Browsing by Subject "circumstellar interaction"

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A Panchromatic View Of The Restless SN 2009ip Reveals The Explosive Ejection Of A Massive Star Envelope
(2014-01) Margutti, R.; Milisavljevic, Dan; Soderberg, Alicia M.; Chornock, Ryan; Zauderer, B. A.; Murase, K.; Guidorzi, C.; Sanders, N. E.; Kuin, P.; Fransson, C.; Levesque, E. M.; Chandra, P.; Berger, E.; Bianco, F. B.; Brown, Peter J.; Challis, Peter; Chatzopoulos, Emmanouil; Cheung, C. C.; Choi, C.; Chomiuk, L.; Chugai, N.; Contreras, C.; Drout, M. R.; Fesen, R.; Foley, Ryan J.; Fong, W.; Friedman, A. S.; Gall, C.; Gehrels, N.; Hjorth, J.; Hsiao, E.; Kirshner, R.; Im, M.; Leloudas, G.; Lunnan, R.; Marion, G. H.; Martin, J.; Morrell, N.; Neugent, K. F.; Omodei, N.; Phillips, Mark M.; Rest, A.; Silverman, Jeffrey M.; Strader, J.; Stritzinger, Maximillian D.; Szalai, T.; Utterback, N. B.; Vinko, Jozsef; Wheeler, J. Craig; Arnett, D.; Campana, S.; Chevalier, R.; Ginsburg, Adam; Kamble, A.; Roming, Peter W. A.; Pritchard, T.; Stringfellow, G.; Chatzopoulos, Emmanouil; Silverman, Jeffrey M.; Vinko, Jozsef; Wheeler, J. Craig
The double explosion of SN 2009ip in 2012 raises questions about our understanding of the late stages of massive star evolution. Here we present a comprehensive study of SN 2009ip during its remarkable rebrightenings. High-cadence photometric and spectroscopic observations from the GeV to the radio band obtained from a variety of ground-based and space facilities (including the Very Large Array, Swift, Fermi, Hubble Space Telescope, and XMM) constrain SN 2009ip to be a low energy (E similar to 1050 erg for an ejecta mass similar to 0.5 M-circle dot) and asymmetric explosion in a complex medium shaped by multiple eruptions of the restless progenitor star. Most of the energy is radiated as a result of the shock breaking out through a dense shell of material located at similar to 5 x 10(14) cm with M similar to 0.1 M-circle dot, ejected by the precursor outburst similar to 40 days before the major explosion. We interpret the NIR excess of emission as signature of material located further out, the origin of which has to be connected with documented mass-loss episodes in the previous years. Our modeling predicts bright neutrino emission associated with the shock break-out if the cosmic-ray energy is comparable to the radiated energy. We connect this phenomenology with the explosive ejection of the outer layers of the massive progenitor star, which later interacted with material deposited in the surroundings by previous eruptions. Future observations will reveal if the massive luminous progenitor star survived. Irrespective of whether the explosion was terminal, SN 2009ip brought to light the existence of new channels for sustained episodic mass loss, the physical origin of which has yet to be identified.
Variable Sodium Absorption In A Low-Extinction Type Ia Supernova
(2009-09) Simon, Joshua D.; Gal-Yam, Avishay; Gnat, Orly; Quimby, Robert M.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Blondin, Stephane; Li, Weidong D.; Filippenko, Alexei V.; Wheeler, J. Craig; Kirshner, Robert P.; Patat, Ferdinando; Nugent, Peter; Foley, Ryan J.; Vogt, Steven S.; Butler, R. Paul; Peek, Kathryn M. G.; Rosolowsky, Erik; Herczeg, Gregory J.; Sauer, Daniel N.; Mazzali, Paolo A.; Wheeler, J. Craig
Recent observations have revealed that some Type Ia supernovae exhibit narrow, time-variable Na I D absorption features. The origin of the absorbing material is controversial, but it may suggest the presence of circumstellar gas in the progenitor system prior to the explosion, with significant implications for the nature of the supernova (SN) progenitors. We present the third detection of such variable absorption, based on six epochs of high-resolution spectroscopy of the Type Ia supernova SN 2007le from the Keck I Telescope and the Hobby - Eberly Telescope. The data span a time frame of approximately three months, from 5 days before maximum light to 90 days after maximum. We find that one component of the Na I D absorption lines strengthened significantly with time, indicating a total column density increase of similar to 2.5 x 10(12) cm(-2). The data limit the typical timescale for the variability to be more than 2 days but less than 10 days. The changes appear to be most prominent after maximum light rather than at earlier times when the ultraviolet flux from the SN peaks. As with SN 2006X, we detect no change in the Ca II H and K absorption lines over the same time period, rendering line-of-sight effects improbable and suggesting a circumstellar origin for the absorbing material. Unlike the previous two supernovae exhibiting variable absorption, SN 2007le is not highly reddened (EB-V = 0.27 mag), also pointing toward circumstellar rather than interstellar absorption. Photoionization calculations show that the data are consistent with a dense (10(7) cm(-3)) cloud or clouds of gas located similar to 0.1 pc (3 x 10(17) cm) from the explosion. These results broadly support the single-degenerate scenario previously proposed to explain the variable absorption, with mass loss from a nondegenerate companion star responsible for providing the circumstellar gas. We also present possible evidence for narrow Ha emission associated with the SN, which will require deep imaging and spectroscopy at late times to confirm.