226 research outputs found
iPTF13beo: The Double-Peaked Light Curve of a Type Ibn Supernova Discovered Shortly after Explosion
We present optical photometric and spectroscopic observations of the Type Ibn
(SN 2006jc-like) supernova iPTF13beo. Detected by the intermediate Palomar
Transient Factory ~3 hours after the estimated first light, iPTF13beo is the
youngest and the most distant (~430 Mpc) Type Ibn event ever observed. The
iPTF13beo light curve is consistent with light curves of other Type Ibn SNe and
with light curves of fast Type Ic events, but with a slightly faster rise-time
of two days. In addition, the iPTF13beo R-band light curve exhibits a
double-peak structure separated by ~9 days, not observed before in any Type Ibn
SN. A low-resolution spectrum taken during the iPTF13beo rising stage is
featureless, while a late-time spectrum obtained during the declining stage
exhibits narrow and intermediate-width He I and Si II features with FWHM ~
2000-5000 km/s and is remarkably similar to the prototypical SN Ibn 2006jc
spectrum. We suggest that our observations support a model of a massive star
exploding in a dense He-rich circumstellar medium (CSM). A shock breakout in a
CSM model requires an eruption releasing a total mass of ~0.1 Msun over a time
scale of couple of weeks prior to the SN explosion.Comment: 8 pages, 5 figures, submitted to MNRA
Analyse préliminaire de la valeur verte pour les logements
Analyse préliminaire de la valeur verte pour les logement
Atmospheric extinction properties above Mauna Kea from the Nearby Supernova Factory spectro-photometric data set
We present a new atmospheric extinction curve for Mauna Kea spanning
3200--9700 \AA. It is the most comprehensive to date, being based on some 4285
standard star spectra obtained on 478 nights spread over a period of 7 years
obtained by the Nearby SuperNova Factory using the SuperNova Integral Field
Spectrograph. This mean curve and its dispersion can be used as an aid in
calibrating spectroscopic or imaging data from Mauna Kea, and in estimating the
calibration uncertainty associated with the use of a mean extinction curve. Our
method for decomposing the extinction curve into physical components, and the
ability to determine the chromatic portion of the extinction even on cloudy
nights, is described and verified over the wide range of conditions sampled by
our large dataset. We demonstrate good agreement with atmospheric science data
obtain at nearby Mauna Loa Observatory, and with previously published
measurements of the extinction above Mauna Kea.Comment: 22 pages, 24 figures, 6 table
Host Galaxy Properties and Hubble Residuals of Type Ia Supernovae from the Nearby Supernova Factory
We examine the relationship between Type Ia Supernova (SN Ia) Hubble
residuals and the properties of their host galaxies using a sample of 115 SNe
Ia from the Nearby Supernova Factory (SNfactory). We use host galaxy stellar
masses and specific star-formation rates fitted from photometry for all hosts,
as well as gas-phase metallicities for a subset of 69 star-forming (non-AGN)
hosts, to show that the SN Ia Hubble residuals correlate with each of these
host properties. With these data we find new evidence for a correlation between
SN Ia intrinsic color and host metallicity. When we combine our data with those
of other published SN Ia surveys, we find the difference between mean SN Ia
brightnesses in low and high mass hosts is 0.077 +- 0.014 mag. When viewed in
narrow (0.2 dex) bins of host stellar mass, the data reveal apparent plateaus
of Hubble residuals at high and low host masses with a rapid transition over a
short mass range (9.8 <= log(M_*/M_Sun) <= 10.4). Although metallicity has been
a favored interpretation for the origin of the Hubble residual trend with host
mass, we illustrate how dust in star-forming galaxies and mean SN Ia progenitor
age both evolve along the galaxy mass sequence, thereby presenting equally
viable explanations for some or all of the observed SN Ia host bias.Comment: 20 pages, 11 figures, accepted for publication in Ap
Type Ia Supernova Hubble Residuals and Host-Galaxy Properties
Kim et al. (2013) [K13] introduced a new methodology for determining
peak-brightness absolute magnitudes of type Ia supernovae from multi-band light
curves. We examine the relation between their parameterization of light curves
and Hubble residuals, based on photometry synthesized from the Nearby Supernova
Factory spectrophotometric time series, with global host-galaxy properties. The
K13 Hubble residual step with host mass is mag for a supernova
subsample with data coverage corresponding to the K13 training; at , the step is not significant and lower than previous measurements.
