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Post Info TOPIC: V458 VULPECULAE
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Title: An HI shell-like structure associated with nova V458 Vulpeculae?
Authors: Nirupam Roy, N. G. Kantharia, S. P. S. Eyres, G. C. Anupama, M. F. Bode, T. P. Prabhu, T. J. O'Brien

We report the radio detection of a shell-like HI structure in proximity to, and probably associated with, the nova V458 Vul. High spectral resolution observation with the Giant Metrewave Radio Telescope has made it possible to study the detailed kinematics of this broken and expanding shell. Unlike the diffuse Galactic HI emission, this is a single velocity component emission with significant clumping at ~ 0.5' scales. The observed narrow line width of ~ 5 km/s suggests that the shell consists of mostly cold gas. Assuming a distance of 13 kpc to the system, as quoted in the literature, the estimated HI mass of the nebula is about 25 solar masses. However, there are some indications that the system is closer than 13 kpc. If there is a physical association of the HI structure and the nova system, the asymmetric morphology and the off-centred stellar system indicates past strong interaction of the mass loss in the asymptotic giant branch phase with the surrounding interstellar medium. So far, this is the second example, after GK Per, of a large HI structure associated with a classical nova.

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Title: The orbital period of V458 Vulpeculae, a post double common-envelope nova
Authors: P. Rodríguez-Gil (ING, IAC, ULL), M. Santander-García (ING, IAC, ULL), C. Knigge (Southampton), R. L. M. Corradi (IAC, ULL), B. T. Gänsicke (Warwick), M. J. Barlow (UCL), J. J. Drake (CfA), J. Drew (Herts), B. Miszalski (Herts), R. Napiwotzki (Herts), D. Steeghs (Warwick), R. Wesson (UCL), A. A. Zijlstra (Manchester), D. Jones (Manchester), T. Liimets (Tartu, ING), S. Pyrzas (Warwick), M. M. Rubio-Díez (ING, CSIC-INTA)

We present time-resolved optical spectroscopy of V458 Vulpeculae (Nova Vul 2007 No. 1) spread over a period of 15 months starting 301 days after its discovery. Our data reveal radial velocity variations in the HeII \lambda 5412 and HeII \lambda 4686 emission lines. A period analysis of the radial velocity curves resulted in a period of 98.09647 ±0.00025 min (0.06812255 ±0.00000017 d) which we identify with the orbital period of the binary system. V458 Vul is therefore the planetary nebula central binary star with the shortest period known. We explore the possibility of the system being composed of a relatively massive white dwarf (M1 \gsim 1.0 Msun) accreting matter from a post-asymptotic giant branch star which produced the planetary nebula observed. In this scenario, the central binary system therefore underwent two common-envelope episodes. A combination of previous photoionisation modelling of the nebular spectra, post-asymptotic giant branch evolutionary tracks and the orbital period favour a mass of M2 ~ 0.6 Msun for the donor star. Therefore, the total mass of the system may exceed the Chandrasekhar mass, which makes V458 Vul a Type Ia supernova progenitor candidate.

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The Southampton team was part of an international study led by astronomers from UCL (University College London) that recorded the explosion of a binary star inside a planetary nebula.
At the ends of their lives, some stars undergo nova explosions, caused by nuclear reactions on their surface. In August 2007, one such exploding star was discovered in a part of the sky that had been observed by the research team. The pre-explosion images showed that this particular star was surrounded by a planetary nebula.
Although several novae are discovered each year in our Galaxy, this is only the second time that a nova has been seen inside a planetary nebula, the first being Nova Persei in 1901. The opportunity to watch in detail as the nova flash interacts with the nebula is a first in astronomy.

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Astronomers catch binary star explosion inside nebula
The explosion of a binary star inside a planetary nebula has been captured by a team led by UCL (University College London) researchers an event that has not been witnessed for more than 100 years. The study, published in Astrophysical Journal Letters, predicts that the combined mass of the two stars in the system may be high enough for the stars to eventually spiral into each other, triggering a much bigger supernova explosion.

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Title: X-Ray Spectroscopy of the Classical Nova V458 Vulpeculae with Suzaku
Authors: Masahiro Tsujimoto (1,2), Dai Takei (3), Jeremy J. Drake (4), Jan-Uwe Ness (5), Shunji Kitamoto (3) ((1) JAXA/ISAS, (2) Penn State U., (3) Rikkyo U., (4) SAO, (5) Arizona State U.)

We conducted a target of opportunity X-ray observation of the classical nova V458 Vulpeculae 88 days after the explosion using the Suzaku satellite. With a 20 ks exposure, the X-ray Imaging Spectrometer detected X-ray emission significantly harder than typical super-soft source emission. The X-ray spectrum shows K lines from N, Ne, Mg, Si, and S, and L-series emission from Fe in highly ionised states. The spectrum can be described by a single temperature (0.64 keV) thin thermal plasma model in collisional equilibrium with a hydrogen-equivalent extinction column density of ~3e21/cm2, a flux of ~1e-12 erg/s/cm2, and a luminosity of ~6e34 erg/s in the 0.3-3.0 keV band at an assumed distance of 13 kpc. We found a hint of an enhancement of N and deficiencies of O and Fe relative to other metals. The observed X-ray properties can be interpreted as the emission arising from shocks of ejecta from an ONe-type nova.

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  V458 Vulpeculae = Nova Vulpeculae 2007

Discovered by Matsue's Hiroshi Abe, (Hiroshi Abe, Matsue), on August 8 at 22 pm JST, 2007.

Position(2000): RA = 19 h 54 m 24 s .64, Dec = +20 o 52 '51 ".9
Mag 9.4

CBET 1038

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