scholarly journals Identification of a Complete Sample of Northern Rosat All-Sky Survey X-Ray Sources

1998 ◽  
Vol 179 ◽  
pp. 449-449
Author(s):  
J. Krautter ◽  
I. Thiering ◽  
F.-J Zickgraf ◽  
I. Appenzeller ◽  
R. Kneer ◽  
...  
Keyword(s):  
Optical Observations ◽  
Limited Sample ◽  
Ccd Imaging ◽  
X Ray ◽  
The North ◽  
Cluster Of Galaxies ◽  
Faint Object ◽  
Sky Survey ◽  
Faint Object Spectrograph ◽  
North Galactic

We present results of the optical identification of a spatially complete, flux limited sample of about 700 ROSAT All-Sky X-ray sources contained in 6 study areas north of δ = −9° with |bII|> 20° (including one region near the North Galactic pole (NGP), another one near the North Ecliptic pole (NEP)). Countrate limits are 0.01 cts s–1 near the NEP and 0.03 cts s–1 for the other areas. The optical observations were performed at the 2.15-m telescope of the Guillermo Haro Observatory, Mexico, using the Landessterwarte Faint Object Spectrograph Camera which allows to carry out direct CCD imaging and multi-object spectroscopy. The limiting magnitude is about 19m for spectroscopy and about 23m for B and R direct imaging. Our analysis shows a dependency of the ratio of ‘extragalactic’ (e.g., AGN, cluster of galaxies) to ‘stellar’ (e.g., coronal emitters, active binaries) counterparts on NH. In the area near the NGP (low NH) ‘extragalactic’ counterparts dominate, while in the area with the highest NH ‘stellar’ counterparts dominate.

scholarly journals Flare Stars in a Field Near the North Galactic Pole: ROSAT and Optical Observations

1995 ◽  
Vol 151 ◽  
pp. 69-72
Author(s):  
G.A. Richter ◽  
H.-J. Bräuer ◽  
J. Greiner
Keyword(s):  
Optical Observations ◽  
Positional Accuracy ◽  
X Ray ◽  
The North ◽  
Optical Position ◽  
Sky Survey ◽  
Objective Prism ◽  
Flare Stars ◽  
North Galactic ◽  
Calar Alto

In a field of 100 square degrees around 26 Com, 238 X-ray sources have been discovered by ROSAT during the All-Sky-Survey observations. These sources were identified using objective prism spectrograms taken with the Hamburg Schmidt telescope on Calar Alto (courtesy N. Bade) and including the positional accuracy of typically 30" and the X-ray to optical luminosity ratio. In an ongoing investigation of these X-ray sources on more than 400 plates of the Sonneberg astrographs 400/1600 mm and 400/2000 mm, a total of 5 of the M type counterparts were found to be flare stars. In Table 1 we give the ROSAT name (column 1), the new designation as a Sonneberg variable (2), the position of the optical counterpart (3), the magnitude range of the newly discovered flare stars (4), the ROSAT PSPC countrate during the All-Sky-Survey (5), the distance D between X-ray and optical position (6). All 5 objects had not been known to be flaring. The real amplitudes must be larger than those given in column 3 because the (unknown) duration of the flares is usually much shorter than the exposure time of the plates. The figures give APM finding charts of these new flare stars.

scholarly journals X-Ray and Optical Observations of a New X-Ray Soft Intermediate Polar: RX J0512.2–3241

1997 ◽  
Vol 163 ◽  
pp. 689-689
Author(s):  
V. Burwitz ◽  
K. Reinsch ◽  
K. Beuermann ◽  
H.-C. Thomas
Keyword(s):  
Optical Observations ◽  
Galactic Latitude ◽  
Ccd Photometry ◽  
X Ray ◽  
Probable Spin ◽  
Sky Survey ◽  
Intermediate Polars ◽  
Orbital Periods ◽  
Low Magnetic Field

