Discovery of Unusual Jet Orientation Variations in the Microquasar GRS 1915+105

Abstract

We report large day-timescale variations in the orientation of the southeast--northwest jet in the prototype microquasar GRS 1915+105. These results are based on three-epoch East Asia VLBI Network (EAVN) observations at 6.7 GHz, obtained during giant radio flares in 2025 detected by the RATAN-600 monitoring program. Our observations reveal the smallest position angle (PA) of $118^{\circ }\pm 7^{\circ }$ ever measured for the jet in GRS 1915+105, which increases to $152^{\circ }\pm 2^{\circ }$ within 37 days. Based on the literature results, we further suggest that the jet orientation has exhibited significant variations over a PA range of $118^{\circ }$--$188^{\circ }$ since 2023. This unusual jet orientation behavior in GRS 1915+105 during its current X-ray-obscured state may arise from a warped, precessing inner accretion disk, as implied by recent X-ray spectroscopy. Notably, one image reveals a peculiar morphology in GRS 1915+105, which likely indicates lateral spreading of the approaching southeast jet. Future observations are essential to clarify the issues raised in this work.

ApJL in press