IPCUltrasoft ivo://nasa.heasarc/ipcultsoft NASA/GSFC HEASARC Thompson, Shelton, Arning 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source A survey of the entire Einstein IPC database (a total of 5934 sources) has been carried out in order to select objects with strong components of ultrasoft X-ray emission (i.e., emission below 0.5 keV). The selection criteria were based on ratios of counts within three broad energy bands (i.e., X-ray "colors"). A total of 516 objects have been selected, with 202 (39%) having been identified through correlations with other databases. Of the currently identified objects, 45% are active galactic nuclei, 28% are stellar objects, 6% are "normal" galaxies and galaxy clusters, and the remaining 21% are "nonstellar" Galactic objects such as cataclysmic variables, pulsars, and white dwarfs. The selection of sources for this survey was based on the analysis of counts in three broad energy bands defined as C1=0.16-0.56 keV, C2=0.56-1.08 keV, and C3= 1.08-3.5 keV. Ratios of these three bands constituted X-ray 'colors' which in turn were used to estimate the shape of the spectrum over the IPC bandpass. Based on models of X-ray spectra folded through the IPC response function, the following criteria were determined for the selection of ultrasoft sources: C1>0 and R1=C2/C1<0.36. These criteria guarantee an intrinsically soft X-ray spectrum that can be modeled by blackbody temperatures kT<50 keV, power-law spectral indices of >=2, or thermal plasma temperatures T<1 MK (million K). Details of the data analysis can be found in the Thompson et al. (1998) reference. This database was created by the HEASARC in April 1999 based on tables provided by the catalog authors to the CDS/ADC. This is a service provided by NASA HEASARC . 1998AJ....115.2587T https://heasarc.gsfc.nasa.gov/W3Browse/all/ipcultsoft.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=ipcultsoft& GET text/xml 180 99999 true 13.2173 -72.8012 0.0333333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=ipcultsoft GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_ipcultsoft&Action=More+Options&Action=Parameter+Search&ConeAdd=1 EINSTEIN 0.0333333333333333 X-ray public ipcultsoft Einstein IPC Ultrasoft Sources Catalog sequence_num IPC Observation Sequence Number meta.id;obs.field short nullable name Optical Counterpart Name meta.id char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable count_rate Count Rate in 0.2-4 keV Band ct/s phot.count;em.X-ray.medium double nullable count_rate_error RMS Uncertainty of Count Rate ct/s stat.error;phot.count;em.X-ray.medium double nullable snr Signal-to-noise Ratio stat.snr float 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 c3_counts_error RMS Uncertainty of C3 stat.error;phot;em.X-ray.medium double nullable rib_edge_code Rib and Edge Code meta.code short nullable source_num Object Source Number in Field meta.id;meta.main short nullable bii Galactic Latitude degree pos.galactic.lat double nullable c2_counts Counts in Medium Energy Band phot;em.X-ray.soft double nullable c2_counts_error RMS Uncertainty of C2 stat.error;phot;em.X-ray.soft double nullable c1_counts_error RMS Uncertainty of C1 stat.error;phot;em.X-ray.soft double nullable lii Galactic Longitude degree pos.galactic.lon double nullable c3_counts Counts in High Energy Band phot;em.X-ray.medium double nullable c1_counts Counts in Low Energy Band phot;em.X-ray.soft double nullable