJ, 714, 1582, hereafter B10).

Prob_No_Src_Min
The smallest of the 3 band-dependent 'no-source' probabilities (p-values), fb_prob_no_src,sb_prob_no_src and hb_prob_no_src.

FB_Prob_No_Src
The probability for the 'no-source' hypothesis in the full 0.5-8.0 keV band, i.e., the p-value as described in B10, Section 4.3. In statistical hypothesis testing, the p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed when the null hypothesis is true.

SB_Prob_No_Src
The probability for the 'no-source' hypothesis in the full 0.5-2.0 keV band, i.e., the p-value as described in B10, Section 4.3. In statistical hypothesis testing, the p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed when the null hypothesis is true.

HB_Prob_No_Src
The probability for the 'no-source' hypothesis in the full 2.0-8.0 keV band, i.e., the p-value as described in B10, Section 4.3. In statistical hypothesis testing, the p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed when the null hypothesis is true.

Single_KS_Prob
The smallest p-value for the one-sample Kolmogorov-Smirnov statistic under the no-variability null hypothesis within a single observation. See B10, Section 7.6 for a description of the variability metrics and caveats regarding possible spurious indications of variability using the merged_ks_prob metric.

Merged_KS_Prob
The smallest p-value for the one-sample Kolmogorov-Smirnov statistic under the no-variability null hypothesis for the merged observations. See B10, Section 7.6 for a description of the variability metrics and caveats regarding possible spurious indications of variability using the merged_ks_prob metric.

Nominal_Exposure
The total nominal exposure time for the X-ray source in the merged observations, in seconds.

Frac_Exposure
The fraction of the total nominal exposure time that the X-ray source was observed. Due to dithering over inactive portions of the focal plane, a Chandra source is often not observed during some fraction of the nominal exposure time. (See http://cxc.harvard.edu/ciao/why/dither.html.) The reported quantity is the value of FRACEXPO produced by the CIAO tool mkarf.

Num_Obs_Extracted
The total number of observations of the source that were extracted.

Num_Obs_Merged
The number of observations of the source that were merged so as to estimate its photometric properties.

Frac_Expo_Discard
The fraction of exposures that were discarded in the merging of the observations for the source.

Off_Axis_Min
The smallest off-axis angle ThetaLo of the X-ray source among the merged observations, in arcminutes.

Off_Axis
The average off-axis angle Theta of the X-ray source among the merged observations, in arcminutes.

Off_Axis_Max
The largest off-axis angle ThetaHi of the X-ray source among the merged observations, in arcminutes.

PSF_Fraction
The average PSF fraction at 1.5 keV for the X-ray source in the merged observations.

Aperture_Area
The average aperture area for the X-ray source in the merged observations, in number of pixels of 0.492 by 0.492 arcseconds in size.

Afterglow_Fraction
The suspected afterglow fraction. Since the extracted event data are lightly cleaned to avoid removing legitimate X-ray events from bright sources (B10, Section 3), some background events arising from an effect known as "afterglow" (http://cxc.harvard.edu/ciao/why/afterglow.html) will remain and may contaminate source extractions. After extraction, the authors attempted to identify afterglow events using the tool ae_afterglow_report (refer to the ACIS Extract manual at https://ascl.net/1203.001) and report the fraction of extracted events attributed to afterglow in this parameter.

FB_Total_Counts
The observed total-band (0.5-8 keV) total counts in the X-ray source in the merged apertures.

SB_Total_Counts
The observed total-band (0.5-2 keV) total counts in the X-ray source in the merged apertures.

HB_Total_Counts
The observed total-band (2-8 keV) total counts in the X-ray source in the merged apertures.

Bck_Scaling
The scaling of the background extraction. (See B10, Section 5.4.)

FB_Bck_Counts
The observed 0.5-8 keV counts in the merged background regions.

SB_Bck_Counts
The observed 0.5-2 keV counts in the merged background regions.

HB_Bck_Counts
The observed 2-8 keV counts in the merged background regions.

FB_Counts
The net (background-subtracted) 0.5-8 keV counts in the merged apertures.

FB_Counts_Neg_Err
The 1-sigma negative error in the full-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

FB_Counts_Pos_Err
The 1-sigma positive error in the full-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

SB_Counts
The net (background-subtracted) 0.5-2 keV counts in the merged apertures.

