- ID:
- ivo://CDS.VizieR/J/ApJS/218/9
- Title:
- Deep XMM-Newton survey of M33
- Short Name:
- J/ApJS/218/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained a deep 8 field XMM-Newton mosaic of M33 covering the galaxy out to the D_25_ isophote and beyond to a limiting 0.2-4.5keV unabsorbed flux of 5x10^-16^erg/cm2/s (L>4x10^34^erg/s at the distance of M33). These data allow complete coverage of the galaxy with high sensitivity to soft sources such as diffuse hot gas and supernova remnants (SNRs). Here, we describe the methods we used to identify and characterize 1296 point sources in the 8 fields. We compare our resulting source catalog to the literature, note variable sources, construct hardness ratios, classify soft sources, analyze the source density profile, and measure the X-ray luminosity function (XLF). As a result of the large effective area of XMM-Newton below 1keV, the survey contains many new soft X-ray sources. The radial source density profile and XLF for the sources suggest that only ~15% of the 391 bright sources with L>3.6x10^35^erg/s are likely to be associated with M33, and more than a third of these are known SNRs. The log(N)-log(S) distribution, when corrected for background contamination, is a relatively flat power law with a differential index of 1.5, which suggests that many of the other M33 sources may be high-mass X-ray binaries. Finally, we note the discovery of an interesting new transient X-ray source, which we are unable to classify.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/534/A55
- Title:
- Deep XMM-Newton Survey of M31
- Short Name:
- J/A+A/534/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The largest Local Group spiral galaxy, M31, has been completely imaged for the first time, obtaining a luminosity lower limit about 10^35^erg/s in the 0.2-4.5keV band. Our XMM-Newton EPIC survey combines archival observations along the major axis, from June 2000 to July 2004, with observations taken between June 2006 and February 2008 that cover the remainder of the D_25_ ellipse. The main goal of the paper is to study X-ray source populations of M31. An X-ray catalogue of 1897(*) sources was created with 914 detected for the first time. Source classification and identification were based on X-ray hardness ratios, spatial extent of the sources, and cross correlation with catalogues in the X-ray, optical, infrared and radio wavelengths. We also analysed the long-term variability of the X-ray sources and this variability allows us to distinguish between X-ray binaries and active galactic nuclei (AGN). Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed us to detect additional transient or at least highly variable sources, which are good candidate X-ray binaries. (*) the final catalog of table5 icludes 1948 sources.
- ID:
- ivo://CDS.VizieR/J/AJ/115/1253
- Title:
- Deep X-Ray Radio Blazar Survey (DXRBS). I.
- Short Name:
- J/AJ/115/1253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, restricting our candidate list to serendipitous flat radio spectrum sources ({alpha}_r_<=0.70, where S_{nu}_{prop}{nu}^-{alpha}_r_^). We discuss our survey methods, identification procedure, and first results. Our survey is found to be 95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85 identifications) and BL Lacertae objects (22 of our 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 here show that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (LX, LR) parameter space within which large fractions of the blazar population lie. Particularly important is the identification of a large population of FSRQs (>=25% of DXRBS FSRQs) with ratios of X-ray to radio luminosity >=10^-6^({alpha}_rx_<=0.78). In addition, as a result of our greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in complete samples with 5GHz (radio) luminosities between 10^31.5^ and 10^33.5^ergs/s/Hz, and fills in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS is 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/323/757
- Title:
- Deep X-Ray Radio Blazar Survey (DXRBS). II.
- Short Name:
- J/MNRAS/323/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray data base with several publicly available radio catalogues, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum ({alpha}_r_<=0.70, where S_{nu}_~{nu}^-{alpha}^). his makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with our previously published objects and already-known sources, our sample now contains 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ ({alpha}_r_<=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 our selection technique is ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes ~50mJy and 0.1-2.0keV X-ray fluxes a few W10-14erg/cm^2^/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification.
