42 research outputs found
Type II Supernovae as Probes of Cosmology
- Constraining the cosmological parameters and understanding Dark Energy have
tremendous implications for the nature of the Universe and its physical laws.
- The pervasive limit of systematic uncertainties reached by cosmography
based on Cepheids and Type Ia supernovae (SNe Ia) warrants a search for
complementary approaches.
- Type II SNe have been shown to offer such a path. Their distances can be
well constrained by luminosity-based or geometric methods. Competing,
complementary, and concerted efforts are underway, to explore and exploit those
objects that are extremely well matched to next generation facilities.
Spectroscopic follow-up will be enabled by space- based and 20-40 meter class
telescopes.
- Some systematic uncertainties of Type II SNe, such as reddening by dust and
metallicity effects, are bound to be different from those of SNe Ia. Their
stellar progenitors are known, promising better leverage on cosmic evolution.
In addition, their rate - which closely tracks the ongoing star formation rate
- is expected to rise significantly with look- back time, ensuring an adequate
supply of distant examples.
- These data will competitively constrain the dark energy equation of state,
allow the determination of the Hubble constant to 5%, and promote our
understanding of the processes involved in the last dramatic phases of massive
stellar evolution.Comment: Science white paper, submitted to the Decadal committee Astro201
Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope
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 A. Significant diversity is seen in the near-maximum-light spectra (approx.2000-3500 A) 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 the uvw lIF250W filter are found to correlate with the B-band light-curve shape parameter .(Delta)m15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., approx. 0.4 mag versus approx. 0.2 mag for those with 0.8 3(sigma), being brighter than normal SNe Ia such as SN 2005cf by approx. 0,9 mag and approx. 2.0 mag in the uvwl1F250W 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 effect
The carbon-rich type Ic supernova 2016adj in the iconic dust lane of Centaurus A: signatures of interaction with circumstellar hydrogen?
We present a comprehensive data set of supernova (SN) 2016adj located within
the central dust lane of Centaurus A. SN 2016adj is significantly reddened and
after correcting the peak apparent -band magnitude ()
for Milky Way reddening and our inferred host-galaxy reddening parameters
(i.e., and ), we estimate
it reached a peak absolute magnitude of . Detailed inspection of
the optical/NIR spectroscopic time-series reveals a carbon-rich SN Ic and not a
SN Ib/IIb as previously suggested in the literature. The NIR spectra shows
prevalent carbon-monoxide formation occurring already by +41 days past -band
maximum, which is days earlier than previously reported in the
literature for this object. Interestingly around two months past maximum, the
NIR spectrum of SN~2016adj begins to exhibit H features, with a +97~d medium
resolution spectrum revealing both Paschen and Bracket lines with absorption
minima of km/s, full-width-half-maximum emission velocities of
km/s, and emission line ratios consistent with a dense emission
region. We speculate these attributes are due to circumstellar interaction
(CSI) between the rapidly expanding SN ejecta and a H-rich shell of material
formed during the pre-SN phase. A bolometric light curve is constructed and a
semi-analytical model fit suggests the supernova synthesized 0.5 solar masses
of Ni and ejected 4.2 solar masses of material, though these values
should be approached with caution given the large uncertainties associated with
the adopted reddening parameters, possible CSI contamination, and known light
echo emission. Finally, inspection of Hubble Space Telescope archival data
yielded no progenitor detection.Comment: Submitted to A&A, comments are welcom