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Villar, Ashley

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Villar

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Ashley

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Villar, Ashley
Author's Publications: search.filters.isAuthorOfPublication.c1163cea-41e7-411a-aa70-d8b13349cc95

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    The Intermediate Luminosity Optical Transient Sn 2010da: The Progenitor, Eruption, and Aftermath of a Peculiar Supergiant High-Mass X-Ray Binary
    (American Astronomical Society, 2016) Villar, Ashley; Berger, Edo; Chornock, R.; Margutti, R.; Laskar, T.; Brown, P. J.; Blanchard, Peter; Czekala, Ian; Lunnan, R.; Reynolds, M. T.
    We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d = 1.86 Mpc) spanning from −6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10–12 M ⊙ yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M bol lesssim −10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca ii emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L X ≈ 6 × 1039 erg s−1). We additionally attribute He ii 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈1037 erg s−1 to the presence of a compact companion.
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    PS1-14bj: A Hydrogen-poor Superluminous Supernova with a Long Rise and Slow Decay.
    (American Astronomical Society, 2016) Lunnan, R.; Chornock, R.; Berger, Edo; Milisavljevic, Danny; Jones, D. O.; Rest, A.; Fong, W.; Fransson, C.; Margutti, R.; Drout, M. R.; Blanchard, Peter; Challis, P.; Cowperthwaite, Philip; Foley, R. J.; Kirshner, Robert; Morrell, N.; Riess, A. G.; Roth, K. C.; Scolnic, D.; Smartt, S. J.; Smith, K. W.; Villar, Ashley; Chambers, K. C.; Draper, P. W.; Huber, M. E.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Waters, C.
    We present photometry and spectroscopy of PS1-14bj, a hydrogen-poor superluminous supernova (SLSN) at redshift z = 0.5215 discovered in the last months of the Pan-STARRS1 Medium Deep Survey. PS1-14bj stands out by its extremely slow evolution, with an observed rise of ∼ > 125 restframe days, and exponential decline out to ∼ 250 days past peak at a measured rate of 0.01 mag day−1, consistent with fully-trapped 56Co decay. This is the longest rise time measured in a SLSN to date, and the first SLSN to show a rise time consistent with pair-instability supernova (PISN) models. Compared to other slowly-evolving SLSNe, it is spectroscopically similar to the prototype SN 2007bi at maximum light, though lower in luminosity (Lpeak ≃ 4.6×1043ergs−1) and with a flatter peak than previous events. PS1-14bj shows a number of peculiar properties, including a near-constant color temperature for > 200 days past peak, and strong emission lines from [O III] λ5007 and [O III] λ4363 with a velocity width of ∼3400 km s−1 in its late-time spectra. These both suggest there is a sustained source of heating over very long timescales, and are incompatible with a simple 56Ni-powered/PISN interpretation. A modified magnetar model including emission leakage at late times can reproduce the light curve, in which case the blue continuum and [O III] features are interpreted as material heated and ionized by the inner pulsar wind nebula becoming visible at late times. Alternatively, the late-time heating could be due to interaction with a shell of H-poor circumstellar material.