Browsing by Subject "swift ultraviolet/optical telescope"
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Item The Broad-Lined Type Ic SN 2012ap And The Nature Of Relativistic Supernovae Lacking A Gamma-Ray Burst Detection(2015-01) Milisavljevic, Dan; Margutti, R.; Parrent, Jerod T.; Soderberg, Alicia M.; Fesen, Robert A.; Mazzali, P.; Maeda, K.; Sanders, N. E.; Cenko, S. Bradley; Silverman, Jeffrey M.; Filippenko, Alexei V.; Kamble, A.; Chakraborti, S.; Drout, M. R.; Kirshner, Robert P.; Pickering, T. E.; Kawabata, K.; Hattori, T.; Hsiao, Eric Y.; Stritzinger, Maximillian D.; Marion, G. H.; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.; Marion, G. H.; Vinko, Jozsef; Wheeler, J. CraigWe present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from -13 to +272 days past the B-band maximum of -17.4 +/- 0.5mag. The spectra are dominated by Fe II, OI, and Ca II absorption lines at ejecta velocities of nu approximate to 20,000 km s(-1) that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also be present at higher velocities (nu greater than or similar to 27,000 km s(-1)). We use these observations to estimate explosion properties and derive a total ejecta mass of similar to 2.7 M-circle dot, a kinetic energy of similar to 1.0 x 10(52) erg, and a Ni-56 mass of 0.1-0.2 M-circle dot. Nebular spectra (t > 200 days) exhibit an asymmetric double-peaked [O I] lambda lambda 6300, 6364 emission profile that we associate with absorption in the supernova interior, although toroidal ejecta geometry is an alternative explanation. SN 2012ap joins SN2009bb as another exceptional supernova that shows evidence for a central engine (e. g., black hole accretion or magnetar) capable of launching a non-negligible portion of ejecta to relativistic velocities without a coincident gamma-ray burst detection. Defining attributes of their progenitor systems may be related to notable observed properties including environmental metallicities of Z greater than or similar to Z(circle dot), moderate to high levels of host galaxy extinction (E(B - V) > 0.4mag), detection of high-velocity helium at early epochs, and a high relative flux ratio of [Ca II]/[O I] > 1 at nebular epochs. These events support the notion that jet activity at various energy scales may be present in a wide range of supernovae.Item The Evolving Activity Of The Dynamically Young Comet C/2009 P1 (Garradd)(2014-05) Bodewits, D.; Farnham, T. L.; A'Hearn, M. F.; Feaga, L. M.; McKay, A.; Schleicher, D. G.; Sunshine, J. M.; McKay, A.We used the Ultraviolet-Optical Telescope on board Swift to observe the dynamically young comet C/2009 P1 (Garradd) from a heliocentric distance of 3.5 AU pre-perihelion until 4.0 AU outbound. At 3.5 AU pre-perihelion, comet Garradd had one of the highest dust-to-gas ratios ever observed, matched only by comet Hale-Bopp. The evolving morphology of the dust in its coma suggests an outburst that ended around 2.2 AU pre-perihelion. Comparing slit-based measurements and observations acquired with larger fields of view indicated that between 3 AU and 2 AU pre-perihelion a significant extended source started producing water in the coma. We demonstrate that this source, which could be due to icy grains, disappeared quickly around perihelion. Water production by the nucleus may be attributed to a constantly active source of at least 75 km(2), estimated to be > 20% of the surface. Based on our measurements, the comet lost 4 x 10(11) kg of ice and dust during this apparition, corresponding to at most a few meters of its surface. Even though this was likely not the comet's first passage through the inner solar system, the activity of Garradd was complex and changed significantly during the time it was observed.Item The Fast And Furious Decay Of The Peculiar Type Ic Supernova 2005Ek(2013-09) Drout, M. R.; Soderberg, Alicia M.; Mazzali, P. A.; Parrent, Jerod T.; Margutti, R.; Milisavljevic, Dan; Sanders, N. E.; Chornock, Ryan; Foley, Ryan J.; Kirshner, Robert P.; Filippenko, Alexei V.; Li, W.; Brown, Peter J.; Cenko, S. Bradley; Chakraborti, S.; Challis, Peter; Friedman, A.; Ganeshalingam, Mohan; Hicken, M.; Jensen, C.; Modjaz, M.; Perets, H. B.; Silverman, Jeffrey M.; Wong, D. S.; Silverman, Jeffrey M.We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude of MR = -17.3 and decaying by similar to 3 mag in the first 15 days post-maximum, SN 2005ek is among the fastest Type I supernovae observed to date. The spectra of SN 2005ek