SB_Counts_Neg_Err
The 1-sigma negative error in the soft-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

SB_Counts_Pos_Err
The 1-sigma positive error in the soft-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

HB_Counts
The net (background-subtracted) 2-8 keV counts in the merged apertures.

HB_Counts_Neg_Err
The 1-sigma negative error in the hard-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

HB_Counts_Pos_Err
The 1-sigma positive error in the hard-band counts. The 68%-confidence intervals for the net counts quantities were estimated by the CIAO tool aprates (http://asc.harvard.edu/ciao/ahelp/aprates.html). The HEASARC calculated the negative error using the lower bound value given in the original table and the value of the corresponding counts parameter.

FB_ARF_Value
The mean 0.5-8 keV ancillary response file (ARF) value, in units of cm2 count photon-1. The ARF in ACIS data analysis represents both the effective area of the observatory and the fraction of the observation for which data were actually collected for the source (the FRACEXPO parameter).

SB_ARF_Value
The mean 0.5-2 keV ancillary response file (ARF) value, in units of cm2 count photon-1. The ARF in ACIS data analysis represents both the effective area of the observatory and the fraction of the observation for which data were actually collected for the source (the FRACEXPO parameter).

HB_ARF_Value
The mean 2-8 keV ancillary response file (ARF) value, in units of cm2 count photon-1. The ARF in ACIS data analysis represents both the effective area of the observatory and the fraction of the observation for which data were actually collected for the source (the FRACEXPO parameter).

FB_Median_Energy
The median energy of the observed spectrum of the X-ray source, in the 0.5-8 keV band, in keV. This is the AE quantity ENERG_PCT50_OBSERVED, the median energy of extracted events, corrected for background events (B10, Section 7.3).

SB_Median_Energy
The median energy of the observed spectrum of the X-ray source, in the 0.5-2 keV band, in keV. This is the AE quantity ENERG_PCT50_OBSERVED, the median energy of extracted events, corrected for background events (B10, Section 7.3).

HB_Median_Energy
The median energy of the observed spectrum of the X-ray source, in the 2-8 keV band, in keV. This is the AE quantity ENERG_PCT50_OBSERVED, the median energy of extracted events, corrected for background events (B10, Section 7.3).

FB_Log_Photon_Flux
The logarithm of the incident photon flux in the total (0.5-8keV) band, in photon cm-2 s-1. This is the net counts over the product of the mean effective area in this band (the fb_arf_value) and the nominal exposure time (B10, Section 7.4).

SB_Log_Photon_Flux
The logarithm of the incident photon flux in the total (0.5-2keV) band, in photon cm-2 s-1. This is the net counts over the product of the mean effective area in this band (the sb_arf_value) and the nominal exposure time. (See B10, Section 7.4.)

HB_Log_Photon_Flux
The logarithm of the incident photon flux in the total (2-8keV) band, in photon cm-2 s-1. This is the net counts over the product of the mean effective area in this band (the hb_arf_value) and the nominal exposure time. (See B10, Section 7.4.)

HB_Flux_Obs
The observed 2-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

HB_Flux
The absorption-corrected 2-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

HB_Flux_Stat_Err
The 1-sigma statistical uncertainty in the absorption-corrected 2-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT.Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

HB_Flux_Sys_Err
The 1-sigma systematic uncertainty in the absorption-corrected 2-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

FB_Flux_Obs
The observed 0.5-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760). Better estimates for the full-band flux is given by the fb_log_flux_obs field for identified OB stars.

FB_Flux
The absorption-corrected 0.5-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760). Better estimates for the absorption-corrected full-band flux is given by the fb_log_flux field for identified OB stars.

FB_Flux_Stat_Err
The 1-sigma statistical uncertainty in the absorption-corrected 0.5-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

FB_Flux_Sys_Err
The 1-sigma systematic uncertainty in the absorption-corrected 0.5-8 keV energy flux of the source, in erg cm-2 s-1, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

Log_NH
The absorbing gas column density NH, in H atoms cm-2, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760). Better estimates for the NH is given by the apec_log_nh field for identified OB stars.

Log_NH_Stat_Err
The 1-sigma statistical uncertainty in the absorbing gas column density NH, in H atoms cm-2, obtained using XPHOT. Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

Log_NH_Sys_Err
The 1-sigma systematic uncertainty in the absorbing gas column density NH, in H atoms cm-2, obtained using XPHOT.Note that XPHOT assumes X-ray spectral shapes of young, low-mass stars, which come from coronal X-ray emission. XPHOT quantities will therefore be unreliable for high-mass stars, for which X-ray emission is associated with the stellar wind (Getman et al. 2010, J/ApJ/708/1760).