- ID:
- ivo://CDS.VizieR/J/A+A/472/1029
- Title:
- (De)excitation rates of H2O by H2
- Short Name:
- J/A+A/472/1029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interpretation of water line emission from existing observations and future HIFI/Herschel data requires a detailed knowledge of collisional rate coefficients. Among all relevant collisional mechanisms, the rotational (de)excitation of H2O by H2 molecules is the process of most interest in interstellar space. We provide rate coefficients for rotational de-excitation among the lowest 45 para and 45 ortho rotational levels of H2O colliding with both para and ortho-H2 in the temperature range 20-2000K. Rate coefficients are calculated on a recent high-accuracy H2O-H2 potential energy surface using quasi-classical trajectory calculations. Trajectories are sampled by a canonical Monte-Carlo procedure. H2 molecules are assumed rotationally thermalized at the kinetic temperature. By comparison with quantum calculations available for low lying levels, classical rates are found to be accurate within a factor of 1-3 for the dominant transitions, that is those with rates larger than a few 10^-12^cm^3^/s. Large velocity gradient modelling shows that the new rates have a significant impact on emission line fluxes and that they should be adopted in any detailed population model of water in warm and hot environments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/425
- Title:
- (De)excitation rates of ortho-NH3 and para-NH3
- Short Name:
- J/MNRAS/399/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ammonia inversion lines are often used as probes of the physical conditions in the dense ISM. The excitation temperature between the first two para metastable (rotational) levels is an excellent probe of the gas kinetic temperature. However, the calibration of this ammonia thermometer depends on the accuracy of the collisional rates with H2. Here we present new collisional rates for ortho-NH3 and para-NH3 colliding with para-H2 (J=0) and we investigate the effects of these new rates on the excitation of ammonia. Scattering calculations employ a new, high accuracy, potential energy surface computed at the coupled-cluster CCSD(T) level with a basis set extrapolation procedure. Rates are obtained for all transitions involving ammonia levels with J<=3 and for kinetic temperatures in the range 5-100K. We find that the calibration curve of the ammonia thermometer -- which relates the observed excitation temperature between the first two para metastable levels to the gas kinetic temperature -- does not change significantly when these new rates are used. Thus, the calibration of ammonia thermometer appears to be robust. Effects of the new rates on the excitation temperature of inversion and rotation-inversion transitions are also found to be small.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/142
- Title:
- Defining photometric peculiar SNe Ia
- Short Name:
- J/ApJ/795/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometric identification technique for SN 1991bg-like type Ia supernovae (SNe Ia), i.e., objects with light curve characteristics such as later primary maxima and the absence of a secondary peak in redder filters. This method is capable of selecting this sub-group from the normal type Ia population. Furthermore, we find that recently identified peculiar sub-types such as SNe Iax and super-Chandrasekhar SNe Ia have photometric characteristics similar to 91bg-like SNe Ia, namely, the absence of secondary maxima and shoulders at longer wavelengths, and can also be classified with our technique. The similarity of these different SN Ia sub-groups perhaps suggests common physical conditions. This typing methodology permits the photometric identification of peculiar SNe Ia in large upcoming wide-field surveys either to study them further or to obtain a pure sample of normal SNe Ia for cosmological studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/103
- Title:
- Definitive Swift/XRT LC of Swift J164449.3+573451
- Short Name:
- J/ApJ/817/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On 2011 March 28, the Swift Burst Alert Telescope triggered on an object that had no analog in over six years of Swift operations. Follow-up observations by the Swift X-ray Telescope (XRT) found a new, bright X-ray source covering three orders of magnitude in flux over the first few days, that was much more persistent (and variable) than gamma-ray burst afterglows. Ground-based spectroscopy found a redshift of 0.35, implying extremely high luminosity, with integrated isotropic-equivalent energy output in the X-ray band alone exceeding 10^53^erg in the first two weeks after discovery. Strong evidence for a collimated outflow or beamed emission was found. The observational properties of this object are unlike anything ever before observed. We interpret these unique properties as the result of emission from a relativistic jet produced in the aftermath of the tidal disruption of a main sequence star by a massive black hole (BH) in the center of the host galaxy. The source decayed slowly as the stellar remnants were accreted onto the BH, before abruptly shutting off. Here we present the definitive XRT team light curve for Swift J164449.3+573451 and discuss its implications. We show that the unabsorbed flux decayed roughly as a t^-1.5^ power law up to 2012 August 17. The steep turnoff of an order of magnitude in 24 hr seems to be consistent with the shutdown of the jet as the accretion disk transitioned from a thick disk to a thin disk. Swift continues to monitor this source in case the jet reactivates.
- ID:
- ivo://CDS.VizieR/J/A+A/438/507
- Title:
- Degree of lopsidedness for galaxies
- Short Name:
- J/A+A/438/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We quantify the degree of lopsidedness for a sample of 149 galaxies observed in the near-infrared from the Ohio State University Bright Galaxy Survey (OSUBGS, Eskridge et al. 2002, Cat. <J/ApJS/143/73>) sample, and try to explain the physical origin of the observed disk lopsidedness. We confirm previous studies, but for a larger sample, that a large fraction of galaxies have significant lopsidedness in their stellar disks, measured as the Fourier amplitude of the m=1 component normalised to the average or m=0 component in the surface density. Late-type galaxies are found to be more lopsided, while the presence of m=2 spiral arms and bars is correlated with disk lopsidedness. We also show that the m=1 amplitude is uncorrelated with the presence of companions. Numerical simulations were carried out to study the generation of m=1 via different processes: galaxy tidal encounters, galaxy mergers, and external gas accretion with subsequent star formation. These simulations show that galaxy interactions and mergers can trigger strong lopsidedness, but do not explain several independent statistical properties of observed galaxies. To explain all the observational results, it is required that a large fraction of lopsidedness results from cosmological accretion of gas on galactic disks, which can create strongly lopsided disks when this accretion is asymmetrical enough.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A93
- Title:
- de Houtman, Kepler and Halley star catalogs
- Short Name:
- J/A+A/530/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- de Houtman in 1603, Kepler in 1627 and Halley in 1679 published the earliest modern catalogues of the southern sky. We provide machine-readable versions of these catalogues, make some comparisons between them, and briefly discuss their accuracy on the basis of comparison with data from the modern Hipparcos Catalogue. We also compare our results for de Houtman with those by Knobel (1917) finding good overall agreement. About half of the about 200 new stars (with respect to Ptolemaios) added by de Houtman are in twelve new constellations, half in old constellations like Centaurus, Lupus and Argo. The right ascensions and declinations given by de Houtman have error distributions with widths of about 40-arcmin, the longitudes and latitudes given by Kepler have error distributions with widths of about 45-arcmin. Halley improves on this by more than an order of magnitude to widths of about 3-arcmin, and all entries in his catalogue can be identified. The measurement errors of Halley are due to a systematic deviation of his sextant (increasing with angle to 2-arcmin at 60-degrees) and random errors of 0.7-arcmin. The position errors in the catalogue of Halley are dominated by the position errors in the reference stars, which he took from Brahe.