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Progenitor of Supernova 2011dh
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Title: Panchromatic Observations of SN 2011dh Point to a Compact Progenitor Star
Authors: Alicia M. Soderberg, R. Margutti, B. A. Zauderer, M. Krauss, B. Katz, L. Chomiuk, J. A. Dittmann, E. Nakar, T. Sakamoto, N. Kawai, K. Hurley, S. Barthelmy, T. Toizumi, M. Morii, R. A. Chevalier, M. Gurwell, G. Petitpas, M. Rupen, K. D. Alexander, E. M. Levesque, C. Fransson, A. Brunthaler, M. F. Bietenholz, N. Chugai, V. Connaughton, M. Briggs, C. Meegan, A. von Kienlin, X. Zhang, A. Rau, S. Golenetskii, E. Mazets, T. Cline

We report the discovery and detailed monitoring of X-ray emission associated with the Type IIb SN 2011dh using data from the Swift and Chandra satellites, placing it among the best studied X-ray supernovae to date. We further present millimeter and radio data obtained with the SMA, CARMA, and EVLA during the first three weeks after explosion. Combining these observations with early optical photometry, we show that the panchromatic dataset is well-described by non-thermal synchrotron emission (radio/mm) with inverse Compton scattering (X-ray) of a thermal population of optical photons. We derive the properties of the shockwave and the circumstellar environment and find a shock velocity, v~0.1c, and a progenitor mass loss rate of ~6e-5 M_sun/yr. These properties are consistent with the sub-class of Type IIb SNe characterized by compact progenitors (Type cIIb) and dissimilar from those with extended progenitors (Type eIIb). Furthermore, we consider the early optical emission in the context of a cooling envelope model to estimate a progenitor radius of ~1e+11 cm, in line with the expectations for a Type cIIb SN. Together, these diagnostics suggest that the putative yellow supergiant progenitor star identified in archival HST observations is instead a binary companion or unrelated to the SN. Finally, we searched for the high energy shock breakout pulse using X-ray and gamma-ray observations obtained during the purported explosion date range. Based on the compact radius of the progenitor, we estimate that the breakout pulse was detectable with current instruments but likely missed due to their limited temporal/spatial coverage. Future all-sky missions will regularly detect shock breakout emission from compact SN progenitors enabling prompt follow-up observations of the shockwave with the EVLA and ALMA.

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Posts: 131433
Date:
PTF11eon/SN2011dh
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Title: PTF11eon/SN2011dh: Discovery of a Type IIb Supernova From a Compact Progenitor in the Nearby Galaxy M51
Authors: Iair Arcavi, Avishay Gal-Yam, Ofer Yaron, Assaf Sternberg, Itay Rabinak, Eli Waxman, Mansi M. Kasliwal, Robert M. Quimby, Eran O. Ofek, Assaf Horesh, Shrinivas R. Kulkarni, Alexei V. Filippenko, Jeffrey M. Silverman, S. Bradley Cenko, Weidong Li, Joshua S. Bloom, Mark Sullivan, Derek B. Fox, Peter E. Nugent, Dovi Poznanski, Evgeny Gorbikov, Amedee Riou, Stephane Lamotte-Bailey, Thomas Griga, Judith G. Cohen, David Polishook, Dong Xu, Sagi Ben-Ami, Ilan Manulis, Emma S. Walker, Paulo A. Mazzali, Elena Pian, Thomas Matheson, Kate Maquire, Yen-Chen Pan, David Bersier, Philip James, Jonathan M. Marchant, Robert J. Smith, Chris J. Mottram, Robert M. Barnsley, Michael T. Kandrashoff, Kelsey I. Clubb

On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra and the prompt appearance of low-ionisation spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in the near future, this SN is likely a member of the cIIb (compact IIb; Chevalier and Soderberg 2010) class, with progenitor radius larger than that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor. Our data imply that the object identified in pre-explosion Hubble Space Telescope images at the SN location is possibly a companion to the progenitor or a blended source, and not the progenitor star itself, as its radius (~10¹³ cm) would be highly inconsistent with constraints from our post-explosion photometric and spectroscopic data.

