The Astrophysical Journal (Jan 2023)
SN 2017egm: A Helium-rich Superluminous Supernova with Multiple Bumps in the Light Curves
- Jiazheng Zhu,
- Ning Jiang,
- Subo Dong,
- Alexei V. Filippenko,
- Richard J. Rudy,
- A. Pastorello,
- Christopher Ashall,
- Subhash Bose,
- R. S. Post,
- D. Bersier,
- Stefano Benetti,
- Thomas G. Brink,
- Ping Chen,
- Liming Dou,
- N. Elias-Rosa,
- Peter Lundqvist,
- Seppo Mattila,
- Ray W. Russell,
- Michael L. Sitko,
- Auni Somero,
- M. D. Stritzinger,
- Tinggui Wang,
- Peter J. Brown,
- E. Cappellaro,
- Morgan Fraser,
- Erkki Kankare,
- S. Moran,
- Simon Prentice,
- Tapio Pursimo,
- T. M. Reynolds,
- WeiKang Zheng
Affiliations
- Jiazheng Zhu
- ORCiD
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China , Hefei, 230026, People's Republic of China ; [email protected], [email protected]; School of Astronomy and Space Sciences, University of Science and Technology of China , Hefei, 230026, People's Republic of China
- Ning Jiang
- ORCiD
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China , Hefei, 230026, People's Republic of China ; [email protected], [email protected]; School of Astronomy and Space Sciences, University of Science and Technology of China , Hefei, 230026, People's Republic of China
- Subo Dong
- ORCiD
- Kavli Institute for Astronomy and Astrophysics, Peking University , Yi He Yuan Road 5, Hai Dian District, Beijing 100871, People’s Republic of China [email protected]
- Alexei V. Filippenko
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA
- Richard J. Rudy
- ORCiD
- Physical Sciences Laboratory , The Aerospace Corporation M2-266, P.O. Box 92957, Los Angeles, CA 90009, USA; Kookoosint Scientific , 1530 Calle Portada, Camarillo, CA 93010, USA
- A. Pastorello
- ORCiD
- INAF-Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
- Christopher Ashall
- ORCiD
- Department of Physics, Virginia Tech , Blacksburg, VA 24061, USA
- Subhash Bose
- ORCiD
- Department of Astronomy, The Ohio State University , 140 W. 18th Avenue, Columbus, OH 43210, USA; Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University , 191 W. Woodruff Avenue, Columbus, OH 43210, USA
- R. S. Post
- Post Observatory , Lexington, MA 02421, USA
- D. Bersier
- ORCiD
- Astrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF, UK
- Stefano Benetti
- ORCiD
- INAF-Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
- Thomas G. Brink
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA
- Ping Chen
- ORCiD
- Department of Particle Physics and Astrophysics, Weizmann Institute of Science , 234 Herzl Street, 7610001 Rehovot, Israel
- Liming Dou
- ORCiD
- Department of Astronomy, Guangzhou University , Guangzhou 510006, People's Republic of China
- N. Elias-Rosa
- ORCiD
- INAF-Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
- Peter Lundqvist
- ORCiD
- Department of Astronomy and The Oskar Klein Centre, AlbaNova University Center, Stockholm University , SE-10691 Stockholm, Sweden
- Seppo Mattila
- ORCiD
- School of Sciences, European University Cyprus , Diogenes street, Engomi, 1516 Nicosia, Cyprus; Tuorla Observatory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
- Ray W. Russell
- Physical Sciences Laboratory , The Aerospace Corporation M2-266, P.O. Box 92957, Los Angeles, CA 90009, USA
- Michael L. Sitko
- ORCiD
- Center for Exoplanetary Systems , Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
- Auni Somero
- ORCiD
- Tuorla Observatory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
- M. D. Stritzinger
- ORCiD
- Department of Physics and Astronomy, Aarhus University , Ny Munkegade 120, DK-8000 Aarhus C, Denmark
- Tinggui Wang
- ORCiD
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China , Hefei, 230026, People's Republic of China ; [email protected], [email protected]; School of Astronomy and Space Sciences, University of Science and Technology of China , Hefei, 230026, People's Republic of China
- Peter J. Brown
- ORCiD
- George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, Texas A. & M. University , Department of Physics and Astronomy, 4242 TAMU, College Station, TX 77843, USA
- E. Cappellaro
- ORCiD
- INAF-Osservatorio Astronomico di Padova , Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
- Morgan Fraser
- ORCiD
- School of Physics, O’Brien Centre for Science North, University College Dublin , Belfield, Dublin 4, Ireland
- Erkki Kankare
- ORCiD
- Tuorla Observatory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
- S. Moran
- Tuorla Observatory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland
- Simon Prentice
- ORCiD
- Astrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF, UK
- Tapio Pursimo
- ORCiD
- Nordic Optical Telescope , Apartado 474, E-38700 Santa Cruz de La Palma, Spain
- T. M. Reynolds
- ORCiD
- Tuorla Observatory, Department of Physics and Astronomy, University of Turku , FI-20014 Turku, Finland; Cosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 København N, Denmark
- WeiKang Zheng
- ORCiD
- Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA
- DOI
- https://doi.org/10.3847/1538-4357/acc2c3
- Journal volume & issue
-
Vol. 949,
no. 1
p. 23
Abstract
When discovered, SN 2017egm was the closest (redshift z = 0.03) hydrogen-poor superluminous supernova (SLSN-I) and a rare case that exploded in a massive and metal-rich galaxy. Thus, it has since been extensively observed and studied. We report spectroscopic data showing strong emission at around He i λ 10830 and four He i absorption lines in the optical. Consequently, we classify SN 2017egm as a member of an emerging population of helium-rich SLSNe-I (i.e., SLSNe-Ib). We also present our late-time photometric observations. By combining them with archival data, we analyze high-cadence ultraviolet, optical, and near-infrared light curves spanning from early pre-peak (∼−20 days) to late phases (∼+300 days). We obtain its most complete bolometric light curve, in which multiple bumps are identified. None of the previously proposed models can satisfactorily explain all main light-curve features, while multiple interactions between the ejecta and circumstellar material (CSM) may explain the undulating features. The prominent infrared excess with a blackbody luminosity of 10 ^7 –10 ^8 L _⊙ detected in SN 2017egm could originate from the emission of either an echo of a pre-existing dust shell or newly formed dust, offering an additional piece of evidence supporting the ejecta–CSM interaction model. Moreover, our analysis of deep Chandra observations yields the tightest-ever constraint on the X-ray emission of an SLSN-I, amounting to an X-ray-to-optical luminosity ratio ≲10 ^−3 at late phases (∼100–200 days), which could help explore its close environment and central engine.
Keywords
