1303.5482 (G. H. "Howie'' Marion et al.)

Type IIb Supernova SN 2011dh: Spectra and Photometry from the Ultraviolet to the Near-Infrared    [PDF]

G. H. "Howie'' Marion, Jozsef Vinko, Robert P. Kirshner, Ryan J. Foley, Perry Berlind, Allyson Bieryla, Joshua S. Bloom, Michael L. Calkins, Peter Challis, Roger A. Chevalier, Ryan Chornock, Chris Culliton, Jason L. Curtis, Gilbert A. Esquerdo, Mark E. Everett, Emilio E. Falco, Kevin France, Claes Fransson, Andrew S. Friedman, Peter Garnavich, Bruno Leibundgut, Samuel Meyer, Nathan Smith, Alicia M. Soderberg, Jesper Sollerman, Dan L. Starr, Tamas Szklenar, Katalin Takats, J. Craig Wheeler

We report spectroscopic and photometric observations of the Type IIb SN 2011dh obtained between 4 and 34 days after the estimated date of explosion (May 31.5 UT). These data cover a wide wavelength range from 2000 Angstroms in the ultraviolet (UV) to 2.4 microns in the near-infrared (NIR). NIR spectra reveal helium in the atmosphere 3 days before the B-band maximum and confirm the classification of SN 2011dh as a Type IIb. Optical spectra provide line profiles and velocity measurements of H I, He I, Ca II and Fe II. UV spectra obtained with the Space Telescope Imaging Spectrograph show that the UV flux for SN 2011dh is low compared to other SN IIb. H I features are strong early and weaken during the period of our observations. He I features are first detected eleven days after the explosion and become progressively stronger. For all phases at which He is detected, the hydrogen line-forming region is separated from the helium layer by about 4000 km/s. This velocity gap is consistent with a H-rich shell surrounding the progenitor and we estimate the shell mass for SN 2011dh relative to other SN IIb. Both H I and He I maintain a constant velocity after B-max while Ca II and Fe II velocities continue to decline. Light curves are presented for twelve passbands. SN 2011dh reached a maximum bolometric luminosity of 1.7 x 10^{42} erg/s, about 23 days after the explosion. NIR emission contributes more than 35% of the total bolometric flux. We compare our results to other studies of SN 2011dh and to other Type IIb SN. We find that SN IIb with different masses for the H shell have similar peak luminosities, decline rates and colors from the time of maximum. That suggests that the progenitors inside of the H shells are close to the same composition and mass. These data will provide firm constraints for models of SN 2011dh based on the explosion of a yellow supergiant.

View original: http://arxiv.org/abs/1303.5482