The V~17.6 mag optical counterpart of the bright, soft, high-galactic latitude X-ray source RX J0512.2–3241 detected during the ROSAT All-Sky Survey, has been identified as a new, asynchronously rotating, magnetic cataclysmic variable (intermediate polar). The X-ray spectrum of RXJ0512–32 is similar to that of polars, it shows a soft component with no intrinsic absorption and a blackbody temperature kTbb~38 eV. From our optical follow-up B and V CCD photometry (cf. Fig. 1) we derive most probable spin and orbital periods of (863.5 ± 0.7) s and (3.45 ± 0.03) h respectively. A lower limit for the distance to the system is d > 740 pc. From this evidence we suggest that RXJ0512-32 is a further member of the ROSAT discovered class of soft X-ray intermediate polars (for details see Burwitz et al., 1996, A&A 310, L25). This still small class of systems (see Haberl and Motch 1995, A&A 297, L37) has X-ray characteristics similar to those of low magnetic field polars and may be their long sought evolutionary progenitors.

scholarly journals The Performance of Neural Networks in Astronomical Image Classification

1994 ◽  
Vol 161 ◽  
pp. 235-241
Author(s):  
S.C. Odewahn
Keyword(s):  
Neural Network ◽  
Image Classification ◽  
Sky Surveys ◽  
Pattern Recognition Techniques ◽  
The North ◽  
Astronomical Image ◽  
Sky Survey ◽  
Network Pattern ◽  
North Galactic

The use of neural network pattern recognition techniques in the field of astronomy is reviewed. In assessing the quality of image recognition derived from this method particular attention is given to the problem of star/galaxy discrimination in large digital sky surveys. A two color survey of 9 fields of the first epoch Palomar Sky Survey, centered on the North Galactic Pole, has been performed with the Minnesota Automated Plate Scanner. A set of neural network image classifiers are used to automatically perform star/galaxy discrimination. We assess the efficiency of image classification and sample completeness through comparisons with a variety of independent studies of the NGP area.

scholarly journals First Results from the VLA FIRST Survey

1996 ◽  
Vol 175 ◽  
pp. 499-502
Author(s):  
R.H. Becker ◽  
M.D. Gregg ◽  
D.J. Helfand ◽  
C.M. Cress ◽  
R. Mcmahon ◽  
...  
Keyword(s):  
Correlation Function ◽  
Radio Sources ◽  
Optical Identification ◽  
X Ray ◽  
The North ◽  
First Results ◽  
Angular Correlation Function ◽  
Second Year ◽  
North Galactic ◽  
Followup Studies

The VLA FIRST survey is now in its second year. We have completed mapping over 1500 deg2 of the North Galactic Cap and present here the catalog of the 138,000 radio sources detected therein. We discuss the statistics of this new catalog including the two-point angular correlation function for all radio emitters, present our optical identification of 24,000 sources using the APM catalog, and report followup studies on radio variability, X-ray source identification, and our bright quasar sample.

scholarly journals Extended X-Ray Emission from Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 197-197 ◽  
Author(s):  
H.C. Kreysing ◽  
C. Diesch ◽  
J. Zweigle ◽  
R. Staubert ◽  
M. Grewing
Keyword(s):  
Ambient Medium ◽  
Planetary Nebulae ◽  
Central Star ◽  
Boundary Region ◽  
Integration Time ◽  
X Ray ◽  
The North ◽  
Sky Survey ◽  
First Results ◽  
Pointed Observation

We present first results from the ROSAT All Sky Survey on X-ray emission of planetary nebulae (PNe). For the first time extended X-ray emission from PNe was detected. This is the case for NGC 6543, NGC 6853, A 12, NGC 4361 (and LoTr 5). X-ray emission compatible with a point source was detected from BD+30°3639, however, the spectral distribution of the X-ray photons is leading to temperatures beyond 2 106 K. Thus in all cases, with the possible exception of LoTr 5, the central star of the PNe can be excluded as the main source of the observed X-ray emission. X-ray images and ROSAT spectra for all detected PNe are presented. The best observed PN in X-ray emission is NGC 6543. Due to the close vicinity to the north ecliptic pole, this object was regularly observed, every 90 minutes during the whole half year of the ROSAT All Sky Survey, resulting in 41 ksec of integration time. In addition NGC 6543 was observed in a 50 ksec pointed observation to the north ecliptic pole, taken in June 1990 during the calibration phase (Kreysing et al. 1992). A comparison of the semi-ring-like distribution of the X-ray emission of NGC 6543 with optical CCD-images shows, that most of the X-ray emission seems to originate from the boundary region between the nebula and the halo. Neither the central star nor the hot wind from the central star wind is the main source of the X-ray emission, as proposed by the interacting stellar wind model (Kwok 1982). An alternative model employing a possible coronal heating mechanism has been discussed by Kreysing (1992); accoustic waves, travelling outward from the nebula, encounter a sudden density decline at the boundary to the halo. As a consequence the waves degenerate into shock waves, dissipating their energy in a thin region of only some 1015 cm into the ambient medium.

