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Post Info TOPIC: Magnitude 13.9 Supernova?


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RE: Magnitude 13.9 Supernova?
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Supernova 2006jc occurred when its massive progenitor star ended its life in spectacular fashion. The star exploded following a Luminous Blue Variable (LBV)-like outburst two years before (Pastorello et al.2007, Nature, 447, 829). An international team led by Seppa Mattila (Queens University, Belfast and University of Turku) observed the supernova and followed its evolution between days 86-493 after the explosion with an array of telescopes including the Gemini North telescope (using the Near Infrared Imager NIRI), the United Kingdom Infrared Telescope (UKIRT) and the Spitzer Space Telescope. This exceptional event has contributed significantly to our understanding of how core-collapse supernovae (SNe) and their progenitors can add to the dust content of the universe.

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Title: The Peculiar Type Ib Supernova 2006jc: A WCO Wolf-Rayet Star Explosion
Authors: N. Tominaga, M. Limongi, T. Suzuki, M. Tanaka, K. Nomoto, K. Maeda, A. Chieffi, A. Tornambe, T. Minezaki, Y. Yoshii, I. Sakon, T. Wada, Y. Ohyama, T. Tanabé, H. Kaneda, T. Onaka, T. Nozawa, T. Kozasa, K. S. Kawabata, G. C. Anupama, D.K. Sahu, U.K. Gurugubelli, T.P. Prabhu, J. Deng
(Version v3)

We present a theoretical model for Type Ib supernova (SN) 2006jc. We calculate the evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The synthetic bolometric LC is compared with the observed bolometric LC constructed by integrating the UV, optical, near-infrared (NIR), and mid-infrared (MIR) fluxes. The progenitor is assumed to be as massive as 40 solar masses on the zero-age main-sequence. The star undergoes extensive mass loss to reduce its mass down to as small as 6.9 solar masses, thus becoming a WCO Wolf-Rayet star. The WCO star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed. This could explain the NIR brightening and the dust feature seen in the MIR spectrum. We suggest that the progenitor of SN 2006jc is a WCO Wolf-Rayet star having undergone strong mass loss and such massive stars are the important sites of dust formation. We derive the parameters of the explosion model in order to reproduce the bolometric LC of SN 2006jc by the radioactive decays: the ejecta mass 4.9 solar masses, hypernova-like explosion energy 10^{52} ergs, and ejected ^{56}$Ni mass 0.22 solar masses. We also calculate the circumstellar interaction and find that a CSM with a flat density structure is required to reproduce the X-ray LC of SN 2006jc. This suggests a drastic change of the mass-loss rate and/or the wind velocity that is consistent with the past luminous blue variable (LBV)-like event.

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Title: Swift and Chandra Detections of Supernova 2006jc: Evidence for Interaction of the Supernova Shock with a Circumstellar Shell
Authors: S. Immler, M. Modjaz, W. Landsman, F. Bufano, P. J. Brown, P. Milne, L. Dessart, S. T. Holland, M. Koss, D. Pooley, R. P. Kirshner, A. V. Filippenko, N. Panagia, R. A. Chevalier, P. A. Mazzali, N. Gehrels, R. Petre, D. N. Burrows, J. A. Nousek, P. W. A. Roming, E. Pian, A. M. Soderberg, J. Greiner

The peculiar Type Ib supernova (SN) 2006jc has been observed with the UV/Optical Telescope (UVOT) and X-Ray Telescope (XRT) on board the Swift observatory over a period of 19 to 183 days after the explosion. Signatures of interaction of the outgoing SN shock with dense circumstellar material (CSM) are detected, such as strong X-ray emission (L_{0.2-10} > E39 erg/s) and the presence of MgII 2800A line emission visible in the UV spectra. In combination with a Chandra observation obtained on day 40 after the explosion, the X-ray light curve is constructed, which shows a unique rise of the X-ray emission by a factor of ~5 over a period of ~4 months, followed by a rapid decline. We interpret the unique X-ray and UV properties as a result of the SN shock interacting with a shell of material that was deposited by an outburst of the SN progenitor two years prior to the explosion. Our results are consistent with the explosion of a Wolf-Rayet star that underwent an episodic mass ejection qualitatively similar to those of luminous blue variable stars prior to its explosion. This led to the formation of a dense (>E7 cm**-3) shell at a distance of ~E16 cm from the site of the explosion, which expands with the WR wind at a velocity of (1300±300) km/s.

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Title: Properties of newly formed dust by SN2006jc based on near-to-mid infrared observation with AKARI
Authors: I. Sakon, T. Wada, Y. Ohyama, D. Ishihara, T. Tanabé, H. Kaneda, T. Onaka, N. Tominaga, M. Tanaka, T. Suzuki, H. Umeda, K. Nomoto, T. Nozawa, T. Kozasa, T. Minezaki, Y. Yoshii, S. Ohyabu, F. Usui, H. Matsuhara, T. Nakagawa, H. Murakami

We present our latest results on near- to mid- infrared observation of SN2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board AKARI. The near-infrared (2--5 \mu m) spectrum of SN2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800 ± 10K with the mass of 6.9 ± 0.5 x 10^{-5}M_{\odot} that was formed in the supernova ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust forming core collapse supernovae based on recent observations (i.e., 10^{-3}--10^{-5} M_{\odot}). Mid-infrared photometric data with {AKARI} /IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800K. This mid-infrared excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320 ± 10K with the mass of 2.7^{+0.7}_{-0.5} x 10^{-3}M_{\odot} rather than by the band emission of astronomical silicate and/or silica grains. This warm amorphous carbon dust is expected to have been formed in the mass loss wind associated with the Wolf-Rayet stellar activity before the SN explosion. Our result suggests that a significant amount of dust is condensed in the mass loss wind prior to the SN explosion. A possible contribution of emission bands by precursory SiO molecules in 7.5--9.5 \mu m is also suggested.

