Constraining Solar position and velocity with a Nearby Hypervelocity Star

Abstract

Gravitational 3-body interaction among binary stars and the supermassive black hole (SMBH) at the center of the Milky Way occasionally ejects a hypervelocity star (HVS) with a velocity of ~1000 km/s. Due to the ejection location, such a HVS initially has negligible azimuthal angular momentum Lz ~ 0 kpc km/s. Even if the halo is mildly triaxial, Lz of a recently ejected nearby HVS remains negligible, since its flight time from the Galactic Center is too short to accumulate noticeable torque. However, if we make a wrong assumption about the Solar position and velocity, such a HVS would apparently have noticeable non-zero azimuthal angular momentum, due to the wrong reflex motion of the Sun. Conversely, with precise astrometric data for a nearby HVS, we can measure the Solar position and velocity by assuming that the HVS has zero azimuthal angular momentum. Based on this idea, here we propose a method to estimate the Galactocentric distance of the Sun R0 and the Galactocentric Solar azimuthal velocity Vsun by using a HVS. We demonstrate with mock data for a nearby HVS candidate that the Gaia astrometric data, along with the currently available constraint on Vsun/R0 from the proper motion measurement of Sgr A*, can constrain R0 and Vsun with uncertainties of ~0.27 kpc and ~7.8 km/s (or fractional uncertainties of 3 percent), respectively. Our method will be a promising tool to constrain (R0, Vsun), given that Gaia is expected to discover many nearby HVSs in the near future.

ApJ accepted. 15 pages, 5 figures. We added Section 5.5, where the situation after this paper first appeared (on April 23, 2018) is described. Conclusion is unchanged. Comments welcome

References in corpus (19)

• The Gaia mission
• galpy: A Python Library for Galactic Dynamics
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• An Update on Monitoring Stellar Orbits in the Galactic Center
• The GALAH Survey: Observational Overview and Gaia DR1 companion
• BONNSAI: a Bayesian tool for comparing stars with stellar evolution models
• Hypervelocity Stars: From the Galactic Center to the Halo
• Gaia DR2 in 6D: Searching for the fastest stars in the Galaxy
• Runaway and hypervelocity stars in the Galactic halo: Binary rejuvenation and triple disruption
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• Proper Motions and Trajectories for 16 Extreme Runaway and Hypervelocity Stars
• Discovery of two new hypervelocity stars from the LAMOST spectroscopic surveys
• Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars
• An artificial neural network to discover Hypervelocity stars: Candidates in Gaia DR1/TGAS
• Constraining the Solar Galactic Reflex Velocity Using Gaia Observations of the Sagittarius Stream
• Tidal breakup of triple stars in the Galactic Centre
• Measuring the Sun's Motion with Stellar Streams

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• Faint objects in motion: the new frontier of high precision astrometry
• Milky Way archaeology using RR Lyrae and type II Cepheids II. High velocity RR Lyrae stars, and mass of the Milky Way
• Origin of a massive hyper-runaway subgiant star LAMOST-HVS1 -- implication from Gaia and follow-up spectroscopy
• High Velocity Stars in SDSS/APOGEE DR17
• The Chemical Composition of Extreme-Velocity Stars
• Probing modified Newtonian dynamics with hypervelocity stars
• The shape of the dark matter halo revealed from a hypervelocity star