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Titolo: The 1999 Hercules X-1 anomalous low state
Autore: Coburn, W; Heindl, WA; Wilms, J; Gruber, DE; Staubert, R; Rothschild, RE; Postnov, KA; Shakura, N; Risse, P; Kreykenbohm, I; Pelling, MR;
- Indirizzi:
- Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA Univ Calif San Diego La Jolla CA USA 92093 ce Sci, La Jolla, CA 92093 USA Univ Tubingen, Inst Astron & Astrophys, D-72076 Tubingen, Germany Univ Tubingen Tubingen Germany D-72076 rophys, D-72076 Tubingen, Germany Moscow MV Lomonosov State Univ, Fac Phys, Moscow 119899, Russia Moscow MV Lomonosov State Univ Moscow Russia 119899 oscow 119899, Russia Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119899, Russia Moscow MV Lomonosov State Univ Moscow Russia 119899 oscow 119899, Russia
- Titolo Testata:
- ASTROPHYSICAL JOURNAL
fascicolo: 1,
volume: 543,
anno: 2000,
parte:, 1
pagine: 351 - 358
- SICI:
- 0004-637X(20001101)543:1<351:T1HXAL>2.0.ZU;2-3
- Fonte:
- ISI
- Lingua:
- ENG
- Soggetto:
- RAY-TIMING-EXPLORER; 35-DAY CYCLE; HZ HERCULIS; PRE-ECLIPSE; DIPS; ACCRETION; RXTE; PERFORMANCE; SPECTRUM; PERIOD;
- Keywords:
- accretion, accretion disks; binaries : eclipsing; pulsars : individual (Hercules X-1); stars : neutron; X-rays : stars;
- Tipo documento:
- Article
- Natura:
- Periodico
- Settore Disciplinare:
- Physical, Chemical & Earth Sciences
- Citazioni:
- 40
- Recensione:
- Indirizzi per estratti:
- Indirizzo: Coburn, W Univ Calif San Diego, Ctr Astrophys & Space Sci, 9500 Gilman Dr,Code 0424,La Jolla, CA 92093 USA Univ Calif San Diego 9500 Gilman Dr,Code 0424 La Jolla CA USA 92093
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- Citazione:
- W. Coburn et al., "The 1999 Hercules X-1 anomalous low state", ASTROPHYS J, 543(1), 2000, pp. 351-358
Abstract
A failed main-on in the 35 day cycle of Her X-l was observed with the Rossi X-Ray Timing Explorer on 1999 April 26. Exceptions to the normal 35 day cycle have been seen only twice before-in 1983 and again in 1993. We presenttiming and spectral results of this latest anomalous low state (ALS) alongwith comparisons to the main-on and normal low states. Pulsations were observed in the 3-18 keV band with a fractional rms variation of 0.037 +/- 0.003. Spectral analysis indicates that the ALS spectrum has the same shape asthe main-on but is modified by heavy absorption and scattering. We find that 70% of the observed emission has passed through a cold absorber (N-H = 5.0 x 10(23) cm(-2)). This partially absorbing spectral fit can be applied to the normal low state with similar results. We find that the ALS observations may be interpreted as a decrease in inclination of the accretion disk causing the central X-ray source to be obscured over the entire 35 day cycle.
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Documento generato il 25/05/13 alle ore 18:29:37