Radio monitoring of the periodically variable IR source LRLL 54361: No direct correlation between the radio and IR emissions

Abstract

LRLL 54361 is an infrared source located in the star forming region IC 348 SW. Remarkably, its infrared luminosity increases by a factor of 10 during roughly one week every 25.34 days. To understand the origin of these remarkable periodic variations, we obtained sensitive 3.3 cm JVLA radio continuum observations of LRLL 54361 and its surroundings in six different epochs: three of them during the IR-on state and three during the IR-off state. The radio source associated with LRLL 54361 remained steady and did not show a correlation with the IR variations. We suggest that the IR is tracing the results of fast (with a timescale of days) pulsed accretion from an unseen binary companion, while the radio traces an ionized outflow with an extent of $\sim$100 AU that smooths out the variability over a period of order a year. The average flux density measured in these 2014 observations, 27$\pm$5 $\mu$Jy, is about a factor of two less than that measured about 1.5 years before, $53\pm$11 $\mu$Jy, suggesting that variability in the radio is present, but over larger timescales than in the IR. We discuss other sources in the field, in particular two infrared/X-ray stars that show rapidly varying gyrosynchrotron emission.