scholarly journals The stellar content of the XMM-Newton slew survey

2018 ◽  
Vol 614 ◽  
pp. A125 ◽  
Author(s):  
S. Freund ◽  
J. Robrade ◽  
P. C. Schneider ◽  
J. H. M. M. Schmitt
Keyword(s):  
Energy Output ◽  
Short Exposure ◽  
Stellar Content ◽  
Current Version ◽  
Identification Procedure ◽  
X Ray ◽  
Total Luminosity ◽  
Sky Survey ◽  
Stellar Sources ◽  
Matching Probability

Aims. We present a detailed analysis of the stellar content of the current version of the XMM-Newton slew survey (XMMSL2). Methods. Since stars emit only a small fraction of their total luminosity in the X-ray band, the stellar XMMSL2 sources ought to have relatively bright optical counterparts. Therefore the stellar identifications were obtained by an automatic crossmatch of the XMMSL2 catalog with the first Gaia data release (Gaia DR1), 2MASS, and Tycho2 catalogs. The reliability of this procedure was verified by a comparison with the individually classified Einstein Observatory medium sensitivity survey X-ray sources and by a crossmatch with the Chandra Source Catalog. Results. We identify 6815 of the 23 252 unique XMMSL2 sources to be stellar sources, while 893 sources are flagged as unreliable. For every counterpart a matching probability is estimated based upon the distance between the XMMSL2 source and the counterpart. Given this matching probability the sample is expected to be reliable to 96.7 % and complete to 96.3 % . The sample contains stars of all spectral types and luminosity classes, and late-type dwarfs have the largest share. For many stellar sources the fractional contribution of the X-ray band to the total energy output is found above the saturation limit of previous studies (Lx/Lbol = 10−3), because the XMMSL2 sources are more affected by flares owing to their short exposure times of typically 6 s. A comparison with the second ROSAT all-sky survey (2RXS) source catalog shows that about 25 % of the stellar XMMSL2 sources are previously unknown X-ray sources. The results of our identification procedure can be accessed via VizieR.

scholarly journals X-Ray Observations of Stars: First Results from Rosat

1992 ◽  
Vol 9 ◽  
pp. 655-656
Author(s):  
J.H.M.M. Schmitt
Keyword(s):  
White Dwarfs ◽  
Open Clusters ◽  
Pass Band ◽  
Source Population ◽  
Late Type ◽  
Low Mass Stars ◽  
X Ray ◽  
Star Forming ◽  
Sky Survey ◽  
Stellar Sources

At the time of writing (i.e., September 1991), the ROSAT all-sky survey has been completed and almost the entire sky has been scanned with an imaging X-ray telescope down to a limiting flux of approximately 2 10−13erg/s/cm2 in the pass band 0.1 — 2.0 keV; in regions of deeper exposures near the poles of the ecliptic considerably fainter flux limits have been achieved. While the processing and analysis of this huge body of data is still in progress and hence final results on the number of detected sources and their distribution in flux are not yet available, the total number of detected X-ray sources will be around 60 000. Preliminary results from optical identifications of selected fields show that about one quarter of the X-ray sources discovered at high galactic latitudes come from by comparison nearby stellar sources (Fleming 1991), while at lower galactic latitudes up to one half of the detected X-ray sources are of stellar origin; in areas occupied by star forming regions (for example, Orion) or open clusters (for example, Hyades or Pleiades) a large number of the detected X-ray sources can be identified with young stars, yielding up to 80 percent of the total source count as galactic stars. For the whole of the ROSAT all-sky survey we may therefore expect about one third of the total sources to be of stellar origin. The vast majority of these stellar X-ray sources is of coronal origin (i.e., late-type low mass stars). Only a relatively small number of stellar X-ray sources will be associated with early-type massive stars where the X-ray emission is thought to arise from instabilities in their radiatively driven winds or metal-poor degenerate stars where the X-ray emission comes from portions of the atmosphere considerably hotter than the optically visible photosphere. From the preliminary analyses performed so far it is already clear now that supersoft sources such as white dwarfs do not constitute a major fraction of the X-ray source population found in the ROSAT all-sky survey and the number of newly X-ray discovered white dwarfs will certainly be considerably less than one thousand. The X-ray emitting late-type stars are commonly referred to as ”active” stars, and the ROSAT all-sky survey catalog will comprise the most extensive list of such objects.

scholarly journals Stars in the Rosat All-Sky Survey

1992 ◽  
Vol 9 ◽  
pp. 235-239
Author(s):  
J.H.M.M. Schmitt
Keyword(s):  
White Dwarfs ◽  
Open Clusters ◽  
Source Population ◽  
Late Type ◽  
Low Mass Stars ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sky Survey ◽  
Stellar Sources

