Engineering topics

Schachter, Jonathan F.

Publications and source records attributed to Schachter, Jonathan F..

8 records

NASA NTRS1999

FE Features in Highly Obscured AGN

This final report is a summary of the combined study of ASCA (Advanced Satellite for Cosmology and Astrophysics) observations of NGC 7582 with archival ROSAT HRI (High Resolution Imager) and PSPC (Position Sensitive Proportional Counter) data. These observations were important in that they established that X-ray emission in NGC 7582, the most narrow-line of NLXGs (narrow-line X-ray galaxies), is associated with an AGN (Active Galactic Nuclei). Thus implying that all NLXGs are obscured AGN, as has been hypothesized to explain the X-ray spectral background paradox.

Schachter, Jonathan F.↗

NASA NTRS1998

Osse Sky Survey Observations for Cycles Three Extreme Red Egret Blazars

The original purpose of this work was to probe EGRET sources of low significance, and to use statistical techniques to construct a log N - log S of sources at greater than 50 MeV. At this writing, the detection significance of EGRET sources is still an issue. Therefore, we shifted our focus to the known EGRET detections. These came in two groups: (a) the known blazars; and (b) the high-Galactic latitude EGRET sources not identified with optical (or radio) counterparts.

Schachter, Jonathan F.↗

NASA NTRS1995

Discovery of a candidate old, isolated neutron star in the field of a galactic cirrus cloud

New x-ray optical, and radio observations of the bright, unidentified x-ray source MS 0317.7-6647 are presented suggesting that this source is a likely compact stellar remnant. As part of the Einstein Extended Medium Sensivity Survey, this source was discovered serendipitously in the Einstein Imaging Proportional Counter pointing towards the nearby (4.5 Mpc) spiral galaxy NGC 1313. The very high x-ray to optical flux ratio, pointlike ROSAT HRI detection, and extremely soft component in the x-ray spectrum of MS 0317.7-6647 eliminate all the usual classes of optical counterparts to faint x-ray sources except for a very massive x-ray binary (and black hole candidate) in NGC 1313, a nearby, companionless pulsar similar to Geminga, or a very nearby ( approximately 100 pc) isolated, old neutron star slowly accreting interstellar matter onto its magnetic poles. The presence of an IR cirrus cloud which shadows the approximately 0.25 keV x-ray background in this direction supports the latter possibilty.

Stocke, John T.↗

NASA NTRS1993

The new BL Lacertae objects discovered by an efficient X-ray/radio/optical technique

We report the recent discovery of ten BL Lac objects in the Einstein IPC Slew Survey by means of X-ray/radio versus X-ray/optical color-color diagrams and confirming optical spectroscopy. These ten BL Lac objects were discovered using a technique proposed by Stocke et al. (1989) which exploits the characteristic broad-band spectra of BL Lac objects. New VLA detections provide accurate fluxes (limiting f(6 cm) about 0.5 mJy) and about 1 arcsec positions, facilitating the determination of an optical counterpart. All ten new BL Lac objects show essentially featureless optical spectra and lie within the range of radio/X-ray/optical colors of known X-ray-selected BL Lac objects, when about 1 mag optical variability is included. We expect about 50 new BL Lac objects in total, from complete optical follow-up of our now completed VLA work and recent Australia Telescope observations, yielding a complete Slew Survey sample of about 90 BL Lac objects.

Schachter, Jonathan F.↗

NASA NTRS1992

Identifications of Einstein Slew Survey sources

The status of identifications of the Einstien Slew Survey, a bright soft x-ray catalog with 550 new x-ray sources, is discussed. Possible counterparts were found for greater than 95 percent of the Slew Survey based on positional coincidences and color-color diagnostics. The survey will be fully identified via upcoming radio and optical observations.

Schachter, Jonathan F.↗

NASA NTRS1992

Einstein Slew Survey: Data analysis innovations

Several new methods were needed in order to make the Einstein Slew X-ray Sky Survey. The innovations which enabled the Slew Survey to be done are summarized. These methods included experimental approach to large projects, parallel processing on a LAN, percolation source detection, minimum action identifications, and rapid dissemination of the whole data base.

Elvis, Martin S.↗

NASA NTRS1992

Thirteen new BL Lacertae objects discovered by an efficient x ray/radio/optical technique

The discovery of 13 serendipitous BL Lac objects in the Einstein IPC Slew Survey by means of x ray/radio vs. x ray/optical color-color diagrams and confirmation by optical spectroscopy are reported. These 13 BL Lacs were discovered using a technique which exploits the characteristic broad band spectra of BL Lacs. New VLA detections provide accurate fluxes (f(6 cm) is approximately 0.5 mJy) and 2 in. positions, facilitating the determination of an optical counterpart. All 13 new BL Lacs show essentially featureless optical spectra. Nine of these lie within the range of colors of known x ray selected BL Lacs. Of the remaining four, one is apparently x ray louder (by a factor of 1.5) or optically quieter (by 0.8 mags); and three are optically louder (by 1-1.3 mags) than x ray selected BL Lacs. Approximately 50 new BL Lacs in total are expected from VLA work and upcoming Australia Telescope observations, yielding a complete Slew Survey sample of approximately 90 BL Lacs.

Schachter, Jonathan F.↗

NASA NTRS1992

Extragalactic counterparts to Einstein slew survey sources

The Einstein slew survey consists of 819 bright X-ray sources, of which 636 (or 78 percent) are identified with counterparts in standard catalogs. The importance of bright X-ray surveys is stressed, and the slew survey is compared to the Rosat all sky survey. Statistical techniques for minimizing confusion in arcminute error circles in digitized data are discussed. The 238 slew survey active galactic nuclei, clusters, and BL Lacertae objects identified to date and their implications for logN-logS and source evolution studies are described.

Schachter, Jonathan F.↗