- ID:
- ivo://CDS.VizieR/J/A+A/353/1044
- Title:
- ROSAT obs. of T Tauri stars in MBM 12
- Short Name:
- J/A+A/353/1044
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ROSAT PSPC pointed and ROSAT All-Sky Survey (RASS, Cat. <IX/10>) observations and the results of our low and high spectral resolution optical follow-up observations of the T Tauri stars (TTS) and X-ray selected T Tauri star candidates in the region of the high galactic latitude dark cloud MBM 12 (L1453-L1454, L1457, L1458). Table 4 lists all of the X-ray detected sources in the direction of the molecular cloud MBM12 along with relevant X-ray and optical data.
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- ID:
- ivo://CDS.VizieR/J/A+A/317/328
- Title:
- ROSAT PSPC survey of M 31
- Short Name:
- J/A+A/317/328
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on results of the analysis of the first M 31 survey with the ROSAT PSPC performed in July 1991. Within the =~ 6.3deg^2^ field of view we detected 396 individual X-ray sources with (0.1keV-2.4keV) fluxes ranging from =~ 5x10^-15^erg/cm^2^/s^ to =~ 4x10^-12^erg/cm^2^/s. Of these 396 sources, 43 have be en tentatively identified with foreground stars, 29 with globular clusters, 17 with supernova remnants, 3 with other galaxies (including M 32), and 3 with radio sources. A detailed analysis of the integral flux distribution of the sources shows that approximately one fifth are likely to be background objects. By comparison with the results of the Einstein M 31 survey, we find 327 newly detected sources, 15 moderately variable sources, 3 bright and 6 faint possible transient sources. For those sources in M 31, the observed luminosities range from =~ 3x10^35^erg/s to =~ 2x10^38^erg/s (at 690kpc). The total (0.1keV-2.4keV) luminosity of M 31 is (2.9+/-0.3)x10^39^erg/s, roughly one third of which is from the bulge and two thirds of which are from the disk. The luminosity of a diffuse component within the bulge region is estimated to be less than 3.2x10^38^erg/s. An explanation in terms of hot gaseous emission leads to a maximum total gas mass of 1.7x10^6^M_{sun}_. We find that the integral luminosity distribution of sources associated with globular clusters is similar to that of the Milky Way. Finally, the results of spectral fits to 56 of the brightest sources are discussed; we classify 15 objects as "supersoft sources" according to their spectral characteristics.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/87
- Title:
- ROSAT RASS II observations of IRAS galaxies
- Short Name:
- J/A+AS/129/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 120000 X-ray sources detected in the RASS II processing of the ROSAT All-Sky Survey are correlated with the 14315 IRAS galaxies selected from the IRAS Point Source Catalogue: 372 IRAS galaxies show X-ray emission within a distance of 100 arcsec from the infrared position. By inspecting the structure of the X-ray emission in overlays on optical images we quantify the likelihood that the X-rays originate from the IRAS galaxy. For 197 objects the soft X-ray emission is very likely associated with the IRAS galaxy. Their soft X-ray properties are determined and compared with their far-infrared emission.
- ID:
- ivo://CDS.VizieR/IX/11
- Title:
- ROSAT Source Catalog
- Short Name:
- IX/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains sources from PSPC-ROSAT (Position-sensitive Proportional Counter aboard the Roentgen Satellite), as provided by Max-Planck Institut fuer extraterrestrische Physik (MPE) in December 1994. The WGACAT version of the ROSAT PSPC Catalogue (IX/12) is a similar catalogue with slightly different reduction procedures For a description of the ROSAT Mission, see Truemper (1983)
- ID:
- ivo://CDS.VizieR/J/ApJ/514/148
- Title:
- ROSAT survey of bright galaxies clusters
- Short Name:
- J/ApJ/514/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the selection of an X-ray flux-limited sample of bright clusters of galaxies in the southern hemisphere, based on the first analysis of the ROSAT All-Sky Survey data (RASS1). The sample is constructed starting from an identification of candidate clusters in RASS1, after which their X-ray fluxes are remeasured using the steepness-ratio technique. This method is better suited than the RASS1 standard algorithm to measuring flux from extended sources. The final sample is count-rate-limited in the ROSAT hard band (0.5-2.0 keV), so that as a result of the distribution of N_H_, its effective flux limit varies between {~}3 and 4x10^-12^ ergs cm^-2^ s^-1^ over the selected area. This covers the {delta} < 2.5{deg} part of the south Galactic cap region (b < -20{deg}), excluding patches of low RASS1 exposure time and of the Magellanic Clouds area, for a total of 8235 deg^2^. One hundred and thirty candidate sources fulfill our selection criteria for bona fide clusters of galaxies in this area. Of these, 101 are Abell/ACO clusters, while 29 do not have a counterpart in these catalogs. Of these clusters, 126 (97%) have a redshift, and for these we compute an X-ray luminosity. 20% of the cluster redshifts come from new observations, as part of the ESO Key Program survey of RASS clusters that is currently under completion. Considering the intrinsic biases and incompletenesses introduced by the flux selection and source identification processes, we estimate the overall completeness to be better than 90%. The observed number count distribution, log Nlog S, is well fitted by a power law with slope {alpha} =1.34{+/-}0.15 and normalization A=11.87{+/-}1.04 sr^-1^ (10^-11^ ergs cm^-2^ s^-1^)^{alpha}^, in good agreement with other measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/445/280
- Title:
- ROSAT survey of the Orion nebula region
- Short Name:
- J/ApJ/445/280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from three deep ROSAT high-resolution imager observations of the Orion Nebula star-forming region. The X-ray images contain over 1500 catalogued stars in a roughly 0.8deg^2^ region centered on the Trapezium. In all, 389 distinct X-ray sources have been detected, at least two-thirds of which are associated with a single proper-motion cluster member. X-ray emission is detected from stars of all spectral types, from the massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In this paper, we focus primarily on X-ray emission from the late-type PMS stars. Of the ~100 late-type cluster members with measured spectral types, approximately three-fourths have been detected; we have derived X-ray luminosity upper limits for the remaining stars. We found coronal X-ray emission turns on around spectral type F6, with the upper envelope of activity increasing with decreasing effective temperature.
