Luminous, rapidly declining supernovae as stripped transitional objects in low-metallicity environments: The case of SN 2022lxg
: Charalampopoulos, P.; Kotak, R.; Sollerman, J.; Gutierrez, C. P.; Pursiainen, M.; Killestein, T. L.; Schulze, S.; Pessi, P. J.; Maeda, K.; Kangas, T.; Cai, Y. -z.; Fremling, C.; Hinds, K. R.; Jegou du Laz, T.; Kankare, E.; Kasliwal, M. M.; Kuncarayakti, H.; Lundqvist, P.; Masci, F. J.; Mattila, S.; Perley, D. A.; Reguitti, A.; Reynolds, T. M.; Stritzinger, M.; Tartaglia, L.; Van Roestel, J.; Wold, A.
Publisher: EDP SCIENCES S A
: LES ULIS CEDEX A
: 2025
: Astronomy and Astrophysics
: ASTRONOMY & ASTROPHYSICS
: ASTRON ASTROPHYS
: A138
: 700
: 30
: 0004-6361
: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202554648
: https://doi.org/10.1051/0004-6361/202554648
: https://research.utu.fi/converis/portal/detail/Publication/499837017
We present an analysis of the optical and near-infrared properties of SN 2022lxg, a bright (M-g peak = -19.41 mag) and rapidly evolving supernova (SN). It was discovered within a day of explosion, and rose to peak brightness in similar to 10 d. Two distinct phases of circumstellar interaction are evident in the data. The first is marked by a steep blue continuum (T > 15 000 K) with flash-ionisation features due to hydrogen and He II. The second, weaker phase is marked by a change in the colour evolution accompanied by changes in the shapes and velocities of the spectral line profiles. Narrow P-Cygni profiles (similar to 150 km s(-1)) of He I further indicate the presence of slow-moving, unshocked material and suggest partial stripping of the progenitor. The fast decline of the light-curve from the peak (3.48 +/- 0.26 mag (50 d)(-1) in g band) implies that the ejecta mass must be low. Spectroscopically, until +35 d there are similarities with some Type IIb SNe but then there is a transition to spectra that are more reminiscent of an interacting SN II. However, metal lines are largely absent in the spectra, even at epochs of similar to 80 d. Its remote location (similar to 4.6 kpc projected offset) from the presumed host galaxy, a dwarf with M-B similar to -14.4 mag, is consistent with our metallicity estimate - close to the values of the Small Magellanic Cloud - obtained from scaling relations. Furthermore, several lines of evidence (including intrinsic polarisation of p similar to (0.5 - 1.0)%) point to deviations from spherical symmetry. We suggest that a plausible way of uniting the observational clues is to consider a binary system that underwent case C mass transfer. This failed to remove the entire H envelope of the progenitor before it underwent core collapse. In this scenario, the progenitor itself would be more compact and perhaps straddle the boundary between blue and yellow supergiants, which ties in with the early spectroscopic similarity to Type IIb SNe.
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We thank the anonymous referee for the helpful comments that improved the manuscript. We thank T. Nagao for many interesting discussions and providing the imaging polarimetry data presented in Sect. 3.4. R.K. also acknowledges discussions with L. Dessart. P.C., R.K., and T.L.K. acknowledge support via the Research Council of Finland (grant 340613). C.P.G. acknowledges financial support from the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 Research and Innovation Programme of the European Union under the Marie Skłodowska-Curie and the Beatriu de Pinós 2021 BP 00168 programme, from the Spanish Ministerio de Ciencia e Innovación (MCIN) and the Agencia Estatal de Investigación (AEI) 10.13039/501100011033 under the PID2020-115253GA-I00 HOSTFLOWS project, and the program Unidad de Excelencia María de Maeztu CEX2020-001058-M. M.P. acknowledges support from a UK Research and Innovation Fellowship (MR/T020784/1). T.L.K. acknowledges support from the Turku University Foundation (grant no. 081810). S.S. is partially supported by LBNL Subcontract 7707915. K.M. acknowledges support from the Japan Society for the Promotion of Science (JSPS) KAKENHI grant JP24KK0070 and 24H01810. The work is partly supported by the JSPS Open Partnership Bilateral Joint Research Projects between Japan and Finland (JPJSBP120229923). T.K. acknowledges support from the Research Council of Finland project 360274. Y.-Z.C. is supported by the National Natural Science Foundation of China (NSFC, Grant No. 12303054), the National Key Research and Development Program of China (Grant No. 2024YFA1611603), the Yunnan Fundamental Research Projects (Grant Nos. 202401AU070063, 202501AS070078), and the International Centre of Supernovae, Yunnan Key Laboratory (No. 202302AN360001). E.K. acknowledges financial support from the Emil Aaltonen foundation. H.K. was funded by the Research Council of Finland projects 324504, 328898, and 353019. S.M. and T.M.R. acknowledge support from the Research Council of Finland project 350458. A.R. acknowledges financial support from the GRAWITA Large Program Grant (PI P. D’Avanzo) and from the PRIN-INAF 2022 Shedding light on the nature of gap transients: from the observations to the models. T.M.R. is part of the Cosmic Dawn Center (DAWN), which is funded by the Danish National Research Foundation under grant DNRF140. M.D.S. is funded by the Independent Research Fund Denmark (IRFD, grant number 10.46540/2032-00022B) and by an Aarhus University Research Foundation Nova project (AUFF-E-2023-9-28). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grants No. AST-1440341 and AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute of Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum, Northwestern University and former partners the University of Washington, Los Alamos National Laboratories, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). The Gordon and Betty Moore Foundation, through both the Data-Driven Investigator Program and a dedicated grant, provided critical funding for SkyPortal. Based on observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland, and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOT. Observations from the Nordic Optical Telescope were obtained through the NUTS2 collaboration which is supported in part by the Instrument Centre for Danish Astrophysics (IDA), and the Finnish Centre for Astronomy with ESO (FINCA) via Academy of Finland grant nr 306531, through the proposal P65-005 (PI: T. Nagao), and through the fast-track proposal P66-415 (PI: P. Charalampopoulos).
