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Post Info TOPIC: Possible supernova in M95


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Posts: 130035
Date:
SN 2012aw
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Title: LEGUS Discovery of a Light Echo Around Supernova 2012aw
Author: Schuyler D. Van Dyk, Janice C. Lee, Jay Anderson, Jennifer E. Andrews, Daniela Calzetti, Stacey N. Bright, Leonardo Ubeda, Linda J. Smith, Elena Sabbi, Eva K. Grebel, Artemio Herrero, Selma E. de Mink

We have discovered a luminous light echo around the normal Type II-Plateau Supernova (SN) 2012aw in Messier 95 (M95; NGC 3351), detected in images obtained approximately two years after explosion with the Wide Field Channel 3 on-board the Hubble Space Telescope (HST) by the Legacy ExtraGalactic Ultraviolet Survey (LEGUS). The multi-band observations span from the near-ultraviolet through the optical (F275W, F336W, F438W, F555W, and F814W). The apparent brightness of the echo at the time was ~21--22 mag in all of these bands. The echo appears circular, although less obviously as a ring, with an inhomogeneous surface brightness, in particular, a prominent enhanced brightness to the southeast. The SN itself was still detectable, particularly in the redder bands. We are able to model the light echo as the time-integrated SN light scattered off of diffuse interstellar dust in the SN environment. We have assumed that this dust is analogous to that in the Milky Way with R_V=3.1. The SN light curves that we consider also include models of the unobserved early burst of light from the SN shock breakout. Our analysis of the echo suggests that the distance from the SN to the scattering dust elements along the echo is ~45 pc. The implied visual extinction for the echo-producing dust is consistent with estimates made previously from the SN itself. Finally, our estimate of the SN brightness in F814W is fainter than that measured for the red supergiant star at the precise SN location in pre-SN images, possibly indicating that the star has vanished and confirming it as the likely SN progenitor.

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Posts: 130035
Date:
Supernova 2012aw
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Title: Supernova 2012aw - a high-energy clone of archetypal type IIP SN 1999em
Authors: Subhash Bose, Brijesh Kumar, Firoza Sutaria, Brajesh Kumar, Rupak Roy, V. K. Bhatt, S. B. Pandey, H. C. Chandola, Ram Sagar, Kuntal Misra, Sayan Chakraborti

We present densely-sampled UBVRI/griz photometric and low-resolution (6-10A) optical spectroscopic observations from 4 to 270 days after explosion of a newly discovered type II SN 2012aw in a nearby (~9.9 Mpc) galaxy M95. The light-curve characteristics of apparent magnitudes, colours, bolometric luminosity and the presence and evolution of prominent spectral features are found to have striking similarity with the archetypal IIP SNe 1999em, 1999gi and 2004et. The early time observations of SN 2012aw clearly detect minima in the light-curve of V, R and I bands near 37 days after explosion and this we suggest to be an observational evidence for emergence of recombination phase. The mid-plateau MV magnitude (-16.67 ± 0.04) lies in between the bright (~ -18) and subluminous (~ -15) IIP SNe. The mass of nickel is 0.06±0.01 solar masses. The SYNOW modelling of spectra indicate that the value and evolution of photospheric velocity is similar to SN 2004et, but about ~600 km/s higher than that of SNe 1999em and 1999gi at comparable epochs. This trend is more apparent in the line velocities of H alpha and H beta. A comparison of ejecta velocity properties with that of existing radiation-hydrodynamical simulations indicate that the energy of explosion lies in the range 1-2x10^51 ergs; a further comparison of nebular phase [Oi] doublet luminosity with SNe 2004et and 1987A indicate that the mass of progenitor star is about 14-15 solar masses. The presence of high-velocity absorption features in the mid-to-late plateau and possibly in early phase spectra show signs of interaction between ejecta and the circumstellar matter; being consistent with its early-time detection at X-ray and radio wavebands.

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Posts: 130035
Date:
SN 2012aw
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Title: The Long-Lived UV "Plateau" of SN 2012aw
Authors: Amanda J. Bayless, Tyler Pritchard, Peter W. A. Roming, Paul Kuin, Peter J. Brown, Maria Teresa Botticella, Massimo Dall'Ora, Lucille H. Frey, Wesley Even, Chris L. Fryer, Justyn R. Maund, Morgan Fraser

Observations with the Swift UVOT have unambiguously uncovered for the first time a long-lived, UV "plateau" in a Type II-P supernova (SN).
Although this flattening in slope is hinted at in a few other SNe, due to its proximity and minimal line-of-sight extinction, SN 2012aw has afforded the first opportunity to clearly observe this UV plateau. The observations of SN 2012aw revealed all Swift UV and u-band lightcurves initially declined rapidly, but 27 days after explosion the light curves flattened. Some possible sources of the UV plateau are: the same thermal process that cause the optical plateau, heating from radioactive decay, or a combination of both processes.

