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Post Info TOPIC: Supernova 2006bp
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Title: SN 2006bp: Probing the Shock Breakout of a Type II-P Supernova
Authors: Robert M. Quimby, J. Craig Wheeler, Peter Höflich, Carl W. Akerlof, Peter J. Brown, Eli S. Rykoff

HET optical spectroscopy and unfiltered ROTSE-III photometry spanning the first 11 months since explosion of the Type II-P SN 2006bp are presented. Flux limits from the days before discovery combined with the initial rapid brightening suggest the supernova was first detected just hours after shock breakout. Optical spectra obtained about 2 days after breakout exhibit narrow emission lines corresponding to HeII 4200, HeII 4686, and CIV 5805 in the rest frame, and these features persist in a second observation obtained 5 hours later; however, these emission lines are not detected the following night nor in subsequent observations. We suggest that these lines emanate from material close to the explosion site, possibly in the outer layers of the progenitor that have been ionised by the high energy photons released at shock breakout. A P-Cygni profile is observed around 4450 A in the +2 and +3 day spectra. Previous studies have attributed this feature to high velocity H-beta, but we discuss the possibility that this profile is instead due to HeII 4687. Further HET observations (14 nights in total) covering the spectral evolution across the photometric plateau up to 73 days after breakout and during the nebular phase around day +340 are presented, and expansion velocities are derived for key features. The measured decay slope for the unfiltered light curve is 0.0073 ± 0.0004 mag/day between days +121 and +335, which is significantly slower than the decay of rate 56Co. We combine our HET measurements with published X-ray, UV, and optical data to obtain a quasi-bolometric light curve through day +60. We see a slow cooling over the first 25 days, but no sign of an early sharp peak; any such feature from the shock breakout must have lasted less than ~1 day.

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SN2006BP
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Title: X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission
Authors: S. Immler, P. J. Brown, P. Milne, L. Dessart, P. A. Mazzali, W. Landsman, N. Gehrels, R. Petre, D. N. Burrows, J. A. Nousek, R. A. Chevalier, C. L. Williams, M. Koss, C. J. Stockdale, M. T. Kelley, K. W. Weiler, S. T. Holland, E. Pian, P. W. A. Roming, D. Pooley, K. Nomoto, J. Greiner, S. Campana, A. M. Soderberg

We present results on the X-ray and optical/UV emission from the type IIP SN 2006bp and the interaction of the SN shock with its environment, obtained with the X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) on-board the Swift observatory. SN 2006bp is detected in X-rays at a 4.5 sigma level of significance in the merged XRT data from days 1 to 12 after the explosion. If the X-ray luminosity of (1.8 ±0.4)E39 ergs/s is caused by interaction of the SN shock with circumstellar material (CSM), deposited by a stellar wind from the progenitor's companion star, a mass-loss rate of ~E-05 M_sun/yr is inferred. The mass-loss rate is consistent with the non-detection in the radio with the VLA on days 2, 9, and 11 after the explosion and characteristic of a red supergiant progenitor with a mass around 12-15 M_sun prior to the explosion. In combination with a follow-up XMM-Newton observation obtained on day 21 after the explosion, an X-ray rate of decline with index 1.2 ±0.6 is inferred. Since no other SN has been detected in X-rays prior to the optical peak and since type IIP SNe have an extended 'plateau' phase in the optical, we discuss the scenario that the X-rays might be due to inverse Compton scattering of photospheric optical photons off relativistic electrons produced in circumstellar shocks. However, due to the high required value of the Lorentz factor (~10-100) we conclude that Inverse Compton scattering is an unlikely explanation for the observed X-ray emission. The fast evolution of the optical/ultraviolet spectral energy distribution and the spectral changes observed with Swift reveal the onset of metal line-blanketing and cooling of the expanding photosphere during the first few weeks after the outburst.

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Type II Supernova
SWIFT spacecraft image.


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A magnitude 15.5 supernova, 2006bp, was discovered on the 9th April, 2006, by Koichi Itagaki, in the spiral galaxy NGC 3953, 46 million light years away in the constellation Ursa Major. It is located 62" east and 93" north of the nucleus.


Position(2000): R.A. = 11h53m55s.74, Dec. = +52°21'09".4
As yet the Type is unknown

A type II supernova occurred in this galaxy in 2001.

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