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Title: VERITAS Observations of the Nova in V407 Cygni
Authors: E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, A. Bouvier, S. M. Bradbury, J. H. Buckley, V. Bugaev, K. Byrum, A. Cannon, A. Cesarini, L. Ciupik, E. Collins-Hughes, M. P. Connolly, W. Cui, G. Decerprit, R. Dickherber, C. Duke, J. Dumm, V. V. Dwarkadas, M. Errando, A. Falcone, Q. Feng, J. P. Finley, G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, S. Godambe, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, H. Huan, G. Hughes, T. B. Humensky, P. Kaaret, N. Karlsson, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, K. Lee, G. Maier, P. Majumdar, S. McArthur, A. McCann, J. Millis, P. Moriarty, R. Mukherjee, P. D Nuņez, R. A. Ong, M. Orr, A. N. Otte, D. Pandel, N. Park, J. S. Perkins, M. Pohl, H. Prokoph, J. Quinn, K. Ragan, L. C. Reyes, et al. (27 additional authors not shown)

We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging Telescope Array System during 2010 March 19-26 at relatively large zenith angles, due to the position of V407 Cyg. An improved reconstruction technique for large zenith angle observations is presented and used to analyse the data. We do not detect V407 Cygni and place a differential upper limit on the flux at 1.6 TeV of 2.3 x 10^(-12) erg cm^(-2) s^(-1) (at the 95% confidence level). When considered jointly with data from Fermi-LAT, this result places limits on the acceleration of very high energy particles in the nova.

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Title: The X-ray Evolution of the Symbiotic Star V407 Cygni during its 2010 Outburst
Authors: Koji Mukai, Thomas Nelson, Laura Chomiuk, Davide Donato, Jennifer Sokoloski

We present a summary of Swift and Suzaku X-ray observations of the 2010 nova outburst of the symbiotic star, V407 Cyg. The Suzaku spectrum obtained on day 30 indicates the presence of the supersoft component from the white dwarf surface, as well as optically thin component from the shock between the nova ejecta and the Mira wind. The Swift observations then allow us to track the evolution of both components from day 4 to day 150. Most notable is the sudden brightening of the optically thin component around day 20. We identify this as the time when the blast wave reached the immediate vicinity of the photosphere of the Mira. We have developed a simple model of the blast wave-wind interaction that can reproduce the gross features of the X-ray evolution of V407 Cyg, and explore a parameter space of ejected mass, binary separation and Mira mass loss rate. If the model is correct, the binary separation is likely to be larger then previously suggested and the mass loss rate of the Mira is likely to be relatively low.

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Title: The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst. II. The circumstellar environment and the aftermath
Authors: S. N. Shore (Univ. of Pisa, INFN-Pisa), G. M. Wahlgren (CUA, GSFC-NASA), T. Augusteijn (NOT), T. Liimets (NOT, Tartu Obs), P. Koubsky, M. Slechta, V. Votruba (Ondrejov Obs.)

The nova outburst of V407 Cyg in 2010 Mar. 10 was the first observed for this star but its close resemblance to the well known symbiotic-like recurrent nova RS Oph suggests that it is also a member of this rare type of Galactic novae. The nova was the first detected at \gamma-ray energies and is the first known nova explosion for this system. The extensive multiwavelength coverage of this outburst makes it an ideal comparison with the few other outbursts known for similar systems. We extend our previous analysis of the Mira and the expanding shock from the explosion to detail the time development of the photoionised Mira wind, circumstellar medium, and shocked circumstellar environment to derive their physical parameters and how they relate to large scale structure of the environment, extending the previous coverage to more than 500 days after outburst. Absorption lines of Fe-peak ions formed in the Mira wind were visible as P Cyg profiles at low velocity before Day 69, around the time of the X-ray peak and we identified many absorption transitions without accompanying emission for metal lines. The H Balmer lines showed strong P Cyg absorption troughs that weakened during the 2010 observing period, through Day 128. We distinguish the components from the shock, the photoionised environment, and the chromosphere and inner Mira wind using spectra taken more than one year after outburst. The multiple shells and radiative excitation phenomenology are similar to those recently cited for GRBs and SNIa

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Title: The 2010 nova outburst of the symbiotic Mira V407 Cyg
Authors: U. Munari, V.H. Joshi, N.M. Ashok, D.P.K. Banerjee, P. Valisa, A. Milani, A. Siviero, S. Dallaporta, F. Castellani

The nova outburst experienced in 2010 by the symbiotic binary Mira V407 Cyg has been extensively studied at optical and infrared wavelengths with both photometric and spectroscopic observations. This outburst, reminiscent of similar events displayed by RS Oph, can be described as a very fast He/N nova erupting while being deeply embedded in the dense wind of its cool giant companion. The hard radiation from the initial thermonuclear flash ionises and excites the wind of the Mira over great distances (recombination is observed on a time scale of 4 days). The nova ejecta is found to progressively decelerate with time as it expands into the Mira wind. This is deduced from line widths which change from a FWHM of 2760 km/s on day +2.3 to 200 km/s on day +196. The wind of the Mira is massive and extended enough for an outer neutral and unperturbed region to survive at all outburst phases.

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Fermi Detects 'Shocking' Surprise from Supernova's Little Cousin

Astronomers using NASA's Fermi Gamma-ray Space Telescope have detected gamma-rays from a nova for the first time, a finding that stunned observers and theorists alike. The discovery overturns the notion that novae explosions lack the power to emit such high-energy radiation.
A nova is a sudden, short-lived brightening of an otherwise inconspicuous star. The outburst occurs when a white dwarf in a binary system erupts in an enormous thermonuclear explosion.

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Classical nova eruption of the symbiotic star.

At magnitude 9.0 on the 15th March, 2010.

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V407 Cygni
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A possible a nova outburst of the symbiotic Mira V407 Cygni.

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Outburst of the symbiotic Mira V407 Cygni

Date: 10th March 2010
Outburst: 6.8 V
Mira variable: 13.3 - >17.0 V
Period: 745 days

Position (2000): RA= 21h 02m 09.85s, Dec=+45° 46' 33.0"

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