Pulsed Accretion in a Variable Protostar

TL;DR

This paper reports the discovery of a very young protostar exhibiting regular pulsed accretion, with infrared luminosity increasing tenfold every 25.34 days, likely caused by an unseen binary companion, providing new insights into early stellar evolution.

Contribution

It presents the first observation of pulsed accretion in a protostar as young as 10^5 years, expanding understanding of accretion processes in early stellar development.

Findings

Infrared luminosity increases by a factor of 10 every 25.34 days.

The protostar shows periodic variability attributed to pulsed accretion.

The system is approximately ten times younger than previously known pulsed accretors.

Abstract

Periodic increases in luminosity arising from variable accretion rates have been predicted for some close pre-main sequence binary stars as they grow from circumbinary disks. The phenomenon is known as "pulsed accretion" and can affect the orbital evolution and mass distribution of young binaries, as well as the potential for planet formation in the circumbinary environment. Accretion variability is a common feature of young stars, with a large range of amplitudes and timescales as measured from multi-epoch observations at optical and infrared wavelengths. Periodic variations consistent with pulsed accretion have been seen in only a few young binaries via optical accretion tracers, albeit intermittently with accretion luminosity variations ranging from 0-50 percent from orbit to orbit. Here we report on a young protostar (age ~10^5 yr) that exhibits periodic variability in which the infrared luminosity increases by a factor of 10 in roughly one week every 25.34 days. We attribute this to pulsed accretion associated with an unseen binary companion. The strength and regularity of this accretion signal is surprising; it may be related to the very young age of the system, which is a factor of ten younger than the other pulsed accretors previously studied.