31 research outputs found
Initial Hubble Diagram Results from the Nearby Supernova Factory
The use of Type Ia supernovae as distance indicators led to the discovery of
the accelerating expansion of the universe a decade ago. Now that large second
generation surveys have significantly increased the size and quality of the
high-redshift sample, the cosmological constraints are limited by the currently
available sample of ~50 cosmologically useful nearby supernovae. The Nearby
Supernova Factory addresses this problem by discovering nearby supernovae and
observing their spectrophotometric time development. Our data sample includes
over 2400 spectra from spectral timeseries of 185 supernovae. This talk
presents results from a portion of this sample including a Hubble diagram
(relative distance vs. redshift) and a description of some analyses using this
rich dataset.Comment: Short version of proceedings for ICHEP08, Philadelphia PA, July 2008;
see v1 for full-length versio
The Supernovae Integral Field Spectrograph: keys to high-precision spectro-photometry
The Supernovae Integral Field Spectrograph: keys to a better spectro-photometry The Nearby Supernova Factory aims at discovering and observing a sample of type Ia supernovae through the dedicated Supernovae Integral Field Spectrograph, currently in operation since 2004 on Mauna-Kea UH telescope. To reach the targeted spectro-photometric accuracy, attention has been focused on various aspects of the calibration procedure, including: estimate of the night photometricity, derivation of the mean atmospheric extinction over the extended optical domain (320-1000 nm), its modeling in terms of physical components (Rayleigh and aerosol scatterings, ozone absorption and telluric lines) and its variability within a given night. Point-source extraction from the IFS datacube also requires a detailed knowledge of the atmospheric-induced point spread function (PSF). The overall accuracy of the calibration chain is estimated on reference flux standard stars
Nearby Supernova Factory Observations of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor
We present photometric and spectroscopic observations of SN 2007if, an
overluminous (M_V = -20.4), red (B-V = 0.16 at B-band maximum), slow-rising
(t_rise = 24 days) type Ia supernova in a very faint (M_g = -14.10) host
galaxy. A spectrum at 5 days past B-band maximum light is a direct match to the
super-Chandrasekhar-mass candidate SN Ia 2003fg, showing Si II and C II at
~9000 km/s. A high signal-to-noise co-addition of the SN spectral time series
reveals no Na I D absorption, suggesting negligible reddening in the host
galaxy, and the late-time color evolution has the same slope as the Lira
relation for normal SNe Ia. The ejecta appear to be well mixed, with no strong
maximum in I-band and a diversity of iron-peak lines appearing in
near-maximum-light spectra. SN2007 if also displays a plateau in the Si II
velocity extending as late as +10 days, which we interpret as evidence for an
overdense shell in the SN ejecta. We calculate the bolometric light curve of
the SN and use it and the \ion{Si}{2} velocity evolution to constrain the mass
of the shell and the underlying SN ejecta, and demonstrate that SN2007 if is
strongly inconsistent with a Chandrasekhar-mass scenario. Within the context of
a "tamped detonation" model appropriate for double-degenerate mergers, and
assuming no host extinction, we estimate the total mass of the system to be 2.4
+/- 0.2 solar masses, with 1.6 +/- 0.1 solar masses of nickel-56 and with
0.3-0.5 solar masses in the form of an envelope of unburned carbon/oxygen. Our
modeling demonstrates that the kinematics of shell entrainment provide a more
efficient mechanism than incomplete nuclear burning for producing the low
velocities typical of super-Chandrasekhar-mass SNeIa.Comment: 23 pages, 13 figures, 4 tables, emulateapj format; v2 fixed some
typos and added a reference; v3 included minor copy-editing changes + fixed
typos in Figure 9, Table 4; accepted to Ap
The Nearby Supernova Factory: toward a high-precision spectro-photometry
The Nearby Supernova Factory (SNfactory) is an international project to discover and study a large sample of type Ia supernovae in the redshift range 0.03 < z < 0.08. Follow-up spectro-photometric observations are performed using the dedicated Supernovae Integral-Field Spectrograph, mounted since 2004 on 2.2 m UH telescope. The goal is to acquire for each supernova and over its full life-time (more than 10 epochs) high spectro-photometric quality spectra over the extended optical range (320–1000 nm). I will present the current status of the SNfactory project, from search efficiency to first scientific results, with an emphasis on the spectro-photometric calibration issues and achievements
Using Spectral Flux Ratios to Standardize SN Ia Luminosities
We present a new method to standardize Type Ia supernova (SN Ia) luminosities
to ~<0.13 magnitudes using flux ratios from a single flux-calibrated spectrum
per SN. Using Nearby Supernova Factory spectrophotomery of 58 SNe Ia, we
