학술논문
SN 2019ehk: A Double-Peaked Ca-rich Transient with Luminous X-ray Emission and Shock-Ionized Spectral Features
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Working Paper
Author
Jacobson-Galán, Wynn V.; Margutti, Raffaella; Kilpatrick, Charles D.; Hiramatsu, Daichi; Perets, Hagai; Khatami, David; Foley, Ryan J.; Raymond, John; Yoon, Sung-Chul; Bobrick, Alexey; Zenati, Yossef; Galbany, Lluís; Andrews, Jennifer; Brown, Peter J.; Cartier, Régis; Coppejans, Deanne L.; Dimitriadis, Georgios; Dobson, Matthew; Hajela, Aprajita; Howell, D. Andrew; Kuncarayakti, Hanindyo; Milisavljevic, Danny; Rahman, Mohammed; Rojas-Bravo, César; Sand, David J.; Shepherd, Joel; Smartt, Stephen J.; Stacey, Holland; Stroh, Michael; Swift, Jonathan J.; Terreran, Giacomo; Vinko, Jozsef; Wang, Xiaofeng; Anderson, Joseph P.; Baron, Edward A.; Berger, Edo; Blanchard, Peter K.; Burke, Jamison; Coulter, David A.; DeMarchi, Lindsay; DerKacy, James M.; Fremling, Christoffer; Gomez, Sebastian; Gromadzki, Mariusz; Hosseinzadeh, Griffin; Kasen, Daniel; Kriskovics, Levente; McCully, Curtis; Müller-Bravo, Tomás E.; Nicholl, Matt; Ordasi, András; Pellegrino, Craig; Piro, Anthony L.; Pál, András; Ren, Juanjuan; Rest, Armin; Rich, R. Michael; Sai, Hanna; Sárneczky, Krisztián; Shen, Ken J.; Short, Philip; Siebert, Matthew; Stauffer, Candice; Szakáts, Róbert; Zhang, Xinhan; Zhang, Jujia; Zhang, Kaicheng
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Subject
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Abstract
We present panchromatic observations and modeling of the Calcium-rich supernova 2019ehk in the star-forming galaxy M100 (d$\approx$16.2 Mpc) starting 10 hours after explosion and continuing for ~300 days. SN 2019ehk shows a double-peaked optical light curve peaking at $t = 3$ and $15$ days. The first peak is coincident with luminous, rapidly decaying $\textit{Swift}$-XRT discovered X-ray emission ($L_x\approx10^{41}~\rm{erg~s^{-1}}$ at 3 days; $L_x \propto t^{-3}$), and a Shane/Kast spectral detection of narrow H$\alpha$ and He II emission lines ($v \approx 500$ km/s) originating from pre-existent circumstellar material. We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at $r<10^{15}$ cm and the resulting cooling emission. We calculate a total CSM mass of $\sim$ $7\times10^{-3}$ $\rm{M_{\odot}}$ with particle density $n\approx10^{9}\,\rm{cm^{-3}}$. Radio observations indicate a significantly lower density $n < 10^{4}\,\rm{cm^{-3}}$ at larger radii. The photometric and spectroscopic properties during the second light curve peak are consistent with those of Ca-rich transients (rise-time of $t_r =13.4\pm0.210$ days and a peak B-band magnitude of $M_B =-15.1\pm0.200$ mag). We find that SN 2019ehk synthesized $(3.1\pm0.11)\times10^{-2} ~ \rm{M_{\odot}}$ of ${}^{56}\textrm{Ni}$ and ejected $M_{\rm ej} = (0.72\pm 0.040)~\rm{M_{\odot}}$ total with a kinetic energy $E_{\rm k}=(1.8\pm0.10)\times10^{50}~\rm{erg}$. Finally, deep $\textit{HST}$ pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (~10 $\rm{M_{\odot}}$) in binaries that lost most of their He envelope or white dwarfs. The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD + CO WD binaries.
Comment: 51 pages, 27 figures. Accepted for publication in ApJ
Comment: 51 pages, 27 figures. Accepted for publication in ApJ