TY - JOUR
T1 - ASASSN-15nx
T2 - A Luminous Type II Supernova with a "Perfect" Linear Decline
AU - Bose, Subhash
AU - Dong, Subo
AU - Kochanek, C. S.
AU - Pastorello, Andrea
AU - Katz, Boaz
AU - Bersier, David
AU - Andrews, Jennifer E.
AU - Prieto, J. L.
AU - Stanek, K. Z.
AU - Shappee, B. J.
AU - Smith, Nathan
AU - Kollmeier, Juna
AU - Benetti, Stefano
AU - Cappellaro, E.
AU - Chen, Ping
AU - Elias-Rosa, N.
AU - Milne, Peter
AU - Morales-Garoffolo, Antonia
AU - Tartaglia, Leonardo
AU - Tomasella, L.
AU - Bilinski, Christopher
AU - Brimacombe, Joseph
AU - Frank, Stephan
AU - Holoien, T. W. -S.
AU - Kilpatrick, Charles D.
AU - Kiyota, Seiichiro
AU - Madore, Barry F.
AU - Rich, Jeffrey A.
N1 - We thank A. Gal-Yam and M, Fraser for helpful comments. We are grateful to I. Arcavi for providing us the spectroscopic data for PTF10iam. S.B., S.D., and P.C. acknowledge Project 11573003, supported by the NSFC. S.B. is partially supported by the China Postdoctoral Science Foundation through grant No. 2016M600848. A.P., L.T., S.B., and N.E.R. are partially supported by the PRIN-INAF 2014 project "Transient Universe: Unveiling New Types of Stellar Explosions with PESSTO." C.S.K., K.Z.S., and T.A.T. are supported by the U.S. National Science Foundation (NSF) though grants AST-1515927 and AST-1515876. We acknowledge support by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS, Chile (J.L.P., C.R.-C.) and from CONICYT through FONDECYT grants 3150238 (C.R.-C.) and 1151445 (J.L.P.). Support for N.S. was provided by the NSF through grants AST-1312221 and AST-1515559 to the University of Arizona. A.M.G. acknowledges financial support by the University of Cádiz though grant PR2017-64. This work is based on observations made with the Large Binocular Telescope. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. The LBT Corporation partners are: the University of Arizona, on behalf of the Arizona university system; the Istituto Nazionale di Astrofisica, Italy; the LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia. We thank the staff at the MMT Observatory for their assistance with the observations. Observations using Steward Observatory facilities were obtained as part of the large observing program, AZTEC: Arizona Transient Exploration and Characterization. Some of the observations reported in this paper were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Partially based on observations collected at Copernico telescope (Asiago, Italy) of the INAF—Osservatorio Astronomico di Padova. This research was made possible through use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund. This research uses data obtained through the Telescope Access Program (TAP), which has been funded by "The Strategic Priority Research Program: the Emergence of Cosmological Structures" of the Chinese Academy of Sciences (grant No. 11 XDB09000000) and the Special Fund for Astronomy from the Ministry of Finance. We thank the Las Cumbres Observatory and its staff for their continuing support of the ASAS-SN project. We are grateful to M. Hardesty of the OSU ASC technology group. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University and NSF grant AST-1515927. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), the Villum Foundation, and George Skestos. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, with financial support from the UK Science and Technology Facilities Council (STFC). This paper used data obtained with the MODS spectrographs built with funding from NSF grant AST-9987045 and the NSF Telescope System Instrumentation Program (TSIP), with additional funds from the Ohio Board of Regents and The Ohio State University Office of Research. The ModsIDL spectral data reduction reduction pipeline was developed in part with funds provided by NSF Grant AST-1108693. Partially based on observations collected at Copernico telescope (Asiago, Italy) of the INAF—Osservatorio Astronomico di Padova. The Joan Oró Telescope (TJO) of the Montsec Astronomical Observatory (OADM) is owned by the Catalan Government and operated by the Institute for Space Studies of Catalonia (IEEC). Software: MATLAB, Python, IDL, synow (Fisher et al. 1997, 1999; Branch et al. 2002), Astropy (Astropy Collaboration et al. 2013), IRAF (Tody 1993), LT pipeline (Barnsley et al. 2012; Piascik et al. 2014), DAOPHOT (Stetson 1987), FOSCGUI, modsIDL pipeline.
PY - 2018/7/27
Y1 - 2018/7/27
N2 - We report a luminous Type II supernova, ASASSN-15nx, with a peak luminosity of M-v = -20 mag that is between those of typical core-collapse supernovae and super-luminous supernovae. The post-peak optical light curves show a long, linear decline with a steep slope of 2.5 mag (100 day)(-1) (i.e., an exponential decline in flux) through the end of observations at phase approximate to 260 day. In contrast, the light curves of hydrogen-rich supernovae (SNe II-P/L) always show breaks in their light curves at phase similar to 100 day, before settling onto Co-56 radioactive decay tails with a decline rate of about 1 mag (100 day)(-1). The spectra of ASASSN-15nx do not exhibit the narrow emission-line features characteristic of Type IIn SNe, which can have a wide variety of light-curve shapes usually attributed to strong interactions with a dense circumstellar medium (CSM). ASASSN-15nx has a number of spectroscopic peculiarities, including a relatively weak and triangular-shaped H alpha emission profile with no absorption component. The physical origin of these peculiarities is unclear, but the long and linear post-peak light curve without a break suggests a single dominant powering mechanism. Decay of a large amount of Ni-56 (M-Ni = 1.6 +/- 0.2 M-circle dot) can power the light curve of ASASSN-15nx, and the steep light-curve slope requires substantial gamma-ray escape from the ejecta, which is possible given a low-mass hydrogen envelope for the progenitor. Another possibility is strong CSM interactions powering the light curve, but the CSM needs to be sculpted to produce the unique light-curve shape and avoid producing SN IIn-like narrow emission lines.
AB - We report a luminous Type II supernova, ASASSN-15nx, with a peak luminosity of M-v = -20 mag that is between those of typical core-collapse supernovae and super-luminous supernovae. The post-peak optical light curves show a long, linear decline with a steep slope of 2.5 mag (100 day)(-1) (i.e., an exponential decline in flux) through the end of observations at phase approximate to 260 day. In contrast, the light curves of hydrogen-rich supernovae (SNe II-P/L) always show breaks in their light curves at phase similar to 100 day, before settling onto Co-56 radioactive decay tails with a decline rate of about 1 mag (100 day)(-1). The spectra of ASASSN-15nx do not exhibit the narrow emission-line features characteristic of Type IIn SNe, which can have a wide variety of light-curve shapes usually attributed to strong interactions with a dense circumstellar medium (CSM). ASASSN-15nx has a number of spectroscopic peculiarities, including a relatively weak and triangular-shaped H alpha emission profile with no absorption component. The physical origin of these peculiarities is unclear, but the long and linear post-peak light curve without a break suggests a single dominant powering mechanism. Decay of a large amount of Ni-56 (M-Ni = 1.6 +/- 0.2 M-circle dot) can power the light curve of ASASSN-15nx, and the steep light-curve slope requires substantial gamma-ray escape from the ejecta, which is possible given a low-mass hydrogen envelope for the progenitor. Another possibility is strong CSM interactions powering the light curve, but the CSM needs to be sculpted to produce the unique light-curve shape and avoid producing SN IIn-like narrow emission lines.
UR - http://www.scopus.com/inward/record.url?scp=85051843507&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aacb35
DO - 10.3847/1538-4357/aacb35
M3 - مقالة
SN - 0004-637X
VL - 862
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 107
ER -