V838 Monocerotis附近瞬态X射线源的XMM-牛顿探测
XMM-Newton detection of a transient X-ray source in the vicinity of V838 Monocerotis
摘要：
我们报道了2008年3月XMM-Newton/EPIC在神秘的V838 Mon星附近（约6”以内）探测到的一个发光（L_X ~ 10^32-33 erg/s）的可变X射线源，该星在2002年初经历了一次壮观的爆发。XMM-牛顿X射线源的光谱模型表明存在两种等离子体成分，其特征温度分别为TX ~ 2 × 10^6 K和~ 1.5 × 10^7 K，并被吸收柱（N_H ~ 4 × 10^21 cm ^-2）衰减，这与朝向V838 Mon（A_V ~ 2）测量的可见消光一致。在V838 Mon附近，Chandra/ACIS-S在爆发后约一年或最近的2010年1月进行的观测中没有发现这样的发光源。这两个XMM源光谱分量似乎在空间上是边缘分辨的，硬分量的空间质心比宽带源或软源分量更靠近V838 Mon的位置（在~2”内）;然而，如果在V838 Mon或附近有两个源，钱德拉未检测意味着它们都是可变的。另一种可能性是存在单一的变量源，并且明显的空间分离实际上可能是由于光子计数统计，或者可能是起源的工具。我们考虑放置的约束条件的X射线检测和nondetection上的恒星合并模型为2002年V838 Mon爆发，其中自旋合并产品驱动一个强大的磁发电机。或者，X射线源的瞬态行为可能表明，X射线是V838 Mon的喷出物与其早期型（B3 V）伴星之间相互作用的结果。
英文摘要：
We report the XMM-Newton/EPIC detection in 2008 March of a luminous (L_X ~ 10^32-33 erg/s), variable X-ray source in the vicinity (within ~6") of the enigmatic star V838 Mon, which underwent a spectacular outburst in early 2002. Spectral modeling of the XMM-Newton X-ray source indicates the presence of two plasma components with characteristic temperatures of TX ~ 2x10^6K and ~1.5x10^7K, attenuated by an absorbing column (N_H ~ 4 x 10^21cm^-2) that is consistent with the visual extinction measured toward V838 Mon (A_V ~ 2). No such luminous source was detected in the immediate vicinity of V838 Mon in Chandra/ACIS-S observations obtained about one year after outburst or, most recently, in 2010 January. The two XMM source spectral components appear to be marginally spatially resolved, with the spatial centroid of the hard component lying closer to (within ~2" of) the position of V838 Mon than the broad-band source or the soft source component; however, if there are two sources at or near V838 Mon, the Chandra nondetections would imply that both of them are variable. An alternative is that there is a single variable source, and that the apparent spatial separation may actually be due to photon-counting statistics or is perhaps instrumental in origin. We consider constraints placed by the X-ray detection and nondetections on a stellar merger model for the 2002 V838 Mon outburst, in which the spun-up merger product drives a powerful magnetic dynamo. Alternatively, the transient behavior of the X-ray source could indicate that the X-rays arose as a consequence of an interaction between V838 Mon's ejecta and its early-type (B3 V) companion.
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