分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. M. DerKacy
S. Paugh
E. Baron
P. J. Brown
C. Ashall
C. R. Burns
E. Y. Hsiao
S. Kumar
J. Lu
N. Morrell
M. M. Phillips
M. Shahbandeh
B. J. Shappee
M. D. Stritzinger
M. A. Tucker
Z. Yarbrough
K. Boutsia
P. Hoeflich
L. Wang
L. Galbany
摘要： We present ultraviolet (UV) to near-infrared (NIR) observations and analysis of the nearby Type Ia supernova SN 2021fxy. Our observations include UV photometry from Swift/UVOT, UV spectroscopy from HST/STIS, and high-cadence optical photometry with the Swope 1-m telescope capturing intra-night rises during the early light curve. Early $B-V$ colours show SN 2021fxy is the first "shallow-silicon" (SS) SN Ia to follow a red-to-blue evolution, compared to other SS objects which show blue colours from the earliest observations. Comparisons to other spectroscopically normal SNe Ia with HST UV spectra reveal SN 2021fxy is one of several SNe Ia with flux suppression in the mid-UV. These SNe also show blue-shifted mid-UV spectral features and strong high-velocity Ca II features. One possible origin of this mid-UV suppression is the increased effective opacity in the UV due to increased line blanketing from high velocity material, but differences in the explosion mechanism cannot be ruled out. Among SNe Ia with mid-UV suppression, SNe 2021fxy and 2017erp show substantial similarities in their optical properties despite belonging to different Branch subgroups, and UV flux differences of the same order as those found between SNe 2011fe and 2011by. Differential comparisons to multiple sets of synthetic SN Ia UV spectra reveal this UV flux difference likely originates from a luminosity difference between SNe 2021fxy and 2017erp, and not differing progenitor metallicities as suggested for SNe 2011by and 2011fe. These comparisons illustrate the complicated nature of UV spectral formation, and the need for more UV spectra to determine the physical source of SNe Ia UV diversity.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
S. Moran
M. Fraser
R. Kotak
A. Pastorello
S. Benetti
S. J. Brennan
C. P. Gutiérrez
E. Kankare
H. Kuncarayakti
S. Mattila
T. M. Reynolds
J. P. Anderson
P. J. Brown
S. Campana
K. C. Chambers
T. -W. Chen
M. Della Valle
M. Dennefeld
N. Elias-Rosa
L. Galbany
摘要： In this study we present the results of a five-year follow-up campaign of the long-lived type IIn supernova SN 2017hcc, found in a spiral dwarf host of near-solar metallicity. The long rise time (57 $\pm$ 2 days, ATLAS $o$ band) and high luminosity (peaking at $-$20.78 $\pm$ 0.01 mag in the ATLAS $o$ band) point towards an interaction of massive ejecta with massive and dense circumstellar material (CSM). The evolution of SN 2017hcc is slow, both spectroscopically and photometrically, reminiscent of the long-lived type IIn, SN 2010jl. An infrared (IR) excess was apparent soon after the peak, and blueshifts were noticeable in the Balmer lines starting from a few hundred days, but appeared to be fading by around +1200 days. We posit that an IR light echo from pre-existing dust dominates at early times, with some possible condensation of new dust grains occurring at epochs >$\sim$+800 days.
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