- ID:
- ivo://CDS.VizieR/J/A+A/310/384
- Title:
- Optical brightness of 3 ROSAT Seyfert galaxies
- Short Name:
- J/A+A/310/384
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The printed version of this paper describes the X-ray and optical properties of four new active galaxies discovered in the ROSAT All-Sky Survey. While one object (RX J1257.5+2412) is identified as a BL Lac object, the other three (RX J1239.3+2431, RX J1225.7+2055, and RX J1250.2+1923) are narrow line Seyfert 1 galaxies. Three of these four objects are bright enough to be studied on archival photographic plates of Sonneberg Observatory. The present list contains the individual brightness measurements of these objects all of which turned out to be variable on timescales of weeks to years. Some lightcurves (long-term as well as short-term) are given in the printed version.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/274/1194
- Title:
- Optical Identifications of ROSAT EUV Sources
- Short Name:
- J/MNRAS/274/1194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical identifications for 195 EUV sources located in the ROSAT Wide Field Camera all-Sky survey are presented. We list 69 previous unknown EUV-emitting white dwarfs, 114 active stars, 7 new magnetic cataclysmic variables and 5 active galaxies. Several of the white dwarfs have resolved M-type companions, while five are unresolved white dwarf/M-star pairs. Finding charts are given for the optical counterparts.
- ID:
- ivo://CDS.VizieR/J/A+A/299/39
- Title:
- Orion Trapezium area ROSAT PSPC obs. I.
- Short Name:
- J/A+A/299/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep ROSAT PSPC image centred on the Orion Trapezium has revealed that most of the X-ray emission originates from discrete sources, in contrast to previous EINSTEIN data which suggested a diffuse emission component. We present a list of 171 X-ray sources all situated in the so-called inner ring of the field of view (20' radius). The field is crowded with sources. A special procedure had to be developed to cope with the severe blending of sources. The present list is not complete for L_X_<3.5*10^29^erg/s due to this reason and many more sources can still be expected by a next step in the reduction. Nearly all of the sources could be identified with pre-main sequence stars of the Ori OB 1 association in its subgroups Ic and Id. The statistics of this ensemble are discussed. It seems that members of the above subgroups can be distinguished on the basis of an additional amount of X-ray extinction seen in their spectra or hardness ratios. The O stars in the area ({teta}1 Ori C, {teta}2 Ori A and {iota} Ori) are briefly discussed. Six B stars are identified with X-ray sources.
- ID:
- ivo://CDS.VizieR/J/AN/321/81
- Title:
- Orion Trapezium area ROSAT PSPC obs. II.
- Short Name:
- J/AN/321/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep ROSAT PSPC image centred on the Orion Trapezium has been reduced a second time using an improved version of the PSF to fit the data. The outer rim of the field of view was also included. The new catalogue contains 316 X-ray sources which are easily identified with pre-main sequence stars of the Ori OB1 Ic and Id association. All 316 sources were tested for variability. No variations were found inside the single exposures of about 45 minutes length each. Between the 4 exposures spaced over 5 days about 1/3 of the sources show signs of activities of various forms. As above 25% of these have somewhat regular lights curves (monotonically rising or falling or hill- shaped) we infer that at least some outbursts with time scales longer than a day are present and that past searches for X-ray flares of pre-main sequence stars were biased towards shorter time scales.
- ID:
- ivo://CDS.VizieR/J/A+A/341/L79
- Title:
- Proper motions of faint ROSAT WTT stars
- Short Name:
- J/A+A/341/L79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present proper motions of 59 stars of the ROSAT All-Sky Survey (RASS) located in direction of the Chamaeleon star forming region (SFR) in the magnitude range B=5.1-17mag. Proper motions of the fainter stars were newly derived utilizing survey Schmidt plates from the GSC~II plate archive and from a set of special plates taken with the ESO Schmidt telescope. The vector point diagram (VPD) indicates that the certified weak emission-line T Tauri (WTT) stars cluster away from the region occupied by the brighter pre-main-sequence stars (PMS) in Cha I. The distance to this new association is estimated at ~100pc, sensibly smaller than the 150pc generally assumed for the SFR. This yields an upper limit of 2km/s for the velocity dispersion of this new kinematic group. The de-reddened CM diagram of the group members suggest the WTT stars are still PMS objects, but older (3-30Myr) and less massive than previous determinations. These revised age estimates, the newly derived group peculiar velocity, and current distance estimates to the Cha~I/II/III complex would favour in-situ formation against that predicted by high velocity cloud models. Finally, based on a redetermination of the peculiar motions of stars and gas, we speculate that the whole SFR originated from the local Orion spur as a result of more classical mechanisms like interactions with the spiral arms.
36. RASS AGN sample
- ID:
- ivo://CDS.VizieR/J/A+AS/139/575
- Title:
- RASS AGN sample
- Short Name:
- J/A+AS/139/575
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a program to identify the unknown bright active galactic nuclei (AGN) in the ROSAT All Sky Survey Bright Source Catalog (RASS-BSC). We have used logC+0.4R as an alternative expression for log(f_X_/f_opt_), where C is X-ray count rate and R stands for R magnitude. Then a high X-ray-to-optical flux ratio criterion has been used to select an AGN sample with 165 unidentified X-ray sources for optical spectroscopy. Those 165 X-ray sources have been identified in the following classes: 115 emission line AGN (QSOs and Seyferts), 2 BL Lac objects and 4 BL Lac candidates, 22 clusters of galaxies, 12 Galactic stars and 10 objects remain unidentified. This represent a success rate of about 73% for detecting AGN using our selection criteria. Plausibility is based upon the optical classification and X-ray characteristics of the sources.
