PTF 14jg: The Remarkable Outburst and Post-Burst Evolution of a Previously Anonymous Galactic Star

Abstract

We report the outbursting source PTF 14jg, which prior to the onset of its late 2013 eruption, was a faint, unstudied, and virtually uncatalogued star. The salient features of the PTF 14jg outburst are: (i) projected location near the W4 HII region and radial velocity consistent with physical association; (ii) a lightcurve that underwent a $\sim$6-7 mag optical (R-band) through mid-infrared (L-band) brightening on a few month time scale, that peaked and then faded by $\sim$3 mag, but plateaued still $>$3.5 mag above quiescence by $\sim$8 months post-peak, lasting to at least five years after eruption; (iii) strong outflow signatures, with velocities reaching -530 km/s; (iv) a low gravity and broad ($\sim$100-150 km/s FWHM) optical absorption line spectrum that systematically changes its spectral type with wavelength; (v) lithium; and (vi) ultraviolet and infrared excess. We tentatively identify the outburst as exhibiting characteristics of a young star FU Ori event. However, the burst would be unusually hot, with an absorption spectrum exhibiting high-excitation ($\sim$11,000-15,000 K) lines in the optical, and no evidence of CO in the near-infrared, in addition to exhibiting an unusual lightcurve. We thus also consider alternative scenarios including various forms of novae, nuclear burning instabilities, massive star events, and mergers -- finding them all inferior to the atypically hot FU Ori star classification. The source eventually may be interpreted as a new category of young star outburst with larger amplitude and shorter rise time than most FU Ori-like events. Continued monitoring of the lightcurve and spectral evolution will reveal its true nature.

Accepted to ApJ

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Cited by in corpus (13)

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• The New EXor Outburst of ESO-H-alpha~99 observed by Gaia ATLAS and TESS
• Discovery of a mid-infrared protostellar outburst of exceptional amplitude
• Magnetically-activated accretion outbursts of pre-main sequence discs
• A multi-epoch, multi-wavelength study of the classical FUor V1515 Cyg approaching quiescence
• Measuring Optical Extinction Towards Young Stellar Objects Using Diffuse Interstellar Bands
• Outbursting Young Stellar Object PGIR 20dci in the Perseus Arm
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• Gaia21bty: An EXor lightcurve exhibiting an FUor spectrum
• Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO
• Gaia20bdk -- a new FUor in Sh 2-301 Star Forming Region