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Published May 20, 2009 | Published + Submitted
Journal Article Open

The Golden Standard Type Ia Supernova 2005cf: Observations from the Ultraviolet to the Near-Infrared Wavebands

Abstract

We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal Type Ia supernova (SN Ia) 2005cf. The optical photometry, performed at eight different telescopes, shows a 1σ scatter of ≾0.03 mag after proper corrections for the instrument responses. From the well-sampled light curves, we find that SN 2005cf reached a B-band maximum at 13.63 ± 0.02 mag, with an observed luminosity decline rate Δm _(15)(B) = 1.05 ± 0.03 mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded SN Ia sample, yield a consistent estimate for the host-galaxy reddening of SN 2005cf, E(B – V)_(host) = 0.10 ± 0.03 mag. The UV photometry was obtained with the Hubble Space Telescope and the Swift Ultraviolet/Optical Telescope, and the results match each other to within 0.1-0.2 mag. The UV light curves show similar evolution to the broadband U, with an exception in the 2000-2500 Å spectral range (corresponding to the F220W/uvm2 filters), where the light curve appears broader and much fainter than that on either side (likely owing to the intrinsic spectral evolution). Combining the UV data with the ground-based optical and NIR data, we establish the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the bolometric corrections in the absence of UV and/or NIR data. The overall spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with variety in the strength and profile of the main feature lines. The spectra at early times displayed strong, high-velocity (HV) features in the Ca II H&K doublet and NIR triplet, which were distinctly detached from the photosphere (v ≈ 10,000 km s^(–1)) at a velocity ranging from 20,000 to 25,000 km s^(–1). One interesting feature is the flat-bottomed absorption observed near 6000 Å in the earliest spectrum, which rapidly evolved into a triangular shape and then became a normal Si II λ6355 absorption profile at about one week before maximum brightness. This premaximum spectral evolution is perhaps due to the blending of the Si IIλ6355 at photospheric velocity and another HV absorption component (e.g., an Si II shell at a velocity ~18,000 km s^(–1)) in the outer ejecta, and may be common in other normal SNe Ia. The possible origin of the HV absorption features is briefly discussed.

Additional Information

© 2009. The American Astronomical Society. Received 2008 November 7; accepted 2009 March 6; published 2009 May 1. We thank Ryan Chornock and Stephane Blondin for useful discussions. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA); the observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank the Lick Observatory, Palomar Observatory, NAOC, and CTIO staffs for their assistance with the observations. The research of A.V.F.'s supernova group at UC Berkeley is supported by NSF grant AST–0607485, the TABASGO Foundation, Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, US Department of Energy SciDAC grant DE-FC02-06ER41453, and US Department of Energy grant DE-FG02-08ER41563. Additional, crucial support was provided by NASA grant GO-10182 from the Space Telescope Science Institute (STScI), which is operated by AURA, Inc., under NASA contract NAS5-26555. We are also grateful to the National Natural Science Foundation of China (NSFC grant 10673007), the 973 Key Program of China (2009CB824800), and the Basic Research Funding at Tsinghua University (JCqn2005036). Supernova research at Harvard University is supported by NSF grant AST–0606772. M.M. is supported by a fellowship from the Miller Institute for Basic Research in Science at UC Berkeley. The work of A.G. is supported by grants from the Israeli Science Foundation, the EU Marie Curie IRG program, the Benoziyo Center for Astrophysics, a research grant from the Peter and Patricia Gruber Awards, and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute. The KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett–Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. The PAIRITEL project is operated by the Smithsonia Astrophysical Observatory (SAO) and was made possible by a grant from the Harvard University Milton Fund, a camera loan from the University of Virginia, and continued support of the SAO and UC Berkeley. PAIRITEL is further supported by the NASA/Swift Guest Investigator grant NNG06GH50G. The CTIO 1.3 m telescope is operated by the Smart and Moderate Aperture Research Telescope System (SMARTS) Consortium; we are particularly grateful for the scheduling flexibility of SMARTS. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. We made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

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Created:
August 21, 2023
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October 25, 2023