The ROSAT all-sky survey has now been completed and the analysis of this huge body of data is in progress. While final results on the number of detected X-ray sources and their distribution in flux are not yet available, the total number of X-ray sources is expected to be around 60 000. Preliminary results from optical identifications of selected fields show that about one quarter of the X-ray sources discovered at high galactic latitudes come from by comparison nearby stellar sources (Fleming 1991), while at lower galactic latitudes up to one half of the detected X-ray sources are of stellar origin; in areas occupied by star forming regions (for example, Orion) or open clusters (for example, Hyades or Pleiades) a large number of the detected X-ray sources can be identified with young stars, yielding up to 80 percent of the total source count as galactic stars. For the whole of the ROSAT all-sky survey we may therefore expect about one third of the total sources to be of stellar origin. The vast majority of these stellar X-ray sources is of coronal origin (i.e., late-type low mass stars). Only a relatively small number of stellar X-ray sources will be associated with early-type massive stars where the X-ray emission is thought to arise from instabilities in their radiatively driven winds or metal-poor degenerate stars where the X-ray emission comes from portions of the atmosphere considerably hotter than the optically visible photosphere. From the preliminary analyses performed so far it is already clear now that supersoft sources such as white dwarfs do not constitute a major fraction of the X-ray source population found in the ROSAT all-sky survey and the number of newly X-ray discovered white dwarfs will certainly be considerably less than one thousand. The X-ray emitting late-type stars are commonly referred to as “active” stars, and the ROSAT all-sky survey catalog will comprise the most extensive list of such objects.

scholarly journals Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

2021 ◽  
Vol 38 ◽  
Author(s):  
C. S. Anderson ◽  
G. H. Heald ◽  
J. A. Eilek ◽  
E. Lenc ◽  
B. M. Gaensler ◽  
...  
Keyword(s):  
X Ray ◽  
Main Cluster ◽  
Rotation Measure ◽  
Sky Survey ◽  
Low Mass ◽  
Fornax Cluster ◽  
Depth Enhancement ◽  
Projected Distance ◽  
Density Regime ◽  
New Reservoir

Abstract We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster—the Fornax cluster—which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe’s Magnetism (POSSUM) covering a ${\sim}34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ${\sim}25$ RMs per square degree from a 280-MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency ${\sim}3\pi$ -steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm2.4$ rad m−2 within 1 $^\circ$ (360 kpc) projected distance to the cluster centre, which is 2–4 times larger than the spatial extent of the presently detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM and exists in a density regime that broadly matches expectations for moderately dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a subcluster to the southwest. The shock’s Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

scholarly journals CN Com: a Typical RS Canum Venaticorum Star

1995 ◽  
Vol 151 ◽  
pp. 106-107
Author(s):  
G.A. Richter ◽  
J. Greiner
Keyword(s):  
Time Interval ◽  
Optical Counterpart ◽  
X Ray ◽  
Sky Survey ◽  
Error Circle

CN Com = CSV 6907 was dicovered by Romano (1958). First we note that the GCVS (and Simbad) coordinates are wrong by ≈2′. Using the finding chart of Romano (1958) and the APM data (digitized POSS), the correct coordinates of CN Com are R.A.(2000.0) = 12h19m47s.0, DEC(2000.0) = +16°30′50″.CN Com is only 8″ distant from the ROSAT X-ray source RX J1219.7+1630 detected during the All-Sky-Survey at a PSPC countrate of 0.022 cts/s. Due to the positional proximity and the absence of other optical objects brighter than 20rmm within the about 30″ error circle, CN Com is very probably the optical counterpart of RX J1219.7+1630.CN Com was investigated on some 600 photographic plates (Sonneberg astrographs 400/1600 mm and 400/2000 mm) of the fields 26 Com and 5 Com, covering the time interval from 1962 to 1994 (with only a very few plates from the years 1967-1974).

scholarly journals Clustering and Halo Occupation Distribution of Active Galactic Nuclei

2013 ◽  
Vol 9 (S304) ◽  
pp. 243-243
Author(s):  
Takamitsu Miyaji ◽  
M. Krumpe ◽  
A. Coil ◽  
H. Aceves ◽  
B. Husemann
Keyword(s):  
Cross Correlation ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halo ◽  
Bias Parameter ◽  
X Ray ◽  
Sky Survey ◽  
Galaxy Population ◽  
Halo Occupation Distribution

AbstractWe present the results of our series of studies on correlation function and halo occupation distribution of AGNs utilizing data the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) in the redshift range of 0.07<z<0.36. In order to improve the signal-to-noise ratio, we take cross-correlation approach, where cross-correlation functions (CCF) between AGNs and much more numerous AGNs are analyzed. The calculated CCFs are analyzed using the Halo Occupation Distribution (HOD) model, where the CCFs are divided into the term contributed by the AGN-galaxy pairs that reside in one dark matter halo (DMH), (the 1-halo term) and those from two different DMHs (the 2-halo term). The 2-halo term is the indicator of the bias parameter, which is a function of the typical mass of the DMHs in which AGNs reside. The combination of the 1-halo and 2-halo terms gives, not only the typical DMH mass, but also how the AGNs are distributed among the DMHs as a function of mass separately for those at the center of the DMHs and satellites. The main results are as follows: (1) the range of typical mass of the DMHs in various sub-samples of AGNs log (MDMH/h−1MΘ) ~ 12.4–13.4, (2) we found a dependence of the AGN bias parameter on the X-ray luminosity of AGNs, while the optical luminosity dependence is not significant probably due to smaller dynamic range in luminosity for the optically-selected sample, and (3) the growth of the number of AGNs per DMH (N (MDMH)) with MDMH is shallow, or even may be flat, contrary to that of the galaxy population in general, which grows with MDMH proportionally, suggesting a suppression of AGN triggering in denser environment. In order to investigate the origin of the X-ray luminosity dependence, we are also investigating the dependence of clustering on the black hole mass and the Eddington ratio, we also present the results of this investigation.

