Examinando por Autor "Singh, Mridweeka"
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Ítem Bridging between Type IIb and Ib Supernovae: SN IIb 2022crv with a Very Thin Hydrogen Envelope(Institute of Physics, 2023-11) Gangopadhyay, Anjasha; Maeda, Keiichi; Singh, Avinash; Nayana A.J.; Nakaoka, Tatsuya; Kawabata, Koji S.; Taguchi, Kenta; Singh, Mridweeka; Chandra, Poonam; Ryder, Stuart D.; Dastidar, Raya; Yamanaka, Masayuki; Kawabata, Miho; Alsaberi, Rami Z. E.; Dukiya, Naveen; Teja, Rishabh Singh; Ailawadhi, Bhavya; Dutta, Anirban; Sahu, D.K.; Moriya, Takashi J.; Misra, Kuntal; Tanaka, Masaomi; Chevalier, Roger; Tominaga, Nozomu; Uno, Kohki; Imazawa, Ryo; Hamada, Taisei; Hori, Tomoya; Isogai, KeisukeWe present optical, near-infrared, and radio observations of supernova (SN) SN IIb 2022crv. We show that it retained a very thin H envelope and transitioned from an SN IIb to an SN Ib; prominent Hα seen in the pre-maximum phase diminishes toward the post-maximum phase, while He i lines show increasing strength. SYNAPPS modeling of the early spectra of SN 2022crv suggests that the absorption feature at 6200 Å is explained by a substantial contribution of Hα together with Si ii, as is also supported by the velocity evolution of Hα. The light-curve evolution is consistent with the canonical stripped-envelope SN subclass but among the slowest. The light curve lacks the initial cooling phase and shows a bright main peak (peak M V = −17.82 ± 0.17 mag), mostly driven by radioactive decay of 56Ni. The light-curve analysis suggests a thin outer H envelope (M env ∼ 0.05 M ⊙) and a compact progenitor (R env ∼ 3 R ⊙). An interaction-powered synchrotron self-absorption model can reproduce the radio light curves with a mean shock velocity of 0.1c. The mass-loss rate is estimated to be in the range of (1.9−2.8) × 10−5 M ⊙ yr−1 for an assumed wind velocity of 1000 km s−1, which is on the high end in comparison with other compact SNe IIb/Ib. SN 2022crv fills a previously unoccupied parameter space of a very compact progenitor, representing a beautiful continuity between the compact and extended progenitor scenario of SNe IIb/Ib.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 2017gmr: An Energetic Type II-P Supernova with Asymmetries(Institute of Physics Publishing, 2019-11-01) Andrews, Jennifer E.; Sand D.J.; Valenti S.; Smith, Nathan; Dastidar, Raya; Sahu D.K.; Misra, Kuntal; Singh, Avinash; Hiramatsu D.; Brown P.J.; Hosseinzadeh G.; Wyatt S.; Vinko J.; Anupama G.C.; Arcavi I.; Ashall, Chris; Benetti S.; Berton, Marco; Bostroem K.A.; Bulla M.; Burke J.; Chen S.; Chomiuk L.; Cikota A.; Congiu E.; Cseh B.; Davis, Scott; Elias-Rosa N.; Faran T.; Fraser, Morgan; Galbany L.; Gall C.; Gal-Yam A.; Gangopadhyay, Anjasha; Gromadzki M.; Haislip J.; Howell D.A.; Hsiao E.Y.; Inserra C.; Kankare E.; Kuncarayakti H.; Kouprianov V.; Kumar, Brajesh; Li, Xue; Lin, Han; Maguire K.; Mazzali P.; McCully C.; Milne P.; Mo, Jun; Morrell N.; Nicholl M.; Ochner P.; Olivares F.; Pastorello A.; Patat F.; Phillips M.; Pignata G.; Prentice S.; Reguitti A.; Reichart D.E.; Rodríguez Ó.; Rui, Liming; Sanwal, Pankaj; Sárneczky K.; Shahbandeh M.; Singh, Mridweeka; Smartt S.; Strader J.; Stritzinger M.D.; Szakáts R.; Tartaglia L.; Wang, Huijuan; Wang, Lingzhi; Wang, Xiaofeng; Wheeler J.C.; Xiang, Danfeng; Yaron O.; Young D.R.; Zhang, JunboWe present high-cadence UV, optical, and near-infrared data on the luminous Type II-P supernova SN 2017gmr from hours after discovery through the first 180 days. SN 2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early light curve indicates a ∼500 R o progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130 ± 0.026 M o of 56Ni are present, if the light curve is solely powered by radioactive decay, although the 56Ni mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of Hα and [O i] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first 2 days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.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.Ítem Unveiling the nature of two dwarf novae: CRTS J080846.2+313106 and V416 Dra(EDP Sciences, 2024-09-01) Joshi, Arti; Catelan, Márcio; Scaringi, Simone; Schwope, Axel; Anupama G.C.; Rawat, Nikita; Sahu, Devendra K.; Singh, Mridweeka; Dastidar, Raya; Subramanian, Rama Venkata; Rao, Srinivas M.We present the analysis of optical photometric and spectroscopic observations of two non-magnetic cataclysmic variables, namely CRTS J080846.2+313106 and V416 Dra. We find CRTS J080846.2+313106 to vary with a period of 4.9116 ± 0.0003 h, which was not found in earlier studies and which we provisionally suggest is the orbital period of the system. In both long-period systems, the observed dominant signal at the second harmonic of the orbital frequency and the orbital modulation during quiescence are suggestive of ellipsoidal variation from changing aspects of the secondary, with an additional contribution from the accretion stream or hotspot. However, during the outburst, the hotspot itself is overwhelmed by the increased brightness, which is possibly associated with the accretion disc. The mid-eclipse phase for V416 Dra occurs earlier and the width of the eclipse is greater during outbursts compared to quiescence, suggesting an increased accretion disc radius during outbursts. Furthermore, from our investigation of the accretion disc eclipse in V416 Dra, we find that a total disc eclipse is possible during quiescence, whereas the disc seems to be partially obscured during outbursts, which further signifies that the disc may grow in size as the outburst progresses. The optical spectra of CRTS J080846.2+313106 and V416 Dra are typical of dwarf novae during quiescence, and they both show a significant contribution from the M2-4V secondary. The light curve patterns, orbital periods, and spectra observed in the two systems look remarkably similar, and seem to resemble the characteristics of U Gem-type dwarf novae.