title: The binary progenitor of Tycho Brahe's 1572 supernova.
abstract: The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova is one of only two type Ia supernovae observed in our Galaxy, and so provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0-G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova.
authors.affiliation: Department of Astronomy, University of Barcelona, Marti i Franques 1, E-08028 Barcelona, Spain. pilar@am.ub.es
authors.forename: Pilar
authors.initials: P
authors.lastname: Ruiz-Lapuente
authors.forename: Fernando
authors.initials: F
authors.lastname: Comeron
authors.forename: Javier
authors.initials: J
authors.lastname: Méndez
authors.forename: Ramon
authors.initials: R
authors.lastname: Canal
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Smartt
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Filippenko
authors.forename: Robert L
authors.initials: RL
authors.lastname: Kurucz
authors.forename: Ryan
authors.initials: R
authors.lastname: Chornock
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Foley
authors.forename: Vallery
authors.initials: V
authors.lastname: Stanishev
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ibata