- ID:
- ivo://nasa.heasarc/omegcencxo
- Title:
- Omega Centauri Globular Cluster Chandra X-Ray Point Source Catalog
- Short Name:
- OMEGCENCXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors analyzed a ~ 70 ks Chandra Advanced CCD Imaging Spectrometer (ACIS) exposure of the globular cluster Omega Cen (NGC 5139). The ~ 17' x 17' field of view fully encompasses three cluster core radii and almost twice the half-mass radius. They detected 180 sources to a limiting flux of ~ 4.3 x10 <sup>-16</sup> erg/cm<sup>2</sup>/s (L<sub>x</sub> = 1.2 x 10<sup>30</sup> erg/s at the 4.9 kpc distance to the cluster). After accounting for the number of active galactic nuclei and possible foreground stars among the detected X-ray sources, they estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as accreting compact binaries in the cluster - three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields 8 matches, of which 5 are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, the authors estimate that 20 - 35 of the sources are CVs and a similar number are active binaries. This likely represents most of the CVs in the cluster, but only a small fraction of all the active binaries. The authors place a 2-sigma upper limit of L<sub>x</sub> < 3 x 10<sup>30</sup> erg/s on the integrated luminosity of any additional faint, unresolved population of sources in the core of the cluster. In their paper, they explore the significance of these findings in the context of primordial versus dynamical channels for CV formation. They note that the number of CVs per unit mass in Omega Cen is at least 2 - 3 times lower than in the field, suggesting that primordial binaries that would otherwise lead to CVs are being destroyed in the cluster environment. The authors obtained 2 exposures of Omega Cen using the imaging array of the Advanced CCD Imaging Spectrometer (ACIS-I) on 2000 January 24 - 25, in "very faint" (VF) mode. The total exposure time was 72.4 ks. The authors determined source counts using 95% encircled energy radii as determined from model PSFs, derived using the CIAO tool mkpsf at an intermediate energy of ~ 1.5 keV (the PSF shape being somewhat energy dependent). Counts were extracted in three bands: "soft" (0.5 - 1.5 keV), "medium" (0.5 - 4.5 keV), and "hard" (1.5 - 6.0 keV). The authors determined the background to subtract from each source by dividing the image into 1 arcminute-wide annuli centered on the aim point in chip 3 (the innermost "annulus" being a circle of radius 1.5 arcminutes). Background values adopted for sources in a given annulus were averages determined from several source-free regions within that annulus, after verifying that the background levels were azimuthally symmetric. For 12 sources ( source_numbers 11b, 12b, 13e, 22c, 32c, 41b, 41c, 84a, 84b, 84c, 93a, and 93b) that fell in the chip gaps or near the outer edge of a chip, background regions were chosen specifically to reflect these conditions. Local background determinations were also made for a small number of sources to the west of the cluster center that lie on or near a large diffuse X-ray source ~7 arcminutes west of the cluster center (see below). Following background subtraction, the authors applied aperture corrections and also corrected for reduced effective exposure times off-axis and in the chip gaps using the exposure map. This table was created by the HEASARC in June 2011 based on the electronic versions of Table 1 from the reference paper which was obtained from the CDS (their catalog J/ApJ/697/224 file table1.dat). This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/omegcenxmm
- Title:
- Omega Centauri XMM-Newton X-Ray Point Source Catalog
- Short Name:
- OMEGCENXMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Omega Centauri (NGC 5139) is one of the best studied objects in our galaxy. It is the most massive globular cluster (5.1 x 10<sup>6</sup> solar masses), and is characterized by large core and half mass radii (154.88 and 250.8 arcseconds, respectively (Harris 1996, AJ, 112, 1487). The authors observed Omega Cen with XMM-Newton on August 13th, 2001. The observation lasted 37 ks and was performed with the medium filter. The authors detected 11 and 27 faint X-ray sources in the core and half mass radii, respectively, searching down to a luminosity of 1.3 x 10<sup>31</sup> ergs s<sup>-1</sup> in the 0.5 - 5 keV range (for an assumed distance to Omega Cen of 5.3 kpc). Most sources have bolometric X-ray luminosities between ~ 10<sup>31</sup> - 10<sup>32</sup> ergs s<sup>-1</sup>. The bulk of sources are