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TOPIC: CD-30 11223

Blobrana

L

Posts: 131433

Date: Apr 17 23:59 2013

CD-30 11223	Permalink

Title: A progenitor binary and an ejected mass donor remnant of faint type Ia supernovae Authors: S. Geier, T. R. Marsh, B. Wang, B. Dunlap, B. N. Barlow, V. Schaffenroth, X. Chen, A. Irrgang, P. F. L. Maxted, E. Ziegerer, T. Kupfer, B. Miszalski, U. Heber, Z. Han, A. Shporer, J. H. Telting, B. T. Gaensicke, R. H. Oestensen, S. J. O'Toole, R. Napiwotzki Type Ia supernovae (SN Ia) are the most important standard candles for measuring the expansion history of the universe. The thermonuclear explosion of a white dwarf can explain their observed properties, but neither the progenitor systems nor any stellar remnants have been conclusively identified. Underluminous SN Ia have been proposed to originate from a so-called double-detonation of a white dwarf. After a critical amount of helium is deposited on the surface through accretion from a close companion, the helium is ignited causing a detonation wave that triggers the explosion of the white dwarf itself. We have discovered both shallow transits and eclipses in the tight binary system CD-30 11223 composed of a carbon/oxygen white dwarf and a hot helium star, allowing us to determine its component masses and fundamental parameters. In the future the system will transfer mass from the helium star to the white dwarf. Modelling this process we find that the detonation in the accreted helium layer is sufficiently strong to trigger the explosion of the core. The helium star will then be ejected at so large a velocity that it will escape the Galaxy. The predicted properties of this remnant are an excellent match to the so-called hypervelocity star US 708, a hot, helium-rich star moving at more than 750 km/s, sufficient to leave the Galaxy. The identification of both progenitor and remnant provides a consistent picture of the formation and evolution of underluminous type Ia supernovae. Read more (1965kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Oct 5 20:37 2012

GALEX J1411-3053	Permalink

Title: The shortest period sdB plus white dwarf binary CD-30 11223 (GALEX J1411-3053) Authors: S. Vennes, A. Kawka, S.J. O'Toole, P. Nemeth, D. Burton We report on the discovery of the shortest period binary comprising a hot subdwarf star (CD-30 11223, GALEX J1411-3053) and a massive unseen companion. Photometric data from the All Sky Automated Survey show ellipsoidal variations of the hot subdwarf primary and spectroscopic series revealed an orbital period of 70.5 minutes. The large velocity amplitude suggests the presence of a massive white dwarf in the system (M_2/solar masses > 0.77) assuming a canonical mass for the hot subdwarf (0.48 solar masses), although a white dwarf mass as low as 0.75 solar masses is allowable by postulating a subdwarf mass as low as 0.44 solar masses. The amplitude of ellipsoidal variations and a high rotation velocity imposed a high-inclination to the system (i > 68 deg) and, possibly, observable secondary transits (i > 74 deg). At the lowest permissible inclination and assuming a subdwarf mass of ~0.48 solar masses, the total mass of the system reaches the Chandrasekhar mass limit at 1.35 solar masses and would exceed it for a subdwarf mass above 0.48 solar masses. The system should be considered, like its sibling KPD 1930+2752, a candidate progenitor for a type Ia supernova. The system should become semi-detached and initiate mass transfer within ~30 Myr. Read more (66kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Sep 24 08:15 2012

CD-30 11223	Permalink

Title: Discovery of the closest hot subdwarf binary with white dwarf companion Authors: S. Geier, T. R. Marsh, B. H. Dunlap, B. N. Barlow, V. Schaffenroth, E. Ziegerer, U. Heber, T. Kupfer, P. F. L. Maxted, B. Miszalski, A. Shporer, J. H. Telting, R. H. Oestensen, S. J. O'Toole, B. T. Gaensicke, R. Napiwotzki We report the discovery of an extremely close, eclipsing binary system. A white dwarf is orbited by a core He-burning compact hot subdwarf star with a period as short as \simeq0.04987 days making this system the most compact hot subdwarf binary discovered so far. The subdwarf will start to transfer helium-rich material on short timescales of less than 50 Myr. The ignition of He-burning at the surface may trigger carbon-burning in the core although the WD is less massive than the Chandrasekhar limit (>0.74 solar masses) making this binary a possible progenitor candidate for a supernova type Ia event. Read more (39kb, PDF) __________________

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