The New Variable Nebula in Cepheus - A Sign of a Recent FUOr Event
ATel #13834; Bringfried Stecklum (Thueringer Landessternwarte Tautenburg)
on 25 Jun 2020; 23:36 UT
Credential Certification: Bringfried Stecklum (stecklum@tls-tautenburg.de)
Subjects: Infra-Red, Variables, Young Stellar Object
Very recently, Borisov & Denisenko reported on the detection of a new variable nebula in Cepheus (ATel #13832) which emerged in mid-2013 as evidenced by their analysis of PanSTARRS-1 images. The nebula is situated in the dark cloud TGU H642. The authors checked for past transients within 30" of the location but could not find any. Here we report on the detection of an outburst from a young stellar object (YSO) which very likely gave rise to the new nebula about 30" west of it. Our inspection of (NEO)WISE images taken in the W1 (3.4 micron) and W2 (4.6 micron) bands using the WiseView tool revealed the presence of a new source in NEOWISE frames which was not seen during the WISE mission. Thus, it appeared between 2011-01-11 (last WISE visit) and 2014-01-14 (first NEOWISE visit). The sequence of images can be seen using the (NEO)WISE animation link below. The object magnitudes on the discovery image are W1 = 13.75+/-0.07 and W2 = 11.40+/-0.02, respectively. Notably it brightened since then by 0.3 in W1 and 0.20 in W2 until 2019-07-18. During the WISE mission a fainter source of W1 = 14.79+/-0.22 and W2 = 13.24+/-0.04 was detected 2.5" east of the new object. If it is the precursor of the burster the brightness rise of the latter amounts to one and two magnitudes in W1 and W2, respectively. The new infrared source is located at R.A. = 21 37 23.5, Decl. = +66 51 45 (Equinox 2000), i.e. about 11" north of IRAS 21363+6638. It is likely the mid-infrared (MIR) counterpart of the IRAS source which was detected at 60 micron only. Remarkably, its outburst was accompanied by the appearance of an adjacent 3.4 micron nebulosity to the north-west. The emergence of this source, its MIR brightness increase as well as the steady light curve since more than five years argue for an FUOr-type accretion burst of a low-mass YSO which is harbored by the Planck cold core PGCC G105.50+10.83.
(NEO)WISE animation
