M16CXO ivo://nasa.heasarc/m16cxo NASA/GSFC HEASARC Guarcello et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source Mechanisms regulating the origin of X-rays in young stellar objects and the correlation with their evolutionary stage are under debate. Studies of the X-ray properties in young clusters allow us to understand these mechanisms. One ideal target for this analysis is the Eagle Nebula (M 16), with its central cluster NGC 6611. At 1750 pc from the Sun, it harbors 93 OB stars, together with a population of low-mass stars from embedded protostars to disk-less Class III objects, with age <= 3 Myr. The authors study an archival 78 ks Chandra/ACIS-I observation of NGC 6611 and two new 80-ks observations of the outer region of M 16, one centered on the Column V and the other on a region of the molecular cloud with ongoing star formation. They detect 1755 point sources with 1183 candidate cluster members (219 disk-bearing and 964 disk-less), studying the global X-ray properties of M 16 and comparing them with those of the Orion Nebula Cluster. The authors also compare the level of X-ray emission of Class II and Class III stars and analyze the X-ray spectral properties of OB stars. Their study supports the lower level of X-ray activity for the disk-bearing stars with respect to the disk-less members. The X-ray luminosity function (XLF) of M 16 is similar to that of Orion, supporting the universality of the XLF in young clusters. Eighty-five percent of the O-type stars of NGC 6611 have been detected in X-rays. With only one possible exception, they show soft spectra with no hard components, indicating that mechanisms for the production of hard X-ray emission in O stars are not operating in NGC 6611. The determination of the absorption corrected X-ray luminosity (L<sub>X</sub>), as well as the plasma temperature (kT) and hydrogen column density (N<sub>H</sub>), requires the analysis of the X-ray spectra. The authors fit the observed spectra with thermal plasma (with both one and two temperatures) and power-law models. They use the APEC ionization-equilibrium thermal plasma code, assuming the sub-solar elemental abundances of Maggio et al. (2007, APJ, 660, 1462). The absorption was treated using the WABS model. The one-temperature (1T) thermal model was applied to all the sources with more than 25 counts, while the two-temperature (2T) thermal model was applied to each source with more than 80 counts. The power-law model has been applied to those sources with hard spectra for which the best-fit thermal model predicts a plasma temperature kT > 5 keV. When more than one model has been used for a given source, the authors chose the best model by the chi-squared probability and visual inspection of the spectrum. This table contains a description of the X-ray properties of 1754 sources (one less than stated in the abstract of the reference paper) derived from three Chandra/ACIS-I observations, together with a source classification based on the optical and infrared properties of each source. Data come from three ACIS-I observations (central or 'c', east or 'e', and north-east or 'ne') and many values are not averaged but presented for each observation as indicated by the parameter prefixes 'c_', 'e_', and 'ne_', respectively. Source detection has been performed with PWDetect, adopting a threshold corresponding to 10 spurious detections. The HEASARC eliminated the 3 parameters describing the plasma temperature of the second spectral component and its associated negative and positive errors for sources in the north-east observation, as these were blank for all entries in the original table as obtained from the CDS. This table was created by the HEASARC in March 2013 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/753/117">CDS Catalog J/ApJ/753/117</a> file xraycat.dat. Some of the values for the alt_name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC . 2012ApJ...753..117G https://heasarc.gsfc.nasa.gov/W3Browse/all/m16cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=m16cxo& GET text/xml 180 99999 true 274.86434 -13.952071 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=m16cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_m16cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public m16cxo M 16 (Eagle Nebula) Chandra X-Ray Point Source Catalog name Source Designation 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 c_count_rate Count Rate in 0.5-8keV Band in the Central Observation ct/s phot.count;em.X-ray double nullable e_count_rate Count Rate in 0.5-8keV Band in the East Observation ct/s phot.count;em.X-ray double nullable ne_count_rate