Browsing by Subject "ia supernova"
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Item The Early Asymmetries Of Supernova 2008D/XRF 080109(2009-11) Maund, Justyn R.; Wheeler, J. Craig; Baade, Dietrich; Patat, Ferdinando; Hoflich, Patat; Wang, Lifan F.; Clocchiatti, Alejandro; Wheeler, J. CraigSpectropolarimetry of the Type Ib SN 2008D, associated with the X-ray Flash (XRF) 080109, at two separate epochs, is presented. The epochs of these observations correspond to V-band light curve maximum and 15 days after light curve maximum (or 21 and 36 days after the XRF). We find SN 2008D to be significantly polarized, although the largest contribution is due to the interstellar polarization component of Q(ISP) = 0% +/- 0.1% and U(ISP) = -1.2% +/- 0.1%. At the two epochs, the spectropolarimetry of SN 2008D is classified as being D1+L(He I)+L(Ca II). The intrinsic polarization of continuum wavelength regions is < 0.4%, at both epochs, implying an asymmetry of the photosphere of < 10%. Similar to other Type Ibc SNe, such as 2005bf, 2006aj, and 2007gr, we observed significant polarization corresponding to the spectral features of Ca II, He I, Mg I, Fe II and, possibly, O I lambda 7774, about a close-to-spherically symmetric photosphere. We introduce a new plot showing the chemically distinct line-forming regions in the ejecta and comment on the apparent ubiquity of highly polarized high-velocity Ca II features in Type Ibc SNe. The polarization angle of Ca II IR triplet was significantly different, at both epochs, to those of the other species, suggesting high-velocity Ca II forms in a separate part of the ejecta. The apparent structure in the outer layers of SN 2008D has implications for the interpretation of the early-time X-ray emission associated with shock breakout. We present two scenarios, within the jet-torus paradigm, which explain the lack of an apparent geometry discontinuity between the two observations: (1) a jet which punched a hole straight through the progenitor and deposited Ni outside the ejecta and (2) a jet which stalled inside the radius of the photosphere as observed at the second epoch. The lack of a peculiar polarization signature, suggesting strongly asymmetric excitation of the ejecta, and the reported properties of the shock-breakout favor the second scenario.Item Interaction Between the Broad-Lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands(2014-02) Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Foster, Jonathan B.; Soderberg, Alicia M.; Fesen, Robert A.; Parrent, Jerod T.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish; Chakraborti, Sayan; Pickering, Timothy E.; Cenko, S. Bradley; Silverman, Jeffrey M.; Filippenko, Alexei V.; Kirshner, Robert P.; Mazzali, Paolo; Maeda, Keiichi; Marion, G. H. Howie; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.; Marion, G. H. Howie; Vinko, Jozsef; Wheeler, J. CraigDiffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (less than or similar to 30 days) timescales. The 4428 angstrom and 6283 angstrom DIB features get weaker with time, whereas the 5780 angstrom feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique inFormation about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers.Item Spectropolarimetry Of The Type IIb Supernova 2001Ig(1)(2007-12) Maund, Justyn R.; Wheeler, J. Craig; Patat, Ferdinando; Wang, Lifan; Baade, Dietrich; Hoflich, Peter A.; Maund, Justyn R., J. Craig Wheeler, Ferdinando Patat, Lifan Wang, Dietrich Baade, and A. H. Peter. "Spectropolarimetry of the Type IIb Supernova 2001ig." The Astrophysical Journal, Vol. 671, No. 2 (Dec., 2007): 1944.We present spectropolarimetric observations of the Type IIb SN 2001ig in NGC 7424; conducted with the ESO VLT FORS1 on 2001 December 16, 2002 January 3, and 2002 August 16, or 13, 31, and 256 days postexplosion. These observations are at three different stages of the SN evolution: (1) the hydrogen-rich photospheric phase, (2) the Type II to Type Ib transitional phase, and (3) the nebular phase. At each of these stages, the observations show remarkably different polarization properties as a function of wavelength. We show that the degree of interstellar polarization is 0.17%. The low intrinsic polarization (similar to 0.2%) at the first epoch is consistent with an almost spherical (<10% deviation from spherical symmetry) hydrogen-dominated ejecta. Similar to SN 1987A and to Type IIP SNe, a sharp increase in the degree of the polarization (similar to 1%) is observed when the outer hydrogen layer becomes optically thin by day 31; only at this epoch is the polarization well described by a "dominant axis.'' The polarization angle of the data shows a rotation through similar to 40 degrees between the first and second epochs, indicating that the asymmetries of the first epoch were not directly coupled with those observed at the second epoch. For the most polarized lines, we observe wavelength-dependent loop structures in addition to the dominant axis on the Q-U plane. We show that the polarization properties of Type IIb SNe are roughly similar to one another, but with significant differences arising due to line blending effects especially with the high velocities observed for SN 2001ig. This suggests that the geometry of SN 2001ig is related to SN 1993J and that these events may have arisen from a similar binary progenitor system.Item The Transitional Stripped-Envelope Sn 2008Ax: Spectral Evolution And Evidence For Large Asphericity(2011-09) Chornock, Ryan; Filippenko, Alexei V.; Li, W.; Marion, G. H.; Foley, Ryan J.; Modjaz, M.; Rafelski, M.; Becker, G. D.; de Vries, W. H.; Garnavich, Peter; Jorgenson, R. A.; Lynch, D. K.; Malec, A. L.; Moran, E. C.; Murphy, M. T.; Rudy, R. J.; Russell, R. W.; Silverman, Jeffrey M.; Steele, Thea N.; Stockton, A.; Wolfe, A. M.; Woodward, C. E.; Marion, G. H.; Stockton, A.Supernova (SN) 2008ax in NGC 4490 was discovered within hours after shock breakout, presenting the rare opportunity to study a core-collapse SN beginning with the initial envelope-cooling phase immediately following shock breakout. We present an extensive sequence of optical and near-infrared spectra, as well as three epochs of optical spectropolarimetry. Our initial spectra, taken two days after shock breakout, are dominated by hydrogen Balmer lines at high velocity. However, by maximum light, He I lines dominated the optical and near-infrared spectra, which closely resembled those of normal Type Ib supernovae (SNe Ib) such as SN 1999ex. This spectroscopic transition defines Type IIb SNe, but the strong similarity of SN 2008ax to normal SNe Ib beginning near maximum light, including an absorption feature near 6270 angstrom due to H alpha at high velocities, suggests that many objects classified as SNe Ib in the literature may have ejected similar amounts of hydrogen as SN 2008ax, roughly a few x 0.01 M-circle dot. Only the unusually early discovery of SN 2008ax allowed us to observe the spectroscopic signatures of the hydrogen-rich outer ejecta. Early-time spectropolarimetry (six and nine days after shock breakout) revealed strong line polarization modulations of 3.4% across H alpha, indicating the presence of large asphericities in the outer ejecta and possibly that the spectrum of SN 2008ax could be dependent on the viewing angle. After removal of interstellar polarization, the continuum shares a common polarization angle with the hydrogen, helium, and oxygen lines, while the calcium and iron absorptions are oriented at different angles. This is clear evidence of deviations from axisymmetry even in the outer ejecta. Intrinsic continuum polarization of 0.64% only nine days after shock breakout shows that the outer layers of the ejecta were quite aspherical. A single epoch of late-time spectropolarimetry as well as the shapes of the nebular line profiles demonstrate that asphericities extended from the outermost layers all the way down to the center of this core-collapse SN. SN 2008ax may in some ways be an extragalactic analog of the explosion giving rise to Cassiopeia A, which has recently been determined to be a remnant of an SN IIb.