Transient nature of radio source NVSS J1957+35

Abstract

We have searched for transient and variable radio sources in the field of Galactic micro-quasar Cygnus X-1 near 1.4 GHz (L band) using data from the Karl G. Jansky Very Large Array. We used twenty years of data between 1983 and 2003. We found a source NVSS J1957+35 showing transient behavior. The source was also mentioned earlier in NVSS and WENSS catalog but its transient nature was not reported earlier. The source is located 23.8 arcminutes far from Cygnus X-1. It is detected many times during the span of our study and it varied between less than 1.9 mJy (3r) to 201 mJy. NVSS J195754+353513 also showed high intra-day variability. In one occasion, the source rose from 15 mJy to 170 mJy within 700 s. We detected circularly polarized emission from the source for a limited number of cases with fractional circular polarization varies between 0.14 and 0.17. 2MASS J19575420+3535152 may be the near-infrared counterpart of the source. We compared the properties of the source with other Galactic transient sources having similar properties. The nature of the source is still unknown. We discussed the possible nature of the source. 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.