2005/10/04 by Sébastien Lépine, Sebastien Lepine, R. Michael Rich +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Blue dwarf #Galactic halo #Halo #Milky Way #Proper motion #Radial velocity #Sky #Stellar, planetary, and galactic studies #White dwarf #astro-ph
paper · pdf · doi:10.1086/498504
published as Astrophys.J.633:L121-L124,2005 · 4 pages, to appear in The Astrophysical Journal Letters
arxiv created 2005/10/04 · openalex publication_date 2005/10/24 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report the discovery of PM J13420-3415, a faint ( V = 17) white dwarf with a very high proper motion μ = 2 55 yr -1 . The star was found in the southern sky extension of the SUPERBLINK proper-motion survey. A red spectrum shows the classical signature of a DA white dwarf, with a weak Hα line in absorption as the only prominent feature. The star is also found to have a large radial velocity V rad = +212 ± 15 km s -1 . At the adopted distance of 18 pc, the star has a very large space motion of 313 km s -1 relative to the Sun. An integration of the space motion shows that the star is on a nearly polar Galactic orbit and is thus an unambiguous member of the Galactic halo. However, with an estimated effective temperature 5000 K < T eff < 5500 K, the white dwarf appears to be much younger than expected for a denizen of the halo. The apparent paradox can be explained if the white dwarf is the relatively young (~2 Gyr) remnant of a longer lived (10-14 Gyr) main-sequence star, in which case the object is predicted to be a low-mass white dwarf with M ≈ 0.45 M ☉ .