- ID:
- ivo://nasa.heasarc/dxrbs
- Title:
- ROSAT Deep X-Ray Radio Blazar Survey Catalog
- Short Name:
- ROSAT/DXRBS
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter (PSPC) data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, restricting their candidate list to serendipitous flat radio spectrum sources (Alpha<sub>r</sub> <= 0.70, where S<sub>Nu</sub> ~ Nu<sup>-Alpha<sub>r</sub></sup>). In their first paper (DXRBS-I), the authors discuss their survey methods, identification procedure, and first results. Their survey was found to be 95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of their first 85 identifications) and BL Lacertae objects (22 of their first 85 identifications), a figure that is comparable to or greater than that achieved by other radio and X-ray survey techniques. The identifications presented therein showed that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (L<sub>X</sub>, L<sub>R</sub>) parameter space within which large fractions of the blazar population lie. Particularly important was the identification of a large population of FSRQs (>=25% of DXRBS-I FSRQs) with ratios of X-ray to radio luminosity >= 10<sup>-6</sup> (Alpha<sub>rx</sub> <= 0.78). In addition, as a result of their greater sensitivity, the DXRBS-I already more than doubled the number of FSRQs in complete samples with 5-GHz (radio) luminosities between 10<sup>31.5</sup> and 10<sup>33.5</sup> ergs/s/Hz, and filled in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS-I was the very first sample to contain statistically significant numbers of blazars at low luminosities, approaching what should be the lower end of the FSRQ luminosity function. In DXRBS-II, the authors presented new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with the DXRBS-I objects and already-known sources, their sample now contained 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ (Alpha<sub>r</sub> <= 0.50) and 53 steep-spectrum quasars: SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus, the selection technique was ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes of ~ 50 mJy and 0.1 - 2.0 keV X-ray fluxes of a few times 10<sup>-14</sup> erg/cm<sup>2</sup>/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification. The DXRBS-I entries in this catalog (identified by having values of the parameter dxrbs_part equal to 1) contain data for 85 identified sources meeting the authors' selection criteria. A number of sources were serendipitously observed by ROSAT on more than one occasion, and, for completeness, the WGACAT positions and values for these multiply observed sources are listed separately, resulting in 102 DXRBS-I entries in this catalog (71 sources with 1 X-ray observation, 11 sources with 2 X-ray observations, and 3 sources with 3 X-ray observations). The DXRBS-II entries in this catalog (identified by having values of the parameter dxrbs_part equal to 2) contain data for 106 identified sources meeting the authors' selection criteria. A number of sources were serendipitously observed by ROSAT on more than one occasion, and, for completeness, the WGACAT positions and values for these multiply observed sources are listed separately. In one case (1WGA J0513.8+0156') the source was detected twice by ROSAT and there are two possible optical counterparts: there are 2 entries for each X-ray observation corresponding to the different conterparts, resulting in a total of 4 entries for this source. There are 92 DXRBS-II sources with 1 X-ray observation, 11 sources with 2 X-ray observations, 2 sources with 4 X-ray observations and 1 source with 5 X-ray observations) resulting in 127 DXRBS-II entries for 106 sources in this catalog. Four of the DXRBS-I objects (1WGA J0421.5+1433, 1WGA J0528.5-5820, 1WGA J1057.6-7724 and 1WGA J1222.6+2934) were also included in DXRBS-II as higher signal-to-noise ratio (S/N) spectra were available. Thus, in the sum of the 2 DXRBS parts presented here, there are 229 entries corresponding to 191 newly discovered sources. The 109 previously identified blazars, 97 of which were listed in Table 6 of DXRBS-I, are not included in this table. This table was created by the HEASARC in March 2012 based on the merger of files table3.dat and table4.dat from the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/115/1253">CDS Catalog J/AJ/115/1253</a> (DXRBS-I) and files table4.dat and table5.dat from the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/323/757">CDS Catalog J/MNRAS/323/757</a> (DXRBS-II). (Note that it does not include the list of 97 previously identified blazars given in table6.dat of the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/115/1253">CDS Catalog J/AJ/115/1253</a>.) The current DXRBS table replaced a previous version (ingested in March 1999) which included only the DXRBS-I tables 3 and 4. This is a service provided by NASA HEASARC .
