Examinando por Autor "Howell, D. Andrew"

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    Monthly Notices of the Royal Astronomical Society
    (Oxford University Press, 2020-02) Clark, Peter; Maguire, Kate; Inserra, Cosimo; Prentice, Simon; Stephen, J. Smartt; Contreras, Carlos; Hossenizadeh, Griffin; Hsiao, Eric Y.; Kankare, Erkki; Kasliwal, Mansi; Nugent, Peter; Shahbandeh, Melissa; Baltay, Charles; Rabinowitz, David; Arcavi, Iair; Ashall, Chris; Burns, Christopher R.; Callis, Emma; Chen, Ting-Wan; Diamond, Tiara; Fraser, Morgan; Howell, D. Andrew; Karamehmetoglu, Emir; Kotak, Rubina; Lyman, Joseph; Morrell, Nidia; Phillips, Mark; Pignata, Giuliano; Pursiainen, Miika; Sollerman, Jesper; Stritzinger, Maximilian; Sullivan, Mark; Young, David
    This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of −19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive 56Ni powering but can be explained through a combination of CSM interaction and an underlying 56Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib. © 2019 The Author(s)
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    Optical studies of a bright type Iax supernova SN 2020rea
    (Oxford University Press, 2022-12) Singh, Mridweeka; Misra, Kuntal; Sahu, Devendra K.; Ailawadhi, Bhavya; Dutta, Anirban; Howell, D. Andrew; Anupama, G.C.; Bostroem, K. Azalee; Burke, Jamison; Dastidar, Raya; Gangopadhyay, Anjasha; Hiramatsu, Daichi; Im, Hyobin; Mccully, Curtis; Pellegrino, Craig; Srivastav, Shubham; Teja, Rishabh Singh
    We present optical photometric and spectroscopic analysis of a Type Iax supernova (SN) 2020rea situated at the brighter luminosity end of Type Iax supernovae (SNe). The light curve decline rate of SN 2020rea is m15(g) = 1.31 ± 0.08 mag which is similar to SNe 2012Z and 2005hk. Modelling the pseudo-bolometric light curve with a radiation diffusion model yields a mass of 56Ni of 0.13 ± 0.01 M and an ejecta mass of 0.77+0.11 −0.21 M . Spectral features of SN 2020rea during the photospheric phase show good resemblance with SN 2012Z. TARDIS modelling of the early spectra of SN 2020rea reveals a dominance of Iron Group Elements (IGEs). The photospheric velocity of the Si II line around maximum for SN 2020rea is ∼ 6500 km s−1 which is less than the measured velocity of the Fe II line and indicates significant mixing. The observed physical properties of SN 2020rea match with the predictions of pure deflagration model of a Chandrasekhar mass C–O white dwarf. The metallicity of the host galaxy around the SN region is 12 + log(O/H) = 8.56 ± 0.18 dex which is similar to that of SN 2012Z.
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    SN 2020udy: A New Piece of the Homogeneous Bright Group in the Diverse Iax Subclass
    (Institute of Physics, 2024-04-01) Singh, Mridweeka; Sahu, Devendra K.; Barna, Barnabás; Gangopadhyay, Anjasha; Dastidar, Raya; Teja, Rishabh Singh; Misra, Kuntal; Howell, D. Andrew; Wang, Xiaofeng; Mo, Jun; Yan, Shengyu; Hiramatsu, Daichi; Pellegrino, Craig; Anupama G.C.; Joshi, Arti; Bostroem, K. Azalee; Burke, Jamison; McCully, Curtis; Subramanian V, Rama; Li, Gaici; Xi, Gaobo; Li, Xin; Li, Zhitong; Srivastav, Shubham; Im, Hyobin; Dutta, Anirban
    We present optical observations and analysis of the bright type Iax supernova SN 2020udy hosted by NGC 0812. The evolution of the light curve of SN 2020udy is similar to that of other bright type Iax SNe. Analytical modeling of the quasi-bolometric light curves of SN 2020udy suggests that 0.08 ± 0.01 M ⊙ of 56Ni would have been synthesized during the explosion. The spectral features of SN 2020udy are similar to those of the bright members of type Iax class, showing a weak Si ii line. The late-time spectral sequence is mostly dominated by iron group elements with broad emission lines. Abundance tomography modeling of the spectral time series of SN 2020udy using TARDIS indicates stratification in the outer ejecta; however, to confirm this, spectral modeling at a very early phase is required. After maximum light, uniform mixing of chemical elements is sufficient to explain the spectral evolution. Unlike in the case of normal type Ia SNe, the photospheric approximation remains robust until +100 days, requiring an additional continuum source. Overall, the observational features of SN 2020udy are consistent with the deflagration of a carbon-oxygen white dwarf.