10,392 research outputs found
GeV Gamma-Ray Sources
We report on the preliminary extension of our work on cataloging the GeV sky to approximately 7 years of CGRO/EGRET observations with special emphasis on a search for transient sources. The search method and significance levels are presented. Our initial results on 13 possible transients indicate that 3 may be new gamma-ray sources. Sixteen new steady GeV sources are also detected, 3 of which have never been reported as gamma-ray sources
Three New Long Period X-ray Pulsars Discovered in the Small Magellanic Cloud
The Small Magellanic Cloud is increasingly an invaluable laboratory for
studying accreting and isolated X-ray pulsars. We add to the class of compact
SMC objects by reporting the discovery of three new long period X-ray pulsars
detected with the {\it Chandra X-ray Observatory}. The pulsars, with periods of
152, 304 and 565 seconds, all show hard X-ray spectra over the range from 0.6 -
7.5 keV. The source positions of the three pulsars are consistent with known
H-alpha emission sources, indicating they are likely to be Be type X-ray binary
star systems.Comment: Accepted for publication in the Astrophysical Journa
Recommended from our members
Urspelerpes, U. brucei
Number of Pages: 3Integrative BiologyGeological Science
Non-association of a celestial gamma ray source with the new Milky Way satellite galaxy
The newly discovered satellite galaxy located in the Milky Way galactic anti-center region is discussed along with the possibility that a nearby gamma ray source is associated with it. The factors which led to the conclusion that the gamma ray excess is not associated with the galaxy are considered
Gamma-Ray Bursts are Produced Predominately in the Early Universe
It is known that some observed gamma-ray bursts (GRBs) are produced at
cosmological distances and that the GRB production rate may follow the star
formation rate. We model the BATSE-detected intensity distribution of long GRBs
in order to determine their space density distribution and opening angle
distribution. Our main results are: the lower and upper distance limits to the
GRB production are z 0.24 and >10, respectively; the GRB opening angle follows
an exponential distribution and the mean opening angle is about 0.03 radians;
and the peak luminosity appears to be a better standard candle than the total
energy of a GRB.Comment: 12 pages, 2 figur
Observation of gamma rays with a 4.8 hour periodicity from CYG X-3
Energetic (E35 MeV) Gamma rays were observed from Cyg X-3 with the SAS-2 Gamma ray telescope. They are modulated at the 4.8 sup h period observed in the X-ray and infrared regions, and within the statistical error are in phase with this emission. The flux above 100 MeV has an average value of (4.4 + or - 1.1)x 10 to the -6 power/sq cm/sec. If the distance to Cyg X-3 is 10 kpcs, this flux implies a luminosity of more than 10 to the 37th power ergs/s if the radiation is isotropic and about 10 to the 36th power ergs/s if the radiation is restricted to a cone of one steradian, as it might be in a pulsar
Final SAS-2 gamma ray results on sources in the galactic anticenter region
Analysis of SAS-2 high energy Gamma ray data from the direction of the galactic anticenter shows that this region is characterized by: a diffuse emission from the galactic plane which has a maximum along b=0 deg and an enhancement toward negative latitudes associated with Gould's Belt, a strong point source in the direction of the Crab nebula, and a second intense localized source near galactic coordinates 195 deg, +5 deg. Gamma ray emission from the Crab source is dominated by a pulsed flux from PSR 0531+21. The total flux above 100MeV is 3.7 + or - 0.8 million/sq cm s. The source near 195 deg, + 5 deg has a flux above 100 MeV of 4.3 + or - 0.9 million/sq cm s. Its spectrum appears flatter than that of the Crab. The diffuse galactic plane emission at negative lattitudes shows a general correlation with the local matter distribution associated with Gould's Belt. The calculated Gamma ray intensity agrees well with the SAS-2 observations
Gamma-Ray Bursts as a Probe of the Very High Redshift Universe
We show that, if many GRBs are indeed produced by the collapse of massive
stars, GRBs and their afterglows provide a powerful probe of the very high
redshift (z > 5) universe.Comment: To appear in Proc. of the 5th Huntsville Gamma-Ray Burst Symposium, 5
pages, LaTe
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