hard and spectrally similar to CVs. The lack of soft faint sources might be related to the absence of millisecond pulsars in the cluster. The XMM-Newton observations reveal the presence of an excess of sources well outside the core of the cluster where several RS CVn binaries have already been found. The authors also analyzed a publicly available Chandra ACIS-I observation performed on January 24 - 25th, 2000, to improve the XMM-Newton source positions and to search for source intensity variations between the two data sets. 63 XMM-Newton sources have a Chandra counterpart, and 15 sources within the half-mass radius have shown time variability. Overall, the general properties of the faint X-ray sources in omega Cen suggest that they are predominantly CVs and active binaries (RS CVn or BY Dra). This table lists all 146 X-ray sources detected in the XMM-Newton observation above a maximum likelihood threshold in the 0.5 - 5 keV band of 12, including the 27 sources within the half-mass radius (listed in Table 1 of the reference paper), and the 119 sources outside the half-mass radius (listed in Table 2 of the reference paper). About 9 of the 27 sources within the half-mass radius are expected to be background sources, as are ~ 65 of the sources within 12.5 arcminutes of the cluster center, i.e., a significant fraction of the 146 total observed X-ray sources. For each XMM-Newton source, its position, count rate, correlation with previous X-ray observation, and their associated errors are given. The detailed spectral information given in Table 5 of the reference paper for 17 selected X-ray sources is however not included in this HEASARC table. This table was created by the HEASARC in May 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/400/521">CDS catalog J/A+A/400/521</a> files table1.dat, table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/osqsonvss
- Title:
- Optically-Selected QSOS NVSS-Detected Source Catalog
- Short Name:
- OSQSONVSS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors used the 1.4-GHz NRAO VLA Sky Survey (NVSS) to study radio sources in two color-selected QSO samples: a volume-limited sample of 1,313 QSOs defined by M<sub>i</sub> < -23 in the redshift range 0.2 < z < 0.45 and a magnitude-limited sample of 2,471 QSOs with m<sub>r</sub> <= 18.5 and 1.8 < z < 2.5. About 10% were detected above the 2.4-mJy NVSS catalog limit and are powered primarily by active galactic nuclei (AGNs). The space density, rho, of the low-redshift QSOs evolves as rho ~ (1 + z)<sup>6</sup>. In both redshift ranges, the flux-density distributions and luminosity functions of QSOs stronger than 2.4 mJy are power laws, with no features to suggest more than one kind of radio source. Extrapolating the power laws to lower luminosities predicts the remaining QSOs should be extremely radio quiet, but they are not. Most were detected statistically on the NVSS images with median peak flux densities S<sub>p</sub> of ~ 0.3 mJy/beam and ~ 0.05 mJy/beam in the low- and high-redshift samples, corresponding to spectral luminosities log L<sub>1.4GHz</sub> ~ 22.7 and ~ 24.1 W/Hz, respectively. The authors suggest that the faint radio sources are powered by star formation at rates dM/dt of ~ 20 M_{sun}_/yr in the moderate luminosity (median M<sub>i</sub> of ~ -23.4) low-redshift QSOs and dM/dt ~ 500M<sub>sun</sub>/yr in the very luminous (median M<sub>i</sub> ~ -27.5) high-redshift QSOs. Such luminous starbursts (<log(L<sub>IR</sub>/L<sub>sun</sub>)> ~ 11.2 and ~ 12.6, respectively) are consistent with "quasar mode" accretion in which cold gas flows fuel both AGN and starburst. The SDSS DR7 QSO catalog (Schneider et al. 2010, AJ, 139, 2360) is complete to i = 19.1 mag over a solid angle of 2.66 sr around the North Galactic Pole. It contains the small sample of 179 color-selected QSOs defined by M<sub>i</sub> < -23 in the narrow redshift range 0.2 < z < 0.3 studied by Kimball et al. (2011, ApJ, 739, L29) and the larger sample of 1,313 QSOs in the wider redshift range 0.2 < z < 0.45 discussed here. Note that these magnitudes were calculated for an H<sub>0</sub>= 71 km/s/Mpc and Omega<sub>M</sub> = 0.27 modern flat LambdaCDM cosmology. The entire SDSS DR7 area is covered by the NVSS, whose source catalog is complete for statistical purposes above a peak flux density S<sub>p</sub> ~ 2.4 mJy/beam at 1.4 GHz. In the redshift range 0.2 < z < 0.45 the 45" FWHM (full width between half-maximum points) beam of the NVSS spans 150 - 250 kpc. There are 163 (12%) NVSS detections of the 1,313 QSOs in the redshift range 