A search for runaway stars in 12 Galactic supernova remnants

Abstract

Runaway stars can result from core-collapse supernovae in multiple stellar systems. If the supernova disrupts the system, the companion is ejected with its former orbital velocity. A clear identification of a runaway star can yield the time and place of the explosion, as well as orbital parameters of the pre-supernova binary system. Previous searches have mostly considered O-and B-type stars as runaway stars because they are always young in absolute terms (not much older than the lifetime of the progenitor) and can be detected up to larger distances. Here, we present a search for runaway stars of all spectral types. For late-type stars, a young age can be inferred from the lithium test. We used Gaia data to identify and characterize runaway star candidates in nearby supernova remnants, obtained spectra of 39 stars with UVES at the VLT and HDS at the Subaru telescope, and found a significant amount of lithium in the spectra of six dwarf stars. We present the spectral analysis, including measurements of radial velocities, atmospheric parameters, and lithium abundances. Then, we estimate the ages of our targets from the Hertzsprung-Russell diagram and, using the lithium test, present a selection of promising runaway star candidates and draw constraints on the number of ejected runaway stars compared to model expectations.

Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18

“…The results of our Gaia DR2 StarHorse run presented in A19 have been used in a wide variety of science cases, including exoplanetary research (Sozzetti et al 2021), interstellar extinction (Leike et al 2020), runaway stars from supernova remnants (Lux et al 2021), X-ray transients (Lamer et al 2021), ,γ-ray astronomy (Steppa & Egberts 2020), ,the Galactic escape speed curve (Monari et al 2018), the three-dimensionl phasespace structure of the Milky Way disc (Carrillo et al 2019), and spectroscopic survey simulations (Chiappini et al 2019).…”

The Peculiar Ejecta Rings in the O-Rich Supernova Remnant Puppis A: Evidence of a Binary Interaction?

“…There have in fact been at least two recent efforts to search for a binary companion in Pup A using the newly available data from the Gaia Early Data Release 3. Lux et al (2021) and Kochanek (2021) extracted proper motions for stars near the center of Pup A and found no evidence of an unbound binary companion. Indeed, using statistical searches for surviving binaries in additional SNRs, Kochanek (2021) estimated that nearly 70% of core-collapse SNe are unlikely to be binary systems at the time of explosion, with the remaining fraction divided nearly evenly between bound and unbound systems.…”

“…However, this is still not zero. Furthermore, earlier studies (Kochanek 2021;Lux et al 2021) utilized a search area centered on the geometric center of Pup A, well separated from the location of the Swirl. A larger search area may be necessary.…”

Supernovae Producing Unbound Binaries and Triples

“…Its Gaia EDR3 parallax of ̟ = 0.923 ± 0.025 mas is inconsistent with that of MWC 148 (̟ = 0.540±0.023 mas) at ∼ 130σ. The remaining Lux et al (2021) candidates in this SNR also have parallaxes incompatible with MWC 148.…”

“…They identify four candidates, one of which is HD 37424. Lux et al (2021) did the same for 12 SNRs using Gaia DR2 proper motions. Fraser & Boubert (2019) used Gaia DR2 proper motions for both the stars and the compact objects in the Crab, Cas A and Vela SNRs, confirming the Kochanek (2018) result for the Crab and Cas A and only finding very low luminosity candidates in Vela.…”