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Halpern, J.

Publications and source records attributed to Halpern, J..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A ROSAT high resolution x ray image of NGC 1068

The soft x ray properties of the Seyfert 2 galaxy NGC 1068 are a crucial test of the 'hidden Seyfert 1' model. It is important to determine whether the soft x rays come from the nucleus, or from a number of other possible regions in the circumnuclear starburst disk. We present preliminary results of a ROSAT HRI observation of NGC 1068 obtained during the verification phase. The fraction of x rays that can be attributed to the nucleus is about 70 percent so the 'soft x ray problem' remains. There is also significant diffuse x ray flux on arcminute scales, which may be related to the 'diffuse ionized medium' seen in optical emission lines, and the highly ionized Fe K(alpha) emission seen by BBXRT.

Halpern, J.↗
NASA NTRS1982

Discovery of a 50 minute binary period and a likely 22 magnitude optical counterpart for the X-ray burster 4U 1915-05

Absorption dips which recur with a period of 2985 s have been observed from the X-ray burst source 4U 1915-05. It is suggested that the dips are caused by obscuration of the X-ray source by material at the point where the gas stream from the companion meets the accretion disk, and that the 2985 s periodicity is the orbital period of the binary system. These observations represent the first direct evidence of the binary nature of X-ray burst sources. In addition, a new optical identification of 4U 1915-05 is suggested: a 22 magnitude candidate observed in a CCD image of the optical field at the arcsec-accurate HRI X-ray position.

Walter, F. M.↗
NASA NTRS1981

Analysis of IUE observations of CS in Comet Bradfield (1979 l)

The high resolution rotational band profiles were fitted with theoretical band profiles which are derived using a Boltzmann temperature of 70 K. A very rapid variation with heliocentric distance for the CS brightness was found. The implications of these results for models of the coma along with the origin of the CS species are discussed.

Rahe, J.↗
NASA NTRS1977

Ultrasoft X-rays from the southern galactic hemisphere

Results are reported for sounding-rocket measurements of the X-ray background at ultrasoft energies (90 to 280 eV) in selected regions of the southern galactic hemisphere. The spectrum of the background is found to be extremely soft, being characterized by a kinetic temperature of less than 100 eV in thermal models. A lower limit of about 0.2 per cu pc is set on the space density of stellar sources in a discrete-source model for the background. The results show that the observed background radiation in the southern galactic hemisphere is about 50% less intense than that sampled at corresponding northern latitudes, the intensity at energies less than 150 eV varies along the scan path and is strongest south of -60 deg, there is no evidence for the existence of any ultrasoft pointlike sources, and the background is probably diffuse in origin. A temperature of about 600,000 K and an electron density of the order of 0.007 per cu cm are derived from a simple model where the radiation originates in a hot interstellar plasma interspersed with cold gas along the line of sight.

Levine, A.↗
NASA NTRS1976

Solar photochemistry using the space shuttle

A continuing source of difficulty in cometary astrophysics is understanding the origin of C2, C3, NH and CO(+) species in comets. An experiment is proposed to investigate these problems by continuously releasing suspected parent gases from the space shuttle and using a dye laser to selectively excite fragments produced as a result of solar photochemical decomposition of the molecules. The backscattered fluorescence is gathered by a telescope, spectrally filtered, and measured as a function of time after the laser pulse.

Jackson, W. M.↗