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M. T. Botticella,
A. Pastorello,
S. J. Smartt,
W. P. S. Meikle,
S. Benetti,
R. Kotak,
E. Cappellaro,
R. M. Crockett,
S. Mattila,
M. Sereno, [......],
K. Maguire, J. Mendez,
M. Mobberley,
H. Navasardyan,
C. Ries,
V. Stanishev,
S. Taubenberger,
C. Trundle,
M. Turatto,
I. M. Volkov
[show abstract]
[hide abstract]
ABSTRACT: We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a high density CS medium. The light curve is similar in shape to that of SN 1998S and SN 1979C, although significantly fainter at maximum light. Our quasi-bolometric lightcurve extends to 300 days and shows a tail phase decay rate consistent with that of ^{56}Co. We propose that this is evidence for an explosion and formation of ^{56}Ni (0.0015 +/- 0.0004 M_Sun). The large MIR flux detected shortly after explosion can be explained by a light echo from pre-exisiting dust. The late NIR flux excess is plausibly due to a combination of warm newly-formed ejecta dust together with shock-heated dust in the CS environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90AU and outer radius of 450AU, and an inferred heating source of 3000 K and luminosity of L ~ 10^{4.6} L_Sun. The combination of our monitoring data and the evidence from the progenitor analysis leads us to support the scenario of a weak electron capture supernova explosion in a super-AGB progenitor star (of initial mass 6-8 M_sun) embedded within a thick CS gaseous envelope. We suggest that all of main properties of the electron capture SN phenomenon are observed in SN 2008S and future observations may allow a definitive answer. Comment: accepted for publication in MNRAS (2009 May 7)
03/2009;
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M. Kowalski,
D. Rubin,
G. Aldering,
R. J. Agostinho,
A. Amadon,
R. Amanullah,
C. Balland,
K. Barbary,
G. Blanc,
P. J. Challis, [......],
A. L. Spadafora,
L.-G. Strolger,
M. Strovink,
N. B. Suntzeff,
N. Suzuki,
R. C. Thomas,
N. A. Walton,
L. Wang,
W. M. Wood-Vasey,
and J. L. Yun
[show abstract]
[hide abstract]
ABSTRACT: We present a new compilation of Type Ia supernovae (SNe Ia), a new data set of low-redshift nearby-Hubble-flow SNe, and new analysis procedures to work with these heterogeneous compilations. This "Union" compilation of 414 SNe Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older data sets, as well as the recently extended data set of distant supernovae observed with the Hubble Space Telescope (HST). A single, consistent, and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density is ΩΛ = 0.713+ 0.027−0.029(stat)+ 0.036−0.039(sys) , for a flat, ΛCDM universe. Assuming a constant equation of state parameter, w, the combined constraints from SNe, BAO, and CMB give w = − 0.969+ 0.059−0.063(stat)+ 0.063−0.066(sys) . While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a w that varies with redshift. In particular, the current SN data do not yet significantly constrain w at z > 1. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available.
The Astrophysical Journal 12/2008; 686(2):749. · 6.02 Impact Factor
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R. A. Knop,
G. Aldering,
R. Amanullah,
P. Astier,
G. Blanc,
M. S. Burns,
A. Conley,
S. E. Deustua,
M. Doi,
R. Ellis, [......],
K. Schahmaneche,
E. Smith,
A. L. Spadafora,
V. Stanishev,
M. Sullivan,
N. A. Walton,
L. Wang,
W. M. Wood-Vasey,
N. Yasuda,
and (The Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z = 0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM = 0.25 (statistical) ± 0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ = 0.75 (statistical) ± 0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w = -1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w = -1.05 (statistical) ± 0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ > 0) > 0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.
The Astrophysical Journal 12/2008; 598(1):102. · 6.02 Impact Factor
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P. A. Mazzali,
S. Benetti,
G. Altavilla,
G. Blanc,
E. Cappellaro,
N. Elias-Rosa,
G. Garavini,
A. Goobar,
A. Harutyunyan,
R. Kotak, [......],
Ph. Podsiadlowski,
P. Ruiz-Lapuente,
M. Salvo,
B. P. Schmidt,
J. Sollerman,
V. Stanishev,
M. Stehle,
C. Tout,
M. Turatto,
and W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: Evidence of high-velocity features (HVFs) such as those seen in the near-maximum spectra of some Type Ia supernovae (SNe Ia; e.g., SN 2000cx) has been searched for in the available SN Ia spectra observed earlier than 1 week before B maximum. Recent observational efforts have doubled the number of SNe Ia with very early spectra. Remarkably, all SNe Ia with early data (seven in our Research Training Network sample and 10 from other programs) show signs of such features, to a greater or lesser degree, in Ca II IR and some also in the Si II λ6355 line. HVFs may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material (CSM) by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disk and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in single degenerate systems. Large-scale angular fluctuations in the radial density and abundance distribution may also be responsible: this could originate in the explosion and would suggest a deflagration as the more likely explosion mechanism. CSM interaction and surface fluctuations may coexist, possibly leaving different signatures on the spectrum. In some SNe, the HVFs are narrowly confined in velocity, suggesting the ejection of blobs of burned material.
