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Spectroscopic Observations and Analysis of the Peculiar SN 1999aa
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics. (Kosmologi Partikelastrofysik och Strängteori)
(Kosmologi Partikelastrofysik och Strängteori)
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2004 (English)In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 128, 387-404 p.Article in journal (Refereed) Published
Abstract [en]

We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Ourdata set includes 25 optical spectra between 11 and +58 days with respect to B-band maximum light, providingan unusually complete time history. The early spectra resemble those of an SN 1991T–like object but with arelatively strong Ca H and K absorption feature. The first clear sign of Si ii k6355, characteristic of Type Iasupernovae, is found at day 7, and its velocity remains constant up to at least the first month after B-bandmaximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggestingSN 1999aa as a possible link between SN 1991T–like and Branch-normal supernovae. Comparing the observationswith synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristicof SN 1991T–like objects. Furthermore, in the day 11 spectrum, evidence is found for an absorptionfeature that could be identified as high velocity C ii k6580 or H. At the same epoch C iii k4648.8 at photosphericvelocity is probably responsible for the absorption feature at 4500 8. High-velocity Ca is found aroundmaximum light together with Si ii and Fe ii confined in a narrow velocity window. Implied constraints onsupernovae progenitor systems and explosion hydrodynamic models are briefly discussed.

Place, publisher, year, edition, pages
The American Astronomical Society. , 2004. Vol. 128, 387-404 p.
Keyword [en]
supernovae: general — supernovae: individual (SN 1999aa)
URN: urn:nbn:se:su:diva-25304OAI: diva2:199407
Part of urn:nbn:se:su:diva-80Available from: 2004-03-25 Created: 2004-03-25 Last updated: 2010-09-14Bibliographically approved
In thesis
1. Type Ia Supernova Cosmology: Quantitative Spectral Analysis
Open this publication in new window or tab >>Type Ia Supernova Cosmology: Quantitative Spectral Analysis
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Type Ia supernovae have been successfully used as standardized candles to study the expansion history of the Universe. In the past few years, these studies led to the exciting result of an accelerated expansion caused by the repelling action of some sort of dark energy. This result has been confirmed by measurements of cosmic microwave background radiation, the large-scale structure, and the dynamics of galaxy clusters. The combination of all these experiments points to a “concordance model” of the Universe with flat large-scale geometry and a dominant component of dark energy.

However, there are several points related to supernova measurements which need careful analysis in order to doubtlessly establish the validity of the concordance model. As the amount and quality of data increases, the need of controlling possible systematic effects which may bias the results becomes crucial. Also important is the improvement of our knowledge of the physics of supernovae events to assure and possibly refine their calibration as standardized candle.

This thesis addresses some of those issues through the quantitative analysis of supernova spectra. The stress is put on a careful treatment of the data and on the definition of spectral measurement methods. The comparison of measurements for a large set of spectra from nearby supernovae is used to study the homogeneity and to search for spectral parameters which may further refine the calibration of the standardized candle. One such parameter is found to reduce the dispersion in the distance estimation of a sample of supernovae to below 6%, a precision which is comparable with the current lightcurve-based calibration, and is obtained in an independent manner. Finally, the comparison of spectral measurements from nearby and distant objects is used to test the possibility of evolution with cosmic time of the intrinsic brightness of type Ia supernovae.

Place, publisher, year, edition, pages
Stockholm: Fysikum, 2004. 137 p.
Supernova, Cosmology, Spectroscopy
National Category
Physical Sciences
urn:nbn:se:su:diva-80 (URN)91-7265-847-9 (ISBN)
Public defence
2004-04-16, sal FA32, AlbaNova universitetscentrum, Roslagstullbacken 21, Stockholm, 10:00
Available from: 2004-03-25 Created: 2004-03-25Bibliographically approved

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