A MULTIPHASE SUZAKU STUDY OF X-RAYS FROM τ Sco

被引:20
作者
Ignace, R. [1 ]
Oskinova, L. M. [2 ]
Jardine, M. [3 ]
Cassinelli, J. P. [4 ]
Cohen, D. H. [5 ]
Donati, J. -F. [6 ]
Townsend, R. H. D. [4 ]
ud-Doula, A. [7 ]
机构
[1] E Tennessee State Univ, Dept Phys & Astron, Johnson City, TN 37614 USA
[2] Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany
[3] Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland
[4] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
[5] Swarthmore Coll, Dept Phys & Astron, Swarthmore, PA 19081 USA
[6] Observ Midi Pyrenees, LATT, F-31400 Toulouse, France
[7] Penn State Worthington Scranton, Dept Phys, Dunmore, PA 18512 USA
关键词
stars: early-type; stars: individual (tau Sco); stars: magnetic field; stars:; winds; outflows; X-rays: stars; MAGNETIC-FIELD MEASUREMENTS; INFRARED-EMISSION LINES; DRIVEN STELLAR WINDS; SPECTROSCOPY; STARS; TOPOLOGY; SCORPII; VARIABILITY; ABSORPTION; DISCOVERY;
D O I
10.1088/0004-637X/721/2/1412
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We obtained relatively high signal-to-noise X-ray spectral data of the early massive star tau Sco (B0.2V) with the Suzaku X-ray Imaging Spectrometer (XIS) instrument. This source displays several unusual features that motivated our study: (1) redshifted absorption in UV P Cygni lines to approximately +250 km s(-1) suggestive of infalling gas, (2) unusually hard X-ray emission requiring hot plasma at temperatures in excess of 10 MK whereas most massive stars show relatively soft X-rays at a few MK, and (3) a complex photospheric magnetic field of open and closed field lines. In an attempt to understand the hard component better, X-ray data were obtained at six roughly equally spaced phases within the same epoch of tau Sco's 41 day rotation period. The XIS instrument has three operable detectors: XIS1 is back-illuminated with sensitivity down to 0.2 keV; XIS0 and XIS2 are front-illuminated with sensitivity only down to 0.4 keV and have an overall less effective area than XIS1. The XIS0 and XIS3 detectors show relatively little variability. In contrast, there is a approximate to 4 sigma detection of a approximate to 4% drop in the count rate of the XIS1 detector at one rotational phase. In addition, all three detectors show a approximate to 3% increase in count rate at the same phase. The most optimistic prediction of X-ray variability allows for a 40% change in the count rate, particularly near phases where we have pointings. Observed modulations in the X-ray light curve on the rotation cycle is an order of magnitude smaller than this, which places new stringent constraints on future modeling of this interesting magnetic massive star.
引用
收藏
页码:1412 / 1420
页数:9
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