* Astronomy

Blobrana · L

RE: QU Carinae

Blobrana · L

Supernova progenitor found?

Type Ia supernovae are violent stellar explosions. Observations of their brightness are used to determine distances in the universe and have shown scientists that the cosmos is expanding at an accelerating rate. But there is still too little known about the specifics of the processes by which these supernovae form. New research, led by Stella Kafka of the Carnegie Institution for Science in the United States, identifies a star system, prior to explosion, which will possibly become a type Ia supernova. The work will appear in the journal Monthly Notices of the Royal Astronomical Society.
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Blobrana · L

Title: QU Carinae: Supernova Ia in the making?
Authors: Stella Kafka, Kent Honeycutt, Bob Williams

Variable NaI absorption lines have been reported in a number of type Ia supernovae (SNeIa). The presence of this circumstellar material suggests that cataclysmic variables (CVs) with a giant donor star may be the progenitors of these SNeIa (Patat et al. 2007). We present echelle spectra of the CV QU Carinae which strengthen the connection between CVs of the V Sge class, the Accretion Wind Evolution scenario, variable wind features, variable NaI absorption, and SNIa. This thread not only provides insight into the spectral peculiarities of QU Car, but also links SNeIa as a class with their parent systems.

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Blobrana · L

Title: QU Carinae: a SNeIa progenitor?
Authors: S. Kafka, R. Anderson, R.K. Honeycutt

Optical spectra obtained in 2006-07 of the nova-like cataclysmic variable QU Car are studied for radial velocities, line profiles, and line identifications. We are not able to confirm the reported 10.9 hr orbital period from 1982,partly because our sampling is not ideal for this purpose and also, we suspect, because our radial velocities are distorted by line profile changes due to an erratic wind. P-Cygni profiles are found in several of the emission lines, including those of C IV. Carbon lines are abundant in the spectra, suggesting a carbon enrichment in the donor star. The presence of [O III] 5007\AA and [N II] 6584\AA is likely due to a diffuse nebula in the vicinity of the system.
The wind signatures in the spectra and the presence of nebular lines are in agreement with the accretion wind evolution scenario that has been suggested to lead to SNeIa. We argue that QU Car is a member of the V Sge subclass of CVs, and a possible SNeIa progenitor. It is shown that the recent light curve of QU Car has ~1 mag low states, similar to the light curve of V Sge, strengthening the connection of QU Car with V Sge stars, supersoft x-ray sources, and SNeIa progenitors.

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Blobrana · L

QU Carinae (= HDE 310376)
Spectral type: B+

QU Carinae.kmz
Google Sky file (1kb, kmz)

Position(2000): RA 11:05:42.80, Dec -68:37:58.0

Blobrana · L

Title: Synthetic Spectrum Constraints on a Model of the Cataclysmic Variable QU Carinae
Authors: Albert P. Linnell, Patrick Godon, Ivan Hubeny, Edward M. Sion, Paula Szkody, Paul E. Barrett

Neither standard model SEDs nor truncated standard model SEDs fit observed spectra of QU Carinae with acceptable accuracy over the range 900A to 3000SA. Non-standard model SEDs fit the observation set accurately. The non-standard accretion disk models have a hot region extending from the white dwarf to R=1.36R_wd,a narrow intermediate temperature annulus, and an isothermal remainder to the tidal cutoff boundary. The models include a range of \dot{M} values between 1.0 x 10^{-7} solar masses yr^{-1} and 1.0 x 10^{-6}solar masses yr^{-1} and limiting values of M_wd between 0.6 solar masses and 1.2 solar masses. A solution with M_wd=1.2 solar masses is consistent with an empirical mass-period relation. The set of models agree on a limited range of possible isothermal region T_eff} values between 14,000K and 18,000K. The model-to-model residuals are so similar that it is not possible to choose a best model. The Hipparcos distance, 610 pc, is representative of the model results. The orbital inclination is between 40° and 60°.

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