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Foltz, C. B.

Publications and source records attributed to Foltz, C. B..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

ROSAT observations of z greater than 3 quasars

Successful pointed observations using the Roentgen Satellite (ROSAT) Position Sensitive Proportional Counter (PSPC) were made of seven z greater than 3 optically selected quasars from the Large Bright Quasar Survey (LBQS). Four detections and three 3 sigma upper limits resulted. Combining these data with the heterogeneous sample of Avni & Tananbaum (1986) confirms their conclusion that the ratio of x-ray to optical luminosity is correlated with optical luminosity and probably not correlated with redshift. This suggests that x-ray luminosity evolves more slowly than optical luminosity. These results are then used in conjunction with the LBQS database to estimate the contribution to the 2 keV x-ray background of bright, optically selected quasars with m(sub B(sub J)) less than 18.85; the result is about 5%.

Pickering, T. E.↗
NASA NTRS1994

Observational evidence linking a quasar with an optical transient

We present evidence for the association of a quasi stellar object (QSO) with a bright optical transient (OT). A V = 20.6 mag QSO with redshift z = 1.78 has been found within the 38 seconds x 62 seconds error ellipse of a bright OT discovered on a Harvard Patrol Camera plate taken in 1905. The chance of finding a random QSO at V less than or equal to 20.6 mag within this area is estimated as approximately 0.5%. Although the OT is within the error circle of the gamma-ray burst (GRB) GB 910219 position determined from the WATCH experiment, the localization for this same event determined from the Third Interplanetary Network does not include the OT or the QSO. Whether the GRB is related to the OT/QSO or not, the probable association of a bright OT with a QSO is a discovery that warrants further investigation.

Vrba, F. J.↗
NASA NTRS1992

The x ray properties of a large, uniform QSO sample: Einstein observations of the LBQS

Although there are large numbers of Quasi Stellar Objects (QSO's) now observed in X rays, extensive X-ray observations of uniformly selected, 'complete' QSO samples are more rare. The Large Bright QSO Survey (LBQS) consists of about 1000 objects with well understood properties, most brighter than B = 18.8 and thus amenable to X-ray detections in relatively brief exposures. The sample is thought to be highly complete in the range 0.2 less than z less than 3.3, a significantly broader interval than many other surveys. The Einstein IPC observed 150 of these objects, mostly serendipitously, during its lifetime. We report the results of an analysis of these IPC data, considering not only the 20 percent of the objects we find to have positive X-ray detections, but also the ensemble X-ray properties derived by 'image stacking'.

Margon, B.↗