0.2 < z < 0.45 which are listed in Table 1 of the reference paper. The authors also chose a magnitude-limited sample of all 2,471 color-selected DR7 QSOs brighter than m<sub>r</sub> = 18.5 in the redshift range 1.8 < z < 2.5. The NVSS detected radio emission stronger than S = 2.4 mJy from only 191 (8%) of them: these are listed in Table 3 of the reference paper. This HEASARC table contains the contents of both samples described above. It thus has 163 + 191 = 354 entries, the sum of Tables 1 and 3 from the reference paper. To select only the entries from Table 1, the user should select entries with redshifts from 0.2 to 0.45. To select only the entries from Table 3, the user should select entries with redshifts > 1.8. This table was created by the HEASARC in January 2015 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/768/37">CDS Catalog J/ApJ/768/37</a> files table1.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/osrilqxray
- Title:
- Optically Selected Radio-Intermediate and Loud Quasars X-ray Emission Catalog
- Short Name:
- OSRILQXRAY
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog contains some of the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). The authors have combined large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the luminosity-redshift (l-z) plane, including at high redshifts (22% of the objects have z = 2-5), and it extends to high radio-loudness R<sub>L</sub> values (33% of objects have R<sub>L</sub> = log(L<sub>r</sub>/L<sub>o</sub>) = 3 - 5), where L<sub>r</sub> and L<sub>o</sub> are the rest-frame monochromatic luminosities at 5 GHz and 2500 Angstroms, respectively). The authors measure the "excess" X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parametrize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (R<sub>L</sub> >~ 3.5) and radio luminosity that RLQs become strongly X-ray bright. This HEASARC table contains the primary sample from the reference paper. The authors consider three categories of quasars in this work: RQQs, RIQs, and RLQs (rather than just RQQs and RLQs), where the define RIQs to consist of objects with 1 <= R<sub>L</sub> < 2; consequently, the objects they classify as RLQs satisfy R<sub>L</sub> >= 2. The primary sample contained herein consists of 654 optically selected RIQs and RLQs with SDSS/FIRST observations and high-quality X-ray coverage from Chandra (171), XMM-Newton (202), or ROSAT (281). The primary sample is split nearly evenly between spectroscopic (312) and high-confidence photometric (342) quasars. Most (562) of the primary sample objects possess serendipitous off-axis X-ray coverage, while the remainder (92) were targeted in the observations used in this sample. The X-ray detection fraction for the primary sample is 84%; the detection fraction for those objects with Chandra/XMM-Newton/ROSAT coverage is 95%/92%/70% (typical ROSAT observations are comparatively less sensitive and have higher background). The authors adopt a standard cosmology with H<sub>0</sub> = 70 km s<sup>-1</sup> Mpc<sup>-1</sup>, Omega<sub>M</sub> = 0.3, and Omega<sub>Lambda</sub> = 0.7 throughout their study. This table was created by the HEASARC in October 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/726/20">CDS Catalog J/ApJ/726/20</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/orionffcxo
- Title:
- Orion Flanking Fields Chandra X-Ray Point Source Catalog
- Short Name:
- ORIONFFCXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of Chandra observations of two flanking fields (FFs) in Orion outside the Orion Nebula Cluster (ONC), in the form of a catalog of 417 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. 91 variable sources were found, 33 of which have flarelike light curves, and 11 of which have a pattern of a steady increase or decrease over a 10 hour period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main-sequence stars with ages younger than 10 Myr. The two flanking fields in Orion were observed with the Advanced CCD Imaging Spectrometer (ACIS) detector on board the Chandra X-Ray Observatory. The north Orion flanking field (NOFF) is centered at a J2000 RA and Declination of 05:35:19, -04:48:15, which is about 36' (~5 pc, at a distance of 470 pc) north of the Trapezium cluster and was observed on 2002 August 26 with a total exposure time of 48.8 ks. The south Orion flanking field (SOFF), centered at a J2000 RA and Declination of 05:35:06, -05:40:48, which is about 17' (~ 2.5pc, at a distance of 470 pc) south of the Trapezium cluster, was observed on 2002 September 6 with a total exposure time of 47.9 ks. The data analysis for these observations was performed in the same manner as described in Ramirez et al. (2004, AJ, 127, 2659) for a similar observation of a field in NGC 2264, which should be consulted for the full details. (See also the help file for the HEASARC version of the catalog from the latter reference available at /W3Browse/chandra/ngc2264cxo.html ). This table was created by the HEASARC in February 2007 based on the CDS table J/AJ/128/787, files table1.dat, table3.dat and table4.dat. It does not include the results from the spectral analysis of 44 bright X-ray sources which were presented in Table 2 of the reference paper. