The outburst of an embedded low-mass YSO in L1641

TL;DR

This paper reports the discovery and detailed analysis of a rare, strong outburst in a very low-mass embedded young stellar object, providing insights into accretion processes in early stellar evolution.

Contribution

It presents the first detailed photometric and spectroscopic follow-up of an outburst in a low-mass embedded YSO, revealing its properties and accretion dynamics.

Findings

Brightness increased by up to 4.6 magnitudes in near-IR bands.

Estimated mass accretion rate of approximately 1.2x10^{-6} solar masses per year.

Identified as one of the lowest mass YSOs exhibiting such an outburst.

Abstract

Strong outbursts in very young and embedded protostars are rare and not yet fully understood. They are believed to originate from an increase of the mass accretion rate onto the source. We report the discovery of a strong outburst in a low-mass embedded young stellar object (YSO), namely 2MASS-J05424848-0816347 or [CTF93]216-2, as well as its photometric and spectroscopic follow-up. Using near- to mid-IR photometry and NIR low-resolution spectroscopy, we monitor the outburst, deriving its magnitude, duration, as well as the enhanced accretion luminosity and mass accretion rate. [CTF93]216-2 increased in brightness by ~4.6, 4.0, 3.8, and 1.9 mag in the J, H, Ks bands and at 24 um, respectively, corresponding to an L_bol increase of ~20 L_sun. Its early spectrum, probably taken soon after the outburst, displays a steep almost featureless continuum, with strong CO band heads and H_2O broad-band absorption features, and Br gamma line in emission. A later spectrum reveals more absorption features, allowing us to estimate T_eff~3200 K, M~0.25 M_sun, and mass accretion rate~1.2x10^{-6} M_sun yr^{-1}. This makes it one of the lowest mass YSOs with a strong outburst so far discovered.