M108CXO ivo://nasa.heasarc/m108cxo NASA/GSFC HEASARC Wang et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains a list of discrete sources found in a 60-ks Chandra ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556 (M108). In the reference paper in which the authors present this table, they also give a multiwavelength analysis of the various discrete X-ray sources and of the diffuse X-ray features. Among 33 discrete X-ray sources detected within the I<sub>B</sub> = 25 mag arcsec<sup>-2</sup> isophotal ellipse of the galaxy, the authors identify a candidate for the galactic nucleus, an ultraluminous X-ray source that might be an accreting intermediate-mass black hole, a possible X-ray binary with a radio counterpart, and two radio-bright giant H II regions. They also detect large amounts of extraplanar diffuse X-ray emission, which extend about 10 kpc radially in the disk and >~4 kpc away from the galactic plane. The diffuse X-ray emission exhibits significant substructures, possibly representing various blown-out superbubbles or chimneys of hot gas heated in massive star-forming regions. This Chandra observation of NGC 3556 (observation ID 2025) was taken between 2001 September 8 and 9 for an exposure of 60 ks. The ACIS-S instrument was at the focal plane of the telescope. This table was created by the HEASARC in August 2015 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/598/969">CDS Catalog J/ApJ/598/969</a> file table2.dat. This is a service provided by NASA HEASARC . 2003ApJ...598..969W https://heasarc.gsfc.nasa.gov/W3Browse/all/m108cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=m108cxo& GET text/xml 180 99999 true 167.87179167 55.60588889 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=m108cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_m108cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 X-ray public m108cxo M 108 Chandra X-Ray Compact Source Catalog source_number Sequential Identification Number for Each Source in the Catalog meta.id;src short nullable 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 Position Uncertainty arcsec stat.error;pos double nullable count_rate On-Axis (Exposure-Corrected) Source Count Rate in the 0.3-7keV Band ct/s phot.count;em.X-ray double nullable count_rate_error RMS Uncertainty in Count Rate ct/s stat.error;phot.count;em.X-ray double nullable hardness_ratio_1 Hardness Ratio 1, HR1=(S2-S1)/S phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio_1_error RMS Uncertainty in Hardness Ratio 1 stat.error;phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio_2 Hardness Ratio 2, HR2=(H2-H1)/H phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio_2_error RMS Uncertainty in Hardness Ratio 2 stat.error;phot.flux;arith.ratio;em.X-ray double nullable hardness_ratio Hardness Ratio, HR=(H-S)/(H+S) phot.flux;arith.ratio;em.X-ray double nullable bii Galactic Latitude degree pos.galactic.lat double nullable log_prob_ns False Detection Probability stat.probability;src;em.X-ray double nullable best_position_band Flag [BSH] Indicates Band in Which Source Detected with Most Accurate Position meta.code;pos char nullable lii Galactic Longitude degree pos.galactic.lon double nullable hardness_ratio_error RMS Uncertainty in Hardness Ratio stat.error;phot.flux;arith.ratio;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