Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope

The Astrophysical Journal (Impact Factor: 5.99). 10/2011; 749(2). DOI: 10.1088/0004-637X/749/2/126
Source: arXiv


We present ultraviolet (UV) spectroscopy and photometry of four Type Ia
supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism
of the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset
provides unique spectral time series down to 2000 Angstrom. Significant
diversity is seen in the near maximum-light spectra (~ 2000--3500 Angstrom) for
this small sample. The corresponding photometric data, together with archival
data from Swift Ultraviolet/Optical Telescope observations, provide further
evidence of increased dispersion in the UV emission with respect to the
optical. The peak luminosities measured in uvw1/F250W are found to correlate
with the B-band light-curve shape parameter dm15(B), but with much larger
scatter relative to the correlation in the broad-band B band (e.g., ~0.4 mag
versus ~0.2 mag for those with 0.8 < dm15 < 1.7 mag). SN 2004dt is found as an
outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia
such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W
filters, respectively. We show that different progenitor metallicity or
line-expansion velocities alone cannot explain such a large discrepancy.
Viewing-angle effects, such as due to an asymmetric explosion, may have a
significant influence on the flux emitted in the UV region. Detailed modeling
is needed to disentangle and quantify the above effects.

Download full-text


Available from: Cecilia Kozma,
  • Source
    • "Unfortunately, there are many factors involved in supernova light production, dispersal and observations. For many reasons SNe Ia information suffers significant intrinsic errors and each event must be thoroughly analyzed before use as a distance indicator[10] [11]. The situation is now known to be quite complicated with significant systematic uncertainties[12] and fluxaveraging SNe observations has a significant impact on the calculated distanceredshift values[13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We derive several, detailed relationships in terms of the Friedmann-Robertson-Walker (FRW) generalization which describe the Universe during both the radiation and matter dominated epochs. We explicitly provide for the influence of radiation, rather than burying this term within the matter term. Several models allow the cosmological constant (CC) to vary with universe expansion in differing manners. We evaluate these and other popular models including the ΛCDM(standard model), quintessence as presented by Vishwakarma, Equation of State (EoS) and the Carmeli model with data from the 580 Union2.1 supernovae type Ia collection, using several minimization routines and find models built about the CC, the ΛCDM models, fare no better than those without.
    International Journal of Theoretical Physics 08/2014; 53(8). DOI:10.1007/s10773-014-2061-5 · 1.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan Baade telescope at NIR wavelengths. These data provide the opportunity to examine the entire maximum-light SN Ia spectral-energy distribution. Since the UV region of a SN Ia spectrum is extremely sensitive to the composition of the outer layers of the explosion, which are transparent at longer wavelengths, this unprecedented spectrum can provide strong constraints on the composition of the SN ejecta, and similarly the SN explosion and progenitor system. SN 2011iv is spectroscopically normal, but has a relatively fast decline (Delta m_15 (B) = 1.69 +/- 0.05 mag). We compare SN 2011iv to other SNe Ia with UV spectra near maximum light and examine trends between UV spectral properties, light-curve shape, and ejecta velocity. We tentatively find that SNe with similar light-curve shapes but different ejecta velocities have similar UV spectra, while those with similar ejecta velocities but different light-curve shapes have very different UV spectra. Through a comparison with explosion models, we find that both a solar-metallicity W7 and a zero-metallicity delayed-detonation model provide a reasonable fit to the spectrum of SN 2011iv from the UV to the NIR.
    The Astrophysical Journal Letters 02/2012; 753(1). DOI:10.1088/2041-8205/753/1/L5 · 5.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Type Ia supernovae (SNe Ia) play an important role in astrophysics and are crucial for the studies of stellar evolution, galaxy evolution and cosmology. They are generally thought to be thermonuclear explosions of accreting carbon-oxygen white dwarfs (CO WDs) in close binaries, however, the nature of the mass donor star is still unclear. In this article, we review various progenitor models proposed in the past years and summarize many observational results that can be used to put constraints on the nature of their progenitors. We also discuss the origin of SN Ia diversity and the impacts of SN Ia progenitors on some fields. The currently favourable progenitor model is the single-degenerate (SD) model, in which the WD accretes material from a non-degenerate companion star. This model may explain the similarities of most SNe Ia. It has long been argued that the double-degenerate (DD) model, which involves the merger of two CO WDs, may lead to an accretion-induced collapse rather than a thermonuclear explosion. However, recent observations of a few SNe Ia seem to support the DD model, and this model can produce normal SN Ia explosion under certain conditions. Additionally, the sub-luminous SNe Ia may be explained by the sub-Chandrasekhar mass model. At present, it seems likely that more than one progenitor model, including some variants of the SD and DD models, may be required to explain the observed diversity of SNe Ia.
    New Astronomy Reviews 04/2012; 214. DOI:10.1016/j.newar.2012.04.001 · 6.43 Impact Factor
Show more