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- ID:
- ivo://CDS.VizieR/J/A+A/319/413
- Title:
- ROSAT detected quasars. I.
- Short Name:
- J/A+A/319/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of all quasars with measured radio emission from the Veron-Cetty - Veron catalogue (1993, VV93 <VII/166>) detected by ROSAT in the ALL-SKY SURVEY (RASS, Voges 1992), as targets of pointed observations, or as serendipitous sources from pointed observations as publicly available from the ROSAT point source catalogue (ROSAT-SRC, Voges et al. 1995). The total number of ROSAT detected radio quasars from the above three sources is 654 objects. 69 of the objects are classified as radio-quiet using the defining line at a radio-loudness of 1.0, and 10 objects have no classification. The 5GHz data are from the 87GB radio survey, the NED database, or from the Veron-Cetty - Veron catalogue. The power law indices and their errors are estimated from the two hardness ratios given by the SASS assuming Galactic absorption. The X-ray flux densities in the ROSAT band (0.1-2.4keV) are calculated from the count rates using the energy to counts conversion factor for power law spectra and Galactic absorption. For the photon index we use the value obtained for a individual source if the estimated 1 sigma error is smaller than 0.5, otherwise we use the mean value 2.14.
- ID:
- ivo://CDS.VizieR/J/A+A/330/108
- Title:
- ROSAT detected quasars. II.
- Short Name:
- J/A+A/330/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of all radio-quiet quasars or quasars without radio detection from the Veron-Cetty - Veron catalogue (1993, VV93, Cat. <VII/166>) detected by ROSAT in the ALL-SKY SURVEY (RASS, Voges 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.9, See Cat. <IX/10>), as targets of pointed observations, or as serendipitous sources from pointed observations publicly available from the ROSAT point source catalogue (ROSAT-SRC, Voges et al. 1995, Cat. <IX/11>). For all sources we used the results of the Standard Analysis Software System (SASS, Voges et al. 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.223), employing the most recent processing for the Survey data (RASS-II, Voges et al. 1996, Cat. <IX/10>). The total number of quasars is 846. 69 of the radio-quiet objects with radio detections have already been presented in a previous paper (Brinkmann, Yuan, & Siebert 1997, Cat. <J/A+A/319/413>) using the RASS-I results. 17 objects were found to be radio-loud from recent radio surveys and were marked in the table. When available, the power law photon indices and the corresponding absorption column densities (NH) were estimated from the two hardness ratios given by the SASS, both with free fitted NH and for Galactic absorption. The unabsorbed X-ray flux densities in the ROSAT band (0.1-2.4keV) were calculated from the count rates using the energy to counts conversion factor for power law spectra and Galactic absorption. As the photon index we used the value obtained for the individual source if the estimated 1-{sigma} error is smaller than 0.5, otherwise we used the redshift-dependent mean value (see the paper for details).
- ID:
- ivo://CDS.VizieR/J/A+A/323/739
- Title:
- ROSAT detected quasars. II.
- Short Name:
- J/A+A/323/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the broad band, radio - to - X-ray, properties of a large sample of mostly previously optically unidentified radio-loud X-ray sources from the correlation of a ROSAT All-Sky Survey source list with the 5GHz Green Bank Survey of the northern sky (RGB sample) which is one of the largest well-defined flux-limited surveys of AGN ever obtained. Further, the RGB pushes 1-2 orders of magnitude deeper in both X-ray and radio flux compared to previous unbiased wide-area AGN surveys. Follow up VLA observations of the candidate objects yielded positions with arcsec accuracy which were used to find optical counterparts to the sources from digitized POSS plates. The sources are divided into three classes according to the positional offset between the X-ray and radio candidates and the spatial resolution of the radio observations, reflecting the various degrees of confidence about the correctness of the proposed association. Although the nature of the sources as well as their redshifts remain to be determined in spectroscopic follow up observations, the derived flux ratios lead to the conclusion that the majority of them are quasars. Hardly any correlations could be found between different source parameters, possibly due to the fact that most of the objects are found in a relatively small flux range near the sensitivity limit of the radio catalogue. The majority of the new RGB sources have broad-band properties between those of traditional radio-selected and X-ray selected AGN. There is no bimodal distribution in the radio-loudness distribution, and the traditional division between radio-quiet and radio-loud AGN may not be warranted.