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/onccxoopt
- Title:
- Orion Nebula Cluster Chandra HRC Optical Sample
- Short Name:
- ONCCXOOPT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- In the first of two companion papers on the Orion Nebula Cluster (ONC), the authors presented their analysis of a 63 ks Chandra HRC-I observation that yielded 742 X-ray detections within the 30' x 30' field of view. To facilitate their interpretation of the X-ray image, they compiled a multi-wavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. They defined two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low-extinction, well-characterized ONC members. They showed for both samples that field object contamination is generally low. Their X-ray sources are primarily low-mass ONC members. The detection rate for optical sample stars increases monotonically with stellar mass from zero at the brown dwarf limit to ~100% for the most massive stars but shows a pronounced dip between 2 and 10 M<sub>sun</sub>. They determined L<sub>X</sub> and L<sub>X</sub>/L<sub>bol</sub> or all stars in their optical sample and utilized this information in their companion paper to study correlations between X-ray activity and other stellar parameters. In particular, the authors assembled an extensive catalog of known X-ray/optical/IR and radio objects that fell within the HRC FOV. In addition to their list of HRC sources and the Chandra source lists of Garmire et al. (2000, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/1426">CDS Cat. <J/AJ/120/1426></a>) and Schulz et al. (2001, CDS Cat. <J/ApJ/549/441>), they considered 14 catalogs from recent publications, producing a database of nearly 2900 distinct objects reported in at least one of the studies considered. A full list of references is given in the first column of Table 2 of the reference paper, along with a concise classification of the work and the referenced table number(s) from the original work. The authors' ONC optical sample is comprised of stars in the HRC FOV for which they have a mass estimate, whose values of the visual absorption A<sub>V</sub> are less than 3.0, and which are either confirmed proper motion members or have unknown proper motion (see Section 3.4.1 of the reference paper). For the 696 stars of this optical sample, this HEASARC table (the full version of Table 4 of the reference paper) lists sky position, mass, age, rotational period, Ca II line equivalent width, HRC basal count rate (see Section 5 of the reference paper), X-ray luminosity, and L<sub>X</sub>/L<sub>bol</sub> (see Sections 4 and 5 of the reference paper). This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/582/382, file table4.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/onccxoxray
- Title:
- Orion Nebula Cluster Chandra HRC X-Ray Point Source Catalog
- Short Name:
- ONCCXOXRAY
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- In the first of two companion papers on the Orion Nebula Cluster (ONC), the authors presented their analysis of a 63 ks Chandra HRC-I observation that yielded 742 X-ray detections within the 30' x 30' field of view. To facilitate their interpretation of the X-ray image, they compiled a multi-wavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. They defined two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low-extinction, well-characterized ONC members. They showed for both samples that field object contamination is generally low. Their X-ray sources are primarily low-mass ONC members. The detection rate for optical sample stars increases monotonically with stellar mass from zero at the brown dwarf limit to ~100% for the most massive stars but shows a pronounced dip between 2 and 10 M<sub>sun</sub>. They determined L<sub>X</sub> and L<sub>X</sub>/L<sub>bol</sub> or all stars in their optical sample and utilized this information in their companion paper to study