RECENT X-RAY VARIABILITY OF {eta} CARINAE: THE QUICK ROAD TO RECOVERY

Journal Article · Mon Dec 20 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/725/2/1528· OSTI ID:21476691

Corcoran, M F; Hamaguchi, K ^[1]; Pittard, J M ^[2]; Russell, C M. P.; Owocki, S P ^[3]; Parkin, E R ^[4]; Okazaki, A ^[5]

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1. CRESST and X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)
3. Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
4. Institut d'Astrophysique et de Geophysique, Universite de Liege, 17, Allee du 6 Aout, B5c, B-4000 Sart Tilman (Belgium)
5. Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo 062-8605 (Japan)

We report continued monitoring of the superluminous binary system {eta} Car by the Proportional Counter Array on the Rossi X-ray Timing Observatory (RXTE) through the 2009 X-ray minimum. The RXTE campaign shows that the minimum began on 2009 January 16, consistent with the phasings of the two previous minima, and overall, the temporal behavior of the X-ray emission was similar to that observed by RXTE in the previous two cycles. However, important differences did occur. The 2-10 keV X-ray flux and X-ray hardness decreased in the 2.5 year interval leading up to the 2009 minimum compared to the previous cycle. Most intriguingly, the 2009 X-ray minimum was about 1 month shorter than either of the previous two minima. During the egress from the 2009 minimum the X-ray hardness increased markedly as it had during egress from the previous two minima, although the maximum X-ray hardness achieved was less than the maximum observed after the two previous recoveries. We suggest that the cycle-to-cycle variations, especially the unexpectedly early recovery from the 2009 X-ray minimum, might have been the result of a decline in {eta} Car's wind momentum flux produced by a drop in {eta} Car's mass loss rate or wind terminal velocity (or some combination), though if so the change in wind momentum flux required to match the X-ray variation is surprisingly large.

• OSTI ID: 21476691
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 725; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

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ELECTROMAGNETIC RADIATION
EMISSION
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MEASURING INSTRUMENTS
PROPORTIONAL COUNTERS
RADIATION DETECTORS
RADIATIONS
STARS
WIND
X RADIATION