Compact radio sources in the vicinity of the ultracompact HII region G78.4+2.6

TL;DR

This study identifies four new compact radio sources near the ultracompact HII region G78.4+2.6 using VLA observations, suggesting they may be pre-main sequence stars, with one source showing rapid radio variability.

Contribution

First detection of multiple compact radio sources near G78.4+2.6, including variable emission, supporting their association with young stellar objects.

Findings

Four new compact radio sources identified near G78.4+2.6

One source shows variability on hours timescale

Additional sources detected northwest of the HII region

Abstract

Using the Very Large Array (VLA) at 3.6~cm we identify four new compact radio sources in the vicinity of the cometary HII region G78.4+2.6 (VLA~1). The four compact radio sources (named VLA~2 to VLA~5), have near-infrared counterparts, as seen in the 3.6 $\mu$m Spitzer image. One of them (VLA~5) clearly shows evidence of radio variability in a timescale of hours. We explore the possibility that these radio sources are associated with pre-main sequence (PMS) stars in the vicinity of the UC HII region G78.4+2.6. Our results favor the smaller distance value of 1.7 kpc for G78.4+2.6. In addition to the detection of the radio sources in the vicinity of G78.4+2.6, we detected another group of five sources which appear located about 3' to the northwest of the HII region. Some of them exhibit extended emission.