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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2601.00415 |
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| _version_ | 1866918430421024768 |
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| author | Ravi, Aravind P. Kumar, Sahana Baer-Way, Raphael Valenti, Stefano Modjaz, Maryam van Baal, Bart F. A. Jerkstrand, Anders Dong, Yize Kwok, Lindsey A. Pearson, Jeniveve Sand, David J. Hiramatsu, Daichi Filippenko, Alexei V. Andrews, Jennifer Andrews, Moira Arunachalam, Prasiddha Bostroem, K. Azalee Brink, Thomas G. Christy, Collin Chen, Liyang Davis, Kyle W. Esamdin, Ali Farah, Joseph Foley, Ryan J. Hoang, Emily Hosseinzadeh, Griffin Howell, D. Andrew Hsu, Brian Huang, Ruifeng Iskander, Abdusamatjan Janzen, Daryl Jha, Saurabh W. Kaur, Ravjit Lundquist, Michael J. McCully, Curtis Mehta, Darshana Ni, Yuan Qi Retamal, Nicolas Meza Patra, Kishore C. Ransome, Conor Shrestha, Manisha Smith, Nathan Subrayan, Bhagya Taggart, Kirsty Wang, Xiaofeng Wynn, Kathryn Yang, Yi Yan, Shengyu Zheng, Weikang Coe, Dan |
| author_facet | Ravi, Aravind P. Kumar, Sahana Baer-Way, Raphael Valenti, Stefano Modjaz, Maryam van Baal, Bart F. A. Jerkstrand, Anders Dong, Yize Kwok, Lindsey A. Pearson, Jeniveve Sand, David J. Hiramatsu, Daichi Filippenko, Alexei V. Andrews, Jennifer Andrews, Moira Arunachalam, Prasiddha Bostroem, K. Azalee Brink, Thomas G. Christy, Collin Chen, Liyang Davis, Kyle W. Esamdin, Ali Farah, Joseph Foley, Ryan J. Hoang, Emily Hosseinzadeh, Griffin Howell, D. Andrew Hsu, Brian Huang, Ruifeng Iskander, Abdusamatjan Janzen, Daryl Jha, Saurabh W. Kaur, Ravjit Lundquist, Michael J. McCully, Curtis Mehta, Darshana Ni, Yuan Qi Retamal, Nicolas Meza Patra, Kishore C. Ransome, Conor Shrestha, Manisha Smith, Nathan Subrayan, Bhagya Taggart, Kirsty Wang, Xiaofeng Wynn, Kathryn Yang, Yi Yan, Shengyu Zheng, Weikang Coe, Dan |
| contents | Supernova (SN) 2025coe at a distance of $\sim$25 Mpc is the second-closest calcium-strong (CaST) transient. It was discovered at a large projected offset of $\sim$34 kpc from its potential host galaxy NGC 3277. Multiband photometry of SN 2025coe indicates the presence of two peaks at day $\sim$2 and day $\sim$11 after explosion. Modeling the bolometric light curve, we find that the first peak can be reproduced either by shock cooling of a compact envelope ($R_\mathrm{env}$ $\approx $6-40 $R_{\odot}$; $M_\mathrm{env}$ $\approx $0.1-0.2 $M_{\odot}$) or by interaction with close-in circumstellar material (CSM; $R_{\mathrm{CSM}} \lesssim 6 \times10^{14}$ cm), or a combination of both. The second peak is dominated by radioactive decay of $^{56}$Ni ($M_{\mathrm{ej}} \approx $0.4-0.5 $M_{\odot}$; $M_{^{56}\mathrm{Ni}} \approx 1.4 \times 10^{-2}$ $M_{\odot}$). SN 2025coe rapidly evolves from the photospheric phase dominated by He I P-Cygni profiles to nebular phase spectra dominated by strong [Ca II] $λλ$7291, 7323 and weak [O I] $λλ$6300, 6364 emission lines. Simultaneous line profile modeling of [Ca II] and [O I] at nebular phases shows that an asymmetric core-collapse explosion of a low-mass ($\lesssim$3.3 $M_{\odot}$) He-core progenitor can explain the observed line profiles. Alternatively, lack of local star formation at the site of the SN explosion combined with a low ejecta mass is also consistent with a thermonuclear explosion due to a low-mass hybrid He-C/O white dwarf + C/O white dwarf merger. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_00415 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Double-Peaked Calcium-Strong SN 2025coe: Progenitor Constraints from Early Interaction and Ejecta Asymmetries Ravi, Aravind P. Kumar, Sahana Baer-Way, Raphael Valenti, Stefano Modjaz, Maryam van Baal, Bart F. A. Jerkstrand, Anders Dong, Yize Kwok, Lindsey A. Pearson, Jeniveve Sand, David J. Hiramatsu, Daichi Filippenko, Alexei V. Andrews, Jennifer Andrews, Moira Arunachalam, Prasiddha Bostroem, K. Azalee Brink, Thomas G. Christy, Collin Chen, Liyang Davis, Kyle W. Esamdin, Ali Farah, Joseph Foley, Ryan J. Hoang, Emily Hosseinzadeh, Griffin Howell, D. Andrew Hsu, Brian Huang, Ruifeng Iskander, Abdusamatjan Janzen, Daryl Jha, Saurabh W. Kaur, Ravjit Lundquist, Michael J. McCully, Curtis Mehta, Darshana Ni, Yuan Qi Retamal, Nicolas Meza Patra, Kishore C. Ransome, Conor Shrestha, Manisha Smith, Nathan Subrayan, Bhagya Taggart, Kirsty Wang, Xiaofeng Wynn, Kathryn Yang, Yi Yan, Shengyu Zheng, Weikang Coe, Dan High Energy Astrophysical Phenomena Supernova (SN) 2025coe at a distance of $\sim$25 Mpc is the second-closest calcium-strong (CaST) transient. It was discovered at a large projected offset of $\sim$34 kpc from its potential host galaxy NGC 3277. Multiband photometry of SN 2025coe indicates the presence of two peaks at day $\sim$2 and day $\sim$11 after explosion. Modeling the bolometric light curve, we find that the first peak can be reproduced either by shock cooling of a compact envelope ($R_\mathrm{env}$ $\approx $6-40 $R_{\odot}$; $M_\mathrm{env}$ $\approx $0.1-0.2 $M_{\odot}$) or by interaction with close-in circumstellar material (CSM; $R_{\mathrm{CSM}} \lesssim 6 \times10^{14}$ cm), or a combination of both. The second peak is dominated by radioactive decay of $^{56}$Ni ($M_{\mathrm{ej}} \approx $0.4-0.5 $M_{\odot}$; $M_{^{56}\mathrm{Ni}} \approx 1.4 \times 10^{-2}$ $M_{\odot}$). SN 2025coe rapidly evolves from the photospheric phase dominated by He I P-Cygni profiles to nebular phase spectra dominated by strong [Ca II] $λλ$7291, 7323 and weak [O I] $λλ$6300, 6364 emission lines. Simultaneous line profile modeling of [Ca II] and [O I] at nebular phases shows that an asymmetric core-collapse explosion of a low-mass ($\lesssim$3.3 $M_{\odot}$) He-core progenitor can explain the observed line profiles. Alternatively, lack of local star formation at the site of the SN explosion combined with a low ejecta mass is also consistent with a thermonuclear explosion due to a low-mass hybrid He-C/O white dwarf + C/O white dwarf merger. |
| title | The Double-Peaked Calcium-Strong SN 2025coe: Progenitor Constraints from Early Interaction and Ejecta Asymmetries |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2601.00415 |