Repository logo

Type Ibn Supernovae Show Photometric Homogeneity and Spectral Diversity at Maximum Light

Published version

Change log


Hosseinzadeh, G 
Arcavi, I 
Valenti, S 
McCully, C 
Howell, DA 


Type Ibn supernovae (SNe) are a small yet intriguing class of explosions whose spectra are characterized by low-velocity helium emission lines with little to no evidence for hydrogen. The prevailing theory has been that these are the core-collapse explosions of very massive stars embedded in helium-rich circumstellar material (CSM). We report optical observations of six new SNe Ibn: PTF11rfh, PTF12ldy, iPTF14aki, iPTF15ul, SN 2015G, and iPTF15akq. This brings the sample size of such objects in the literature to 22. We also report new data, including a near-infrared spectrum, on the Type Ibn SN 2015U. In order to characterize the class as a whole, we analyze the photometric and spectroscopic properties of the full Type Ibn sample. We find that, despite the expectation that CSM interaction would generate a heterogeneous set of light curves, as seen in SNe IIn, most Type Ibn light curves are quite similar in shape, declining at rates around 0.1 mag day−1 during the first month after maximum light, with a few significant exceptions. Early spectra of SNe Ibn come in at least two varieties, one that shows narrow P Cygni lines and another dominated by broader emission lines, both around maximum light, which may be an indication of differences in the state of the progenitor system at the time of explosion. Alternatively, the spectral diversity could arise from viewing-angle effects or merely from a lack of early spectroscopic coverage. Together, the relative light curve homogeneity and narrow spectral features suggest that the CSM consists of a spatially confined shell of helium surrounded by a less dense extended wind.



supernovae: general, supernovae: individual (PTF11rfh, PTF12ldy, iPTF14aki, SN 2015U, iPTF15ul, SN 2015G, iPTF15akq)

Journal Title

The Astrophysical Journal

Conference Name

Journal ISSN


Volume Title



IOP Science
European Research Council (320360)
This work is based on observations obtained with the 48 inch Samuel Oschin Telescope and the 60 inch telescope at the Palomar Observatory as part of the intermediate Palomar Transient Factory (iPTF) project, a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin–Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the universe; the New Technology Telescope, operated by the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, as part of PESSTO, ESO program 191.D-0935(C); the Las Cumbres Observatory Global Telescope Network; both the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association, and the Telescopio Nazionale Galileo, operated by the Fundación Galileo Galilei of the Italian Istituto Nazionale di Astrofisica, at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias; the Lick Observatory owned and operated by the University of California; and the W. M. Keck Observatory, which was made possible by the generous financial support of the W. M. Keck Foundation and is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). We thank the staffs at all of these observatories for their assistance with the observations. We thank Lars Bildsten and Matteo Cantiello for useful discussions, and all those whose observations and data reduction contributed to this work. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The authors made extensive use of the Astropy package Astropy Collaboration et al. (2013) for data analysis. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. LANL participation in iPTF was funded by the US Department of Energy as part of the Laboratory Directed Research and Development program. G.H., D.A.H., and C.M. are supported by the National Science Foundation (NSF) under Grant No. 1313484. A.P., S.B., and N.E.R. are partially supported by PRININAF 2014 with the project “Transient universe: unveiling new types of stellar explosions with PESSTO.” J.S., C.F., E.K., and F.T. gratefully acknowledge support from the Knut and Alice Wallenberg Foundation. The Oskar Klein Centre is funded by the Swedish Research Council. M.F., A.G.-Y., and M.S. acknowledge support from the European Union FP7 programme through ERC grant numbers 320360, 307260, and 615929, respectively. A.G.-Y. is also supported by the Quantum universe I-Core program by the Israeli Committee for Planning and Budgeting and the ISF; by Minerva and ISF grants; by the Weizmann-UK “making connections” program; and by Kimmel and YeS awards. A.C. acknowledges support from NSF CAREER award #1455090. M.M.K. acknowledges support from NSF PIRE program grant 1545949. The supernova research of A.V.F.’s group at UC Berkeley is supported by the Christopher R. Redlich Fund, the TABASGO Foundation, and NSF grant AST–1211916. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. Research at Lick Observatory is partially supported by a generous gift from Google.