THE GOLDEN STANDARD TYPE Ia SUPERNOVA 2005cf: OBSERVATIONS FROM THE ULTRAVIOLET TO THE NEAR-INFRARED WAVEBANDS
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138 (United States)
- Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States)
- Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom)
- Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rhovot (Israel)
- Department of Physics, Texas A and M University, College Station, Texas, 77843 (United States)
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 1{sigma} scatter of {approx}<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 {delta}m {sub 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){sub 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 A 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 and K doublet and NIR triplet, which were distinctly detached from the photosphere (v {approx} 10,000 km s{sup -1}) at a velocity ranging from 20,000 to 25,000 km s{sup -1}. One interesting feature is the flat-bottomed absorption observed near 6000 A in the earliest spectrum, which rapidly evolved into a triangular shape and then became a normal Si II {lambda}6355 absorption profile at about one week before maximum brightness. This premaximum spectral evolution is perhaps due to the blending of the Si II{lambda}6355 at photospheric velocity and another HV absorption component (e.g., an Si II shell at a velocity {approx}18,000 km s{sup -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.
- OSTI ID:
- 21300583
- Journal Information:
- Astrophysical Journal, Vol. 697, Issue 1; Other Information: DOI: 10.1088/0004-637X/697/1/380; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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