Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-degenerate Double-detonation Type Ia Supernovae

By K. Shen, D. Boubert, B. Gänsicke, S. Jha, J. Andrews, L. Chomiuk, R. Foley, Morgan Fraser, M. Gromadzki, J. Guillochon and 16 more. Astrophysical Journal, 2018

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Double detonations in double white dwarf (WD) binaries undergoing unstable mass transfer have emerged in recent years as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. One potential outcome of this “dynamically driven double-degenerate double-detonation” (D6) scenario is that the companion WD survives the explosion and is flung away with a velocity equal to its >1000 km s−1 pre-SN orbital velocity. We perform a search for these hypervelocity runaway WDs using Gaia's second data release. In this paper, we discuss seven candidates followed up with ground-based instruments. Three sources are likely to be some of the fastest known stars in the Milky Way, with total Galactocentric velocities between 1000 and 3000 km s−1, and are consistent with having previously been companion WDs in pre-SN Ia systems. However, although the radial velocity of one of the stars is >1000 km s−1, the radial velocities of the other two stars are puzzlingly consistent with 0. The combined five-parameter astrometric solutions from Gaia and radial velocities from follow-up spectra yield tentative 6D confirmation of the D6 scenario. The past position of one of these stars places it within a faint, old SN remnant, further strengthening the interpretation of these candidates as hypervelocity runaways from binary systems that underwent SNe Ia.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8345e81a0bb437d6dcca9495be6688d8689d9dfc

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Citations in the corpus

Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18 (2019, background): “…et al. 2019; Bossini et al. 2019; de Boer et al. 2019; Meingast & Alves 2019), the Galactic star-formation history (Helmi et al. 2018; Mor et al. 2019), hyper-velocity stars (e.g. Bromley et al. 2018; Scholz 2018; Shen et al. 2018; Boubert et al. 2018, 2019; Erkal et al. 2019), among others.”
Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation (2019, background): “The mission will produce light curves for about 200,000 nearby late-type stars sampled at a 2 minute cadence to open a new era of stellar variability exploration 3 (e.g., Dragomir et al. 2018; Huang et al. 2018; Ball et al. 2018; Shen et al. 2018; Wang et al. 2019).”
Observational Predictions for Sub-Chandrasekhar Mass Explosions: Further Evidence for Multiple Progenitor Systems for Type Ia Supernovae (2018, background): “This can be seen in Figure 9 and in Figure 15 of Shen et al. (2018a) where the Si II velocity is proportional to the mass of the WD.”