Catching the Next Burst: the periodic young stellar object EC 53 in Serpens Main is sharply brightening at 850 microns and at near-IR H-band and K-band

ATel #11614; Doug Johnstone (NRC Herzberg Astronomy and Astrophysics, University of Victoria), Steve Mairs (East Asian Observatory), Tim Naylor (University of Exeter), Carlos Contreras Pena (University of Exeter), Watson Varricatt (UKIRT), Klaus Hodapp (University of Hawaii), Gregory J. Herczeg (Kavli Institute for Astronomy and Astrophysics), Jeong-Eun Lee (Kyung Hee University), Hyunju Yoo (Kyung Hee University), Graham S. Bell (East Asian Observatory), Geoffrey C. Bower (Academia Sinica Institute of Astronomy and Astrophysics), Yuri Aikawa (University of Tokyo), Huei-Ru Vivien Chen (National Tsing Hua University), Jennifer Hatchell (University of Exeter), Sunkyung Park (Kyung Hee University)
on 7 May 2018; 01:57 UT
Credential Certification: Doug Johnstone (doug.johnstone@nrc-cnrc.gc.ca)

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As part of our young stellar object (YSO) sub-mm monthly monitoring programme, the JCMT-Transient Survey (Herczeg et al. 2017 ApJ, 849, 43; Johnstone et al. 2018 ApJ, 854, 31), we are using SCUBA2 to monitor the 850 micron peak brightness of the YSO EC 53 (R.A. 18:29:51.2, Dec. +01:16:39.5) in Serpens Main (d=436 pc). The near-IR and sub-mm continuum emission are variable, with bursts that repeat every approximately 18 months (Hodapp et al. 2012, ApJ, 744, 56; Yoo et al. 2017, ApJ, 849, 69). Our recent measurements at 850 microns and at H- and K-band confirm that EC 53 is once again brightening. On March 30, 2018 the mean peak brightness of the source at 850 microns was 1.12 +/-0.02 Jy/bm, within the JCMT (15'') beam. On April 25, 2018 the mean peak brightness had risen to 1.26 +/- 0.03 Jy/bm, a ~12% increase over 25 days. While the absolute calibration of the JCMT is typically uncertain by about 10%, the relative calibration of the JCMT Transient Survey between epochs is significantly better, roughly 2% (Mairs et al. 2017 ApJ, 843, 55). Contemporaneous H-band photometry from the Liverpool Telescope and K-band photometry from UKIRT's Wide Field Camera (WFCAM) reveal that EC 53 has brightened by 0.8 mag in both bands over the last month. A finder chart and light curves at sub-mm and near-IR can be found at the URL linked below.

The YSO EC 53 (Yoo et al. 2017; Hodapp et al. 2012) is classified as a Class I source yet remains embedded in a significant dust envelope. Hodapp et al. (2012) first recognized the source as periodic with a roughly 18 month period, based on near-IR K-band observations taken over many years. The periodicity in the light curve of EC 53 is hypothesized to be due to variations in the accretion rate onto the young stellar object, possibly mediated by a companion star or planet forming within EC 53’s surrounding accretion disk.

Monitoring observations in the infrared, sub-mm/mm, and radio are highly encouraged as EC 53 proceeds through this burst. Peak brightness is anticipated somewhere between late May and early July, 2018. Determination of any significant lag between the near-IR brightening and the sub-mm brightening is essential for modelling the structure of the surrounding envelope. Near-IR spectra during this time are also desirable.

EC 53's Light Curves and Location.