ngVLA searches for pulsars at the Galactic center
Abstract
Detection of one or more pulsars in orbit about our galaxy's central supermassive black hole (Sgr A*) is a long-standing, yet still elusive, goal in physics and astrophysics. Timing observations of a pulsar as it orbits Sgr A* would provide high-precision measurements of the black hole properties (mass, spin), and new tests of fundamental predictions of general relativity such as the no-hair theorem and cosmic censorship conjecture. Characterizing a population of pulsars at the Galactic center would also give new astrophysical insight into the mass distribution, interstellar medium (ISM) properties, magnetic field, and star formation history of this complex and interesting region. The presence of young massive stars in the region leads to predictions of large numbers of neutron stars. However despite many observational attempts, only a handful of pulsars have been detected in the central ~degree, and none close enough to Sgr A* to have orbital timescales of ~years or faster. The conventional explanation for this is that strong scattering in the ISM broadens pulsed radio signals in time, to the point that they become undetectable; observing at higher frequencies reduces this effect, but the steep spectrum of most radio pulsars means the signals also become much fainter. The 2013 discovery of the magnetar J1745-2900 only 0.1 pc in projection from Sgr A* challenged this viewpoint, leading to some claims of a "missing pulsar" problem. However even with the reduced scattering strength inferred from this source, no existing radio telescopes have yet had the sensitivity to detect faint millisecond pulsars (MSPs) at the Galactic center. The proposed next-generation Very Large Array (ngVLA) will have nearly an order of magnitude more sensitivity than any current telescope in the ~5--30 GHz range that is expected to be the sweet spot for detection of pulsars -- including MSPs -- at the Galactic center. In this presentation we will outline the motivations, current knowledge, and predictions for a pulsar search in the Galactic center using the ngVLA, one of the key science goals for the instrument.
- Publication:
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American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23336124D