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PTF12os and iPTF13bvn: Two stripped-envelope supernovae discovered by the Palomar Transient Factory
Stockholm University, Faculty of Science, Department of Astronomy.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF], and it is particularly closely tied to the still ongoing research on the stripped-envelope (SE) supernova (SN), iPTF13bvn (Type Ib), that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet (WR) star, but I have shown that this is very likely not the case. I suggest instead that the most likely scenario is that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion star, in a similar way as for the very well studied Type IIb SN 2011dh. I have also investigated another SE SN, PTF12os (Type IIb), that occurred in the same galaxy as iPTF13bvn, with the conclusion that PTF12os and iPTF13bvn are very similar amongst themselves, and that both of them are also remarkably similar to SN 2011dh, in terms of all of the available observations (light-curves, spectra). Hydrodynamical models have been used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063 − 0.075 M⊙, ejecta masses in the range 1.85 − 1.91 M⊙. Using the 56Ni-masses derived from our hydrodynamical modeling in combination with nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ∼ 12 M⊙ for iPTF13bvn and ≲ 15 M⊙ for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their hydrogen envelopes and become SE SNe without binary interactions.

Place, publisher, year, edition, pages
Stockholm: Stockholm University, 2016. , 64 p.
Keyword [en]
sovernovae
National Category
Other Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-135752OAI: oai:DiVA.org:su-135752DiVA: diva2:1048673
Presentation
2016-11-08, Albanova, 19:42 (English)
Opponent
Supervisors
Available from: 2016-11-22 Created: 2016-11-21 Last updated: 2016-11-22Bibliographically approved
List of papers
1. The rise and fall of the Type Ib supernova iPTF13bvn Not a massive Wolf-Rayet star
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2014 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 565, A114Article in journal (Refereed) Published
Abstract [en]

Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progenitor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly classify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario. Methods. We present a large set of observational data, consisting of multi-band light curves (UBVRI, g' r' i' z') and optical spectra. We perform standard spectral line analysis to track the evolution of the SN ejecta. We also construct a bolometric light curve and perform hydrodynamical calculations to model this light curve to constrain the synthesized radioactive nickel mass and the total ejecta mass of the SN. Late-time photometry is analyzed to constrain the amount of oxygen. Furthermore, image registration of pre- and post-explosion HST images is performed. Results. Our HST astrometry confirms the location of the progenitor candidate of iPTF13bvn, and follow-up spectra securely classify this as a SN Ib. We use our hydrodynamical model to fit the observed bolometric light curve, estimating the total ejecta mass to be 1.9 M-circle dot and the radioactive nickel mass to be 0.05 M-circle dot. The model fit requires the nickel synthesized in the explosion to be highly mixed out in the ejecta. We also find that the late-time nebular r'-band luminosity is not consistent with predictions based on the expected oxygen nucleosynthesis in very massive stars. Conclusions. We find that our bolometric light curve of iPTF13bvn is not consistent with the previously proposed single massive WR-star progenitor scenario. The total ejecta mass and, in particular, the late-time oxygen emission are both significantly lower than what would be expected from a single WR progenitor with a main-sequence mass of at least 30 M-circle dot.

Keyword
supernovae: general, supernovae: individual: iPTF13bvn
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-105926 (URN)10.1051/0004-6361/201423884 (DOI)000336730900114 ()
Funder
EU, European Research Council, 307260
Note

AuthorCount:12;

Available from: 2014-07-08 Created: 2014-07-08 Last updated: 2016-11-21Bibliographically approved
2. PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 5806
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2016 (English)In: \aap, Vol. 593Article in journal (Refereed) Published
Keyword
supernovae: general, supernovae: individual: PTF12os, galaxies: individual: NGC 5806, techniques: image processing, supernovae: individual: iPTF13bvn
National Category
Natural Sciences
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-135750 (URN)10.1051/0004-6361/201628275 (DOI)
Available from: 2016-11-21 Created: 2016-11-21 Last updated: 2016-11-21

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