Sub-mm non-detection of GRS 1915+105
A. J. Tetarenko, E. Pattie, T. Maccarone (Texas Tech)
GRS 1915+105 is a famed microquasar known for its spectacular variability patterns and bright relativistic jets (Mirabel and Rodriguez 1994, Belloni et al. 2000). This system spent almost 26 years in a persistently high luminosity state, until 2018 when it began to fade (Negoro et al. 2018, Motta et al. 2019). By 2019, the system had settled into an extended faint X-ray state (Homan et al. 2019), which is now thought to be driven by Compton-thick obscuration, with parallels being drawn to changing look AGN (Miller et al. 2019). The radio jet behaviour in this new fainter state has been shown to switch between low flux and little variability to displaying strong flares (e.g., Motta et al. 2021; ATels: #12773, #12839).

To sample the current jet behaviour in GRS 1915+105, we observed the source with the SCUBA-2 instrument on the James Clerk Maxwell Telescope (JCMT), located on the slopes of Maunakea in Hawaii. Our observations were taken on October 26 between 05:17:58-05:50:43 UTC (MJD=59513.22-59513.24). GRS 1915+105 was not detected at 850μm (350 GHz), with a 3-sigma upper limit of ~14 mJy. Given the recent low fluxes reported from radio monitoring (Motta et al. 2021), our new sub-mm measurement suggests that GRS 1915+105 likely has a flatter jet spectrum (α=0 for Sν ∝ να) in its current state.

We thank the JCMT for rapidly scheduling our observations.
radio,millimeter,sub-millimeter,x-ray,agn,black hole,transient