AU-Scale Synchrotron Jets and Superluminal Ejecta in GRS 1915+105

By V. Dhawan, I. Mirabel, L. F. R. Nrao, Usa, Saclay, France, Unam, Mexico. 2000

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Radio imaging of the microquasar GRS 1915+105 with the Very Long Baseline Array (VLBA) over a range of wavelengths (13, 3.6, 2.0, and 0.7 cm), in different states of the black hole binary, always resolves the nucleus as a compact jet of length ~10λcm AU. The nucleus is best imaged at the shorter wavelengths, on scales of 2.5-7 AU (0.2-0.6 mas resolution). The brightness temperature of the core is TB ≥ 109 K, and its properties are better fitted by a conically expanding synchrotron jet model rather than a thermal jet. The nuclear jet varies in ~30 minutes during minor X-ray/radio outbursts and reestablishes within ~18 hr of a major outburst, indicating the robustness of the X-ray/radio (or disk/jet) system to disruption. At lower resolution (80-240 AU), more extended ejecta are imaged at ~500 AU separation from the stationary core. Time-lapse images clearly detect the superluminal motion of the ejecta in a few hours. The measured velocity is 1.5c ± 0.1c (D/12 kpc) for the approaching component and is consistent with ballistic motion of the ejecta from 500 AU outward, perhaps even since birth. The axis of the ejecta differs by ≤12° clockwise from the axis of the AU-scale jet, measured in the same observation. Both axes are stable in time (±5°), the AU scale for 2 yr and the large scale for over 4 yr. Astrometry over 2 yr relative to an extragalactic reference locates the black hole to ±1.5 mas, and its secular parallax due to Galactic rotation is 5.8 ± 1.5 mas yr-1, consistent with a distance of 12 kpc. Finally, a limit of ≤100 km s-1 is placed on its proper motion with respect to its neighborhood. Some accreting black holes of stellar mass (e.g., Cyg X-1, 1E 1740-2942, GRS 1758-258, GX 339-4) and supermassive black holes at the center of galaxies (e.g., Sgr A*) lack evidence of large flares and discrete transient ejecta but have compact radio cores with steady, flat-spectrum "plateau" states, like GRS 1915+105. To the present day GRS 1915+105 is the only system where both AU-scale steady jets and large-scale superluminal ejections have been unambiguously observed. Our observations suggest that the unresolved flat-spectrum radio cores of accreting black holes are compact quasi-continuous synchrotron jets.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5f120559a8d185772bbb2bbf1f073e2df91f47f4

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Citations in the corpus

Hard X‐ray states and radio emission in GRS 1915+105 (2001, background): “It is only for χ3 that the quasi-continuous ejections and the discrete ejections corresponding to the quasi-continuous radio jet and the radio flares respectively are directly observed (Dhawan et al. 2000).”
Scorpius X-1: The Evolution and Nature of the Twin Compact Radio Lobes (2001, background): “The general consensus from the other well-studied Galactic-jet objects like GRS1915+105 (Dhawan et al. 2000, Fender et al. 1999), GRSJ1655 (Tingay et al. 1995; Hjellming & Rupen 1995), CygX-3 (Geldzahler et al. 1984; Marti et al. 1992.”
The Spin of the Near-Extreme Kerr Black Hole GRS 1915+105 (2006, background): “…fitting the broadband X-ray spectrum, one must input known values of the massM of the BH, the distanceD to the binary, and the inclination i of the black-hole spin axis, which for GRS1915 we take to be the inclination of the nonprecessing and stable jets (Fender et al. 1999; Dhawan et al. 2000b).”
WATCHDOG: A COMPREHENSIVE ALL-SKY DATABASE OF GALACTIC BLACK HOLE X-RAY BINARIES (2015, unknown): “…Bradt & McClintock (1983), [374] Motch et al. (1998), [375] Samus et al. (1999), [376] Garnavich et al. (1999), [377] Kennea et al. (2012d), [378] Dhawan et al. (2000), [379] Okamura & Noguchi (1988), [380] Miller-Jones et al. (2009), [381] Kaplin et al. (1980), [382] Bradt et al. (1979), [383]…”
GRS 1915+105 and the Disc-Jet Coupling in Accreting Black Hole Systems (2004, background): “Dhawan et al. (2000) and Fuchs et al. (2003b) have reported direct imaging of an apparently steady radio jet during this phase (Figure 20).”
A Unified Model for Black Hole X-Ray Binary Jets? (2004, background): “…X-ray luminosity (Corbel et al. 2003; Gallo, Fender & Pooley 2003) and has only been directly spatially resolved in the case of Cyg X-1 (Stirling et al. 2001), although the ‘plateau’ jet of GRS 1915+105is phenomenologically similar and has also been resolved (Dhawan et al. 2000; Fuchs et al. 2003).”
A PARALLAX DISTANCE TO THE MICROQUASAR GRS 1915+105 AND A REVISED ESTIMATE OF ITS BLACK HOLE MASS (2014, methodology): “Values from Dhawan et al. (2000) are for observations where moving ejecta are seen. both jet orientation and internal flow speed can affect apparent motion, the ratio of approaching to receding motions measured by Rodrı́guez & Mirabel and Fender et al. are similar and most readily explained with a…”
The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes (2014, background): “In some phases, it produces steady, compact jets; in other states, it has been observed to launch discrete “cannonballs” with apparent speeds in excess of c ([269]).”