Examinando por Autor "Srivastav, Shubham"
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Ítem Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg(Institute of Physics, 2023-08) Singh, Mridweeka; Sahu, Devendra. K.; Dastidar, Raya; Barna, Barnabás; Misra, Kuntal; Gangopadhyay, Anjasha; Howell, D. Andrew; Jha, Saurabh W.; Im, Hyobin; Taggart, Kirsty; Andrews, Jennifer; Hiramatsu, Daichi; Teja, Rishabh Singh; Pellegrino, Craig; Foley, Ryan J.; Joshi, Arti; Anupama G.C.; Bostroem, K. Azalee; Burke, Jamison; Camacho-Neves, Yssavo; Dutta, Anirban; Kwok, Lindsey A. i; McCully, Curtis; Pan, Yen-Chen; Siebert, Matt; Srivastav, Shubham; Szalai, Tamás; Swift, Jonathan J.; Yang, Grace; Zhou, Henry; DiLullo, Nico; Scheer, JacksonWe present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN (M V,peak = −17.81 ± 0.21 mag), whereas SN 2020kyg (M V,peak = −14.52 ± 0.21 mag) is a faint one. We derive 56Ni mass of 0.07 and 0.002 M ⊙and ejecta mass of 0.48 and 0.14 M ⊙ for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R/r-band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe. © 2023. The Author(s). Published by the American Astronomical Society.Ítem 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 SinghWe 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.Ítem SN 2020kyg and the rates of faint Iax supernovae from ATLAS(Oxford University Press, 2022-04-01) Srivastav, Shubham; Smartt, S.J.; Huber, M.E.; Chambers, K.C.; Angus, C.R.; Chen, T.-W.; Callan, F.P.; Gillanders, J.H.; McBrien, O.R.; Sim, S.A.; Fulton, M.; Hjorth, J.; Smith, K.W.; Young, D.R.; Auchettl, K.; Anderson, J.P.; Pignata, G.; De Boer, T.J.L.; Lin, C.-C.; Magnier, E.A.We present multiwavelength follow-up observations of the ATLAS discovered faint Iax supernova SN 2020kyg that peaked at an absolute magnitude of Mg ≈-14.9 ± 0.2, making it another member of the faint Iax supernova population. The bolometric light curve requires only ≈7 × 10-3 M· of radioactive 56Ni, with an ejected mass of Mej ∼0.4 M· and a low kinetic energy of E ≈ 0.05 ± 0.02 × 1051 erg. We construct a homogeneous volume-limited sample of 902 transients observed by ATLAS within 100 Mpc during a 3.5 yr span. Using this sample, we constrain the rates of faint Iax (Mr ≳-16) events within 60 Mpc at 12+14-8 per cent of the SN Ia rate. The overall Iax rate, at 15+17-9 per cent of the Ia rate, is dominated by the low-luminosity events, with luminous SNe Iax (Mr ≲-17.5) like 2002cx and 2005hk, accounting for only 0.9+1.1-0.5 per cent of the Ia rate (a 2σ upper limit of approximately 3 per cent). We favour the hybrid CONe WD + He star progenitor channel involving a failed deflagration of a near Chandrasekhar mass white dwarf, expected to leave a bound remnant and a surviving secondary companion, as a candidate explanation for faint Iax explosions. This scenario requires short delay times, consistent with the observed environments of SNe Iax. Furthermore, binary population synthesis calculations have suggested rates of 1-18 per cent of the SN Ia rate for this channel, consistent with our rate estimates. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Ítem 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, AnirbanWe 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.