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Halpern, Jules

Publications and source records attributed to Halpern, Jules.

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Confirmation of IGR J01363 plus 6610 as a Be X-Ray Binary with Very Low Quiescent X-Ray Luminosity

The field containing the candidate High Mass X-ray Binary IGR J01 363+6610 was observed by XMM-Newton on 2009 July 31 for 28 ks. A Be star was previously suggested as the possible counterpart of the INTEGRAL source, and although Chandra, during a 2007 observation, did not detect an X-ray source at the position of the Be star, we find a variable source (XMMU 101 3549.5+661243) with an average X-ray flux of 2 x 10(exp -13)ergs/sq cm/s (0.2-12 keV, unabsorbed) at this position with XMM-Newton. The spectrum of this source is consistent with a hard power law with a photon index of r = 1.4+/-0.3 and a column density of N(sub H) = (15(+0.7/-0.5)) x 10(exp 22)/sq cm (90% confidence errors). These results, along with our optical investigation of other X-ray sources in the field, make the association with the Be star very likely, and the 2 kpc distance estimate for the Be star indicates an X-ray luminosity of 9.1 x 10(exp 31) ergs/s. This is lower than typical for a Be X-ray binary, and the upper limit on the luminosity was even lower ( < 1.4 x 10(exp 3)ergs/s assuming the same spectral model) during the Chandra observation. We discuss possible implications of the very low quiescent luminosity for the physical properties of IGR 101363+6610.

Tomsick, John A.↗
NASA NTRS1999

Interpreting Broad Double-Peaked Emission Lines in Active Galactic Nuclei

The principal objectives of this project were to probe the inner regions of active galactic nuclei and to test general relativity in the strong-field limit. The approach takes advantage of broad atomic line emission observed from material deep in the potential well of an active galactic nucleus which contains key information as to the physics of the system. Line profiles in a wide range of wavebands from optical to X-ray have provided compelling evidence of the existence of a relativistic accretion disk around a supermassive black hole in a number of galaxies. The simplest model posits a geometrically thin disk in Keplerian orbit, with general relativistic effects in evidence. This model is the point of departure for the proposed work. We developed a high-performance numerical code to calculate photon trajectories in a Schwarzschild or Kerr metric and implemented it on parallel supercomputers. This code includes a general purpose ray tracer that calculates line profiles, light curves, and other observable quantities for a wide variety of emitter configurations. The versatility comes from the fact that the ray tracing algorithm does not depend on any symmetries regarding emitter locations. The speed comes from parallel implementation which enables us to sample hitherto unattainable volumes of disk model parameter space. During the period 1 March 1997 through 28 February 1998, two papers, supported in whole or in part by this grant, were published in refereed journals. They are reproduced in their entirety in the next two sections of this report.

Halpern, Jules↗
NASA NTRS1993

Was 49: Mirror for a hidden Seyfert 1 galaxy

Was 49 is an interacting pair of Seyfert galaxies at z = 0.063, one of which contains a hidden Seyfert 1 nucleus as evidenced by the highly polarized broad wings on its Balmer lines. The disk of the main galaxy, Was 49a, appears to be globally photoionized by a powerful continuum source, undoubtedly the hidden Seyfert 1 companion, Was 49b. The intrinsic luminosity of Was 49b is at least 100 times larger than the observed (scattered) luminosity. A single SWP spectrum of the pair, which can be spatially resolved in the large aperture was obtained. A narrow Ly-alpha line was detected from Was 49b, the hidden Seyfert 1, at a flux level consistent with that of an unreddened Seyfert 2 galaxy. The lack of detection of a continuum is consistent with a power-law of v(sup -1) or steeper extrapolated from the optical, again consistent with the spectrum of other Seyfert 2 and hidden Seyfert 1 galaxies.

Halpern, Jules↗
NASA NTRS1991

IUE and ROSAT monitoring of the bright QSO H1821+643

The analysis is presented of IUE observations of the bright QSO H1821+643, obtained during the ROSAT All Sky Survey (the RIASS program). The objectives were: (1) to establish whether the UV and soft X ray radiation have the same physical origin; and (2) to determine if this physical origin is an accretion disk. Supporting ground based spectrophotometry was also obtained. The analysis shows that the shape and flux level of the UV continuum did not vary among the seven IUE observation spanning one month, to an upper limit of about 8 percent. So it is of great interest to determine whether the soft X ray flux varied during this period. Since X ray variability in AGNs is often more rapid and of higher amplitude than in the UV, detection of X ray variability in the ROSAT data could severely challenge the accretion disk model for the soft X ray excess.

Halpern, Jules↗
NASA NTRS1991

A search for periodicities in the X-ray emission from cataclysmic variables

Results are reported from a search for periodicities in the X-ray emission from cataclysmic variables observed with the Einstein Observatory's IPC at 0.16-3.5 keV and 0.01-2.5 Hz. Power spectra are shown for 51 observations of 31 systems, and upper limits are derived to the pulse fractions of signals that are not detected. The majority of systems show no coherent periodicities in their X-ray emission, which is consistent with a model in which the X-rays are produced in a disk/white-dwarf boundary layer.

Eracleous, Michael↗
NASA NTRS1990

X ray spectra of cataclysmic variables

X ray spectral parameters of cataclysmic variables observed with the 'Einstein' imaging proportional counter were determined by fitting an optically thin, thermal bremsstrahlung spectrum to the raw data. Most of the sources show temperatures of order a few keV, while a few sources exhibit harder spectra with temperatures in excess of 10 keV. Estimated 0.1 to 3.5 keV luminosities are generally in the range from 10(exp 30) to 10(exp 32) erg/sec. The results are consistent with the x rays originating in a disk/white dwarf boundary layer of non-magnetic systems, or in a hot, post-shock region in the accretion column of DQ Her stars, with a negligible contribution from the corona of the companion. In a few objects column densities were found that are unusually high for interstellar material. It was suggested that the absorption occurs in the system itself.

Patterson, Joseph↗