1. Massive stars exploding in a He-rich circumstellar medium - X : flash spectral features in the Type Ibn SN 2019cj and observations of SN 2018jmtZ.-Y. Wang, A. Pastorello, K. Maeda, A. Reguitti, Y.-Z. Cai, D. Andrew Howell, S. Benetti, Mateusz Bronikowski, E. Concepcion, Tanja Petrushevska, 2024, original scientific article Abstract: We present optical and near-infrared observations of two Type Ibn supernovae (SNe), SN\,2018jmt and SN\,2019cj. Their light curves have rise times of about ten days, reaching an absolute peak magnitude of $M_g$(SN\,2018jmt) = $-$19.07 pm 0.37 and $M_V$(SN\,2019cj) = $-$18.94 pm 0.19 mag, respectively. The early-time spectra of SN\,2018jmt are dominated by a blue continuum, accompanied by narrow (600$-$1000 km $) He i lines with the P-Cygni profile. At later epochs, the spectra become more similar to those of the prototypical SN Ibn 2006jc. At early phases, the spectra of SN\,2019cj show flash ionisation emission lines of C iii N iii and He ii superposed on a blue continuum. These features disappear after a few days, and then the spectra of SN\,2019cj evolve similarly to those of SN\,2018jmt. The spectra indicate that the two SNe exploded within a He-rich circumstellar medium (CSM) lost by the progenitors a short time before the explosion. We modelled the light curves of the two SNe Ibn to constrain the progenitor and the explosion parameters. The ejecta masses are consistent with either what is expected for a canonical SN Ib (sim 2 odot $) or for a massive Wolf Rayet star ($>$ sim 4 M$_ odot $), with the kinetic energy on the order of $10^ $ erg. The lower limit on the ejecta mass ($>$ sim 2 M odot $) argues against a scenario involving a relatively low-mass progenitor (e.g. $M_ ZAMS $ sim 10 M$_ odot $). We set a conservative upper limit of sim 0.1 M$_ odot $ for the 56Ni masses in both SNe. From the light curve modelling, we determined a two-zone CSM distribution, with an inner, flat CSM component and an outer CSM with a steeper density profile. The physical properties of SN\,2018jmt and SN\,2019cj are consistent with those expected from the core collapse of relatively massive envelope-stripped stars.
Keywords: supernovae
Published in RUNG: 06.11.2024; Views: 317; Downloads: 3
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2. Spectroscopic analysis of the strongly lensed SN Encore : constraints on cosmic evolution of Type Ia supernovaeS. Dhawan, Justin Pierel, M. Gu, A. B. Newman, C. Larison, M. Siebert, Tanja Petrushevska, F. Poidevin, S. W. Jha, W. Chen, 2024, original scientific article Abstract: Abstract
Strong gravitational lensing magnifies the light from a background source, allowing us to study these sources in detail. Here, we study the spectra of a z = 1.95 lensed Type Ia supernova SN Encore for its brightest Image A, taken 39 days apart. We infer the spectral age with template matching using the supernova identification (SNID) software and find the spectra to be at 29.0 ±5.0 and 37.4 ±2.8 rest-frame days post maximum respectively, consistent with separation in the observer frame after accounting for time-dilation. Since SNe Ia measure dark energy properties by providing relative distances between low- and high-z SNe, it is important to test for evolution of spectroscopic properties. Comparing the spectra to composite low-z SN Ia spectra, we find strong evidence for similarity between the local sample and SN Encore. The line velocities of common SN Ia spectral lines, Si II 6355 and Ca II NIR triplet are consistent with the distribution for the low-z sample as well as other lensed SNe Ia, e.g. iPTF16geu (z = 0.409)and SN H0pe (z = 1.78). The consistency between the low-z sample and lensed SNe at high-z suggests no obvious cosmic evolution demonstrating their using as high-z distance indicators, though this needs to be confirmed/refuted via a larger sample. We also find that the spectra of SN Encore match the predictions for explosion models very well. With future large samples of lensed SNe Ia e.g. with the Vera C. Rubin Observatory, spectra at such late phases will be important to distinguish between different explosion scenarios.