FB_Log_Lum
The logarithm of the X-Ray (0.5-8 keV) luminosity (in erg/s), assuming a distance of 1.59 kpc.

FB_Log_Lum_Error
The 1-sigma uncertainty in the logarithm of the X-Ray (0.5-8 keV) luminosity (in erg/s), assuming a distance of 1.59 kpc.

SB_Log_Lum
The logarithm of the X-Ray (0.5-2 keV) luminosity (in erg/s), assuming a distance of 1.59 kpc.

SB_Log_Lum_Error
The 1-sigma uncertainty in the logarithm of the X-Ray (0.5-2 keV) luminosity (in erg/s), assuming a distance of 1.59 kpc.

Alt_Name
The IAU-style J2000 position-based source designation, e.g., 'CXOVVV JHHMMSS.ss+DDMMSS.s'. Notice that these designations are non-standard according to the guidelines of the Dictionary of Nomenclature of Celestial Objects, which would suggest that they should be of the form 'CXOVVV JHHMMSS.s+DDMMSS', i.e., with more truncated positions.

HD_Number
The OB star source number in the HD catalog (Cannon, 1936AnHar.100....1C).

CPD_Number
The OB star source number in the CPD catalog (Gill & Kapteyn, 1897AnCap...4....1G).

Segg_Number
The OB star source number in the Seggewiss (1968ZA.....68..142S) catalog.

SBL98_Number
The OB star source number in the Sung et al. (1998, J/AJ/115/734) catalog.

BVF99_Number
The OB star source number in the Baume et al. (1999, J/A+AS/137/233) catalog.

Spect_Type
The spectral type tabulated by Sana et al. (2006, J/MNRAS/372/661).

Ref_Spect_Type
The reference(s) for spectral type given by Sana et al. (2006, J/MNRAS/372/661) coded as follows:

          Bra67  = Braes 1967BANS....2....1B;
          GM01   = Garcima & Mermilliod 2001A&A...368..122G;
          GaS79  = Garrison & Schild 1979AJ.....84.1020G;
          LM80   = Levato & Malaroda 1980PASP...92..323L;
          LM83   = Levato & Morrell 1983ApL....23..183L;
          Lav72  = Laval 1972A&A....21..271L;
          PHYB90 = Perry et al. 1990A&AS...86..415P;
          SAR05  = Sana et al. 2005A&A...441..213S;
          SGR06  = Sana, Rauw & Gosset 2007ApJ...659.1582S;
          SIMBAD = SIMBAD database, http://simbad.u-strasbg.fr/sim-fid.pl;
          SNW71  = Schild et al. 1971AJ.....76..237S;
          SRG01  = Sana et al. 2001A&A...370..121S;
          San05  = Sana 2005, PhD Thesis, Liege University, Belgium;
          San06  = Sana et al. 2007MNRAS.377..945S.
  

DMS2016_Number
The source number in the DMS2016 catalog (Damiani et al. 2016, J/A+A/596/A82), available also as NGC6231CXO.

DMS2016_Flag
The membership classification, based on the DMS2016 Catalog, corresponding to the parameter 'Stellar_group' in NGC6231CXO. This classification is given by the grouping within the V-I versus V color-magnitude diagram, and coded as follows:

          Group 1:  O-B (main-sequence or evolved) spectral type stars;
          Group 2:  A-F spectral type stars which have just arrived on the main
                    sequence (or are about to arrive);
          Group 3:  Pre-main sequence (PMS) stars (the bulk of the X-ray
                    detections);
          Group 4:  Field main-sequence stars, typically X-ray detections that
                    lie distinctly below the PMS band in the V-I vs. V plane;
          Group 5:  Foreground stars, typically X-ray detections that lie
                    distinctly above the PMS band in the V-I vs. V plane;
          Group 6:  Unidentified sources, i.e., X-ray sources with no optical
                    IDs.
  

VVV_Name
The source designation in the catalog of Ks variables in VVV, given in the form of HHMMSS.ss+DDMMSS.s.

VVV_RA
The right ascension of VVV source, in J2000 decimal degrees.

VVV_Dec
The declination of VVV source, given in J2000 decimal degrees.