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Posts: 130035
Date:
Supernova 2012AW
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Title: On Absorption by Circumstellar Dust, With the Progenitor of SN2012aw as a Case Study
Authors: C.S. Kochanek (1 and 2), R. Khan (1), X. Dai (3) ((1) Department of Astronomy, The Ohio State University, (2) Center for Cosmology and AstroParticle Physics, The Ohio State University, (3) Department of Physics and Astronomy, University of Oklahoma)

We use the progenitor of SN2012aw to illustrate the consequences of modelling circumstellar dust using Galactic (interstellar) extinction laws that (1) ignore dust emission in the near-IR and beyond; (2) average over dust compositions, and (3) mis-characterize the optical/UV absorption by assuming that scattered photons are lost to the observer. The primary consequences for the progenitor of SN2012aw are that both the luminosity and the absorption are significantly over-estimated. In particular, the stellar luminosity is most likely in the range 10^4.8 < L/Lsun < 10^5.0 and the star was not extremely massive for a Type IIP progenitor, with M < 15Msun. Given the properties of the circumstellar dust and the early X-ray/radio detections of SN2012aw, the star was probably obscured by an on-going wind with Mdot ~ 10^-5.5 to 10^-5.0 solar masses/year at the time of the explosion, roughly consistent with the expected mass loss rates for a star of its temperature (T_* ~ 3600K) and luminosity. In the spirit of Galactic extinction laws, we supply simple interpolation formulas for circumstellar extinction by dusty graphitic and silicate shells as a function of wavelength (>0.3 micron) and total (absorption plus scattering) V-band optical depth (tau < 20). These do not include the contributions of dust emission, but provide a simple, physical alternative to incorrectly using interstellar extinction laws.

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RE: Possible supernova in M95
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Title: The Red Supergiant Progenitor of Supernova 2012aw (PTF12bvh) in Messier 95
Authors: Schuyler D. Van Dyk (1), S. Bradley Cenko (2), Dovi Poznanski (3), Iair Arcavi (4), Avishay Gal-Yam (4), Alexei V. Filippenko (2), Kathryn Silverio (2), Alan Stockton (5), Jean-Charles Cuillandre (6), Geoffrey W. Marcy (2), Andrew W. Howard (2), Howard Isaacson (2) ((1) SSC/Caltech, (2) UC Berkeley, (3) Tel-Aviv Univ., (4) Weizmann Institute, (5) U. Hawaii, (6) CFHT)

We report on the direct detection and characterisation of the probable red supergiant progenitor of the intermediate-luminosity Type II-Plateau (II-P) supernova (SN) 2012aw in the nearby (10.0 Mpc) spiral galaxy Messier 95 (M95; NGC 3351). We have identified the star in both Hubble Space Telescope images of the host galaxy, obtained 17-18 yr prior to the explosion, and near-infrared ground-based images, obtained 6-12 yr prior to the SN. The luminous supergiant showed evidence for substantial circumstellar dust, manifested as excess line-of-sight extinction. The effective total-to-selective ratio of extinction to the star was R'_V \approx 4.35, which is significantly different from that of diffuse interstellar dust (i.e., R_V=3.1), and the total extinction to the star was therefore, on average, A_V \approx 3.1 mag. We find that the observed spectral energy distribution for the progenitor star is consistent with an effective temperature of 3600 K (spectral type M3), and that the star therefore had a bolometric magnitude of -8.29. Through comparison with recent theoretical massive-star evolutionary tracks we can infer that the red supergiant progenitor had an initial mass 15 \lesssim M_{ini} solar masses < 20. Interpolating by eye between the available tracks, we surmise that the star had initial mass ~17-18 solar masses. The circumstellar dust around the progenitor must have been destroyed in the explosion, as the visual extinction to the SN is found to be low (A_V=0.24 mag with R_V=3.1).

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Posts: 130035
Date:
Supernova 2012AW
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Supernova 2012AW in the galaxy M95 is now at magnitude 13.6

Messier_95220512.jpg

Date: 22nd May, 2012



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Posts: 130035
Date:
RE: Possible supernova in M95
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Supernova 2012AW in the galaxy M95 is now at magnitude 12.9

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Posts: 130035
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Title: Red and dead: The progenitor of SN 2012aw in M95
Authors: M. Fraser, J. R. Maund, S. J. Smartt, M.-T. Botticella, M. Dall'Ora, C. Inserra, L. Tomasella, S. Benetti, S. Ciroi, J. J. Eldridge, M. Ergon, R. Kotak, S. Mattila, P. Ochner, A. Pastorello, E. Reilly, J. Sollerman, A. Stephens, F. Taddia, S. Valenti

Core-collapse supernovae (SNe) are the spectacular finale to massive stellar evolution. In this Letter, we identify a progenitor for the nearby core-collapse SN 2012aw in both ground based near-infrared, and space based optical pre-explosion imaging. The SN itself appears to be a normal Type II Plateau event, reaching a bolometric luminosity of 10^{42} erg s^{-1} and photospheric velocities of ~11,000 kms from the position of the H \beta P-Cygni minimum in the early SN spectra. We use an adaptive optics image to show that the SN is coincident to within 27 mas with a faint, red source in pre-explosion HST+WFPC2, VLT+ISAAC and NTT+SOFI images. The source has magnitudes F555W=26.70 ± 0.06, F814W=23.39 ±0.02, J=21.1 ± 0.2, K=19.1 ± 0.4, which when compared to a grid of stellar models best matches a red supergiant. Interestingly, the spectral energy distribution of the progenitor also implies an extinction of A_V>1.2 mag, whereas the SN itself does not appear to be significantly extinguished. We interpret this as evidence for the destruction of dust in the SN explosion. The progenitor candidate has a luminosity between 5.0 and 5.6 log L/\lsun, corresponding to a ZAMS mass between 14 and 26 solar masses (depending on A_V), which would make this one of the most massive progenitors found for a core-collapse SN to date.

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Posts: 130035
Date:
SN 2012aw
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 Image of supernova 2012aw by the Aberdeen Astronomical Society

522919_359330727444256_145955732115091_1015450_847040656_n.jpg

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Posts: 130035
Date:
Supernova 2012aw
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  New Supernova Found "Next Door"

A new supernova has been found in the nearby galaxy M95, astronomers have confirmed, and it's one of the closest stellar deaths yet witnessed.
On March 16 professional astronomers and amateur observers detected the bright point of light on the outskirts of M95, a barred spiral galaxy in the constellation Leo, the lion. Since then, various teams have been watching the object closely.

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