scholarly journals ASCA Observation of A1674

1998 ◽  
Vol 188 ◽  
pp. 323-324
Author(s):  
T. Takai ◽  
K. Hayashida ◽  
K. Hashimotodani ◽  
W. Kawasaki
Keyword(s):  
X Ray ◽  
Cluster Of Galaxies ◽  
Sky Survey ◽  
Order Of Magnitude

A cluster of galaxies Abell 1674 is a nearby cluster(z=0.106) and an unique sample among Briel & Henry's(1993, A&A 278,379) catalogue. Although it has the largest number of galaxies within the Abell radius, 165, its X-ray luminosity measured in the ROSAT all-sky survey is 5 × 1043erg/s (in 0.5-2.5keV), about one order of magnitude lower than the brightest one.

scholarly journals An X-ray and Radio Study of the Hubble Frontier Field Cluster Abell S1063

2021 ◽  
Author(s):  
Majidul Rahaman ◽  
Ramij Raja ◽  
Abhirup Datta ◽  
Jack O Burns ◽  
Brian Alden ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Large Scale ◽  
High Fidelity ◽  
Radio Flux ◽  
X Ray ◽  
Radio Halo ◽  
Average Temperature ◽  
North East ◽  
The North ◽  
Cluster Of Galaxies

Abstract We present results from Chandra X-ray observations and 325 MHz Giant Metrewave Radio Telescope (GMRT) observations of the massive and X-ray luminous cluster of galaxies Abell S1063. We report the detection of large-scale “excess brightness” in the residual Chandra X-ray surface brightness map, which extends at least 2.7 Mpc towards the north-east from the center of the cluster. We also present a high fidelity X-ray flux and temperature map using Chandra archival data of 122 ksec, which shows the disturbed morphology in the cluster. The residual flux map shows the first observational confirmation of the merging axis proposed in earlier simulations. The average temperature within R500 is 11.7 ± 0.56 keV, which makes AS1063 one of the hottest clusters in the nearby Universe. The integrated radio flux density at 325 MHz is found to be 62.0 ± 6.3 mJy. The integrated spectrum of the radio halo follows a power-law with a spectral index α = −1.43 ± 0.13. The radio halo is found to be significantly under-luminous, which favored for both the hadronic as well as the turbulent re-acceleration mechanism for its origin.

scholarly journals 2–20 keV X-ray sky background

1970 ◽  
Vol 37 ◽  
pp. 309-314 ◽  
Author(s):  
E. A. Boldt ◽  
U. D. Desai ◽  
S. S. Holt ◽  
P. J. Serlemitsos
Keyword(s):  
Energy Spectrum ◽  
Lower Energy ◽  
X Rays ◽  
X Ray ◽  
Collisional Energy ◽  
The North ◽  
Spectral Break ◽  
Diffuse Background ◽  
Image Position ◽  
North Galactic

The diffuse background of 2–20 keV X-rays over a band of the sky extending from Scorpius to the North galactic pole is found to be isotropic to within 5%, with a spectrum given bywheren= (1.35 ±0.100.07).A comparison with spectra at higher energies indicates that the lower energy spectrum is flatter, corresponding to an apparent unit change in spectral index within the band 20–80 keV. A spectral break in this energy region has been discussed in connection with the collisional energy loss lifetime for metagalactic protons that radiate X-rays via inverse bremsstrahlung collisions with the ambient electrons of the intergalactic medium (Boldt and Serlemitsos, 1969; Hayakawa, 1970).

Sign in / Sign up

Export Citation Format

Share Document