J. Craig Wheeler

The Chemical Distribution in a Subluminous Type Ia Supernova: Hubble Space Telescope Images of the SN 1885 Remnant*

SN 1885 was a probable subluminous Type Ia supernova which occurred in the bulge of the Andromeda galaxy, M31, at a projected location 16 from the nucleus. Here we present and analyze Hubble Space Telescope images of the SN 1885 remnant seen in absorption against the M31 bulge via the resonance lines of Ca I, Ca II, Fe I, and Fe II. Viewed in Ca II H & K line absorption, the remnant appears as a nearly black circular spot with an outermost angular radius of 0. 40 ± 0. 025, implying a maximum linear radius of 1.52± 0.15 pc at M31’s estimated distance of 785± 30 kpc and hence a 120 yr average expansion velocity of 12,400± 1400 kms. The strongest Ca II absorption is organized in a broken ring structure with a radius of 0. 2 (= 6000 km s) with several apparent absorption ‘clumps’ of an angular size around that of the image pixel scale of 0. 05 (= 1500 km s). Ca I and Fe I absorption structures appear similar except for a small Fe I absorption peak displaced 0. 1 off-center of the Ca II structure by a projected velocity of about 3000 km s. Analyses of these images using off-center, delayed-detonation models suggest a low Ni production similar to the subluminous SN Ia explosion of SN 1986G. The strongly lopsided images of of Ca I and Fe I can be understood as resulting from an aspherical chemical distribution, with the best agreement found using an off-center model viewed from an inclination of ∼ 60. The detection of small scale Ca II clumps is the first direct evidence for some instabilities and the existence of a deflagration phase in SNe Ia or, alternatively, mixing induced by radioactive decay of Ni over time scales of seconds or days. However, the degree of mixing allowed by the observed images is much smaller than current 3D calculations for Rayleigh-Taylor dominated deflagration fronts. Moreover, the images require a central region of no or little Ca but iron group elements indicative for burning under sufficiently high densities for electron capture taking place, i.e., burning prior to a significant pre-expansion of the WD. Using time-dependent ionization calculations, we show that the presence today of neutral ions in this 120 yr old remnant can be understood as ejecta self-shielding from the UV radiation in the M31 bulge. Subject headings: supernovae: general supernovae: individual (SN 1885) ISM: kinematics and dynamics ISM: abundances supernova remnants

The chemical composition of the ejecta of the rare type IIb supernova 2013df

T. Szalai, J. Vinkóa,b, J.M. Silverman, G.H. Marion, J.C. Wheeler, G. Dhungana, R. Kehoe a Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9., Szeged H-6720, Hungary E-mail: szaszi@titan.physx.u-szeged.hu b Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259, USA NSF Astronomy and Astrophysics Postdoctoral Fellow c Department of Physics, Southern Methodist University, Dallas, TX, 75275, USA

The Chemical Distribution in a Subluminous Type Ia Supernova: Hubble Space Telescope Images of the SN 1885 RemnantBased on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

SN 1885 was a probable subluminous Type Ia supernova which occurred in the bulge of the Andromeda galaxy, M31, at a projected location 16 from the nucleus. Here we present and analyze Hubble Space Telescope images of the SN 1885 remnant seen in absorption against the M31 bulge via the resonance lines of Ca I, Ca II, Fe I, and Fe II. Viewed in Ca II H & K line absorption, the remnant appears as a nearly black circular spot with an outermost angular radius of 0. 40 ± 0. 025, implying a maximum linear radius of 1.52± 0.15 pc at M31’s estimated distance of 785± 30 kpc and hence a 120 yr average expansion velocity of 12,400± 1400 kms. The strongest Ca II absorption is organized in a broken ring structure with a radius of 0. 2 (= 6000 km s) with several apparent absorption ‘clumps’ of an angular size around that of the image pixel scale of 0. 05 (= 1500 km s). Ca I and Fe I absorption structures appear similar except for a small Fe I absorption peak displaced 0. 1 off-center of the Ca II structure by a projected velocity of about 3000 km s. Analyses of these images using off-center, delayed-detonation models suggest a low Ni production similar to the subluminous SN Ia explosion of SN 1986G. The strongly lopsided images of of Ca I and Fe I can be understood as resulting from an aspherical chemical distribution, with the best agreement found using an off-center model viewed from an inclination of ∼ 60. The detection of small scale Ca II clumps is the first direct evidence for some instabilities and the existence of a deflagration phase in SNe Ia or, alternatively, mixing induced by radioactive decay of Ni over time scales of seconds or days. However, the degree of mixing allowed by the observed images is much smaller than current 3D calculations for Rayleigh-Taylor dominated deflagration fronts. Moreover, the images require a central region of no or little Ca but iron group elements indicative for burning under sufficiently high densities for electron capture taking place, i.e., burning prior to a significant pre-expansion of the WD. Using time-dependent ionization calculations, we show that the presence today of neutral ions in this 120 yr old remnant can be understood as ejecta self-shielding from the UV radiation in the M31 bulge. Subject headings: supernovae: general supernovae: individual (SN 1885) ISM: kinematics and dynamics ISM: abundances supernova remnants

The type Ib/c supernova, gamma-ray burst, soft gamma-ray repeater, magnetar connection

The polarization of core-collapse supernovae shows that many if not all of these explosions must be strongly bi-polar. The most obvious way to produce this axial symmetry is by the imposition of a jet as an intrinsic part of the explosion process. These jets could arise by MHD processes in the formation of pulsars and be especially strong in the case of magnetars. The jets will blow iron-peak material out along the axes and other elements from the progenitor along the equator, a very different composition structure than pictured in simple spherical “onion skin” models. In extreme cases, these processes could lead to the production of γ-ray bursts powered by strong Poynting flux.