Examinando por Autor "Milne, P. A."

Mostrando 1 - 2 de 2
  • Miniatura
    Ítem
    The high-metallicity explosion environment of the relativistic supernova 2009bb1
    (2011) Levesque, E. M.; Soderberg, A. M.; Foley, R. J.; Berger, E.; Kewley, L. J.; Chakraborti, A. Ray; Torres, M. A. P.; Challis, P.; Kirshner, R. P.; Barthelmy, S. D.; Bietenholz, M. F.; Chandra, P.; Chaplin, V.; Chevalier, R. A.; Chugai, N.; Connaughton, V.; Copete, A.; Fox, O.; Fransson, C.; Grindlay, J. E.; Hamuy, M. A.; Milne, P. A.; Pignata, G.; Stritzinger, M. D.; Wieringa, M. H.
    We investigate the environment of the nearby (d 40 Mpc) broad-lined Type Ic supernova SN 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of ISM properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a metallicity between 1.7Z⊙ and 3.5Z⊙, in agreement with other broadined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb’s unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow.
  • Miniatura
    Ítem
    Ultraviolet diversity of Type Ia Supernovae
    (OXFORD UNIV PRESS, 2016-06) Foley, Ryan J.; Pan, Yen-Chen; Brown, P.; Filippenko, A. V.; Fox, O. D.; Hillebrandt, W.; Kirshner, R. P.; Marion, G. H.; Milne, P. A.; Parrent, J. T.; Pignata, G.; Stritzinger, M. D.
    Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) probe the outermost layers of the explosion, and UV spectra of SNe Ia are expected to be extremely sensitive to differences in progenitor composition and the details of the explosion. Here, we present the first study of a sample of high signal-to-noise ratio SN Ia spectra that extend blueward of 2900 angstrom. We focus on spectra taken within 5 d of maximum brightness. Our sample of 10 SNe Ia spans, the majority of the parameter space of SN Ia optical diversity. We find that SNe Ia have significantly more diversity in the UV than in the optical, with the spectral variance continuing to increase with decreasing wavelengths until at least 1800 angstrom (the limit of our data). The majority of the UV variance correlates with optical light-curve shape, while there are no obvious and unique correlations between spectral shape and either ejecta velocity or host-galaxy morphology. Using light-curve shape as the primary variable, we create a UV spectral model for SNe Ia at peak brightness. With the model, we can examine how individual SNe vary relative to expectations based on only their light-curve shape. Doing this, we confirm an excess of flux for SN 2011fe at short wavelengths, consistent with its progenitor having a subsolar metallicity. While most other SNe Ia do not show large deviations from the model, ASASSN-14lp has a deficit of flux at short wavelengths, suggesting that its progenitor was relatively metal rich.