1110.5809 (Xiaofeng Wang et al.)

Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope    [PDF]

Xiaofeng Wang, Lifan Wang, Alexei V. Filippenko, Greg Aldering, Pierre Antilogus, David Arnett, Dietrich Baade, Eddie Baron, Brian J. Barris, Stefano Benetti, Patrice Bouchet, Adam S. Burrows, Ramon Canal, Enrico Cappellaro, Raymond Carlberg, Elisa di Carlo, Peter Challis, Arlin Crotts, John I. Danziger, Massimo Della Valle, Dennis Jack, Michael Fink, Ryan J. Foley, Claes Fransson, Avishay Gal-Yam, Peter Garnavich, Chris L. Gerardy, Mario Hamuy, Wolfgang Hillebrandt, Peter A. Hoeflich, Stephen T. Holland, Daniel E. Holz, John P. Hughes, David J. Jeffrey, Saurabh W. Jha, Dan Kasen, Alexei M. Khokhlov, Robert P. Kirshner, Robert Knop, Cecilia Kozma, Kevin Krisciunas, Markus Kromer, Brian C. Lee, Bruno Leibundgut, Eric J. Lentz, Douglas C. Leonard, Walter H. G. Lewin, Weidong Li, Mario Livio, Peter Lundqvist, Dan Maoz, Thomas Matheson, Paolo Mazzali, Peter Meikle, Gajus Miknaitis, Peter Milne, Stefan Mochnacki, Ken'Ichi Nomoto, Peter E. Pugent, Elaine Oran, Nino Panagia, Ferdinando Patat, Saul Perlmutter, Mark M. Phillips, Philip Pinto, Dovi Poznanski, Christopher J. Pritchet, Martin Reinecke, Adam Riess, Pilar Ruiz-Lapuente, Richard Scalzo, Eric M. Schlegel, Brian Schmidt, James Siegrist, Alicia M. Soderberg, Jesper Sollerman, George Sonneborn, Jason Spyromilio, Richard A. Sramek, Sumner G. Starrfield, Louis G. Strolger, Nicholas B. Suntzeff, Rollin Thomas, John L. Tonry, Amedeo Tornambe, James W. Truran, Massimo Turatto, Michael Turner, Schuyler D. Van Dyk, Kurt Weiler, J. Craig Wheeler, Michael Wood-Vasey, Stan Woosley, Hitoshi Yamaoka, Tianmeng Zhang

We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset provides unique spectral time series down to 2000 Angstrom. Significant diversity is seen in the near maximum-light spectra (~ 2000--3500 Angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in uvw1/F250W are found to correlate with the B-band light-curve shape parameter dm15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., ~ 0.4 mag versus ~0.2 mag for those with 0.8 < dm15 < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe~Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.

View original: http://arxiv.org/abs/1110.5809