The Astrophysical Journal 12/2008; 623(1):L37. · 6.02 Impact Factor
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M. Kowalski,
D. Rubin,
G. Aldering,
R. J. Agostinho,
A. Amadon,
R. Amanullah,
C. Balland,
K. Barbary,
G. Blanc,
P. J. Challis, [......],
A. L. Spadafora,
L. -G. Strolger,
M Strovink,
N. B. Suntzeff,
N Suzuki,
R. C. Thomas,
N. A. Walton,
L Wang,
W. M. Wood-Vasey,
J. L. Yun
[show abstract]
[hide abstract]
ABSTRACT: We present a new compilation of Type Ia supernovae (SNe Ia), a new dataset of low-redshift nearby-Hubble-flow SNe and new analysis procedures to work with these heterogeneous compilations. This ``Union'' compilation of 414 SN Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older datasets, as well as the recently extended dataset of distant supernovae observed with HST. A single, consistent and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density is $\Omega_\Lambda= 0.713^{+0.027}_{-0.029} (stat)}^{+0.036}_{-0.039} (sys)}$, for a flat, LCDM Universe. Assuming a constant equation of state parameter, $w$, the combined constraints from SNe, BAO and CMB give $w=-0.969^{+0.059}_{-0.063}(stat)^{+0.063}_{-0.066} (sys)$. While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a $w$ that varies with redshift. In particular, the current SN data do not yet significantly constrain $w$ at $z>1$. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available.
05/2008;
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G. Pignata,
S. Benetti,
P. A. Mazzali,
R. Kotak,
F. Patat,
P. Meikle,
M. Stehle,
B. Leibundgut,
N. B. Suntzeff,
L. M. Buson,
E. Cappellaro,
A. Clocchiatti,
M. Hamuy,
J. Maza, J. Mendez,
P. Ruiz-Lapuente,
M. Salvo,
B. P. Schmidt,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: As part of the European Supernova Collaboration we obtained extensive photometry and spectroscopy of the type Ia SN 2002dj covering epochs from 11 days before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-IR colours and a reduced spectral emission beyond 6500 A. For high-velocity gradient Type Ia supernovae, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to ``normal'' SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of Type Ia supernovae displaying high velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored. Comment: Equations A4, A5 and A7 in the appendix section have been corrected. Part of text in the appendix has been removed
05/2008;
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G. Garavini,
G. Aldering,
A. Amadon,
R. Amanullah,
P. Astier,
C. Balland,
G. Blanc,
A. Conley,
T. Dahlén,
S. E. Deustua, [......],
P. Ruiz-Lapuente,
B. E. Schaefer,
K. Schahmaneche,
E. Smith,
A. L. Spadafora,
V. Stanishev,
R. C. Thomas,
N. A. Walton,
L. Wang,
and W. M. Wood-Vasey
[show abstract]
[hide abstract]
ABSTRACT: We present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac. The data extend from -15 to +42 days with respect to B-band maximum and reveal an event that is unusual in several respects. Prior to B-band maximum, the spectra resemble those of SN 1999aa, a slowly declining event, but possess stronger Si II and Ca II signatures (more characteristic of a spectroscopically normal SN). Spectra after the B-band maximum appear more normal. The expansion velocities inferred from the iron lines appear to be lower than average, whereas the expansion velocity inferred from calcium H and K are higher than average. The expansion velocities inferred from Si II are among the slowest ever observed, although SN 1999ac is not particularly dim. The analysis of the parameters v10(Si II), R(Si II), , and Δm15 further underlines the unique characteristics of SN 1999ac. We find convincing evidence of C II λ6580 in the day -15 spectrum with ejection velocity v > 16,000 km s-1, but this signature disappears by day -9. This rapid evolution at early times highlights the importance of extremely early-time spectroscopy.
