@article{13594be5bf10420bbe8ff49782c9900d,
title = "Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-degenerate Double-detonation Type Ia Supernovae",
abstract = "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.",
keywords = "binaries: close, nuclear reactions, nucleosynthesis, abundances, supernovae: general, white dwarfs",
author = "Shen, {Ken J.} and Douglas Boubert and Gansicke, {Boris T.} and Jha, {Saurabh W.} and Andrews, {Jennifer E.} and Laura Chomiuk and Foley, {Ryan J.} and Morgan Fraser and Mariusz Gromadzki and James Guillochon and Kotze, {Marissa M.} and Kate Maguire and Siebert, {Matthew R.} and Nathan Smith and Jay Strader and Carles Badenes and Kerzendorf, {Wolfgang E.} and Detlev Koester and Markus Kromer and Broxton Miles and R{\"u}diger Pakmor and Josiah Schwab and Odette Toloza and Silvia Toonen and Townsley, {Dean M.} and Williams, {Brian J.}",
note = "Funding Information: We thank Josh Bloom, Brian Metzger, Alison Miller, Peter Nugent, and Eliot Quataert for discussions, and the referee for helpful comments. K.J.S. is supported by NASA through the Astrophysics Theory Program (NNX17AG28G). D.B. thanks the UK Science and Technology Facilities Council for supporting his PhD. We thank Encarni Romero Colmenero and Petri Vaisanen for the Director{\textquoteright}s Discretionary Time award on SALT. S.W.J. is supported in part by NSF award AST-1615455. The UCSC group is supported in part by NASA grant NNG17PX03C, NSF grant AST-1518052, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by fellowships from the Alfred P. Sloan Foundation and the David and Lucile Packard Foundation to R.J.F. M.F. is supported by a Royal Society-Science Foundation Ireland University Research Fellowship. K.M. is supported by STFC through an Ernest Rutherford fellowship. W.E.K. is supported by an ESO Fellowship and the Excellence Cluster Universe, Technische Universit{\"a}t M{\"u}nchen, Boltzmannstrasse 2, D-85748 Garching, Germany. Support for J.S. is provided by NASA through Hubble Fellowship grant #HST-HF2-51382.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. We acknowledge the “Observational Signatures of Type Ia Supernova Progenitors III” workshop at the Lorentz Center, where some of the preparatory work for this study was performed. Funding Information: The NOT data were obtained through NUTS, which is supported in part by the Instrument Center for Danish Astrophysics (IDA). Support also comes from the European Research Council under the European Union{\textquoteright}s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement n. 320964 (WDTracer). Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT). PyRAF is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. Funding Information: The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen{\textquoteright}s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. Funding Information: This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/ gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC,https://www.cosmos.esa.int/web/gaia/ dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Funding Information: S.W.J. is supported in part by NSF award AST-1615455. The UCSC group is supported in part by NASA grant NNG17PX03C, NSF grant AST-1518052, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, and by fellowships from the Alfred P. Sloan Foundation and the David and Lucile Packard Foundation to R.J.F. M.F. is supported by a Royal Society-Science Foundation Ireland University Research Fellowship. K.M. is supported by STFC through an Ernest Rutherford fellowship. W.E.K. is supported by an ESO Fellowship and the Excellence Cluster Universe, Technische Universitat Munchen, Boltzmannstrasse 2, D-85748 Garching, Germany. Support for J.S. is provided by NASA through Hubble Fellowship grant #HST-HF2-51382.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Publisher Copyright: {\textcopyright} 2018. The American Astronomical Society. All rights reserved.",
year = "2018",
month = sep,
day = "20",
doi = "10.3847/1538-4357/aad55b",
language = "English (US)",
volume = "865",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}