Engineering topics

Boehringer, H.

Publications and source records attributed to Boehringer, H..

4 records

NASA NTRS1996

X-ray search for dark lens objects

The quasi-stellar object (QSO) MG 2016+112 is searched for and probably identified as an X-ray cluster of galaxies by the Advanced Satellite for Cosmology and Astrophysics (ASCA) observations. The MG 2016+112 is a gravitational lensed system with three confirmed lensed images of the QSO at a redshift of 3.27. The X-ray spectrum suggests that the new record of the highest redshift of clusters of galaxies, from which X-ray and iron K-line emission were detected, was reached.

Hattori, M.↗

NASA NTRS1994

RX J1759.4+6638: An x-ray selected quasars at a redshift of 4.320

We report the discovery of an x-ray selected Quasi-Stellar Objects (QSO) at a redshift of 4.320 +/- 0.005. This is the most distant x-ray selected object known, and it is the eighth most distant QSO known. The properties of this QSO are very similar to other QSOs at redshifts greater than 4. The x-ray discovery of this object, and that of high redshift clusters of galaxies, shows that present x-ray surveys are reaching depths competitive with other methods.

Henry, J. P.↗

NASA NTRS1992

Observation of the Coma cluster of galaxies with ROSAT during the all-sky survey

The Coma cluster of galaxies was observed with the position sensitive proportional counter (PSPC) during the ROSAT all sky survey. We find evidence for substructure in this cluster. Diffuse X-ray emission is detected from the regions of the NGC 4839 and 4911 subgroups at 6 percent and 1 percent of the total cluster emission respectively. There may be emission associated with the NGC 4874 and 4889 subgroups as well. The NGC 4839 group appears to be in the process of merging with the cluster. These X-ray data show that at least some of the groups previously found in projection are in fact physical objects possessing potential wells deep enough to trap their own X-ray gas. Because of the unlimited field of view of the all sky survey and the low background of the PSPC, we were able to measure the azimuthally averaged surface brightness of Coma out to approximately 100 arcmin, twice as far as was previously possible. Given the validity of our mass models, these new X-ray data imply that within 5/h(50) Mpc the binding mass of the Coma cluster is 1.8 +/- 0.6 x 10 exp 15/h(50) solar mass, and the fraction of cluster mass contained in hot gas is 0.30 +/- 0.14h(50) exp -3/2. Furthermore, the binding mass is more centrally concentrated than is the X-ray gas.

Briel, U. G.↗

NASA NTRS1991

The X-ray morphology of the relaxed cluster of galaxies A2256. I - Evidence for a merger event

The rich cluster of galaxies A2256 are studied by utilizing the imaging proportional counter on board the X-ray observatory ROSAT. A2256 is considered to be a relaxed Coma-like cluster which is dynamically well evolved. Cleara evidence, however, is found for substructure in A2256. The X-ray surface brightness distribution reveals two separate maxima in the center; one of which is coincident with the central cD galaxy while the morphology of the other shows indications that it is merging with the main cluster body. The X-ray temperatures of the two maxima are different; the probable merging object being about a factor of five cooler than the cluster. The previously measured broad velocity distribution supports the idea that a merger is occurring in this cluster.

Briel, U. G.↗