correlations between X-ray activity and other stellar parameters. In particular, the authors assembled an extensive catalog of known X-ray/optical/IR and radio objects that fell within the HRC FOV. In addition to their list of HRC sources and the Chandra source lists of Garmire et al. (2000, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/1426">CDS Cat. <J/AJ/120/1426></a>) and Schulz et al. (2001, CDS Cat. <J/ApJ/549/441>), they considered 14 catalogs from recent publications, producing a database of nearly 2900 distinct objects reported in at least one of the studies considered. A full list of references is given in the first column of Table 2 of the reference paper, along with a concise classification of the work and the referenced table number(s) from the original work. The HRC on board the Chandra X-Ray Observatory (Weisskopf et al., 2002PASP..114....1W) observed the ONC for 63.2ks on 2000 February 4. The pointing (R.A. = 5h 35m 17s, DE=-5{deg} 23' 16" (J2000.0)) was chosen to place the Trapezium region and the bright O star Theta<sup>1</sup> Ori C in the center of the field of view (FOV). A good fraction of the ONC region was included in the 30' x 30' HRC FOV. This HEASARC table lists the properties of the 742 X-ray sources detected in this observation as presented in the full version of Table 1 of the reference paper. This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/582/382, file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/oriysoir
- Title:
- Orion Nebula YSO IR Properties
- Short Name:
- ORIYSOIR
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The origin and evolution of the X-ray emission in very young stellar objects (YSOs) are not yet well understood because it is very hard to observe YSOs in the protostellar phase. Using COUP data, the authors studied in their reference paper the X-ray properties of stars in the Orion Nebula Cluster (ONC) in different evolutionary classes: luminosities, hydrogen column densities N<sub>H</sub>, effective plasma temperatures, and time variability were compared to understand if the interaction between the circumstellar material and the central object can influence the X-ray emission. They have assembled the deepest and most complete photometric catalog of objects in the ONC region from the UV to 8 microns (µm) using data from the HST Treasury Program; deep and almost simultaneous UBVI and JHK images taken, respectively, with WFI at ESO 2.2m and ISPI at CTIO 4m telescopes; and Spitzer IRAC imaging. They selected high-probability candidate Class 0-I protostars, a sample of "bona fide" Class II stars, and a set of Class III stars with IR emission consistent with normal photospheres. Their principal result is that Class 0-Ia objects are significantly less luminous in X-rays, in both the total and hard bands, than the more evolved Class II stars with mass larger than 0.5M_{sun}_; the latter show X-ray luminosities similar to those of Class 0-Ib stars. This table contains the JHK and IRAC data, as well as the protostar classifications, for 398 ONC YSOs. This online catalog was created by the HEASARC in October 2010 based on the machine-readable versions of Tables 2, 3, 4 and 5 from the reference paper which were obtained from the CDS (their catalog J/ApJ/677/401). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ovro31ghz
- Title:
- Owens Valley Radio Observatory 40-m 31-GHZ Radio Source Catalog
- Short Name:
- OVRO31GHZ
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The 100m Robert C. Byrd Green Bank Telescope (GBT) and the 40m Owens Valley Radio Observatory (OVRO) telescope have been used to conduct a 31-GHz survey of 3165 known extragalactic radio sources over 143 deg<sup>2</sup> of the sky. Target sources were selected from the NRAO VLA Sky Survey (NVSS) in fields observed by the Cosmic Background Imager (CBI); most are extragalactic active galactic nuclei (AGNs) with 1.4-GHz flux densities of 3-10 mJy. Using a maximum-likelihood analysis to obtain an unbiased estimate of the distribution of the 1.4 - 31 GHz spectral indices of these sources, the authors find a mean 31 - 1.4 GHz flux ratio of 0.110 +/- 0.003 corresponding to a spectral index alpha = -0.71+/-0.01 (S<sub>nu</sub> ~ nu<sup>alpha</sup>); 9.0% +/- 0.8% of the sources have alpha > -0.5 and 1.2% +/- 0.2% have alpha > 0. By combining this spectral-index distribution with 1.4GHz source counts, the authors predict 31-GHz source counts in the range 1 mJy <S<sub>31</sub> < 4 mJy, N(>S<sub>31</sub>) = (16.7+/-1.7)deg<sup>-2</sup>(S<sub>31</sub>/1mJy)<sup>(-0.80+/-0.07)</sup>. In