Count Rate in 0.5-8keV Band in the North-East Observation ct/s phot.count;em.X-ray double nullable broad_type Source Classification Based on Optical-Infrared Colors src.class char 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 c_photon_index_pos_err Upper Error for Photon Index in the Central Observation stat.error;spect.index;em.X-ray double nullable ne_raw_counts North-East Observation Total Count in 0.5-8keV ct phot;em.X-ray double nullable e_psf_fraction Fraction of PSF at 1.497keV Corresponding to the extraction Region in East Obs. instr.det.psf double nullable c_prob_no_source Probability of No Association with This Position in Central Observation stat.probability double nullable ne_significance North-East Observation Source Significance stat.likelihood;em.X-ray double nullable ne_log_lx_calc_flag Flag Indicates Spectral Information Obtained from the North-East Observation meta.code;phys.luminosity;em.X-ray short nullable ne_kt_1 Plasma Temperature in the North-East Observation keV phys.temperature double nullable alt_name Alternative Catalog-Based Source Designation meta.id char nullable ne_ks_prob_constant K-S Statistic That Source Is Not Variable in 0.5-8keV Band in North-East Obs. stat.probability double nullable c_nh Hydrogen Column Density in the Central Observation cm^-2 phys.columnDensity double nullable e_kt_2 Second Plasma Temperature in the East Observation keV phys.temperature double nullable c_significance Central Observation Source Significance stat.likelihood;em.X-ray double nullable ne_log_lx Logarithm of the X-Ray Luminosity in 0.5-8keV in the North-East Observation log(erg/s) phys.luminosity;em.X-ray double nullable c_ks_prob_constant K-S Statistic That Source Is Not Variable in 0.5-8keV Band in Central Obs. stat.probability double nullable c_median_energy Median Photon Energy in 0.5-8keV Band in the Central Observation keV phys.energy double nullable ne_prob_no_source Probability of No Association with This Position in the North-East Observation stat.probability double nullable source_number Sequential Identification Number for Each Source in Catalog meta.id;src short nullable ne_log_lx_flag Flag [i] Indicates Infinity meta.code;phys.luminosity;em.X-ray char nullable e_raw_counts East Observation Total Count in 0.5-8keV ct phot;em.X-ray double nullable c_nh_pos_err Upper Error for Hydrogen Column Density in the Central Observation cm^-2 stat.error;phys.columnDensity double nullable e_nh Hydrogen Column Density in the East Observation cm^-2 phys.columnDensity double nullable ne_photon_index_pos_err Upper Error for Photon Index in the North-East Observation stat.error;spect.index;em.X-ray double nullable e_kt_1 Plasma Temperature in the East Observation keV phys.temperature double nullable c_kt_1_pos_err Upper Error for Plasma Temperature in the Central Observation keV stat.error;phys.temperature double nullable ne_nh_pos_err Upper Error for Hydrogen Column Density in the North-East Observation cm^-2 stat.error;phys.columnDensity double nullable e_median_energy Median Photon Energy in 0.5-8keV Band in the East Observation keV phys.energy double nullable ne_nh_neg_err Lower Error for Hydrogen Column Density in the North-East Observation cm^-2 stat.error;phys.columnDensity double nullable c_photon_index Photon Index in the Central Observation spect.index;em.X-ray double nullable e_photon_index_pos_err Upper Error for Photon Index in the East Observation stat.error;spect.index;em.X-ray double nullable c_kt_2_pos_err Upper Error for Second Plasma Temperature in the Central Observation keV stat.error;phys.temperature double nullable ne_kt_1_neg_err Lower Error for Plasma Temperature in the North-East Observation keV stat.error;phys.temperature double nullable ne_psf_fraction Fraction of PSF at 1.497keV Corresponding to the extraction Region in NE Obs. instr.det.psf double nullable c_log_lx_pos_err Upper Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in Central Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable ne_median_energy Median Photon Energy in 0.5-8keV Band in the North-East Observation keV phys.energy double nullable e_nh_pos_err Upper Error for Hydrogen Column Density in the East Observation cm^-2 stat.error;phys.columnDensity double nullable e_off_axis Offset in the East Observation arcmin instr.offset double nullable c_log_lx Logarithm of the X-Ray Luminosity in 0.5-8keV in the Central Observation log(erg/s) phys.luminosity;em.X-ray double nullable e_prob_no_source Probability of No Association with This Position in the East Observation stat.probability double nullable c_spectral_model Spectral Model Used to Fit the Source