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A team of astronomers tracked the powerful jet of the microquasar GRS 1915+105 with very long baseline interferometry during a period in which the system’s X‑ray emission was heavily obscured. Four high‑resolution observations – one with the Very Long Baseline Array and three with the European VLBI Network – were carried out between 2019 and 2021. The jet’s orientation on milliarcsecond scales changed dramatically. In the most extreme case the jet direction was measured 57 ± 8° away from the normal, pre‑obscuration axis that was previously defined as 142 ± 7°. The offsets varied among the epochs, from a compact source with a large deviation, to a flaring source with a comparable shift, to a more extended jet whose position angle was closer to the older mean, and finally to a non‑detection. The team found no evidence for rapid swings of the position angle within individual 8‑hour observing windows, effectively ruling out rapid Lense–Thirring precession of the inner accretion disc as the driver of the observed jet re‑orientation. The pattern of changes instead points to longer‑term processes, such as a radiation‑driven warp in the accretion disc, that could both cause the persistent obscuration and steer the jet over months.
| Epoch | MJD | PA (∘) | Instrument | νc (GHz) | References |
|---|---|---|---|---|---|
| 1994 Jan 29 | 49381 | 159±8 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1994 Feb 19 | 49402 | 157±6 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1994 Mar 19 | 49430 | 149±4 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1994 Apr 21 | 49463 | 147±6 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1994 Apr 23 | 49465 | 149.7±0.7 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1995 Aug 10 | 49939 | 140±10 | VLA | 8.4 | Rodríguez and Mirabel (1999) |
| 1997 Oct 23 | 50744 | 157±2 | VLBA | 15 | Dhawan et al. (2000) |
| 1997 Oct 31 | 50752 | 133±2 | VLBA | 2.3 | Dhawan et al. (2000) |
| 1997 Nov 6 | 50758 | 142±2 | MERLIN | 5.0 | Fender et al. (1999) |
| 1998 Apr 11 | 50914 | 155±2 | VLBA | 15 | Dhawan et al. (2000) |
| 1998 May 2 | 50935 | 154±4 | VLBA | 15 | Dhawan et al. (2000) |
| 2006 Feb 8 | 53794 | 144.1±1 | VLBA | 8.4 | Miller-Jones et al. (2007) |
| 2006 Feb 8 | 53794 | 140.1±1 | VLBA | 2.3 | Miller-Jones et al. (2007) |
| 2006 Feb 12 | 53798 | 143.4±1 | VLBA | 8.4 | Miller-Jones et al. (2007) |
| 2006 Feb 14 | 53800 | 145.3±1 | VLBA | 8.4 | Miller-Jones et al. (2007) |
| 2006 Feb 14 | 53800 | 138.5±1 | VLBA | 2.3 | Miller-Jones et al. (2007) |
| 2006 Feb 17 | 53803 | 150.7±1 | VLBA | 8.4 | Miller-Jones et al. (2007) |
| 2006 Apr 21 | 53846 | 140±2 | eEVN | 5.0 | Rushton et al. (2007) |
| 2013 May 24 | 56436 | 130±1 | VLBA | 22 | Reid et al. (2014) |
| 2015 Mar 5 | 57086 | 140±8 | VLA | 22 | 15A-460 (PI: A. King) |
| 2019 Oct 12 | 58768 | 15.3±1.2 | VLBA | 8.4 | This paper |
| 2020 Oct 30 | 59152 | 18.61±0.03 | EVN | 4.9 | This paper |
| 2021 Mar 5 | 59278 | 170.9±0.3 | EVN | 4.9 | This paper |
| 2023 Apr 15 | 60049 | 12±1 | EAVN | 6.7 | Jiang et al. (2026) |
| 2023 Apr 16 | 60050 | 158±7 | EAVN | 43 | Jiang et al. (2026) |
| 2023 Apr 17 | 60051 | 6±1 | EAVN | 6.7 | Jiang et al. (2026) |
| 2023 Apr 19 | 60053 | 146±4 | EAVN | 43 | Jiang et al. (2026) |
| 2023 Apr 23 | 60057 | 6±1 | EAVN | 6.7 | Jiang et al. (2026) |
| 2023 May 23 | 60088 | 138±9 | VLA | 5.5 | SS192168 (PI: A. Shaw) |
| 2023 Sep 30 | 60217 | 148±3 | VLA | 10 | Jiang et al. (2026) |
| 2023 Sep 30 | 60217.5 | 174.3±0.5 | VLA | 8.0 | 23B-314 (PI: S.E. Motta) |
| 2024 May 25 | 60455 | 152±1 | VLA | 5.5 | 24A-474 (PI: S.E. Motta) |
| 2024 Jun 23 | 60484 | 149±1 | VLA | 5.5 | 24A-474 (PI: S.E. Motta) |
| 2025 Jan 18 | 60693 | 118±7 | EAVN | 6.7 | Yan et al. (2026a) |
| 2025 Jan 25 | 60700 | 131±6 | EAVN | 6.7 | Yan et al. (2026a) |
| 2025 Feb 24 | 60730 | 152±2 | EAVN | 6.7 | Yan et al. (2026a) |
| Instrument | Proposal Code | Date | Tsource | Time | νc | Bandwidth | Synthesized beam |
|---|---|---|---|---|---|---|---|
| (minutes) | (UTC) | (GHz) | (MHz) | (mas × mas, ∘ N to E) | |||
| VLBAa | BM500 | 2019-10-12 | 260.9 | 20:48 – 03:48c | 8.4 | 256 | 1.03 × 2.39, 171.35 |
| EVNb | EM144A | 2020-10-30 | 235.5 | 12:30 – 20:30 | 4.9 | 256 | 1.39 × 3.50, 6.84 |
| EVNb | EM144B | 2021-03-05 | 235.5 | 04:00 – 12:00 | 4.9 | 256 | 2.49 × 3.11, 67.21 |
| EVNb | EM144C | 2021-06-17 | 235.5 | 21:30 – 05:30 | 4.9 | 256 | 1.49 × 2.83, 9.69 |