Investigating episodic accretion in a very low-mass young stellar object
Artikel i vetenskaplig tidskrift, 2020

Very low-mass Class I protostars have been investigated very little thus far. Variability of these young stellar objects (YSOs) and whether or not they are capable of strong episodic accretion is also left relatively unstudied. Aims. We investigate accretion variability in IRS 54 (YLW52), a Class I very low-mass protostar with a mass of M∗ ∼ -0.2 M⊙. Methods. We obtained spectroscopic and photometric data with VLT/ISAAC and VLT/SINFONI in the near-infrared (J, H, and K bands) across four epochs (2005, 2010, 2013, and 2014). We used accretion-tracing lines (Paβ and Brγ) and outflow-tracing lines (H2 and [Fe II]) to examine physical properties and kinematics of the object. Results. A large increase in luminosity was found between the 2005 and 2013 epochs of more than 1 magnitude in the K band, followed in 2014 by a steep decrease. Consistently, the mass accretion rate (Macc) rose by an order of magnitude from ∼10-8 M⊙ yr-1 to ∼10-7 M⊙ yr-1 between the two early epochs. The visual extinction (AV) has also increased from ∼15 mag in 2005 to ∼24 mag in 2013. This rise in AV in tandem with the increase in Macc is explained by the lifting up of a large amount of dust from the disc of IRS 54, following the augmented accretion and ejection activity in the YSO, which intersects our line of sight due to the almost edge-on geometry of the disc. Because of the strength and timescales involved in this dramatic increase, this event is believed to have been an accretion burst possibly similar to bursts of EXor-type objects. IRS 54 is the lowest mass Class I source observed to have an accretion burst of this type, and therefore potentially one of the lowest mass EXor-type objects known so far.

Stars: individual: IRS 54

Techniques: spectroscopic

Infrared: stars

Stars: protostars


Accretion disks

Stars: jets


C. Stock

Trinity College Dublin

Dublin Institute for Advanced Studies

A. Caratti o. Garatti

University College Dublin

Dublin Institute for Advanced Studies

P. McGinnis

Dublin Institute for Advanced Studies

R. Garcia-Lopez

Dublin Institute for Advanced Studies

University College Dublin

S. Antoniucci

Osservatorio Astronomico di Roma

Rubén Fedriani

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Tom Ray

Trinity College Dublin

Dublin Institute for Advanced Studies

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 643 A181


Subatomär fysik


Astronomi, astrofysik och kosmologi



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