Spectrum in the Central Observation meta.code;spect;meta.modelled char nullable c_kt_2_neg_err Lower Error for Second Plasma Temperature in the Central Observation keV stat.error;phys.temperature double nullable e_photon_index_neg_err Lower Error for Photon Index in the East Observation stat.error;spect.index;em.X-ray double nullable lii Galactic Longitude degree pos.galactic.lon double nullable e_log_lx_flag [i] i for infinity meta.code;phys.luminosity;em.X-ray char nullable e_kt_1_pos_err Upper Error for Plasma Temperature in the East Observation keV stat.error;phys.temperature double nullable ne_counts North-East Observation Net Count in 0.5-8keV ct phot;em.X-ray double nullable e_nh_neg_err Lower Error for Hydrogen Column Density in the East Observation cm^-2 stat.error;phys.columnDensity double nullable e_spectral_model Spectral Model Used to Fit the Source Spectrum in the East Observation meta.code;spect;meta.modelled char nullable e_ks_prob_constant K-S Statistic That Source Is Not Variable in 0.5-8keV Band in East Obs. stat.probability double nullable e_kt_1_neg_err Lower Error for Plasma Temperature in the East Observation keV stat.error;phys.temperature double nullable c_kt_1_neg_err Lower Error for Plasma Temperature in the Central Observation keV stat.error;phys.temperature double nullable e_kt_2_neg_err Lower Error for Second Plasma Temperature in the East Observation keV stat.error;phys.temperature double nullable e_log_lx_pos_err Upper Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in the East Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable c_log_lx_neg_err Lower Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in Central Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable c_photon_index_neg_err Lower Error for Photon Index in the Central Observation stat.error;spect.index;em.X-ray double nullable ne_nh Hydrogen Column Density in the North-East Observation cm^-2 phys.columnDensity double nullable e_kt_2_pos_err Upper Error for Second Plasma Temperature in the East Observation keV stat.error;phys.temperature double nullable e_photon_index Photon Index in the East Observation spect.index;em.X-ray double nullable c_psf_fraction Fraction of PSF at 1.497keV Corresponding to Extraction Region in Central Obs. instr.det.psf double nullable ne_log_lx_pos_err Upper Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in North-East Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable c_kt_2 Second Plasma Temperature in the Central Observation keV phys.temperature double nullable e_log_lx_neg_err Lower Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in the East Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable ne_log_lx_neg_err Lower Error for Logarithm of the X-Ray Luminosity in 0.5-8keV in North-East Obs. log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable c_nh_neg_err Lower Error for Hydrogen Column Density in the Central Observation cm^-2 stat.error;phys.columnDensity double nullable e_log_lx Logarithm of the X-Ray Luminosity in 0.5-8keV in the East Observation log(erg/s) phys.luminosity;em.X-ray double nullable bii Galactic Latitude degree pos.galactic.lat double nullable ne_photon_index Photon Index in the North-East Observation spect.index;em.X-ray double nullable c_log_lx_calc_flag Flag Indicates Spectral Information Obtained from the Central Observation meta.code;phys.luminosity;em.X-ray short nullable c_raw_counts Central Observation Total Count in 0.5-8keV ct phot;em.X-ray double nullable ne_photon_index_neg_err Lower Error for Photon Index in the North-East Observation stat.error;spect.index;em.X-ray double nullable c_counts Central Observation Net Count in 0.5-8keV ct phot;em.X-ray double nullable c_log_lx_flag Flag [i] Indicates Infinity meta.code;phys.luminosity;em.X-ray char nullable ne_kt_1_pos_err Upper Error for Plasma Temperature in the North-East Observation keV stat.error;phys.temperature double nullable e_counts East Observation Net Count in 0.5-8keV ct phot;em.X-ray double nullable e_log_lx_calc_flag Flag Indicates Spectral Information Obtained from the East Observation meta.code;phys.luminosity;em.X-ray short nullable c_kt_1 Plasma Temperature in the Central Observation keV phys.temperature double nullable ne_spectral_model Spectral Model Used to Fit the Source Spectrum in the North-East Observation meta.code;spect;meta.modelled char nullable e_significance East Observation Source Significance stat.likelihood;em.X-ray double nullable c_off_axis Offset in the Central Observation arcmin instr.offset double nullable ne_off_axis Offset in the North-East Observation arcmin instr.offset double nullable