VVV_Ks_Mag
The VVV Ks-band magnitude.

VVV_Ks_Mag_Error
The 1-sigma uncertainty in the VVV Ks-band magnitude.

VVV_Ks_Mag_Flag
The Cambridge Astronomical Survey Unit (CASU) flag for VVV Ks-band magnitude that indicate the morphological classifications of sources, which are generated based on curve-of-growth analysis (Irwin et al. 2004SPIE.5493..411I). Sources are flagged as follows:

          -1 = Stellar;
          -2 = Borderline stellar;
          -9 = Saturated in the analysis.
  

VVV_Hmag
The VVV H-band magnitude.

VVV_Hmag_Error
The 1-sigma uncertainty in the VVV H-band magnitude.

VVV_Hmag_Flag
The Cambridge Astronomical Survey Unit (CASU) flag for VVV H-band magnitude that indicate the morphological classifications of sources, which are generated based on curve-of-growth analysis (Irwin et al. 2004SPIE.5493..411I). Sources are flagged as described above for the vvv_ks_mag_flag.

VVV_Jmag
The VVV J-band magnitude.

VVV_Jmag_Error
The 1-sigma uncertainty in the VVV H-band magnitude.

VVV_Jmag_Flag
The Cambridge Astronomical Survey Unit (CASU) Flag for VVV J-band magnitude that indicate the morphological classifications of sources, which are generated based on curve-of-growth analysis (Irwin et al. 2004SPIE.5493..411I). Sources are flagged as described above for the vvv_ks_mag_flag.

VVV_Ymag
The VVV Y-band magnitude.

VVV_Ymag_Error
The 1-sigma uncertainty in the VVV Y-band magnitude.

VVV_Ymagv_Flag
The Cambridge Astronomical Survey Unit (CASU) Flag for VVV J-band magnitude that indicate the morphological classifications of sources, which are generated based on curve-of-growth analysis (Irwin et al. 2004SPIE.5493..411I). Sources are flagged as described above for the vvv_ks_mag_flag.

VVV_Zmag
The VVV z-band magnitude.

VVV_Zmag_Error
The 1-sigma uncertainty in the VVV z-band magnitude.

VVV_Zmag_Flag
The Cambridge Astronomical Survey Unit (CASU) flag for VVV z-band magnitude that indicate the morphological classifications of sources, which are generated based on curve-of-growth analysis (Irwin et al. 2004SPIE.5493..411I). Sources are flagged as described above for the vvv_ks_mag_flag.

TwoMASS_Name
The source designation in the 2MASS catalog, given in the form of HHMMSSss+DDMMSSs.

TwoMASS_Jmag
The 2MASS J-band magnitude.

TwoMASS_Jmag_Error
The 1-sigma uncertainty in J-band magnitude.

TwoMASS_Hmag
The 2MASS H-band magnitude.

TwoMASS_Hmag_Error
The 1-sigma uncertainty in H-band magnitude.

TwoMASS_Ks_Mag
The 2MASS Ks-band magnitude.

TwoMASS_Ks_Mag_Error
The 1-sigma uncertainty in Ks-band magnitude.

TwoMASS_Flags
The 2MASS photometric quality flag, which is given as a three character flag, one character per band [JHK], that provides a summary of the net quality of the default photometry in each band. The value is set for a band according to the precedence of the table below. For example, a source that is tested and meets the conditions for category "X" is not tested for subsequent qualities. The categories are given as follows:

          X = There is a detection at this location, but no valid brightness
                   estimate can be extracted using any algorithm.
          U = Upper limit on magnitude. Source is not detected in this band
                    (Rflg="0"), or it is detected, but not resolved in a
                    consistent fashion with other bands (Rflg="6").
          F = This category includes Rflg="1" or Rflg="3" sources where a
                   reliable estimate of the photometric error, [jhk]cmsig, could
                   not be determined. The uncertainties reported for these
                   sources in [jhk]cmsig and e_[jhk]mag are flags and have
                   numeric values >8.0.
          E = This category includes detections where the goodness-of-fit
                   quality of the profile-fit photometry was very poor (Rflg=2
                   and [jhk]psfchi>10.0), or detections where psf fit
                   photometry did not converge and an aperture magnitude is
                   reported (Rflg=4), or detections where the number of frames
                   was too small in relation to the number of frames in which a
                   detection was geometrically possible (Rflg="1" or Rflg="2").
          A = Detections in any brightness regime where valid measurements
                   were made (Rflg="1","2" or "3") with [jhk]snr>10 AND
                   [jhk]cmsig<0.10857.
          B = Detections in any brightness regime where valid measurements
                   were made (Rflg="1","2" or "3") with [jhk]snr>7 AND
                   [jhk]cmsig<0.15510.
          C = Detections in any brightness regime where valid measurements were
                   made (Rflg="1","2" or "3") with [jhk]snr>5 AND
                   [jhk]cmsig<0.21714.
          D = Detections in any brightness regime where valid measurements were
                   made (Rflg="1","2" or "3") with no [jhk]snr OR [jhk]cmsig
                   requirement.
  

