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ASCA measurements of the grain-scattered X-ray halos of eclipsing massive X-ray binaries: VELA X-1 and Centaurus X-3

1994; IOP Publishing; Volume: 436; Linguagem: Inglês

10.1086/187620

1538-4357

Jonathan Woo, G. W. Clark, Charles S. Day, F. Nagase, Toshiaki Takeshima,

Geological and Geochemical Analysis

view Abstract Citations (34) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ASCA Measurements of the Grain-scattered X-Ray Halos of Eclipsing Massive X-Ray Binaries: VELA X-1 and Centaurus X-3 Woo, Jonathan W. ; Clark, George W. ; Day, Charles S. R. ; Nagase, Fumiaki ; Takeshima, Toshiaki Abstract We have measured the decaying dust-scattered X-ray halo of Cen X-3 during its binary eclipse with the ASCA solid-state imaging spectrometer (SIS). The surface brightness profile (SBP) of the image in the low-energy band (0.5-3 keV) lies substantially above the point-spread function (PSF) of the X-ray telescope, while the SBP in the high-energy band (5-10 keV) exhibits no significant deviation. By contrast, the SBPs of Vela X-1 during its eclipse are consistent with the PSF in both the low- and high-energy bands -- strong evidence that a dust halo is indeed present in Cen X-3. Accordingly, we modeled the SBP of Cen X-3 taken from six consecutive time segments under the principal assumptions that the dust is distributed uniformly along a segment of the line of sight, the grains have a power-law size distribution, and the low-energy source flux was the same function of orbital phase before as during our observation. The best-fit set of parameters included a grain density value of 1.3 g/cu cm, substanially less than the density of 'astronomical silicate.' This result supports the idea that interstellar grains are 'fluffy' aggregates of smaller solid particles. We attribute the failure to detect a halo of Vela X-1 during its eclipse phase to extended strong circumsource absorption that probably occurred before the eclipse and allowed the halo to decay away before the observation began. Publication: The Astrophysical Journal Pub Date: November 1994 DOI: 10.1086/187620 Bibcode: 1994ApJ...436L...5W Keywords: Eclipsing Binary Stars; Halos; Massive Stars; Pulsars; X Ray Binaries; X Ray Scattering; Imaging Spectrometers; Interstellar Matter; Light Curve; Astrophysics; STARS: BINARIES: ECLIPSING; ISM: DUST; EXTINCTION; STARS: PULSARS: INDIVIDUAL NAME: VELA X-1; STARS: PULSARS: INDIVIDUAL NAME: CENTAURUS X-3; X-RAYS: STARS full text sources ADS | data products SIMBAD (3) HEASARC (1)