The JCMT Transient Survey: Four-year Summary of Monitoring the Submillimeter Variability of Protostars
The JCMT Transient Survey: Four-year Summary of Monitoring the Submillimeter Variability of Protostars
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JCMT 瞬态巡天：监测原恒星亚毫米变异性的四年总结
DOI：
10.3847/1538-4357/ac1679
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发表时间：
2021-07
期刊：
影响因子：
--
通讯作者：
Plovie Spencer
中科院分区：
文献类型：
--
作者：
Lee Yong-Hee;Johnstone Doug;Lee Jeong-Eun;Herczeg Gregory;Mairs Steve;Contreras-Peña Carlos;Hatchell Jennifer;Naylor Tim;Bell Graham S.;Bourke Tyler L.;Broughton Colton;Francis Logan;Gupta Aashish;Harsono Daniel;Liu Sheng-Yuan;Park Geumsook;Plovie Spencer
我们介绍了JCMT瞬变调查对附近八个恒星形成区(<；500pc)进行的每月亚毫米监测的四年调查结果。我们应用Lomb-Scarger周期图技术搜索和表征了295个亮度大于0.14 Jy BEAM-1的亚毫米峰值的可变性，其中包括22个盘源(II类)、83颗原恒星(0/I类)和190个非恒星源。我们发现了18个长期变星，它们都是原恒星。没有观测到单历元爆发或下降事件，也没有观察到固有的随机震源。我们根据长期变量的时间尺度将其分为三组：周期变量、曲线变量和线性变量。对于弯曲和周期情况，对于亮度大于~0.5Jy束流-1的源，相对于平均峰值亮度，可检测到的分数幅度为~4%。将我们的样本仅限于这些亮源，观察到的可变比例为37%(43个中的16个)。考虑到源的演化，我们发现0类和I类的明亮变星的比例相似。使用经验驱动的从亚毫米变率到质量吸积率变化的转换，预测有六个源(占整个样本的7%)将有长达数年的吸积事件，在此期间，过量质量增长到超过静止吸积质量总量的40%：两个先前已知的喷发I类源，V1647 Ori和EC 53(V371Ser)，以及四个0类源，Hop 356，Hop 373，Hop 383和West 40。考虑到整个原恒星集合，在几年的时间尺度上，插曲吸积的重要性是微不足道的--只占集合质量的几个百分点。然而，鉴于这一增长主要是由观测时间窗口量级上的事件主导的，仍然不确定事件的重要性是否会随着数十年的监测而继续上升。
We present the four-year survey results of monthly submillimeter monitoring of eight nearby (<500 pc) star-forming regions by the JCMT Transient Survey. We apply the Lomb-Scargle Periodogram technique to search for and characterize variability on 295 submillimeter peaks brighter than 0.14 Jy beam-1, including 22 disk sources (Class II), 83 protostars (Class 0/I), and 190 starless sources. We uncover 18 secular variables, all of them protostars. No single-epoch burst or drop events and no inherently stochastic sources are observed. We classify the secular variables by their timescales into three groups: Periodic, Curved, and Linear. For the Curved and Periodic cases, the detectable fractional amplitude, with respect to mean peak brightness, is ~4% for sources brighter than ~0.5 Jy beam-1. Limiting our sample to only these bright sources, the observed variable fraction is 37% (16 out of 43). Considering source evolution, we find a similar fraction of bright variables for both Class 0 and Class I. Using an empirically motivated conversion from submillimeter variability to variation in mass accretion rate, six sources (7% of our full sample) are predicted to have years-long accretion events during which the excess mass accreted reaches more than 40% above the total quiescently accreted mass: two previously known eruptive Class I sources, V1647 Ori and EC 53 (V371 Ser), and four Class 0 sources, HOPS 356, HOPS 373, HOPS 383, and West 40. Considering the full protostellar ensemble, the importance of episodic accretion on few years timescale is negligible-only a few percent of the assembled mass. However, given that this accretion is dominated by events on the order of the observing time window, it remains uncertain as to whether the importance of episodic events will continue to rise with decades-long monitoring.
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DOI：
10.1086/320657
发表时间：
2001-05
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Minho Choi
通讯作者：
Minho Choi
DOI：
10.3847/0067-0049/225/2/26
发表时间：
2016-08
期刊：
The Astrophysical Journal Supplement Series
影响因子：
--
作者：
Mi-Ryang Kim;C. Lee;M. Dunham;N. Evans II;Gwanjeong Kim;L. Allen
通讯作者：
Mi-Ryang Kim;C. Lee;M. Dunham;N. Evans II;Gwanjeong Kim;L. Allen
DOI：
10.1088/0004-637x/805/2/115
发表时间：
2015-03
期刊：
The Astrophysical Journal
影响因子：
--
作者：
E. Vorobyov;S. Basu
通讯作者：
E. Vorobyov;S. Basu
DOI：
10.1086/301003
发表时间：
1999-09
期刊：
The Astronomical Journal
影响因子：
--
作者：
K. Hodapp
通讯作者：
K. Hodapp
DOI：
10.1086/503193
发表时间：
2006-02
期刊：
The Astrophysical Journal
影响因子：
--
作者：
H. Kirk;D. Johnstone;J. di Francesco
通讯作者：
H. Kirk;D. Johnstone;J. di Francesco