scholarly journals Tidal disruption events seen in the XMM-Newton slew survey

2016 ◽  
Vol 12 (S324) ◽  
pp. 123-126
Author(s):  
Richard Saxton ◽  
S. Komossa ◽  
Andrew Read ◽  
Paulina Lira ◽  
Kate D. Alexander ◽  
...  
Keyword(s):  
Radio Emission ◽  
Real Time ◽  
Power Law ◽  
Early Phase ◽  
Classical Model ◽  
Thermal Processes ◽  
Tidal Disruption ◽  
X Ray ◽  
Hard Power ◽  
Sky Survey

AbstractXMM-Newton performs a survey of the sky in the 0.2-12 keV X-ray band while slewing between observation targets. The sensitivity in the soft X-ray band is comparable with that of the ROSAT all-sky survey, allowing bright transients to be identified in near real-time by a comparison of the flux in both surveys. Several of the soft X-ray flares are coincident with galaxy nuclei and five of these have been interpreted as candidate tidal disruption events (TDE). The first three discovered had a soft X-ray spectrum, consistent with the classical model of TDE, where radiation is released during the accretion phase by thermal processes. The remaining two have an additional hard, power-law component, which in only one case was accompanied by radio emission. Overall the flares decay with the classical index of t−5/3 but vary greatly in the early phase.

scholarly journals Nature of hard X-ray sources from optical identifications of the ASCA Large Sky Survey

1999 ◽  
Vol 320 (4-5) ◽  
pp. 255-256
Author(s):  
M. Akiyama ◽  
K. Ohta ◽  
T. Yamada ◽  
Y. Ueda ◽  
T. Takahashi ◽  
...  
Keyword(s):  
X Ray ◽  
Sky Survey ◽  
Optical Identifications

scholarly journals Cosmological evolution of the AGN kinetic luminosity function

2006 ◽  
Vol 2 (S238) ◽  
pp. 65-70
Author(s):  
Andrea Merloni ◽  
Sebastian Heinz
Keyword(s):  
Galaxy Formation ◽  
Luminosity Function ◽  
Cosmological Evolution ◽  
Energy Output ◽  
Theoretical Assumption ◽  
X Ray ◽  
Spectrum Radio ◽  
Luminosity Functions ◽  
Jet Power ◽  
Joint Evolution

AbstractWe present a first attempt to derive the cosmological evolution of the kinetic luminosity function of AGN based on the joint evolution of the flat spectrum radio and hard X-ray selected AGN luminosity functions. An empirical correlation between jet power and radio core luminosity is found, which is consistent with the theoretical assumption that, below a certain Eddington ratio, SMBH accrete in a radiatively inefficient way, while most of the energy output is in the form of kinetic energy.We show how the redshift evolution of the kinetic power density from such a low-ṁ mode of accretion makes it a good candidate to explain the so-called “radio mode” of AGN feedback as outlined in many galaxy formation schemes.

Extragalactic X-ray sources and the diffuse X-ray background

1979 ◽  
Vol 366 (1726) ◽  
pp. 391-402 ◽  
Keyword(s):  
Spatial Distribution ◽  
Euclidean Space ◽  
Active Galaxies ◽  
Clusters Of Galaxies ◽  
Optical Identification ◽  
X Ray ◽  
Luminosity Functions ◽  
Sky Survey ◽  
Order Of Magnitude ◽  
X Ray Background

Results from the Ariel 5 sky survey instrument relating to the properties and the spatial distribution of extragalactic X-ray sources are discussed. The lg N -lg S relation for sources in the 2A catalogue is consistent with a uniform distribution of sources in Euclidean space. In addition, measure­ments of fluctuations in the X-ray background suggest that the Euclidean form of the source counts can be extrapolated to flux levels at least an order of magnitude fainter than the 2A catalogue limit. Information is also available from the optical identification of 2A sources which, through redshift measurements, enables the X-ray luminosity functions of the two main classes of source, namely clusters of galaxies and active galaxies, to be determined. The luminosity functions can be used to calculate the contribution of clusters of galaxies and active galaxies to the diffuse X-ray background in the 2-10 keV range. It is found that cosmological evolution of one or both populations is required to account for the diffuse X-ray background entirely in terms of the integrated emission from these sources.

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