TwoMASS_Photo_Flags
The read flag indicates the source of J,H,K "default" magnitudes as a 3-digit integer, where the 1st digit corresponds to the J band, the 2nd to the H band, and the 3rd to the Ks band. Rflg values of "1", "2" or "3" generally indicate the best quality detections, photometry and astrometry (although other quality flags must be considered). Values of "0", "4", "6" and "9" in a band indicate either non-detections, or generally poor quality photometry and positions. The definitions of the values are:

          0 = Source is not detected in this band. The default magnitude is the
                  95% confidence upper limit derived from a 4" radius aperture
                  measurement taken at the position of the source on the Atlas
                  Image. The sky background is estimated in an annular region
                  with inner radius of 14" and outer radius of 20".
          1 = The default magnitude is derived from aperture photometry
                  measurements on the 51 ms "Read_1" exposures. The aperture
                  radius is 4", with the sky background measured in an annulus
                  with an inner radius of 14" and an outer radius of 20". Used
                  for sources that saturate one or more of the 1.3s "Read_2"
                  exposures, but are not saturated on at least one of the 51 ms
                  "Read_1" frames.
          2 = The default magnitude is derived from a profile-fitting measurement
                  made on the 1.3 sec "Read_2" exposures. The profile-fit
                  magnitudes are normalized to curve-of-growth corrected
                  aperture magnitudes. This is the most common type in the PSC,
                  and is used for sources that have no saturated pixels in any
                  of the 1.3 sec exposures.
          3 = The default magnitude is derived from a 1-d radial profile
                  fitting measurement made on the 51 ms "Read_1" exposures.
                  Used for very bright sources that saturate all of the 51 ms
                  "Read 1" exposures.
          4 = The default magnitude is derived from curve-of-growth-corrected
                  4" radius aperture photometry measurements on the 1.3 s
                  "Read_2" exposures. This is used for sources that are not
                  saturated in any of the Read_2 frames, but where the
                  profile-fitting measurements fail to converge to a solution.
                  These magnitudes are the same as the standard aperture
                  magnitudes (Jstdap, Hstdap, Kstdap), but when they are the
                  default magnitudes, it generally implies that they are low
                  quality measurements.
          6 = The default magnitude is the 95% confidence upper limit derived
                  from a 4" radius aperture measurement taken at the position
                  of the source on the Atlas Image. The sky background is
                  estimated in an annular region with inner radius of 14" and
                  outer radius of 20". This is used for pairs of sources which
                  are detected and resolved in another band, but are detected
                  and not resolved in this band. This differs from a Rflg="0"
                  because in this case there is a detection of the source in
                  this band, but it is not consistently resolved across all
                  bands.
          9 = The default magnitude is the 95% confidence upper limit derived
                  from a 4" radius aperture measurement taken at the position
                  of the source on the Atlas Image. The sky background is
                  estimated in an annular region with inner radius of 14" and
                  outer radius of 20". This is used for sources that were
                  nominally detected in this band, but which could not have a
                  useful brightness measurement from either profile fitting or
                  aperture photometry. This often occurs in highly confused
                  regions, or very near Tile edges where a significant fraction
                  of the measurement aperture of sky annulus falls off the
                  focal plane.
  

