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dc.creatorChornock, Ryanen_US
dc.creatorFilippenko, Alexei V.en_US
dc.creatorLi, W.en_US
dc.creatorMarion, G. H.en_US
dc.creatorFoley, Ryan J.en_US
dc.creatorModjaz, M.en_US
dc.creatorRafelski, M.en_US
dc.creatorBecker, G. D.en_US
dc.creatorde Vries, W. H.en_US
dc.creatorGarnavich, Peteren_US
dc.creatorJorgenson, R. A.en_US
dc.creatorLynch, D. K.en_US
dc.creatorMalec, A. L.en_US
dc.creatorMoran, E. C.en_US
dc.creatorMurphy, M. T.en_US
dc.creatorRudy, R. J.en_US
dc.creatorRussell, R. W.en_US
dc.creatorSilverman, Jeffrey M.en_US
dc.creatorSteele, Thea N.en_US
dc.creatorStockton, A.en_US
dc.creatorWolfe, A. M.en_US
dc.creatorWoodward, C. E.en_US
dc.date.accessioned2016-04-28T19:37:35Z
dc.date.available2016-04-28T19:37:35Z
dc.date.issued2011-09en
dc.identifierdoi:10.15781/T29C0N
dc.identifier.citationChornock, Ryan, A. V. Filippenko, Wl Li, G. H. Marion, R. J. Foley, M. Modjaz, M. Rafelski et al. "The Transitional Stripped-envelope SN 2008ax: Spectral Evolution and Evidence for Large Asphericity." The Astrophysical Journal, Vol. 739, No. 1 (Sep., 2011): 41.en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/34948
dc.description.abstractSupernova (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.en_US
dc.description.sponsorshipW. M. Keck Foundationen_US
dc.description.sponsorshipNational Aeronautics and Space Administration, Science Mission Directorate NNX-08AE38Aen_US
dc.description.sponsorshipNSF AST-0607485, AST-0908886en_US
dc.description.sponsorshipTABASGO Foundationen_US
dc.description.sponsorshipMiller Institute for Basic Research in Scienceen_US
dc.description.sponsorshipAerospace Corporationen_US
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectpolarizationen_US
dc.subjectsupernovae: generalen_US
dc.subjectsupernovae: individual (sn 2008ax)en_US
dc.subjectcore-collapse supernovaeen_US
dc.subjectdiffuse interstellar bandsen_US
dc.subjectnear-infrareden_US
dc.subjectspectraen_US
dc.subjectremnant cassiopeia-aen_US
dc.subjectgamma-ray burstsen_US
dc.subjectii-p supernovaen_US
dc.subjectiben_US
dc.subjectsupernovaeen_US
dc.subjectx-rayen_US
dc.subjectoptical spectroscopyen_US
dc.subjectia supernovaen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleThe Transitional Stripped-Envelope Sn 2008Ax: Spectral Evolution And Evidence For Large Asphericityen_US
dc.typeArticleen_US
dc.description.departmentAstronomyen_US
dc.identifier.Filename2011_09_transitionalstripped.pdfen_US
dc.rights.restrictionOpenen_US
dc.identifier.doi10.1088/0004-637x/739/1/41en_US
dc.contributor.utaustinauthorMarion, G. H.en_US
dc.contributor.utaustinauthorStockton, A.en_US
dc.relation.ispartofserialAstrophysical Journalen_US


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