A Gigantic Mid-infrared Outburst in an Embedded Class I Young Stellar Object J064722.95+031644.6

Abstract

We report the serendipitous discovery of a giant mid-infrared outburst from a previously unknown source near a star-forming region in the constellation Monoceros. The source gradually brightened by a factor of 5 from 2014–2016 before an abrupt rise by a factor of more than 100 in 2017. A total amplitude increase of >500 at 4.5 μ m has since faded by a factor of about 10. Prior to the outburst, it was only detected at wavelengths longer than 1.8 μ m in UKIDSS, Spitzer, and Herschel with a spectral energy distribution of a Class I young stellar object (YSO). It has not been detected in recent optical surveys, suggesting that it is deeply embedded. With a minimum distance of 3.5 kpc, the source has a bolometric luminosity of at least 9 L _☉ in the quiescent state and 400 L _☉ at the peak of the eruption. The maximum accretion rate is estimated to be at least a few 10 ^−5 M _☉ yr ^−1 . It shares several common properties with another eruptive event, WISE J142238.82-611553.7: exceptionally large amplitude, featureless near-infrared spectrum with the exception of H _2 lines, intermediate eruption duration, an embedded Class I YSO, and a low radiative temperature (6.5 au during the outburst.

Keywords

• Eruptive variable stars
• FU Orionis stars
• Young stellar objects