Results from DROXO - III. Observation, source list, and X-ray properties of sources detected in the “Deep Rho Ophiuchi XMM-Newton Observation”
Results from DROXO - III. Observation, source list, and X-ray properties of sources detected in the “Deep Rho Ophiuchi XMM-Newton Observation”
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DROXO - III 观测结果、源列表以及“深 Rho Ophiuchi XMM-牛顿观测”中检测到的源的 X 射线特性
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发表时间：
2010
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通讯作者：
G. Giardino
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作者：
I. Pillitteri;I. Pillitteri;I. Pillitteri;S. Sciortino;E. Flaccomio;B. Stelzer;G. Micela;F. Damiani;L. Testi;T. Montmerle;N. Grosso;N. Grosso;F. Favata;G. Giardino
语境。来自非常年轻恒星的 X 射线是强大的探测器，可用于研究恒星形成最初阶段的工作机制以及非常年轻恒星中 X 射线发射的起源。目标。我们展示了使用名为 DROXO 的 XMM-Newton 大型程序对 Rho Ophiuchi 云进行 500 ks 长时间观测的结果，旨在研究深嵌年轻恒星物体 (YSO) 的 X 射线发射。方法。 DROXO计划期间获取的数据通过SAS软件进行缩减，并在时间和能量上进行过滤，以提高检测源的信噪比；获得光曲线和光谱。结果。我们检测到 111 个源，其中 61 个与通过 ISOCAM 红外观测识别出的蛇夫座 YSO 相关。具体来说，我们检测到了 11 个 I 类物体中的 9 个、48 个 II 类物体中的 31 个和 16 个 III 类物体中的 15 个。 21 个 III 级候选物体中的 6 个物体也被检测到。同时，我们建议在 logLx [erg/s] < 28.3 时仍未检测到的 15 个 III 类候选者与云群无关。全球检出率约为 64%。我们已经实现了~5 × 10 −15 erg s −1 cm −2 的通量灵敏度。对于在猎户座星云中观察到的 Teff ≤ 5000 K 或 0.7 M� 的恒星，heLX 与 Lbol 的比率显示饱和度为~−3.5。等离子体温度和光谱吸收显示出随 YSO 类别的下降，I 类 YSO 比 II 类和 III 类 YSO 更热且吸收更多。在 2MASS 和斯皮策星表中具有红外对应物的一颗恒星 (GY 266) 中，我们在 X 射线光谱中检测到了软过量，这最适合由比等离子体主要热成分吸收更少的冷热成分来拟合。这种柔软的成分暗示等离子体是由于致密的星周材料外部的射流而受到冲击而加热的。
Context. X-rays from very young stars are powerful probes to investigate the mechanisms at work in the very first stages of the star formation and the origin of X-ray emission in very young stars. Aims. We present results from a 500 ks long observation of the Rho Ophiuchi cloud with a XMM-Newton large program named DROXO, aiming at studying the X-ray emission of deeply embedded young stellar objects (YSOs). Methods. The data acquired during the DROXO program were reduced with SAS software, and filtered in time and energy to improve the signal to noise of detected sources; light curves and spectra were obtained. Results. We detected 111 sources, 61 of them associated with ρ Ophiuchi YSOs as identified from infrared observations with ISOCAM. Specifically, we detected 9 out of 11 Class I objects, 31 out of 48 Class II and 15 out 16 Class III objects. Six objects out of 21 classified Class III candidates are also detected. At the same time we suggest that 15 Class III candidates that remain undetected at logLx [erg/s] < 28.3 are not related to the cloud population. The global detection rate is ∼64%. We have achieved a flux sensitivity of ∼5 × 10 −15 erg s −1 cm −2 .T heLX to Lbol ratio shows saturation at a value of ∼−3.5 for stars with Teff ≤ 5000 K or 0.7 M� as observed in the Orion Nebula. The plasma temperatures and the spectrum absorption show a decline with YSO class, with Class I YSOs being hotter and more absorbed than Class II and III YSOs. In one star (GY 266) with infrared counterpart in 2MASS and Spitzer catalogs we have detected a soft excess in the X-ray spectrum, which is best fitted by a cold thermal component less absorbed than the main thermal component of the plasma. This soft component hints at plasma heated by shocks due to jets outside the dense circumstellar material.