performed an unbiased search for flux ratios which correlate with SN Ia
luminosity. After developing the method and selecting the best ratios from a
training sample, we verified the results on a separate validation sample and
with data from the literature. We identified multiple flux ratios whose
correlations with luminosity are stronger than those of light curve shape and
color, previously identified spectral feature ratios, or equivalent width
measurements. In particular, the flux ratio R(642/443) = F(642 nm) / F(443 nm)
has a correlation of 0.95 with SN Ia absolute magnitudes. Using this single
ratio as a correction factor produces a Hubble diagram with a residual scatter
standard deviation of 0.125 +- 0.011 mag, compared with 0.161 +- 0.015 mag when
fit with the SALT2 light curve shape and color parameters x1 and c. The ratio
R(642/443) is an effective correction factor for both extrinsic dust reddening
and instrinsic variations such as those of SN 1991T-like and SN 1999aa-like
SNe. When combined with broad-band color measurements, spectral flux ratios can
standardize SN Ia magnitudes to ~0.12 mag. These are the first spectral metrics
that improve over the standard normalization methods based upon light curve
shape and color and they provide among the lowest scatter Hubble diagrams ever
published.Comment: 6 pages, 3 figures, 2 tables; accepted by A&A Letters; v2 fixed typos
of literature SNe redshifts in table 2, final language and formatting edits,
small improvements to literature SNe compariso
Gas Turbine Combustor Modeling with and without Nozzle Guide Vanes attached.
Peer reviewed: YesNRC publication: Ye
Host Galaxies for Type Ia Supernovae Observed by the Nearby Supernova Factory
International audienceMaximizing the usefulness of Type Ia supernovae (SNe Ia) as cosmological probes requires a detailed understanding of their intrinsic diversity. One of the primary goals of the Nearby Supernova Factory (SNfactory) is to investigate this diversity through spectrophotometric observation of a large number of nearby SNe Ia. Recent studies of the SNe Ia rate have revealed a strong relationship with stellar progenitor population, a potential source for diversity in SNe Ia. We will present the spectroscopic observations of over 70 host galaxies from the SNfactory set of SNe Ia in parallel with an analysis of spectroscopic properties of those SNe Ia
Generalized Spectral Correlations of Type Ia Supernovae from the Nearby Supernova Factory
International audienceWe present a generalized correlation analysis of type Ia supernova spectra with a focus on spectral features that correlate with absolute magnitude in ways that are not already accounted for by color and lightcurve stretch. The results reveal new spectral correlations beyond those of the classic metrics of feature ratios (RSi, RSiS, RCa, EDCa). These new correlations could be used to improve the calibration of type Ia supernovae for cosmology measurements beyond what is possible with stretch and color alone
Direct Analysis of Type Ia Supernovae Observed by The Nearby Supernova Factory
International audienceOver the past four years, the Nearby Supernova Factory (SNfactory) has obtained hundreds of time-series spectra of Type Ia supernovae (SNe Ia) using its SuperNova Integral Field Spectrograph (SNIFS). This dataset is a promising resource for improving our understanding of SN Ia explosion physics and progenitor models --- key issues that, if resolved, could further improve the utility of and confidence in SNe Ia as reliable cosmological distance indicators. Using a new, automated direct analysis code we have developed (SYNAPPS), we have commenced a systematic study of the SNfactory spectroscopic data set. SYNAPPS solves for a highly parameterized synthetic spectrum consistent with the observed spectrum, enabling line identification and ejecta velocity measurements, while treating line-blending explicitly. These results provide important constraints on stellar explosion models. We present preliminary results including, for example, an investigation of some early-phase spectra, and examine trends in spectral behavior noted previously by others. We also address future directions for code development to bring about a deeper physics analysis of the data
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The Nearby Supernova Factory: Toward A High-Precision Spectro-Photometry
The Nearby Supernova Factory (SNfactory) is an international project to discover and study a large sample of type Ia supernovae in the redshift range 0.03 < z < 0.08. Follow-up spectro-photometric observations are performed using the dedicated Supernovae Integral-Field Spectrograph, mounted since 2004 on 2.2 m UH telescope. The goal is to acquire for each supernova and over its full life-time (more than 10 epochs) high spectro-photometric quality spectra over the extended optical range (320-1000 nm).I will present the current status of the SNfactory project, from search efficiency to first scientific results, with an emphasis on the spectro-photometric calibration issues and achievements