1. The JCMT Transient Survey: Four-year Summary of Monitoring the Submillimeter Variability of Protostars
- Author
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Jonathan M. C. Rawlings, Helen Kirk, Dipen Sahu, Oscar Morata, Samuel Pearson, Yuri Aikawa, James Lane, Aashish Gupta, Jaehan Bae, Fujun Du, Shu-ichiro Inutsuka, Daniel Harsono, Geumsook Park, Giseon Baek, Yi-Jehng Kuan, Geoffrey C. Bower, Gregory J. Herczeg, Spencer Plovie, Aleks Scholz, Doug Johnstone, Chin-Fei Lee, Zhen Guo, Hsien Shang, Hyunju Yoo, Graham S. Bell, Jeong-Eun Lee, Yong-Hee Lee, Carlos Contreras-Peña, Woojin Kwon, Paula S. Teixeira, Sheng-Yuan Liu, Gerald H. Moriarty-Schieven, Bhavana Lalchand, Somnath Dutta, Jan Forbrich, Ziyan Xu, Shih-Yun Tang, Huei-Ru Vivien Chen, Dimitris Stamatellos, Jennifer Hatchell, Colton Broughton, Tim Naylor, Wen Ping Chen, Yao-Te Wang, Tanvi Sharma, Tyler L. Bourke, Andy Pon, Steve Mairs, Shih-Ping Lai, Logan Francis, Miju Kang, Scott Chapman, Tie Liu, University of St Andrews. School of Physics and Astronomy, and University of St Andrews. St Andrews Centre for Exoplanet Science
- Subjects
Variable stars ,FOS: Physical sciences ,01 natural sciences ,0103 physical sciences ,QB Astronomy ,Protostar ,FU Orionis stars ,14. Life underwater ,Pre-main sequence stars ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,QC ,QB ,Physics ,010308 nuclear & particles physics ,Star formation ,F510 ,Astronomy ,Astronomy and Astrophysics ,3rd-DAS ,Astrophysics - Astrophysics of Galaxies ,Young stellar objects ,Protostars ,QC Physics ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Transient (oscillation) ,Submillimeter astronomy - 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., Accepted for publication in the Astrophysical Journal
- Published
- 2021