EVIDENCE FOR TYPE Ia SUPERNOVA DIVERSITY FROM ULTRAVIOLET OBSERVATIONS WITH THE HUBBLE SPACE TELESCOPE
- Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing 100084 (China)
- Physics and Astronomy Department, Texas A and M University, College Station, TX 77843 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- Department of Physics, University of Oklahoma, Norman, OK 73019 (United States)
- Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching (Germany)
- Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg (Germany)
- National Astronomical Observatory of China, Chinese Academy of Sciences, Beijing 100012 (China)
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
- Laboratoire de Physique Nucleaire des Hautes Energies, Paris (France)
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- European Southern Observatory, 85748 Garching (Germany)
- Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)
- Osservatorio Astronomico di Padova, 35122 Padova (Italy)
- CEA/DSM/DAPNIA/Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex (France)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
- Department d'Astronomia i Meterorologia, Universidad de Barcelona, Barcelona 8007 (Spain)
- Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3J3 (Canada)
- INAF, Osservatorio Astronomico di Teramo, 64100 Teramo (Italy)
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 data set provides unique spectral time series down to 2000 A. Significant diversity is seen in the near-maximum-light spectra ({approx}2000-3500 A) 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 the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter {Delta}m{sub 15}(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., {approx}0.4 mag versus {approx}0.2 mag for those with 0.8 mag < {Delta}m{sub 15}(B) < 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 {approx}0.9 mag and {approx}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.
- OSTI ID:
- 22020409
- Journal Information:
- Astrophysical Journal, Vol. 749, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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