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Progenitor of Supernova 2011dh
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Title: The Progenitor of Supernova 2011dh/PTF11eon in Messier 51
Authors: Schuyler D. Van Dyk (1), Weidong Li (2), S. Bradley Cenko (2), Mansi M. Kasliwal (3), Assaf Horesh (3), Eran O. Ofek (3,4), Adam L. Kraus (5,6), Jeffrey M. Silverman (2), Iair Arcavi (7), Alexei V. Filippenko (2), Avishay Gal-Yam (7), Robert M. Quimby (3), Shrinivas R. Kulkarni (3), Ofer Yaron (7), David Polishook (7) ((1) Spitzer Science Center/Caltech, (2) UC Berkeley, (3) Caltech, (4) Einstein Fellow, (5) IfA/Hawaii, (6) Hubble Fellow, (7) Weizmann Institute)

We have identified the progenitor, or progenitor system, responsible for supernova (SN) 2011dh/PTF11eon, in the nearby, nearly face-on galaxy M51. The available early-time spectra and photometry indicate that it is a stripped-envelope core-collapse SN, of Type IIb or transitional Type II/Ib, possibly similar to the famous SN 1993J in M81. The star was identified in pre-SN archival, multi-band images obtained by the Hubble Space Telescope with the Advanced Camera for Surveys. This identification has been confirmed, to the highest available astrometric precision, using a Keck-II adaptive-optics image. We infer that the extinction to SN 2011dh and its progenitor arises from a low Galactic foreground contribution, and that the SN environment is of solar metallicity. We find that if single, the star is a luminous (absolute V \approx -7.7 mag) supergiant of effective temperature ~6100 K, bluer than the red supergiants which explode as the more common Type II-Plateau SNe. This requires that the star's hydrogen-rich envelope had been substantially stripped away. We estimate that the star had an initial mass of 18--21 Msun. We also explore whether this star is in a binary system. If we assume that a hypothetical secondary has the same properties as the putative SN 1993J companion, then the primary progenitor star would have been somewhat cooler and less luminous than if it were single; however, both binary components would still be approximately within the same initial mass range as a single supergiant progenitor.

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Supernova 2011dh
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Title: The Yellow Supergiant Progenitor of the Type II Supernova 2011dh in M51
Authors: J. R. Maund, M. Fraser, M. Ergon, A. Pastorello, S.J. Smartt, J. Sollerman, S. Benetti, M.-T. Botticella, F. Bufano, I.J. Danziger, R. Kotak, L. Magill, A.W. Stephens, S. Valenti

We present the detection of the progenitor of the Type II SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR, the position of the SN in the pre-explosion images was determined to within 23mas. The progenitor object was found to be consistent with a F8 supergiant star (log L/solar luminosity 4.92±0.20 and T_{eff}=6000±280K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M_{ZAMS}=13±3 solar  masses. The possibility of the progenitor source being a cluster is rejected, on the basis of: 1) the source is not spatially extended; 2) the absence of excess H\alpha\, emission; and 3) the poor fit to synthetic cluster SEDs. It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest the companion does not contribute significantly. Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax, and suggest that a large amount of the progenitor's hydrogen envelope was removed before explosion.

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Messier 51



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m51supernovab.jpg
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Date: 8th June, 2011



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Posts: 131433
Date:
Type II Supernova in Messier 51
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Weizmann Institute Observatory Captures Images of a New Supernova

Exploding stars are the "factories" that produce all the heavy elements found, among other places, in our bodies. In this sense, we are all stardust. These exploding stars - supernovae - are highly energetic events that can occasionally light up the night sky. Such an explosion generally involves disruption in the balance between gravity - which pulls the star's material inward - and the thermonuclear reaction at the star's core - which heats it and pushes it outward.
Certain types of stars that go in this way have a much bigger mass (10-100 times) and are much younger than our sun. In them, the nuclear reaction begins like that of our sun - fusing hydrogen into helium - but the fusion then continues, producing heavier and heavier elements. The nuclear reaction eventually stops with iron, as there is no energy benefit to the star to fuse the heavier atoms, and the balance between gravity and thermonuclear activity comes to a halt. Gravity then takes over, and the mass of the star collapses quickly, releasing so much energy in the process that the explosion ensues. The star hurls its outer layers into space, and a new "bright star" appears in the night sky where none was seen before. Just such a new star was observed in the night sky between May 31 and June 1 in a spiral arm of our galaxy's close neighbour, M51.

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Supernova in Messier 51
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Image

(164kb, 440 x 377)

Position (2000):     RA 13 30 05.124 ±0.003 | Dec +47°10'11.301" ±0.016



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Date:
Supernova 2011dh
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SN2011dhB.jpg
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Date: 00:53 UT, 5th June, 2011



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A cosmic celebrity gets some superstar treatment! This week while patrolling the night sky with their telescopes two French backyard astronomers independently managed to snag digital images of a supernova explosion caught in the act - with all the action occurring within the Whirlpool galaxy 31 million light years away.
On May 31st one amateur noticed a new star embedded within one of the spiral arms of the distant galaxy where there wasn't any before. By the next evening other amateur stargazers and robotic supernova patrol telescopes clued in as well and the alarm was sounded to the worldwide observing community.

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Posts: 131433
Date:
SN 2011dh
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SN 2011dh = Supernova in M51 = PSN J13303600+4706330

Coordinates: 13:30:05.08 +47:10:11.2  (J2000.0)
Coordinates source is Silverman et al.

Source 



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