TwoMASS_Fit_Flags
The three character flags, one character per band [JHK], that indicates the number of components that were fit simultaneously when estimating the brightness of a source:

          0 = Source is not detected, or is inconsistently deblended in that
                  band.
          1 = One component was fit to the source in R_2 profile-fitting
                  photometry (Rflg="2"), or default magnitudes are from
                  aperture photometry (Rflg="1" or "4") or saturated star 1-d
                  radial profile-fitting (Rflg="3").
          >1 = More than one component was fit simultaneously during R2
                  profile-fit photometry, where the value of the field is the
                  number of components simultaneously fit. The maximum number
                  of components is 7 in any band for the PSC, so this Bflg is
                  always a three character flag. Multi-component fitting occurs
                  only for profile-fitting, and only when more than one
                  detection is found within ~5". Single detections that are not
                  well-fit by a single PSF are not split.
  

TwoMASS_Conf_Flags
The three character flags, one character per band [JHKs], that indicates that the photometry and/or position measurements of a source may be contaminated or biased due to proximity to an image artifact or nearby source of equal or greater brightness. The flag in each band is set in hierarchical order according to the following table, in the event a source is affected by more than one artifact or condition:

          p = Persistence. Source may be contaminated by a latent image left by
                  a nearby bright star.
          c = Photometric Confusion. Source photometry is biased by a nearby
                  star that has contaminated the background estimation.
          d = Diffraction spike confusion. Source may be contaminated by a
                  diffraction spike from a nearby star.
          s = Electronic stripe. Source measurement may be contaminated by a
                  stripe from a nearby bright star.
          b = Bandmerge confusion. In the process of merging detections in the
                  different bands for this source, there was more than one
                  possible match between the different band components. This
                  occurs in regions of very high source density, or when
                  multiple sources were split in one band but not another.
          0 = Source is unaffected by known artifacts, or is not detected in
                  the band. Non-zero values = the measurements of that source
                  may be contaminated.
  

TwoMASS_Extend_Flag
The extended source contamination flag, denoted as follows:

          0 = Source does not fall within the elliptical profile of an extended
                  source with semi-major axis >10'', or it is not identified
                  exactly with an extended source with semi-major axis >10''.
                  However, the source may correspond exactly to a smaller
                  extended source.
          1 = Source is resolved by 2MASS, and is equivalent to a source in the
                  extended catalog that has a semi-major axis > 10" in size.
          2 = Source falls within the elliptical boundary of an extended source
                  that has a semi-major axis > 10" in size.
  

TwoMASS_A_Flag
Indicates if this source is associated with the predicted position of a known minor planet, comet, planet or planetary satellite. This association does not guarantee that the source is a detection of the solar system object. 0 means that the source is not associated with a known solar system object.

Jmag
The merged 2MASS and VVV J-band photometry in the 2MASS system.

Hmag
The merged 2MASS and VVV H-band photometry in the 2MASS system.

Ks_Mag
The merged 2MASS and VVV Ks-band photometry in the 2MASS system.

VPHAS_Name
The source designation in the VPHAS+ Catalog (Drew et al. 2014, J/MNRAS/440/2036).

Umag
The VPHAS u-band magnitude.

Umag_Error
The 1-sigma uncertainty in VPHAS u-band magnitude.

Gmag
The VPHAS g-band magnitude.

Gmag_Error
The 1-sigma uncertainty in the VPHAS g-band magnitude.

R2_Mag
The VPHAS r2-band magnitude

R2_Mag_Error
The 1-sigma uncertainty in the VPHAS r2-band magnitude.

Halpha_Mag
The VPHAS H-alpha magnitude.

Halpha_Mag_Error
The 1-sigma uncertainty in the VPHAS H-alpha magnitude.

Rmag
The VPHAS r-band magnitude.

Rmag_Error
The 1-sigma uncertainty in the VPHAS r-band magnitude.

Imag
The VPHAS i-band magnitude.

Imag_Error
The 1-sigma uncertainty in the VPHAS i-band magnitude.

SSB2013_Number
The source designation in the Sung et al. catalog (2013, J/AJ/145/37).

Vmag
The V-band magnitude in the CIT system.

Vmag_Error
The 1-sigma uncertainty in the V-band magnitude.

VI_Color
The V-I color, in magnitudes.

VI_Color_Error
The 1-sigma uncertainty in V-I color.

BV_Color
The B-V color, in magnitudes.

BV_Color_Error
The 1-sigma uncertainty in B-V color.

UB_Color
The U-B color, in magnitudes.

UB_Color_Error
The 1-sigma uncertainty in U-B color.

SSB2013_Halpha_Mag
The H-alpha magnitude from the Sung et al. catalog (2013, J/AJ/145/37).