Relaxing the data coverage requirement the Hubble residual step with host mass
is mag for the larger sample; a calculation using the modes of
the distributions, less sensitive to outliers, yields a step of 0.019 mag. The
analysis of this article uses K13 inferred luminosities, as distinguished from
previous works that use magnitude corrections as a function of SALT2 color and
stretch parameters: Steps at significance are found in SALT2 Hubble
residuals in samples split by the values of their K13 and
light-curve parameters. affects the light-curve width and color around
peak (similar to the and stretch parameters), and
affects colors, the near-UV light-curve width, and the light-curve decline 20
to 30 days after peak brightness. The novel light-curve analysis, increased
parameter set, and magnitude corrections of K13 may be capturing features of
SN~Ia diversity arising from progenitor stellar evolution.Comment: 17 pages, 6 figures. Accepted by Astrophysical Journa
Evidence of Environmental Dependencies of Type Ia Supernovae from the Nearby Supernova Factory indicated by Local H{\alpha}
(Abridged) We study the host galaxy regions in close proximity to Type Ia
supernovae (SNe Ia) to analyze relations between the properties of SN Ia events
and environments most similar to where their progenitors formed. We focus on
local H\alpha\ emission as an indicator of young environments. The Nearby
Supernova Factory has obtained flux-calibrated spectral timeseries for SNe Ia
using integral field spectroscopy, allowing the simultaneous measurement of the
SN and its immediate vicinity. For 89 SNe Ia we measure H\alpha\ emission
tracing ongoing star formation within a 1 kpc radius around each SN. This
constitutes the first direct study of the local environment for a large sample
of SNe Ia also having accurate luminosity, color and stretch measurements. We
find that SNe Ia with local H\alpha\ emission are redder by 0.036+/-0.017 mag,
and that the previously-noted correlation between stretch and host mass is
entirely driven by the SNe Ia coming from passive regions. Most importantly,
the mean standardized brightness for SNe Ia with local H\alpha\ emission is
0.094+/-0.031 mag fainter than for those without. This offset arises from a
bimodal structure in the Hubble residuals, that also explains the
previously-known host-mass bias. We combine this bimodality with the cosmic
star-formation rate to predict changes with redshift in the mean SN Ia
brightness and the host-mass bias. This change is confirmed using high-redshift
SNe Ia from the literature. These environmental dependences point to remaining
systematic errors in SNe Ia standardization. The observed brightness offset is
predicted to cause a significant bias in measurements of the dark energy
equation of state. Recognition of these effects offers new opportunities to
improve SNe Ia as cosmological probes - e.g. SNe Ia having local H\alpha\
emission are more homogeneous, having a brightness dispersion of 0.105+/-0.012
mag.Comment: accepted for publication in Section 3. Cosmology of A&A (The official
date of acceptance is 30/08/2013
Host Galaxies of Type Ia Supernovae from the Nearby Supernova Factory
We present photometric and spectroscopic observations of galaxies hosting
Type Ia supernovae (SNe Ia) observed by the Nearby Supernova Factory
(SNfactory). Combining GALEX UV data with optical and near infrared photometry,
we employ stellar population synthesis techniques to measure SN Ia host galaxy
stellar masses, star-formation rates (SFRs), and reddening due to dust. We
reinforce the key role of GALEX UV data in deriving accurate estimates of
galaxy SFRs and dust extinction. Optical spectra of SN Ia host galaxies are
fitted simultaneously for their stellar continua and emission lines fluxes,
from which we derive high precision redshifts, gas-phase metallicities, and
Halpha-based SFRs. With these data we show that SN Ia host galaxies present
tight agreement with the fiducial galaxy mass-metallicity relation from SDSS
for stellar masses log(M_*/M_Sun)>8.5 where the relation is well-defined. The
star-formation activity of SN Ia host galaxies is consistent with a sample of
comparable SDSS field galaxies, though this comparison is limited by systematic
uncertainties in SFR measurements. Our analysis indicates that SN Ia host
galaxies are, on average, typical representatives of normal field galaxies.Comment: 25 pages, 13 figures, accepted for publication in Ap
Standardizing Type Ia Supernova Absolute Magnitudes Using Gaussian Process Data Regression
We present a novel class of models for Type Ia supernova time-evolving
spectral energy distributions (SED) and absolute magnitudes: they are each
modeled as stochastic functions described by Gaussian processes. The values of
the SED and absolute magnitudes are defined through well-defined regression
prescriptions, so that data directly inform the models. As a proof of concept,
we implement a model for synthetic photometry built from the spectrophotometric
time series from the Nearby Supernova Factory. Absolute magnitudes at peak
brightness are calibrated to 0.13 mag in the -band and to as low as 0.09 mag
in the blueshifted -band, where the dispersion includes
contributions from measurement uncertainties and peculiar velocities. The
methodology can be applied to spectrophotometric time series of supernovae that
span a range of redshifts to simultaneously standardize supernovae together
with fitting cosmological parameters.Comment: 47 pages, 15 figures, accepted for publication by Astrophysical
Journa
The Extinction Properties of and Distance to the Highly Reddened Type Ia Supernova SN 2012cu
Correction of Type Ia Supernova brightnesses for extinction by dust has
proven to be a vexing problem. Here we study the dust foreground to the highly
reddened SN 2012cu, which is projected onto a dust lane in the galaxy NGC 4772.
The analysis is based on multi-epoch, spectrophotometric observations spanning
3,300 - 9,200 {\AA}, obtained by the Nearby Supernova Factory. Phase-matched
comparison of the spectroscopically twinned SN 2012cu and SN 2011fe across 10
epochs results in the best-fit color excess of (E(B-V), RMS) = (1.00, 0.03) and
total-to-selective extinction ratio of (RV , RMS) = (2.95, 0.08) toward SN
2012cu within its host galaxy. We further identify several diffuse interstellar
bands, and compare the 5780 {\AA} band with the dust-to-band ratio for the
Milky Way. Overall, we find the foreground dust-extinction properties for SN
2012cu to be consistent with those of the Milky Way. Furthermore we find no
evidence for significant time variation in any of these extinction tracers. We
also compare the dust extinction curve models of Cardelli et al. (1989),
O'Donnell (1994), and Fitzpatrick (1999), and find the predictions of
Fitzpatrick (1999) fit SN 2012cu the best. Finally, the distance to NGC4772,
the host of SN 2012cu, at a redshift of z = 0.0035, often assigned to the Virgo
Southern Extension, is determined to be 16.61.1 Mpc. We compare this
result with distance measurements in the literature.Comment: 48 pages, 13 figures. Accepted for publication in The Astrophysical
Journal. The spectral time series data presented in this article can be found
at http://snfactory.lbl.gov/snf/data
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