Periodic Eruptive Variability of the Isolated Pre-Main Sequence Star V347 Aurigae

TL;DR

V347 Aurigae, an isolated pre-main sequence star, exhibits decades-long periodic brightness variations of about 2 magnitudes every 160 days, linked to accretion activity and possibly caused by an unseen companion or disk structure.

Contribution

This study provides multi-epoch photometry and spectroscopy of V347 Aurigae, revealing its periodic eruptive variability and spectral characteristics, suggesting a new perspective on isolated young stellar objects.

Findings

Decades-long periodic brightness variations of ~160 days.

Spectroscopic evidence of accretion and jet activity.

No binarity detected in high-resolution observations.

Abstract

V347 Aurigae is associated with the small dark cloud L1438 and appears to be an isolated pre-main sequence star located at distance $d\approx$200 pc. Multi-epoch, archival photometry reveals periodic brightness variations with amplitude $V\approx2.0$ magnitudes occurring on timescales of $\sim$160 days that have persisted for decades. Regular cadence, optical imaging of the source with the Zwicky Transient Facility shows that a small reflection nebula illuminated by V347 Aur also fluctuates in brightness, at times fading completely. Multi-epoch, Keck/HIRES data suggests the presence of two distinct spectral components: a prominent emission-line dominated spectrum with a heavily veiled continuum correlated with the bright photometric state, and an M-type absorption line spectrum associated with quiescence. All spectra exhibit strong Balmer and He I line emission, consistent with accretion, as well as high velocity emission arising from the forbidden transitions of [O I], [N II], and [S II] that are generally associated with collimated jets and disk winds. There is no evidence in existing high dispersion spectroscopy or high resolution imaging for binarity of V347 Aur. The repeating outburst events are possibly linked to accretion instabilities induced by an undetected companion or a structure within the circumstellar disk that periodically increases the mass accretion rate. V347 Aur is perhaps analogous to an EXor-type variable, though more regularly recurring.