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Supernova SN2005cs
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Title: SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared
Authors: A. Pastorello, S. Valenti, L. Zampieri, H. Navasardyan, S. Taubenberger, S. J. Smartt, A. A. Arkharov, O. Baernbantner, H. Barwig, S. Benetti, P. Birtwhistle, M. T. Botticella, E. Cappellaro, M. Del Principe, F. Di Mille, G. Di Rico, M. Dolci, N. Elias-Rosa, N. V. Efimova, M. Fiedler, A. Harutyunyan, P. A. Hoeflich, W. Kloehr, V. M. Larionov, V. Lorenzi, J. R. Maund, N. Napoleone, M. Ragni, M. Richmond, C. Ries, S. Spiro, S. Temporin, M. Turatto, J. C. Wheeler

We present the results of the one year long observational campaign of the type II-plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool Galaxy). This extensive dataset makes SN 2005cs the best observed low-luminosity, 56Ni-poor type II-plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km/s) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 days after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 days. In addition to optical observations, we also present near-infrared light curves that (together with already published UV observations) allow us to construct for the first time a reliable bolometric light curve for an object of this class. Finally, comparing the observed data with those derived from a semi-analytic model, we infer for SN 2005cs a 56Ni mass of about 0.003 solar masses, a total ejected mass of 8-13 solar masses and an explosion energy of about 3 x 10^50 erg.

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Title: Ruling out a massive-assymptoic giant-branch star as the progenitor of supernova 2005cs
Authors: J.J. Eldridge, S. Mattila, S.J. Smartt

We calculate the predicted UBVRIJHK absolute magnitudes for models of supernova progenitors and apply the result to the case of supernova 2005cs. We agree with previous results that the initial mass of the star was of low, around 6 to 8 M(sun). However such stars are thought to go through second dredge-up to become AGB stars. We show that had this occurred to the progenitor of 2005cs it would have been observed in JHK pre-explosion images. The progenitor was not detected in these bands and therefore we conclude that it was not an AGB star. Furthermore if some AGB stars do produce supernovae they will have a clear signature in pre-explosion near-infrared images. Electron-capture supernovae are thought to occur in AGB stars, hence the implication is that 2005cs was not an electron-capture supernova but was the collapse of an iron core.

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Title: Distance estimate and progenitor characteristics of SN 2005cs in M51
Authors: Katalin Takats, Jozsef Vinko

Distance to the Whirlpool Galaxy (M51, NGC 5194) is estimated using published photometry and spectroscopy of the Type II-P supernova SN 2005cs. Both the Expanding Photosphere Method (EPM) and the Standard Candle Method (SCM), suitable for SNe II-P, were applied. The average distance (7.1 ± 1.2 Mpc) is in good agreement with earlier SBF- and PNLF-based distances, but slightly longer than the distance obtained by Baron et al. for SN 1994I via the Spectral Fitting Expanding Atmosphere Method (SEAM). Since SN 2005cs exhibited low expansion velocity during the plateau phase, similarly to SN 1999br, the constants of SCM were re-calibrated including the data of SN 2005cs as well. The new relation is better constrained in the low velocity regime (vph(50) ~ 1500 - 2000 km/s), that may result in better distance estimates for such SNe. The physical parameters of SN 2005cs and its progenitor are re-evaluated based on the updated distance. All the available data support the low-mass (~ 9 solar masses) progenitor scenario proposed previously by its direct detection with the Hubble Space Telescope.

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Title: SN 2005cs in M51 I. The first month of evolution of a subluminous SN II plateau
Authors: A. Pastorello, D. Sauer, S. Taubenberger, P. A. Mazzali, K. Nomoto, K. S. Kawabata, S. Benetti, N. Elias-Rosa, A. Harutyunyan, H. Navasardyan, L. Zampieri, T. Iijima, M. T. Botticella, G. Di Rico, M. Del Principe, M. Dolci, S. Gagliardi, M. Ragni, G. Valentini

Early time optical observations of supernova (SN) 2005cs in the Whirlpool Galaxy (M51), are reported. Photometric data suggest that SN 2005cs is a moderately under-luminous Type II plateau supernova (SN IIP). The SN was unusually blue at early epochs (U-B ~ -0.9 about three days after explosion) which indicates very high continuum temperatures. The spectra show relatively narrow P-Cygni features, suggesting ejecta velocities lower than observed in more typical SNe IIP. The earliest spectra show weak absorption features in the blue wing of the He I 5876A absorption component and, less clearly, of Hbeta and Halpha. Based on spectral modelling, two different interpretations can be proposed: these features may either be due to high-velocity H and He I components, or (more likely) be produced by different ions (N II, Si II). Analogies with the low-luminosity, 56Ni-poor, low-velocity SNe IIP are also discussed.
While a more extended spectral coverage is necessary in order to determine accurately the properties of the progenitor star, published estimates of the progenitor mass seem not to be consistent with stellar evolution models.

sn2006cs1
Top: early B–V colour curve of SN 2005cs and those of SNe 1999em, 1999br and 1987A.
Middle: same as above, but for V–R colour.
Bottom: early uvoir pseudo–bolometric light curves for the same sample of SNe IIP and, in addition, SN 2002gd.


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RE: SN2005cs
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While astronomers can predict which stars will end their lives in a fiery explosion, surprisingly only five supernovas before now had been traced back to a known star.
Most supernovas are too distant, or their progenitor stars too faint or in too crowded fields for astronomers to look back in historical sky photos in order to pinpoint the location and type of star.

However, from the new Hubble image and a January 2005 image Hubble had taken of the Whirlpool Galaxy, UC Berkeley research astronomer Weidong Li and Filippenko have pinpointed the location of the progenitor star and identified it as a red supergiant whose mass was about 7 - 10 times that of the sun.

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RE: Supernova SN2005cs
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The Hubble Space Telescope snapped images of supernova (SN) 2005cs, 12 days after its discovery. Astronomers then compared those photos with Hubble images of the same region before the supernova blast to pinpoint the progenitor star

Before
After

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One of the nearest supernovas of recent years was discovered late last month in the bright nearby galaxy M51. It is visible on the right of the above before and after images of the picturesque spiral.
The supernova, discovered originally by Wolfgang Kloehr and now dubbed 2005cs, is visible with a telescope toward the constellation of Canes Venatici (the Hunting Dogs).


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The supernova has been identified as a Type II but has an unusual brightness history, creating speculation that is similar in nature to the brightest supernova of modern times: 1987A. The progenitor star has been identified as a bright blue star. Supernova 2005cs may have left behind a core that has been compressed into a neutron star or black hole.


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RE: SN 2005cs
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A possible progenitor has been identified by M. W. Richmond, Rochester Institute of Technology, who indicated that if the progenitor is indeed the young blue star he identifies, SN 2005cs may evolve like SN 1987A, which was also a type-II supernova with a blue progenitor.

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RE: Supernova SN2005cs
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The Whirlpool Galaxy is a classic spiral galaxy. At only 23 million light years distant and 65 thousand light years across.


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M51, also known as NGC 5194, is one of the brightest galaxies in the sky. The smaller galaxy appearing here below and to the left is well behind M51, as can be inferred by the dust in a foreground spiral arm blocking light from this smaller galaxy.


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The Whirlpool is visible with binoculars in the constellation of Canes Venaciti.
M51 is a spiral galaxy of type Sc and is the dominant member of a whole group of galaxies.
Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with this smaller galaxy.

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Discovered by Wolfgang Kloehr. It is a Type II at mag 13.5 and rising….



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