Letters to the Editor

The outburst of an embedded low-mass YSO in L1641^⋆

A. Caratti o Garatti¹, R. Garcia Lopez¹, A. Scholz¹, T. Giannini², J. Eislöffel³, B. Nisini², F. Massi⁴, S. Antoniucci² and T. P. Ray¹

¹ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
e-mail: alessio@cp.dias.ie
² INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio, Italy
³ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
⁴ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Received: 15 November 2010
Accepted: 30 November 2010

Abstract

Context. Strong outbursts in very young and embedded protostars are rare and not yet fully understood. They are believed to originate from an increase in the mass accretion rate (Ṁ_acc) onto the source.

Aims. 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.

Methods. 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.

Results.[CTF93]216-2 increased in brightness by  ~4.6, 4.0, 3.8, and 1.9 mag in the J, H, K_s bands and at 24 μm, respectively, corresponding to an L_bol increase of  ~20 L_⊙. Its early spectrum, probably taken soon after the outburst, displays a steep almost featureless continuum, with strong CO band heads and H₂O broad-band absorption features, and Brγ line in emission. A later spectrum reveals more absorption features, allowing us to estimate T_eff ~ 3200 K, M_∗ ~ 0.25   M_⊙, and Ṁ_acc ~ 1.2 × 10^-6 M_⊙ yr^-1. This makes it one of the lowest mass YSOs with a strong outburst so far discovered.