Radio Variability Survey of Very Low Luminosity Protostars

TL;DR

This study investigates radio variability in very low luminosity protostars, detecting magnetic activity-related outbursts and suggesting fossil magnetic fields as a possible cause, with about 20-30% showing variability.

Contribution

First radio variability survey of very low luminosity protostars, revealing magnetic flares possibly driven by fossil magnetic fields despite their young age.

Findings

Detected radio outburst in IRAM 04191+1522 IRS with a timescale of about 20 days.

Approximately 20-30% of such protostars are radio variable.

Radio flares likely caused by magnetic activity, possibly from fossil magnetic fields.

Abstract

Ten very low luminosity objects were observed multiple times in the 8.5 GHz continuum in search of protostellar magnetic activities. A radio outburst of IRAM 04191+1522 IRS was detected, and the variability timescale was about 20 days or shorter. The results of this survey and archival observations suggest that IRAM 04191+1522 IRS is in active states about half the time. Archival data show that L1014 IRS and L1148 IRS were detectable previously and suggest that at least 20%-30% of very low luminosity protostars are radio variables. Considering the variability timescale and flux level of IRAM 04191+1522 IRS and the previous detection of the circular polarization of L1014 IRS, the radio outbursts of these protostars are probably caused by magnetic flares. However, IRAM 04191+1522 IRS is too young and small to develop an internal convective dynamo. If the detected radio emission is indeed coming from magnetic flares, the discovery implies that the flares may be caused by the fossil magnetic fields of interstellar origin.