"New" B and V Photometry of the "Old" Type IA Supernova SN 1937C: Implications for HO

Abstract

view Abstract Citations (33) References (60) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS "New" B and V Photometry of the "Old" Type IA Supernova SN 1937C: Implications for HO Pierce, Michael J. ; Jacoby, George H. Abstract We have digitized and analyzed the original Baade and Zwicky 18 in. Palomar Schmidt films of the type Ia supernova SN 1937C. The data set consists of 76 films in the photographic bandpass mpg and a series of 50 previously unreduced photovisual (m_pv_) films. These data were supplemented by the three known, prediscovery plates of SN 1937C taken by Leutenegger and Grenat. The films and plates were scanned using the KPNO PDS microdensitometer and calibrated by fitting the integrated photographic density to a magnitude sequence of local standards on each film/plate. The resulting calibrations have typical rms dispersions of 0.06 and 0.04 mag for m_pg_ and m_pv_, respectively. Our magnitudes at the earliest epochs are systematically 0.30 mag fainter than those reported by Baade & Zwicky, with the two datasets converging by the eighth observation, about 11 days after maximum. We converted our mpg and mpv photometry to B and V using transformations determined both theoretically using synthetic photometry of spectrophotometric standards, and empirically using the local standard stars. The B and V light curves and B - V color evolution of SN 1937C were fitted with template light curves from previously well-observed supernovae to obtain B_max_= 8.94+/- 0.03, V_max_ = 9.00+/-0.03, and (B - V)_B(max)_ = -0.08 +/- 0.04. These correspond to M(B_max_)= - 19.42 and M( V_max_)= - 19.36 when combined with the Cepheid distance to IC 4182, the host galaxy. In comparing our results with the visual photometry of Beyer we found evidence for a color term which when applied to Beyer's data, leads to V_max_ = 8.87. We stress the importance of determining accurate color terms in the photometry of SN Ia due to the wide color range (from B - V ~ 0 to B - V ~1) through which they evolve over the first 30 days after maximum. The SN 1937C light curves were best fit by templates with very slow rates of decline. The correlation between decline rate and luminosity implies that SN 1937C, with {DELTA}m_15_ = 0.85 mag, was as much as 0.44 mag more luminous than average SN Ia and that it was one of the most intrinsically luminous SN Ia studied to date. The luminosity calibration for SN 1937C was applied to the Hubble relation derived by Hamuy et al. for which distant SNe magnitudes were corrected for their decline rates. This calibration of the SN Ia distance scale yields a Hubble Constant between H_0_ = 68+/-5 km s^-1^ Mpc^-1^ and H_0_ = 74+/-6 km s^-1^ Mpc^-1^, depending on the choice of slope for the decline rate relation. Publication: The Astronomical Journal Pub Date: December 1995 DOI: 10.1086/117737 Bibcode: 1995AJ....110.2885P Keywords: SUPERNOVAE: INDIVIDUAL: SN 1937C; ISM: ABUNDANCES full text sources ADS | data products SIMBAD (8) NED (2)