학술논문
The JCMT Transient Survey: Four Year Summary of Monitoring the Submillimeter Variability of Protostars
Document Type
Working Paper
Author
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; Moriarty-Schieven, Gerald H.; Scholz, Aleks; Sharma, Tanvi; Teixeira, Paula Stella; Wang, Yao-Te; Aikawa, Yuri; Bower, Geoffrey C.; Chen, Huei-Ru Vivien; Bae, Jaehan; Baek, Giseon; Chapman, Scott; Chen, Wen Ping; Du, Fujun; Dutta, Somnath; Forbrich, Jan; Guo, Zhen; Inutsuka, Shu-ichiro; Kang, Miju; Kirk, Helen; Kuan, Yi-Jehng; Kwon, Woojin; Lai, Shih-Ping; Lalchand, Bhavana; Lane, James M. M.; Lee, Chin-Fei; Liu, Tie; Morata, Oscar; Pearson, Samuel; Pon, Andy; Sahu, Dipen; Shang, Hsien; Stamatellos, Dimitris; Tang, Shih-Yun; Xu, Ziyan; Yoo, Hyunju
Source
Subject
Language
Abstract
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 $\sim4$ % for sources brighter than $\sim$ 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 of order the observing time-window, it remains uncertain as to whether the importance of episodic events will continue to rise with decades-long monitoring.
Comment: Accepted for publication in the Astrophysical Journal
Comment: Accepted for publication in the Astrophysical Journal