- ID:
- ivo://CDS.VizieR/J/A+A/318/111
- Title:
- ROSAT Galactic Plane Survey
- Short Name:
- J/A+A/318/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the point source content of a low galactic latitude region selected from the ROSAT all-sky survey. The test field is centered at l=90, b=0 and has an area of 64.5deg^2^. A total of 128 soft X-ray sources are detected above a maximum likelihood of 8. Catalogue searches and optical follow-up observations show that in this direction of the galactic plane, 85% of the sources brighter than 0.03PSPC are identified with active coronae. F-K type stars represent 67% (+/-13%) of the stellar identifications and M type stars account for 19% (+/-6%). A small but significant number of X-ray sources are associated with A type stars on the basis of positional coincidence. These results together with those of similar optical campaigns demonstrate that the soft X-ray population of the Milky Way is largely dominated by active stars. We show that the density and distribution in flux and spectral type of the active coronae detected in X-rays are consistent with the picture drawn from current stellar population models and age dependent X-ray luminosity functions. The modelling of this population suggests that most of the stars detected by ROSAT in this direction are younger than 1Gyr. This opens the possibility to extract in a novel way large samples of young stars from the ROSAT all-sky survey. The small number of unidentified sources at low X-ray flux put rather strong constraints on the hypothetical X-ray emission from old neutron stars accreting from the interstellar medium. Our observations clearly rule out models which assume no dynamical heating for this population and a total number of N_ns_=10^9^ neutron stars in the Galaxy. If accretion on polar caps is the dominant mode then our upper limit may imply N_ns_=~10^8^. Among the non coronal identifications are three white dwarfs, a Seyfert 1 active nucleus, two early type stars and one cataclysmic variable. We also report the discovery of a Me+WD close binary system with P_orb_=~12 .
- ID:
- ivo://CDS.VizieR/J/A+AS/122/201
- Title:
- ROSAT Galactic Plane Survey observations
- Short Name:
- J/A+AS/122/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of the part of the ROSAT all-sky survey covering the galactic plane is the scope of a dedicated project called the ROSAT Galactic Plane Survey. In order to statistically understand the nature of the =~14000 sources discovered by ROSAT at |b|<=20{deg}, a number of sample areas have been chosen for follow-up optical identification. In this paper we present the X-ray and optical material gathered in a region located in the Cygnus constellation, centered at l=90{deg}, b=0{deg} and covering an area of 64.5deg^2^. A total of 95 and 128 sources are detected with a maximum likelihood larger than 10 and 8 respectively. With a typical survey exposure time of the order of 700 to 900 s the flux completeness level is =~0.02cts/s corresponding to =~2x10^-13^erg/cm^2^/s. The position of the sample area allows to investigate the soft X-ray content of a rather typical region of the galactic plane. In this paper we describe the details of the observational procedures and data reduction. For each ROSAT source we list the main X-ray characteristics together with those of the proposed optical identification. When appropriate, we also show optical spectra and finding charts. The full analysis and discussion of these data are presented in a companion paper (Motch et al. 1997, Cat. <J/A+A/318/111>).
- ID:
- ivo://CDS.VizieR/J/A+AS/132/341
- Title:
- ROSAT GPS optical identification
- Short Name:
- J/A+AS/132/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on optical searches in the error circles of 93 ROSAT survey sources located at low galactic latitudes (|b|<20{deg}). These sources were extracted from the ROSAT Galactic Plane Survey using various selection criteria on hardness ratio, X-ray and optical brightness and integrated galactic absorption in the direction of the source. We find optical identifications in 76 cases, among which are 25 new AGN, 6 new CVs and a new Be/X-ray binary. In order to illustrate the relevance of the source selections applied here, we cross-correlated the ROSAT all-sky survey bright source list with SIMBAD. Different classes of X-ray emitters populate distinct regions of a multi dimensional parameter space involving flux ratios, galactic latitude and N_H_. This relatively good segregation offers the possibility to build source samples with enhanced probability of identification with a given class. Complete optical identification of such subsamples could eventually be used to compute meaningful probabilities of identification for all sources using as basis a restricted set of multi-wavelength information.