this study, the authors present a detailed characterization of the impact of the discrete source foreground on arcminute-scale 31-GHz anisotropy measurements based upon two observational campaigns. The first campaign (the results of which are given in this table) was carried out with the OVRO 40m telescope at 31 GHz from 2000 September through 2002 December. The second campaign (the results of which are given in the GBT31GHZ table) used the GBT from 2006 February to May. A companion paper (Sievers et al. 2009arXiv0901.4540S) presents the five-year CBI total intensity power spectrum incorporating the results of the point-source measurements discussed here. Reported error bars include a 10% and 5% rms gain uncertainty for GBT and OVRO measurements, respectively. Sources detected at greater than 4 sigma at 31 GHz are flagged (detection_flag = 'Y'); for this calculation, the random gain uncertainty was excluded. In all 3165 sources were observed. The GBT catalog (the HEASARC GBT31GHZ table) contains 1490 sources. Of the 2315 useful OVRO observations many of the non-detections (and a few detections) were superceded by more sensitive GBT observations; the OVRO catalog contained in the present table therefore contains data on 1675 sources. The detection rate of the OVRO measurements was 11%, and that of the GBT measurements 25%. In all, 18% of the sources were detected at 31 GHz. This table was created by the HEASARC in June 2012 based on CDS Catalpog J/ApJ/704/1433 file table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/pg
- Title:
- Palomar-Green Catalog of UV-Excess Stellar Objects
- Short Name:
- PG
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Palomar-Green Catalog of UV-Excess Stellar Objects provides positions (the original_ra and original_dec parameters) accurate to about 8 arcsec in each coordinate, photographic B-magnitudes accurate to 0.29 mag, spectral types, some cross-references, and photoelectric broad-band, multichannel, and Stroemgren colors when available. Of the 1874 objects in the catalog as published in 1986 (1878 in this version), 1715 comprise a statistically complete sample covering 10714 square degrees from 266 fields taken on the Palomar 18-inch Schmidt telescope. Limiting magnitudes vary from field to field, ranging from 15.49 to 16.67. The overall completeness is estimated to be 84%, but that figure and the relative contributions of magnitude, color, and accidental errors vary depending on the magnitude and color distribution of the spectroscopic subsample. The dominant population in this catalog is that of the hot, hydrogen-atmosphere subdwarfs, the sdB stars, which comprise nearly 40 per cent of the sample. The hot white dwarfs of spectral types DA, DB, and DO account for 21, 2.8, and 1.0 per cent of the sample, respectively, while cooler DC or DZ white dwarfs add another 1.2 per cent. Cataclysmic variables and composite-spectrum binaries account for 5 per cent, although many other spectra dominated by a hot star showed evidence for a cool companion at red wavelengths. Planetary nebulae central stars account for another 0.5 per cent. Extragalactic objects comprise about 9 per cent of the complete sample, with QSOs representing 5.4 per cent. Only 0.3 per cent (6 objects) remain with totally unsatisfactory or unknown spectral classes. (Notice that all of these percentage estimates are based on the published version of this catalog, and that the values in the current online version may be slightly different, as the latter includes a small number of updates and additions). In 2009, an additional data resource was added to this catalog by CDS, namely a file containing more accurate (sub-arcsecond) positions and V magnitudes (the skiff_vmag parameter), and also additional comments (the skiff_comments parameter). This new material has now been included in the HEASARC version of the PG Catalog. A full discussion of this addition can be found at <a href="http://cdsarc.u-strasbg.fr/ftp/cats/II/207A/pg_2009.txt">http://cdsarc.u-strasbg.fr/ftp/cats/II/207A/pg_2009.txt</a>. This database was initially made available at the HEASARC in June 1998 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/207A">CDS catalog II/207A</a> file catalog.dat which had been last updated on Oct 17 1997. In 2017, the HEASARC re-ingested this CDS catalog as it had been updated several times in the interim, notably in 2009 when an additional file (pg_pos.dat) with precise coordinates and comments provided by Brian Skiff was added. This is a service provided by NASA HEASARC .