- ID:
- ivo://nasa.heasarc/rassgb
- Title:
- RASS/Green Bank Catalog
- Short Name:
- RASS/GBC
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 5-GHz high-resolution VLA observations of 2,127 radio and X-ray emitting sources found in both the Green Bank (GB) 5-GHz radio catalog and the ROSAT All-Sky Survey (RASS) are presented. This is referred to as the RASS/Green Bank sample: the HEASARC has abbreviated this to RASSGB to conform with the naming convention that we have used for other RASS catalogs (notice the catalog authors use the rather shorter acronym of RGB. Core flux densities and positions accurate to +/- 0.5" are reported, as well as the GB measurements of the total radio emission, for each source. Because of the radio and X-ray selection criteria adopted, this catalog is believed to almost exclusively contain radio- and X-ray-loud active galaxies. These data are used in the paper by Laurent-Muehleisen et al. (1997) that contains the published version of this catalog to derive the core-to-lobe ratio of objects in this sample, and to discuss their core-dominance relative to samples of radio galaxies and BL Lac objects: the authors conclude that this sample is approximately an order of magnitude more core-dominated than the radio galaxy sample, but is more than an order of magnitude less core-dominated than highly-beamed BL Lac objects. The published version of this catalog comprised two main tables, Table 2 and Table 3. Table 2 gave the 5-GHz high resolution radio source properties for the 1861 ROSAT/Green Bank sources for which subarcsecond positions and core radio flux densities had been obtained, while Table 3 gave the 5-GHz radio source properties for the 436 ROSAT/Green Bank sources for which only low resolution data were obtained. A table of the 83 ROSAT/Green Bank sources for which no radio source greater than 5 sigma was observed in the follow-up VLA observations (Table 4 in the paper) is not included in the present HEASARC RASSGB Catalog but is available in data archive at <pre> <a href="https://heasarc.gsfc.nasa.gov/FTP/heasarc/dbase/misc_files/rassgb/">https://heasarc.gsfc.nasa.gov/FTP/heasarc/dbase/misc_files/rassgb/</a> </pre> This HEASARC version of the ROSAT/Green Bank Catalog was created in November 1998 based on the ADC/<a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+AS/122/235">CDS Catalog <J/A+AS/122/235></a> (Tables 2 and 3). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/rassvars
- Title:
- RASS X-Ray Variable Sources Catalog
- Short Name:
- ROSAT/Vars
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The RASS X-Ray Variable Sources Catalog contains the results of a systematic search for variability among the ROSAT All-Sky Survey (RASS) X-ray sources. Lightcurves were generated for about 30,000 X-ray point sources which were detected sufficiently high above the background. For the variability study different search algorithms were developed in order to recognize flares, periods and trends, respectively. The variable X-ray sources were optically identified with counterparts in the SIMBAD, the USNO-A2.0 and NED data bases, but a significant part of the X-ray sources remain without cataloged optical counterparts. A complete list of the 1207 X-ray variable sources that were found is presented in this table. This table was created by the HEASARC in July 2003 based on CDS table J/A+A/403/247/table7.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+AS/146/323
- Title:
- RASS young sources around R CrA
- Short Name:
- J/A+AS/146/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ROSAT All-Sky Survey data in a 126 deg^2^ area in and around the CrA star forming region. With low-resolution spectroscopy of unidentified ROSAT sources we could find 19 new pre-main sequence stars, two of which are classical T Tauri stars, the others being weak-lined. The spectral types of these new T Tauri stars range from F7 to M6. The two new classical T Tauri stars are located towards two small cloud-lets outside of the main CrA cloud. They appear to be ~10 Myrs old, by comparing their location in the H-R diagram with isochrones for an assumed distance of 130 pc, the distance of the main CrA dark cloud. The new off-cloud weak-line T Tauri stars may have formed in similar cloudlets, which have dispersed recently. High-resolution spectra of our new T Tauri stars show that they have significantly more lithium absorption than zero-age main-sequence stars of the same spectral type, so that they are indeed young. From those spectra we also obtained rotational and radial velocities. For some stars we found the proper motion in published catalogs. The direction and velocity of the 3D space motion - south relative to the galactic plane - of the CrA T Tauri stars is consistent with the dark cloud being formed originally by a high-velocity cloud impact onto the galactic plane, which triggered the star formation in CrA. We also present VRIJHK photometry for most of the new T Tauri stars to derive their luminosities, ages, and masses.
- ID:
- ivo://CDS.VizieR/J/MNRAS/311/456
- Title:
- RIXOS source catalogue
- Short Name:
- J/MNRAS/311/456
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the ROSAT International X-ray/Optical Survey (RIXOS), a medium-sensitivity survey and optical identification of X-ray sources discovered in ROSAT high Galactic latitude fields (|b|>280) and observed with the Position Sensitive Proportional Counter (PSPC) detector. We presents a catalogue of the RIXOS sources and their optical identifications.
