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arXiv 1301.3152astro-ph.SR
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用中红外测光系统巡天喷发的年轻恒星天体

A systematic survey for eruptive young stellar objects using mid-infrared photometry

Aleks Scholz, Dirk Froebrich, Kenneth Wood

摘要:

年轻恒星天体(YSO)的吸积至少部分是偶发的,即高吸积率(“爆发”)的时期被静止阶段所穿插。这些爆发表现为爆发性变异。在这里,我们提出了一个系统的调查喷发YSO的目的是限制吸积爆发的频率。我们比较中红外测光从斯皮策和WISE分离约5年的两个样本的YSO,在附近的恒星形成区和银河系平面,每个包括约4000个年轻的来源。所有在3.6和4.5 μ处的亮度在两个时期之间增加至少1等的天体都可能是爆发变星和爆发候选者。对于这些天体,我们在近红外波段进行了跟踪观测。我们发现了两个新的爆发变量在银河系平面,这可能是FU Ori-type对象,与K波段振幅超过1.5马格。一个对象已知进行吸积爆发,V2492天鹅座,是恢复我们的搜索以及。此外,年轻的恒星ISO-Oph-50,以前被怀疑是一个爆发的对象,被发现可以更好地解释为一个磁盘与不同的星周遮蔽。总的来说,4000个YSO样本中的突发事件数量为1 - 4。假设所有的YSO都经历了幕式吸积,这个约束可以用来表明强吸积阶段(> 10 ^-6 Msol/yr)的发生间隔大约为10 ^4年,最有可能在5000年到50000年之间。这是一致的流出的动力学时间尺度,但不与流出的排放节的分离,表明情节吸积可以触发或停止准直大规模的流出。

英文摘要:

Accretion in young stellar objects (YSOs) is at least partially episodic, i.e. periods with high accretion rates ('bursts') are interspersed by quiescent phases. These bursts manifest themselves as eruptive variability. Here we present a systematic survey for eruptive YSOs aiming to constrain the frequency of accretion bursts. We compare mid-infrared photometry from Spitzer and WISE separated by ~5 yr for two samples of YSOs, in nearby star forming regions and in the Galactic plane, each comprising about 4000 young sources. All objects for which the brightness at 3.6 and 4.5 mu is increased by at least 1 mag between the two epochs may be eruptive variables and burst candidates. For these objects, we carry out follow-up observations in the near-infrared. We discover two new eruptive variables in the Galactic plane which could be FU Ori-type objects, with K-band amplitudes of more than 1.5 mag. One object known to undergo an accretion burst, V2492 Cyg, is recovered by our search as well. In addition, the young star ISO-Oph-50, previously suspected to be an eruptive object, is found to be better explained by a disk with varying circumstellar obscuration. In total, the number of burst events in a sample of 4000 YSOs is 1-4. Assuming that all YSOs undergo episodic accretion, this constraint can be used to show that phases of strong accretion (>10^-6 Msol/yr) occur in intervals of about 10^4 yr, most likely between 5000 and 50000 yr. This is consistent with the dynamical timescales for outflows, but not with the separations of emission knots in outflows, indicating that episodic accretion could either trigger or stop collimated large-scale outflows.

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