104 research outputs found
Progenitor constraints on the Type-Ia supernova SN2011fe from pre-explosion Hubble Space Telescope HeII narrow-band observations
We present Hubble Space Telescope (HST) imaging observations of the site of
the Type-Ia supernova SN2011fe in the nearby galaxy M101, obtained about one
year prior to the event, in a narrow band centred on the HeII 4686 \AA{}
emission line. In a "single-degenerate" progenitor scenario, the hard photon
flux from an accreting white dwarf (WD), burning hydrogen on its surface over
Myr should, in principle, create a HeIII Str\"{o}mgren sphere or shell
surrounding the WD. Depending on the WD luminosity, the interstellar density,
and the velocity of an outflow from the WD, the HeIII region could appear
unresolved, extended, or as a ring, with a range of possible surface
brightnesses. We find no trace of HeII 4686 \AA{} line emission in the HST
data. Using simulations, we set upper limits on the HeII 4686 \AA{}
luminosity of erg s for a point
source, corresponding to an emission region of radius pc. The upper
limit for an extended source is erg
s, corresponding to an extended region with pc. The largest
detectable shell, given an interstellar-medium density of 1 cm, has a
radius of pc. Our results argue against the presence, within the
yr prior to the explosion, of a supersoft X-ray source of luminosity
erg s, or of a super-Eddington
accreting WD that produces an outflowing wind capable of producing cavities
with radii of 2-6 pc.Comment: Accepted by MNRAS Letters; revised version following referee report
and readers' comment
The Evolution of the Type Ia Supernova Luminosity Function
Type Ia supernovae (SNe Ia) exhibit a wide diversity of peak luminosities and
light curve shapes: the faintest SNe Ia are 10 times less luminous and evolve
more rapidly than the brightest SNe Ia. Their differing characteristics also
extend to their stellar age distributions, with fainter SNe Ia preferentially
occurring in old stellar populations and vice versa. In this Letter, we
quantify this SN Ia luminosity - stellar age connection using data from the
Lick Observatory Supernova Search (LOSS). Our binary population synthesis
calculations agree qualitatively with the observed trend in the >1 Gyr-old
populations probed by LOSS if the majority of SNe Ia arise from prompt
detonations of sub-Chandrasekhar mass white dwarfs (WDs) in double WD systems.
Under appropriate assumptions, we show that double WD systems with less massive
primaries, which yield fainter SNe Ia, interact and explode at older ages than
those with more massive primaries. We find that prompt detonations in double WD
systems are capable of reproducing the observed evolution of the SN Ia
luminosity function, a constraint that any SN Ia progenitor scenario must
confront.Comment: Accepted for publication in ApJL. Minor changes to previous version
for clarity. Data used to construct the observational CDFs in Figure 4 are
available in an ancillary fil
Spectroscopic identification of a redshift 1.55 supernova host galaxy from the Subaru Deep Field Supernova Survey
Context: The Subaru Deep Field (SDF) Supernova Survey discovered 10 Type Ia
supernovae (SNe Ia) in the redshift range 1.5<z<2.0, as determined solely from
photometric redshifts of the host galaxies. However, photometric redshifts
might be biased, and the SN sample could be contaminated by active galactic
nuclei (AGNs).
Aims: We aim to obtain the first robust redshift measurement and
classification of a z > 1.5 SDF SN Ia host galaxy candidate
Methods: We use the X-shooter (U-to-K-band) spectrograph on the Very Large
Telescope to allow the detection of different emission lines in a wide spectral
range.
Results: We measure a spectroscopic redshift of 1.54563 +/- 0.00027 of
hSDF0705.25, consistent with its photometric redshift of 1.552 +/- 0.018. From
the strong emission-line spectrum we rule out AGN activity, thereby confirming
the optical transient as a SN. The host galaxy follows the fundamental
metallicity relation defined in Mannucci et al. (2010, 2011) showing that the
properties of this high-redshift SN Ia host galaxy is similar to other field
galaxies.
Conclusions: Spectroscopic confirmation of additional SDF SN hosts would be
required to confirm the cosmic SN rate evolution measured in the SDF.Comment: 14 pages, 2 figures, Accepted A&A Upload of the Journal versio
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