Examinando por Autor "Kirshner, Robert P."

Mostrando 1 - 2 de 2
  • Miniatura
    Ítem
    High-density circumstellar interaction in the luminous type IIn SN 2010jl: The first 1100 days
    (Institute of Physics Publishing, 2014) Fransson, Claes; Ergon, Mattias; Challis, Peter J.; Chevalier, Roger A.; France, Kevin; Kirshner, Robert P.; Marion G., H.; Milisavljevic, Dan; Smith, Nathan; Bufano, Filomena; Friedman, Andrew S.; Kangas, Tuomas; Larsson, Josefin; Mattila, Seppo; Benetti, Stefano; Chornock, Ryan; Czekala, Ian; Soderberg, Alicia; Sollerman, Jesper
    Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was ∼ 3 × 1043 erg s-1 and even at 850 days exceeds 1042 erg s-1. A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is ≳ 6.5 × 1050 erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity ∼ 100 km s-1 from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after ∼50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r-2 CSM with a mass-loss rate of M ∼ 0.1 M⊙ yr-1. The total mass lost is ≳3 M⊙. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering. © 2014. The American Astronomical Society. All rights reserved.
  • No hay miniatura disponible
    Ítem
    Type IIb supernova SN 2011dh: Spectra and photometry from the ultraviolet to the near-infrared
    (Institute of Physics Publishing, 2014-02) Marion, G.H.; Vinko, Jozsef; Kirshner, Robert P.; Foley, Ryan J.; Berlind, Perry; Bieryla, Allyson; Bloom, Joshua S.; Calkins, Michael L.; Challis, Peter; Chevalier, Roger A.; Chornock, Ryan; Culliton, Chris; Curtis, Jason L.; Esquerdo, Gilbert A.; Everett, Mark E.; Falco, Emilio E.; France, Kevin; Fransson, Claes; Friedman, Andrew S.; Garnavich, Peter; Leibundgut, Bruno; Meyer, Samuel; Smith, Nathan; Soderberg, Alicia M.; Sollerman, Jesper; Starr, Dan L.; Szklenar, Tamas; Takats, Katalin; Wheeler, J. Craig
    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). The data cover a wide wavelength range from 2000 Å in the ultraviolet (UV) to 2.4μm in the near-infrared (NIR). Optical spectra provide line profiles and velocity measurements of H i, He i, Ca ii, and Fe ii that trace the composition and kinematics of the supernova (SN). NIR spectra show that helium is present in the atmosphere as early as 11 days after the explosion. A UV spectrum obtained with the Space Telescope Imaging Spectrograph reveals that the UV flux for SN 2011dh is low compared to other SN IIb. Modeling the spectrum with SYNOW suggests that the UV deficit is due to line blanketing from Ti ii and Co ii. The H i and He i velocities in SN 2011dh are separated by about 4000 km s−1 at all phases. A velocity gap is consistent with models for a preexplosion structure in which a hydrogen-rich shell surrounds the progenitor. We estimate that the H shell of SN 2011dh is ≈8 times less massive than the shell of SN 1993J and ≈3 times more massive than the shell of SN 2008ax. Light curves (LCs) for 12 passbands are presented: UVW2, UVM2, UVW1,U,u ,B,V,r ,i ,J,H, and Ks. In the B band, SN 2011dh reached peak brightness of 13.17 mag at 20.0 ± 0.5 after the explosion. The maximum bolometric luminosity of 1.8 ± 0.2 × 1042 erg s−1 occurred ≈22 days after the explosion. NIR emission provides more than 30% of the total bolometric flux at the beginning of our observations, and the NIR contribution increases to nearly 50% of the total by day 34. The UV produces 16% of the total flux on day 4, 5% on day 9, and 1% on day 34. We compare the bolometric LCs of SN 2011dh, SN 2008ax, and SN 1993J. The LC are very different for the first 12 days after the explosions, but all three SN IIb display similar peak luminosities, times of peak, decline rates, and colors after maximum. This suggests that the progenitors of these SN IIb may have had similar compositions and masses, but they exploded inside hydrogen shells that have a wide range of masses. SN 2011dh was well observed, and a likely progenitor star has been identified in preexplosion images. The detailed observations presented here will help evaluate theoretical models for this SN and lead to a better understanding of SN IIb.