closely resemble those of normal SN Ic, but with an accelerated evolution. There is evidence for the onset of nebular features at only nine days post-maximum. Spectroscopic modeling reveals an ejecta mass of similar to 0.3 M-circle dot that is dominated by oxygen (similar to 80%), while the pseudo-bolometric light curve is consistent with an explosion powered by similar to 0.03 M-circle dot of radioactive Ni-56. Although previous rapidly evolving events (e. g., SN 1885A, SN 1939B, SN 2002bj, SN 2010X) were hypothesized to be produced by the detonation of a helium shell on a white dwarf, oxygen-dominated ejecta are difficult to reconcile with this proposed mechanism. We find that the properties of SN 2005ek are consistent with either the edge-lit double detonation of a low-mass white dwarf or the iron-core collapse of a massive star, stripped by binary interaction. However, if we assume that the strong spectroscopic similarity of SN 2005ek to other SNe Ic is an indication of a similar progenitor channel, then a white-dwarf progenitor becomes very improbable. SN 2005ek may be one of the lowest mass stripped-envelope core-collapse explosions ever observed. We find that the rate of such rapidly declining Type I events is at least 1%-3% of the normal SN Ia rate.Item GRB 090417B And Its Host Galaxy: A Step Toward An Understanding Of Optically Dark Gamma-Ray Bursts(2010-07) Holland, Steven T.; Sbarufatti, Boris; Shen, Rongfeng; Schady, Patricia; Cummings, Jay R.; Fonseca, Emmanuel; Fynbo, Johan P. U.; Jakobsson, Pall; Leitet, Elisabet; Linne, Staffan; Roming, Peter W. A.; Still, Martin; Zhang, Bing; Shen, RongfengGRB 090417B was an unusually long burst with a T(90) duration of at least 2130 s and a multi-peaked light curve at energies of 15-150 keV. It was optically dark and has been associated with a bright star-forming galaxy at a redshift of 0.345 that is broadly similar to the Milky Way. This is one of the few cases where a host galaxy has been clearly identified for a dark gamma-ray burst (GRB) and thus an ideal candidate for studying the origin of dark bursts. We find that the dark nature of GRB 090417B cannot be explained by high redshift, incomplete observations, or unusual physics in the production of the afterglow. Assuming the standard relativistic fireball model for the afterglow we find that the optical flux is at least 2.5 mag fainter than predicted by the X-ray flux. The Swift/XRT X-ray data are consistent with the afterglow being obscured by a dense, localized sheet of dust approximately 30-80 pc from the burst along the line of sight. Our results suggest that this dust sheet imparts an extinction of A(V) greater than or similar to 12 mag, which is sufficient to explain the missing optical flux. GRB 090417B is an example of a GRBs that is dark due to the localized dust structure in its host galaxy.Item SN 2008In-Bridging The Gap Between Normal And Faint Supernovae Of Type IIp(2011-08) Roy, Rupak; Kumar, Brijesh; Benetti, Stefano; Pastorello, Andrea; Yuan, Fang; Brown, Peter J.; Immler, Stefan; Fatkhullin, Timur A.; Moskvitin, Alexander S.; Maund, Justyn; Akerlof, Carl W.; Wheeler, J. Craig; Sokolov, Vladimir V.; Quimby, Rorbert M.; Bufano, Filomena; Kumar, Brajesh; Misra, Kuntal; Pandey, S. B.; Elias-Rosa, Nancy; Roming, Peter W. A.; Sagar, Ram; Wheeler, J. CraigWe present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M61. Photometric data in the X-ray, ultraviolet, and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was similar to 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. indicates that it is a less energetic event (similar to 5 x 10(50) erg). However, the light curve indicates that the production of radioactive 56Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of AV similar to 0.3 mag and a distance of 13.2Mpc, we estimated a synthesized 56Ni mass of similar to 0.015 M-circle dot. Employing semi-analytical formulae derived by Litvinova and Nadezhin, we derived a pre-SN radius of similar to 126R(circle dot), an explosion energy of similar to 5.4x10(50) erg, and a total ejected mass of similar to 16.7M(circle dot). The latter indicates that the zero-age main-sequence mass of the progenitor did not exceed 20M(circle dot). Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] similar to 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.Item 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. CraigRecent 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.