@article{4fc9b501d61d4bfb8c1c20d47624e347,
title = "The early discovery of sn 2017ahn: Signatures of persistent interaction in a fast-declining type II supernova",
abstract = "We present high-cadence, comprehensive data on the nearby (D; 33 Mpc) Type II supernova (SN II) 2017ahn, discovered within about one day of the explosion, from the very early phases after explosion to the nebular phase. The observables of SN 2017ahn show a significant evolution over the;470 days of our follow-up campaign, first showing prominent, narrow Balmer lines and other high-ionization features purely in emission (i.e., flash spectroscopy features), which progressively fade and lead to a spectroscopic evolution similar to that of more canonical SNe II. Over the same period, the decline of the light curves in all bands is fast, resembling the photometric evolution of linearly declining H-rich core-collapse SNe. The modeling of the light curves and early flash spectra suggests that a complex circumstellar medium surrounds the progenitor star at the time of explosion, with a first dense shell produced during the very late stages of its evolution that is swept up by the rapidly expanding ejecta within the first ∼6 days of the SN evolution, while signatures of interaction are observed also at later phases. Hydrodynamical models support the scenario in which linearly declining SNe II are predicted to arise from massive yellow super- or hypergiants depleted of most of their hydrogen layers.",
author = "L. Tartaglia and Sand, {D. J.} and Groh, {J. H.} and S. Valenti and Wyatt, {S. D.} and Bostroem, {K. A.} and Brown, {P. J.} and S. Yang and J. Burke and Chen, {T. W.} and S. Davis and F. F{\"o}rster and L. Galbany and J. Haislip and D. Hiramatsu and G. Hosseinzadeh and Howell, {D. A.} and Hsiao, {E. Y.} and Jha, {S. W.} and V. Kouprianov and H. Kuncarayakti and Lyman, {J. D.} and C. McCully and Phillips, {M. M.} and A. Rau and Reichart, {D. E.} and M. Shahbandeh and J. Strader",
note = "Funding Information: Based on observations collected at The Gemini Observatory, under program GN-2016B-Q-57, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnolog{\'i}a e Innovaci{\'o}n Productiva (Argentina), and Minist{\'e}rio da Ci{\^e}ncia, Tecnologia e Inova{\c c}{\~a}o (Brazil). Funding Information: The SALT observations presented here were made through Rutgers University programs 2016-1-MLT-007 (PI: Jha); supernova research at Rutgers is supported by NSF award AST-1615455. Funding Information: Part of the funding for GROND (both hardware and personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). Funding Information: L.T. acknowledges support from MIUR (PRIN 2017 grant 20179ZF5KS). Funding Information: Research by D.J.S. is supported by NSF grants AST-1821967, 1821987, 1813708, 1813466, 1908972, and by the Heising-Simons Foundation under grant #2020-1864. Research by S.V. is supported by NSF grants AST-1813176 and AST-2008108 J.S. acknowledges support from the Packard Foundation. R.C. and M.S. acknowledge support from STFC grant ST/ L000679/1 and EU/FP7-ERC grant no [615929]. T.-W.C. acknowledges the EU Funding under Marie Sk{\l}odowska-Curie grant agreement No 842471. H.K. was funded by the Academy of Finland projects 324504 and 328898. D.A.H., J.B., and D.H. are supported by NSF grant AST-1911225 and NASA Swift grant 80NSSC19k1639. L.G. was funded by the European Union{\textquoteright}s Horizon 2020 research and innovation program under the Marie Sk{\l}odowska-Curie grant agreement No. 839090. Funding Information: This work has been partially supported by the Spanish grant PGC2018-095317-B-C21 within the European Funds for Regional Development (FEDER). Funding Information: D.A.H., C.M., and G.H. are supported by NSF grant 1313484. Funding Information: E.Y.H. acknowledges the support provided by the National Science Foundation under grant No. AST-1008343, AST-1613472 and AST-1613426. Publisher Copyright: {\textcopyright} 2021. The American Astronomical Society. All rights reserved.",
year = "2021",
month = jan,
day = "20",
doi = "10.3847/1538-4357/abca8a",
language = "English (US)",
volume = "907",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}