SSB2013_Halpha_Mag_Error
The 1-sigma uncertainty in the H-alpha magnitude from the Sung et al. catalog (2013, J/AJ/145/37).

GLIMPSE_Name
The source designation in the GLIMPSE catalog (Benjamin et al. 2003, Cat. II/293), given in the format GLLL.llll+BB.bbbb.

IRAC_3p6_um_Mag
The Spitzer/IRAC 3.6-um band magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_3p6_um_Mag_Error
The 1-sigma uncertainty in 3.6-um magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_3p6_um_Mag_Flag
The GLIMPSE quality flag for the 3.6-um band, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_4p5_um_Mag
The Spitzer/IRAC 4.5-um band magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_4p5_um_Mag_Error
The 1-sigma uncertainty in 4.5 um magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_4p5_um_Mag_Flag
The GLIMPSE quality flag for the 4.5-um band, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_5p8_um_Mag
The Spitzer/IRAC 5.8-um band magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_5p8_um_Mag_Error
The 1-sigma uncertainty in 5.8 um magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_5p8_um_Mag_Flag
The GLIMPSE quality flag for the 5.8-um band, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_8_um_Mag
The Spitzer/IRAC 8.0-um band magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_8_um_Mag_Error
The 1-sigma uncertainty in 8.0-um magnitude, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

IRAC_8_um_Mag_Flag
The GLIMPSE quality flag for the 5.8-um band, adopted from the GLIMPSE source catalog. (See Benjamin et al. 2003, Cat. II/293 for details.)

Ks_Mag_Absorption
The estimated absorption in the Ks-band.

Age
The age estimated from the V versus V-I color-magnitude diagram.

Log_Mass_3p2Myr
The logarithm of the estimated mass assuming an age of 3.2 Myr.

Log_Mass_6p4Myr
The logarithm of the estimated mass assuming an age of 6.4 Myr.

Log_Lum_3p2Myr
The logarithm of the estimated luminosity assuming an age of 3.2 Myr.

Log_Lum_6p4Myr
The logarithm of the estimated luminosity assuming an age of 6.4 Myr.

Ks_Excess_Flag
The flag indicates Ks-band excess, if set to "1".

YSO_Classi_Flag
The flag, if set to "1", indicates that source is classified as a Class I Young stellar object (YSO).

YSO_Classii_Flag
The flag, if set to "1", indicates that source is classified as a Class II Young stellar object (YSO).

IR_Excess_Flag
The flag indicates, if set to "1", indicates infrared excess.

Alt_Name_2
The massive star name for sources identified as massive OB stars, as given in Sana et al. (2006, J/MNRAS/372/661), available as NGC6231XMM.

KS_Prob_Constant_Limit
The limit flag for the null-hypothesis probability that the flux is constant.

KS_Prob_Constant
The null-hypothesis probability that the flux is constant.

APEC_Log_NH
The logarithm of the hydrogen column density, in cm-2, assuming a model fit given by wabs * apec.

APEC_Log_NH_Error
The logarithm of the 1-sigma uncertainty on the hydrogen column density, in cm-2, assuming a model fit given by wabs * apec.

APEC_kT
The plasma temperature, in keV, assuming a model fit given by wabs * apec.

APEC_kT_Error
The 1-sigma uncertainty on the plasma temperature, in keV, assuming a model fit given by wabs * apec.

FB_Log_Flux_Obs
The logarithm of the observed X-Ray flux in the 0.5-8 keV band, in units of erg cm-2 s-1, assuming a model fit given by wabs * apec.

FB_Log_Flux_Obs_Error
The uncertainty in the logarithm of the observed X-Ray Flux in the 0.5-8 keV band, in units of erg cm-2 s-1.

FB_Log_Flux
The logarithm of the absorption-corrected X-Ray flux in the 0.5-8 keV band, in units of erg cm-2 s-1, assuming a model fit given by wabs * apec.

Chi_Squared
The chi2 statistic for the model fit, given by wabs * apec.

Fit_DoF
The degrees of freedom for the model fit, given by wabs * apec.

Detect_Flag
The detection flag is given as follows:

    0 = Star not detected by Chandra;
    1 = Star detected by Chandra;
    2 = Chandra detection missing X-ray properties.
  

Class
The HEASARC Browse object classification, based on the spect_type parameter value.


Contact Person

Questions regarding the NGC6231CX2 database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Tuesday, 27-Oct-2020 18:43:05 EDT