Volume 605, September 2017
|Number of page(s)||20|
|Section||Stellar structure and evolution|
|Published online||29 August 2017|
The bumpy light curve of Type IIn supernova iPTF13z over 3 years⋆
1 Department of Astronomy and the Oskar Klein CentreStockholm University, AlbaNova, 10691 Stockholm, Sweden
2 Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
3 Benoziyo Center for Astrophysics and the Helen Kimmel Center for Planetary Science, Weizmann Institute of Science, 76100 Rehovot, Israel
4 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
5 Astronomy Department, California Institute of Technology, Pasadena, CA 91125, USA
6 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
7 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USA
8 Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125, USA
Received: 14 October 2017
Accepted: 24 March 2017
A core-collapse (CC) supernova (SN) of Type IIn is dominated by the interaction of SN ejecta with the circumstellar medium (CSM). Some SNe IIn (e.g. SN 2006jd) have episodes of re-brightening (“bumps”) in their light curves. We present iPTF13z, a Type IIn SN discovered on 2013 February 1 by the intermediate Palomar Transient Factory (iPTF). This SN showed at least five bumps in its declining light curve between 130 and 750 days after discovery. We analyse this peculiar behaviour and try to infer the properties of the CSM, of the SN explosion, and the nature of the progenitor star. We obtained multi-band optical photometry for over 1000 days after discovery with the P48 and P60 telescopes at Palomar Observatory. We obtained low-resolution optical spectra during the same period. We did an archival search for progenitor outbursts. We analyse the photometry and the spectra, and compare iPTF13z to other SNe IIn. In particular we derive absolute magnitudes, colours, a pseudo-bolometric light curve, and the velocities of the different components of the spectral lines. A simple analytical model is used to estimate the properties of the CSM. iPTF13z had a light curve peaking at Mr ≲ − 18.3 mag. The five bumps during its decline phase had amplitudes ranging from 0.4 to 0.9 mag and durations between 20 and 120 days. The most prominent bumps appeared in all the different optical bands, when covered. The spectra of this SN showed typical SN IIn characteristics, with emission lines of Hα (with broad component FWHM ~ 103 − 104 km s-1 and narrow component FWHM ~ 102 km s-1) and He i, but also with Fe ii, Ca ii, Na i D and Hβ P Cygni profiles (with velocities of ~ 103km s-1). A pre-explosion outburst was identified lasting ≳ 50 days, with Mr ≈ − 15 mag around 210 days before discovery. Large, variable progenitor mass-loss rates (≳0.01M⊙ yr-1) and CSM densities (≳10-16 g cm-3) are derived. The SN was hosted by a metal-poor dwarf galaxy at redshift z = 0.0328. We suggest that the light curve bumps of iPTF13z arose from SN ejecta interacting with denser regions in the CSM, possibly produced by the eruptions of a luminous blue variable progenitor star.
Key words: supernovae: general / supernovae: individual: iPTF13z / galaxies: individual: SDSS J160200.05+211442.3
Full Tables A.2, A.3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A6
© ESO, 2017
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