Brown, Peter J. and Roming, Peter W. A. and Milne, Peter and Bufano, Filomena and Ciardullo, Robin and Elias-Rosa, Nancy and Filippenko, Alexei V. and Foley, Ryan J. and Gehrels, Neil and Gronwall, Caryl and Hicken, Malcolm and Holland, Stephen T. and Hoversten, Erik A. and Immler, Stefan and Kirshner, Robert P. and Li, Weidong and Mazzali, Paolo and Phillips, Mark M. and Pritchard, Tyler and Still, Martin and Turatto, Massimo and Berk, Daniel Vanden (2010) The Absolute Magnitudes of Type Ia Supernovae in the Ultraviolet. Astrophysical Journal, 721 (2). pp. 1608-1626. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20101022-083635747
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We examine the absolute magnitudes and light-curve shapes of 14 nearby (redshift z = 0.004-0.027) Type Ia supernovae (SNe Ia) observed in the ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and absolute magnitudes are calculated using both a standard Milky Way extinction law and one for the Large Magellanic Cloud that has been modified by circumstellar scattering. We find very different behavior in the near-UV filters (uvw1_(rc) covering ~2600-3300 Å after removing optical light, and u ≈3000-4000 Å) compared to a mid-UV filter (uvm2 ≈2000-2400 Å). The uvw1_(rc) – b colors show a scatter of ~0.3 mag while uvm2–b scatters by nearly 0.9 mag. Similarly, while the scatter in colors between neighboring filters is small in the optical and somewhat larger in the near-UV, the large scatter in the uvm2 – uvw1 colors implies significantly larger spectral variability below 2600 Å. We find that in the near-UV the absolute magnitudes at peak brightness of normal SNe Ia in our sample are correlated with the optical decay rate with a scatter of 0.4 mag, comparable to that found for the optical in our sample. However, in the mid-UV the scatter is larger, ~1 mag, possibly indicating differences in metallicity. We find no strong correlation between either the UV light-curve shapes or the UV colors and the UV absolute magnitudes. With larger samples, the UV luminosity might be useful as an additional constraint to help determine distance, extinction, and metallicity in order to improve the utility of SNe Ia as standardized candles.
|Additional Information:||© 2010 The American Astronomical Society. Received 2010 January 6; accepted 2010 July 1; published 2010 September 13. We are grateful to A. Goobar for extending his circumstellar extinction model into the UV for us. This work is supported at Penn State University by NASA contract NAS5-00136 and Swift Guest Investigator grant NNH06ZDA001N. A.V.F. is grateful for the support of NSF grant AST-0908886 and Swift Guest Investigator grant NNX09AG54G. This work made use of public data in the Swift data archive and the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The CfA Supernova Program at Harvard University is supported by NSF grant AST-0907903. The work of M.T. is supported by grant no. 2006022731 of the PRIN of Italian Ministry of University and Science Research.|
|Subject Keywords:||distance scale – dust, extinction – galaxies: distances and redshifts – supernovae: general – ultraviolet: general|
|Classification Code:||PACS: 97.60.Bw; 97.10.Ri; 98.38.Cp; 98.58.Ca|
|Official Citation:||Peter J. Brown et al 2010 ApJ 721 1608. doi: 10.1088/0004-637X/721/2/1608|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||12 Nov 2010 00:22|
|Last Modified:||26 Dec 2012 12:32|
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