A sudden radio brightening of GRS 1915+105 with Metsahovi Radio Observatory at 37 GHz

ATel #12839; Karri Koljonen (FINCA/MRO), Rafael Vera (MRO), Anne Lahteenmaki (MRO), Merja Tornikoski (MRO)
on 5 Jun 2019; 06:40 UT
Credential Certification: Karri Koljonen (karri.koljonen@utu.fi)

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We report an enhanced flux density at 37 GHz of the microquasar GRS 1915+105 coinciding a large X-ray flare as observed by MAXI/GSC. GRS 1915+105 has been in an unusual, low luminosity state for the past month (e.g. ATels: #12742, #12743, #12755) interspersed by short, intense X-ray flares (ATels: #12761, #12787, #12793, #12805), with enhanced flux densities observed also in the radio (ATel: #12773). We have monitored the source with the 13.7-m diameter Aalto University Metsahovi Radio Observatory telescope, which is a radome enclosed Cassegrain type antenna in Finland (60 d 13' 04'' N, 24 d 23' 35'' E). The source has stayed below the detection limit of the telescope (0.2 Jy in optimal conditions) but observations that were taken on 3 June 2019 at UTC 00:11 and UTC 01:23 both gave a quick-look flux density of 0.30+-0.05 Jy at 37 GHz. During the same time, a large X-ray flare was observed with MAXI/GSC with 2-20 keV photon fluxes reaching ~6 photons/cm^2/s (monitoring data from http://maxi.riken.jp ) indicating strong flaring activity across the electromagnetic spectrum. We encourage further multiwavelength observations.