Keywords: Encore
Published in RUNG: 29.10.2024; Views: 389; Downloads: 1
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4. Strongly lensed supernovae, the past and the future : lecture at the University of Cambridge, 26. 6. 2024Tanja Petrushevska, 2024, invited lecture at foreign university Abstract: The searches and observations of supernovae (SNe) have been motivated by the fact that they are exceptionally useful for various astrophysical and cosmological applications. Most prominently, Type Ia SNe (SNe Ia) have been used as distance indicators showing that the expansion rate of the Universe is accelerating. The strong gravitational lensing effect provides another powerful tool and occurs when a foreground mass distribution is located along the line of sight to a background source. It can happen so that galaxies and galaxy clusters can act as “gravitational telescopes”, boosting the faint signals from distant SNe and galaxies. Thanks to the magnification boost provided by the gravitational telescope, we are able to probe galaxies and SNe that otherwise would be undetectable. Therefore, the combination of the two tools, SNe and strong lensing, in the single phenomenon of strongly lensed SNe, provides a powerful simultaneous probe of several cosmological and astrophysical phenomena. By measuring the time delays of strongly lensed supernovae and having a high-quality strong lensing model of the galaxy cluster, it is possible to measure the Hubble constant with competitive precision. In this talk, I will present some of the past and recent results that have been possible due to the observations of strongly lensed supernovae and anticipate what we can expect in the future from the upcoming telescope surveys, such as the Vera C. Rubin Observatory and Nancy G. Roman Space Telescope.
Keywords: supernova, strong lensing, Hubble constant
Published in RUNG: 26.06.2024; Views: 765; Downloads: 12
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6. Lensed type Ia supernova “Encore” at z=2 : the first instance of two multiply imaged supernovae in the same host galaxyJustin Pierel, A. B. Newman, S. Dhawan, M. Gu, B. A. Joshi, T. Li, S. Schuldt, L. G. Strolger, S. H. Suyu, Tanja Petrushevska, 2024, original scientific article Keywords: supernova, James Webb Space Telescope, Hubble constant
Published in RUNG: 31.05.2024; Views: 1073; Downloads: 9
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8. JWST photometric time-delay and magnification measurements for the triply imaged type ia "SN H0pe" at z=1.78Justin Pierel, B. L. Frye, M. Pascale, Gabriel Bartosch Caminha, W. Chen, S. Dhawan, D. Gilman, M. Grayling, Mateusz Bronikowski, Tanja Petrushevska, 2024, original scientific article Keywords: supernova, strong lensing, cosmology, Hubble constant, James Webb Space Telescope
Published in RUNG: 21.05.2024; Views: 1137; Downloads: 8
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9. Hevreka (Supernove tipa 1a)Tanja Petrushevska, Japelj Jure, radio or television broadcast, podcast, interview, press conference Abstract: V vesolju tudi poka kot za stavo. Zvezde, ki večino življenja ne počnejo nič drugega kot spreminjajo vodik v helij, si včasih zaželijo pozornosti in eksplodirajo kot supernove. Zvezda kar naenkrat postana svetlejša od celotne galaksije, zato supernove vidimo tudi, ko eksplodirajo daleč, daleč stran. Astronomi vesoljski ognjemet seveda z veseljem opazujejo. Supernove namreč niso zgolj izjemno svetle, ampak igrajo pomembno vlogo pri številnih procesih v vesolju. Kozmične eksplozije so različnih tipov in okusov, verjetno najbolj slavne med njimi pa so supernove tipa 1a. Te nam je približala doktorica Tanja Petrushevska, docentka na Fakulteti za naravoslovje Univerze v Novi Gorici. Pred mikrofon jo je povabil dr. Jure Japelj.
Keywords: radio, intervju, supernova
Published in RUNG: 24.11.2023; Views: 1303; Downloads: 4
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