NGC1893CXO ivo://nasa.heasarc/ngc1893cxo NASA/GSFC HEASARC Caramazza et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The outer Galaxy, where the environmental conditions are different from the solar neighbourhood, is a laboratory in which it is possible to investigate the dependence of the star formation process on the environmental parameters. The authors investigate the X-ray properties of NGC 1893, a young cluster (~ 1 - 2 Myr) in the outer part of the Galaxy (galactic radius >= 11 kpc), where they expect differences in the disk evolution and in the mass distribution of the stars, so as to explore the X-ray emission of its members and compare it with that of young stars in star forming regions near to the Sun. The authors analyze 5 deep Chandra ACIS-I observations with a total exposure time of 450 ks. Source events of the 1021 X-ray sources have been extracted with the IDL-based routine ACIS-Extract. Using spectral fitting and quantile analysis of X-ray spectra, they derive X-ray luminosities and compare the respective properties of Class II and Class III members. They also evaluate the variability of sources using the Kolmogorov-Smirnov test and identify flares in the lightcurves. The X-ray luminosity of NGC 1893 X-ray members is in the range 10<sup>29.5</sup> - 10<sup>31.5</sup> erg s<sup>-1</sup>. Diskless stars are brighter in X-rays than disk-bearing stars, given the same bolometric luminosity. The authors find that 34% of the 1021 lightcurves appear variable and that they show 0.16 flares per source, on the average. Comparing their results with those relative to the Orion Nebula Cluster, they find that, after accounting for observational biases, the X-ray properties of NGC 1893 and the Orion stars are very similar. The authors conclude that the X-ray properties of stars in NGC 1893 are not affected by the environment and that the stellar population in the outer Galaxy may have the same coronal properties as nearby star-forming regions. The X-ray luminosity properties and the X-ray luminosity function appear to be universal and can therefore be used for estimating distances and for determining stellar properties. This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/539/A74">CDS Catalog J/A+A/539/A74</a> file catalog.dat, the catalog of 1021 X-ray sources detected towards NGC 1893. This is a service provided by NASA HEASARC . 2012A&A...539A..74C https://heasarc.gsfc.nasa.gov/W3Browse/all/ngc1893cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=ngc1893cxo& GET text/xml 180 99999 true 80.653077 33.317812 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=ngc1893cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_ngc1893cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public ngc1893cxo NGC 1893 Chandra X-Ray Point Source Catalog name Source Designation (CXOU JHHMMSS.ss+DDMMSS.s) meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius Standard Deviation of Position arcsec stat.error;pos double nullable off_axis Off-Axis Angle arcmin instr.offset double nullable counts Net Counts Extracted in the Total Energy Band ct phot;em.X-ray double nullable counts_error Average of the Upper and Lower 1-Sigma Errors ct stat.error;phot;em.X-ray double nullable median_energy Background-Corrected Median Photon Energy (Total Band) keV phys.energy double nullable log_lx Absorption-Corrected X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray double nullable log_lx_flag Flag [abc] Indicates X-Ray Luminosity Origin meta.code;phys.luminosity;em.X-ray char nullable lii Galactic Longitude degree pos.galactic.lon double nullable bii Galactic Latitude degree pos.galactic.lat double nullable source_number Sequential Identification Number for Each Source in Catalog meta.id;src short nullable psf_fraction Fraction of the PSF (at 1.497 keV) Enclosed within the Extraction Region instr.det.psf double nullable ks_prob_constant Kolmogorov-Smirnov Probability That the Lightcurves of the Sources are Constant stat.probability double nullable significance Photometric Significance Computed as Net Counts Divided by Its Upper Uncertainty stat.likelihood;em.X-ray double nullable exposure Effective Exposure Time s time.duration;obs.exposure double nullable bck_counts Background Counts Expected in the Source Extraction Region (Total Band) ct phot;instr.background;em.X-ray 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