- ID:
- ivo://CDS.VizieR/J/ApJS/91/625
- Title:
- ROSAT survey of the Pleiades
- Short Name:
- J/ApJS/91/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT PSPC images, 171 of which we associate with certain or probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, and M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of the Pleiades.
- ID:
- ivo://CDS.VizieR/J/A+A/371/833
- Title:
- ROSAT Ultra Deep Survey
- Short Name:
- J/A+A/371/833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT Ultra Deep Survey in the Lockman Hole consists of a sample of 94 X-ray sources reaching a limiting flux of 1.2x10-15erg/s/cm^2^ in the 0.5-2.0keV energy band. About 90% of the X-ray sources have been spectroscopically identified using low-resolution Keck spectra.
- ID:
- ivo://CDS.VizieR/J/AJ/110/1229
- Title:
- ROSAT X-ray survey in NGC 6475
- Short Name:
- J/AJ/110/1229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A ROSAT X-ray survey, with complementary optical photometry, of the open cluster NGC 6475 has enabled the detection of ~50 late-F to K0 and ~70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low galactic latitude, 220Myr old cluster. The X-ray observations reported here have a typical limiting sensitivity of L_X_ ~ 10^29^erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the X-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the X-rays. The ratio between X-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of X-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in X-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of X-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A103
- Title:
- Second ROSAT all-sky survey (2RXS) source catalog
- Short Name:
- J/A+A/588/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second ROSAT all-sky survey source catalogue, hereafter referred to as the 2RXS catalogue. This is the second publicly released ROSAT catalogue of point-like sources obtained from the ROSAT all-sky survey (RASS) observations performed with the position-sensitive proportional counter (PSPC) between June 1990 and August 1991, and is an extended and revised version of the bright and faint source catalogues. We used the latest version of the RASS processing to produce overlapping X-ray images of 6.4 by 6.4 degrees sky regions. To create a source catalogue, a likelihood-based detection algorithm was applied to these, which accounts for the variable point-spread function (PSF) across the PSPC field of view. Improvements in the background determination compared to 1RXS were also implemented. X-ray control images showing the source and background extraction regions were generated, which were visually inspected. Simulations were performed to assess the spurious source content of the 2RXS catalogue. X-ray spectra and light curves were extracted for the 2RXS sources, with spectral and variability parameters derived from these products. We obtained about 135,000 X-ray detections in the 0.1-2.4keV energy band down to a likelihood threshold of 6.5, as adopted in the 1RXS faint source catalogue. Our simulations show that the expected spurious content of the catalogue is a strong function of detection likelihood, and the full catalogue is expected to contain about 30 per cent spurious detections. A more conservative likelihood threshold of 9, on the other hand, yields about 71,000 detections with a 5 per cent spurious fraction. We recommend thresholds appropriate to the scientific application. X-ray images and overlaid X-ray contour lines provide an additional user product to evaluate the detections visually, and we performed our own visual inspections to flag uncertain detections. Intra-day variability in the X-ray light curves was quantified based on the normalised excess variance and a maximum amplitude variability analysis. X-ray spectral fits were performed using three basic models, a power law, a thermal plasma emission model, and black-body emission. Thirty-two large extended regions with diffuse emission and embedded point sources were identified and excluded from the present analysis. The 2RXS catalogue provides the deepest and cleanest X-ray all-sky survey catalogue in advance of eROSITA.