- ID:
- ivo://nasa.heasarc/rosathard
- Title:
- ROSAT Hard-Spectrum X-Ray Source Catalog
- Short Name:
- ROSATHARD
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a catalog of 147 serendipitous X-ray sources selected to have hard spectra (spectral indices Alpha < 0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. The authors have used Monte Carlo simulations to verify that their technique is very efficient at selecting hard sources: the survey has >= 10 times as much effective area for hard sources as it has for soft sources above a 0.5 - 2 keV flux level of 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in this survey has a spectral slope Alpha ~ 0. The hard sources have a steep number-flux relation (dN/dS ~ _S<sup>-Gamma</sup>, with a best-fitting value of Gamma = 2.72 +/- 0.12), and make up about 15% of all 0.5 - 2 keV sources with S > 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. If their N(S) continues to fainter fluxes, the hard sources will comprise ~ 40% of sources with 5 x 10<sup>-15</sup> < S < 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S < 10<sup>-14</sup>erg cm<sup>-2</sup> s<sup>-1</sup>. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox. This table was created by the HEASARC in March 2012 based on CDS Catalog J/MNRAS/318/1073 file table2.dat, the ROSAT hard X-ray source catalog. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/lmchrixray
- Title:
- ROSAT HRI Catalog of LMC X-Ray Sources (Sasaki et al.)
- Short Name:
- HRI/LMC
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- All 543 pointed observations of the ROSAT High Resolution Imager (HRI) with exposure times higher than 50 seconds, and performed between 1990 and 1998 in a field of 10 by 10 degrees covering the Large Magellanic Cloud were analyzed, and a source catalogue was produced that contains 397 X-ray sources whose properties have been measured with the HRI. The list was cross-correlated with the ROSAT Position Sensitive Proportional Counter (PSPC) LMC source catalogue of Haberl and Pietsch (1999, A&AS, 139, 277; the HEASARC database LMCROSXRAY) in order to obtain the (PSPC) hardness ratios for the X-ray sources detected by both instruments. 138 HRI sources are contained in the PSPC Catalogue, while 259 sources are new detections. The spatial resolution of the HRI being better than that of the PSPC, source positions could be determined with errors smaller than 15 arcsec which are dominated by systematic errors. After cross-correlating the source catalogue with the SIMBAD database and the Tycho Catalogue, 94 HRI sources were identified with known objects based on their positional coincidences and X-ray properties. Whenever more accurate coordinates were given in catalogues or the literature, the X-ray coordinates were corrected and the systematic error of the X-ray position was reduced. For other sources observed simultaneously with an identified source, the positional coordinates were also improved. In total, the X-ray positions of 254 sources were newly determined. The sources identified in this study include 39 foreground stars, 24 supernova remnants (SNR), 5 supersoft sources, 9 X-ray binaries, and 9 active galactic nuclei (AGN) well-known from the literature. Another 8 sources were identified with known candidates for these source classes. An additional 21 HRI sources were suggested by the authors as candidates for SNR, X-ray binaries in the LMC, or background AGN, because of their spatial extents, hardness ratios, X-ray to optical flux ratios, or flux variability. This database was created at the HEASARC in June 2000 based on the ADC/<a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+AS/143/391">CDS Catalog J/A+AS/143/391</a>, and is derived from Table 4 of the reference. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+AS/147/75
- Title:
- ROSAT HRI catalogue of SMC X-ray sources
- Short Name:
- J/A+AS/147/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT HRI SMC source catalogue is based on all 71 pointed observations of the Small Magellanic Cloud by the ROSAT HRI between 1990 and 1998. The data was selected in a 5{deg}x5{deg} field covering the SMC. The catalogue which contains 121 X-ray sources, was cross-correlated with data bases and catalogues like SIMBAD, TYCHO, or USNO as well as other publications in order to classify the X-ray sources and find new candidates for various source classes.