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Supernova 2006jc
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Title: The Peculiar Type Ib Supernova 2006jc: A WC Star Explosion
Authors: N. Tominaga, M. Limongi, T. Suzuki, M. Tanaka, K. Nomoto, K. Maeda, A. Chieffi, A. Tornambe, T. Minezaki, Y. Yoshii, I. Sakon, T. Wada, Y. Ohyama, T. Tanabé, H. Kaneda, T. Onaka, T. Nozawa, T. Kozasa, K. S. Kawabata, G. C. Anupama, D.K. Sahu, U.K. Gurugubelli, T.P. Prabhu, J. Deng

We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue variable (LBV)-like event. We calculate the presupernova evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The observed bolometic LC is constructed by integrating the UV, optical, near-infrared (NIR), and mid-infrared (MIR) fluxes. The progenitor is assumed to be as massive as 40\Msun on the zero-age. The star undergoes extensive mass loss to reduce its mass down to as small as 6.9\Msun, thus becoming a WC Wolf-Rayet star at the presupernova stage. The WC star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed during the explosion. This could explain the brightening in the NIR flux and the observed dust feature in MIR. The typical main-sequence mass of a WC Wolf-Rayet star and thus the progenitor of SN 2006jc is more massive than 40\Msun. We suggest that the explosions of stars more massive than 40\Msun are the important source of dust formation. We derive the parameters of the explosion model in order to reproduce the bolometric LC of SN 2006jc by the radioactive decays; the best model has the ejecta mass of 4.9\Msun, the hypernova-like explosion energy of 10^{52} ergs, and the ejected  56 Ni mass of 0.22\Msun. We also calculate the circumstellar interaction and find that such a shallow CSM density gradient as
ho\propto r^{-1} is required to reproduce the X-ray LC of SN 2006jc. This suggests a drastic change of the mass-loss rate and/or the wind velocity that seems to be consistent with the past LBV-like event.

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RE: Magnitude 13.9 Supernova?
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stingtail21stingtail22

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Posts: 131433
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Supernova 2006jc
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A unique discovery of two celestial explosions at exactly the same position in the sky has led astronomers to suggest they have witnessed the death of one of the most massive stars that can exist. A global collaboration of astronomers, led by Queens University Belfast teamed up with Japanese supernova hunter Koichi Itagaki to report an amazing new discovery in Nature this week (June 14th). This is the first time such a double explosion has been observed and challenges our understanding of star-deaths.

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Two explosions observed in 2004 and 2006 in a galaxy 78 million light years from Earth were part of the fiery death of one of the most massive stars known to exist, astronomers said on Wednesday.
Writing in the journal Nature, the scientists described the supernova death of a star estimated to be 50 to 100 times as massive as our sun in a galaxy called UGC4904 in the Lynx constellation. A supernova is a gigantic explosion that marks the demise of a star.
The researchers said Japanese astronomer Koichi Itagaki discovered a faint celestial explosion that remained visible for about 10 days in 2004, then detected a second, much more powerful explosion two years later.

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Title: A giant outburst two years before the core- collapse of a massive star
Authors: A. Pastorello, S.J. Smartt, S. Mattila, J.J. Eldridge, D. Young, K. Itagaki, H. Yamaoka, H. Navasardyan, S. Valenti, F. Patat, I. Agnoletto, T. Augusteijn, S. Benetti, E. Cappellaro, T. Boles, J.- M. Bonnet- Bidaud, M.T. Botticella, F. Bufano, C. Cao, J. Deng, M. Dennefeld,  N. Elias- Rosa,  A. Harutyunyan, F.P. Keenan, T. Iijima, V. Lorenzi, P.A. Mazzali, X. Meng, S. Nakano, T.B. Nielsen, J.V. Smoker, V. Stanishev, M. Turatto, D. Xu, L. Zampieri

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars 1,2 . The detection of several precursor stars of Type II supernovae have been reported (e.g. Ref. 3), however we do not yet have direct information on the progenitors of the hydrogen deficient Type Ib and Ic supernovae. Here we report that the peculiar Type Ib supernova SN2006jc is spatially coincident with a bright optical transient 4 that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon- oxygen Wolf- Rayet star embedded within a helium- rich circumstellar medium. There are different possible explanations for this pre- explosion transient. It appears similar to the giant outbursts of Luminous Blue Variables (LBV) of 60- 100 solar mass (M) stars 5 , however the progenitor of SN2006jc was helium and hydrogen deficient. An LBV-like outburst of a Wolf- Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively a massive binary system composed of an LBV which erupted in 2004, and a Wolf- Rayet star exploding as SN2006jc, could explain the observations.

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RE: Magnitude 13.9 Supernova?
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On Oct. 20, 2004, Japanese amateur astronomer Koichi Itagaki saw the star let loose an outburst so bright that it was initially mistaken for a supernova. The star survived, but for only two years. On Oct. 11, 2006, professional and amateur astronomers witnessed the star actually blowing itself to smithereens as Supernova 2006jc.

"We have never observed a stellar outburst and then later seen the star explode" - University of California, Berkeley, astronomer Ryan Foley. His group studied the event with ground-based telescopes, including the 10-meter  W. M. Keck telescopes in Hawaii. Narrow helium spectral lines showed that the supernova's blast wave ran into a slow-moving shell of material, presumably the progenitor's outer layers ejected just two years earlier. If the spectral lines had been caused by the supernova's fast-moving blast wave, the lines would have been much broader.

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Supernova 2006jc is a Type Ib

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