The Astronomical Journal 12/2007; 130(5):2278. · 4.03 Impact Factor
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The Supernova Cosmology Project (G. Garavini,
G. Folatelli,
A. Goobar,
S. Nobili,
G. Aldering,
A. Amadon,
R. Amanullah,
P. Astier,
C. Balland,
G. Blanc, [......],
P. Ruiz-Lapuente,
G. Sainton,
B. E. Schaefer,
K. Schahmaneche,
E. Smith,
A. L. Spadafora,
V. Stanishev,
N. A. Walton,
L. Wang,
W. M. Wood-Vasey
[show abstract]
[hide abstract]
ABSTRACT: We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Our data set includes 25 optical spectra between -11 and +58 days with respect to B-band maximum light, providing an unusually complete time history. The early spectra resemble those of an SN 1991T–like object but with a relatively strong Ca H and K absorption feature. The first clear sign of Si II λ6355, characteristic of Type Ia supernovae, is found at day -7, and its velocity remains constant up to at least the first month after B-band maximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggesting SN 1999aa as a possible link between SN 1991T–like and Branch-normal supernovae. Comparing the observations with synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristic of SN 1991T–like objects. Furthermore, in the day -11 spectrum, evidence is found for an absorption feature that could be identified as high velocity C II λ6580 or Hα. At the same epoch C III λ4648.8 at photospheric velocity is probably responsible for the absorption feature at 4500 Å. High-velocity Ca is found around maximum light together with Si II and Fe II confined in a narrow velocity window. Implied constraints on supernovae progenitor systems and explosion hydrodynamic models are briefly discussed.
The Astronomical Journal 12/2007; 128(1):387. · 4.03 Impact Factor
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Joshua A. Frieman,
B. Bassett,
A. Becker,
C. Choi,
D Cinabro,
F. DeJongh,
D. L. DePoy,
B. Dilday,
M Doi,
P. M. Garnavich, [......],
C. Stoughton,
M. Stritzinger,
M. Subbarao,
D. Tucker,
P. Vaisanen,
L. C. Watson,
S. Watters,
J. C. Wheeler,
B. Yanny,
D. York
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5 degrees wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for discovery of new objects. Supernova imaging observations are being acquired between 1 September and 30 November of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.
09/2007;
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V. Stanishev,
A Goobar,
S. Benetti,
R. Kotak,
G. Pignata,
H. Navasardyan,
P. Mazzali,
R. Amanullah,
G. Garavini,
S. Nobili, [......],
M. V. Kichizhieva,
P. Lundqvist,
S. Mattila,
J. Melinder,
E. P. Pavlenko,
N. N. Pavlyuk,
J. Sollerman,
D. Yu. Tsvetkov,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: An extensive set of optical and NIR photometry and low-resolution spectra the Type Ia supernova (SN Ia) 2003du was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique. The UBVRIJHK light curves and the color indices of SN 2003du closely resemble those of normal SNe Ia. SN 2003du reached a B-band maximum of 13.49 (+/-0.02) mag on JD2452766.38 (+/-0.5). We derive a B-band stretch parameter of 0.988 (+/-0.003), which corresponds to dM15=1.02 (+/-0.05), indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. We estimate a distance modulus of 32.79 (+/-0.15) mag to the host galaxy, UGC 9391. The peak UVOIR bolometric luminosity of 1.35(+/-0.20) 10^43 erg/s and Arnett's rule implies that M(Ni56)=0.68 (+/-0.14)M_sun of Ni56 was synthesized during the explosion. Modeling of the UVOIR bolometric light curve also indicates M(Ni56) in the range 0.6-0.8 M_sun. The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II)=0.22 (+/-0.02) and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Ca II H&K doublet and infrared triplet, and possibly in Si II 6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of Si II 6355 line in many SNe Ia is due to the presence of two blended absorption components. Comment: accepted for publication in A&A
04/2007;
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G. Garavini,
G. Folatelli,
S. Nobili,
G. Aldering,
R. Amanullah,
P Antilogus,
P. Astier,
G. Blanc,
J. Bronder,
M. S. Burns, [......],
G. Sainton,
K. Schahmaneche,
E Smith,
A. L. Spadafora,
V. Stanishev,
R. C. Thomas,
N. A. Walton,
L Wang,
W. M. Wood-Vasey,
N. Yasuda. The Supernova Cosmology Project
[show abstract]
[hide abstract]
ABSTRACT: We develop a method to measure the strength of the absorption features in Type Ia supernova (SN Ia) spectra and use it to make a quantitative comparison between the spectra of Type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 < z < 0.912) SNe Ia observed by the Supernova Cosmology Project . Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca II H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z=0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae. Comment: accepted for publication on A&A
03/2007;
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G. Altavilla,
P. Ruiz-Lapuente,
A. Balastegui, J. Mendez,
M. Irwin,
C. Espana-Bonet,
K. Schamaneche,
C. Balland,
R. S. Ellis,
S. Fabbro,
G. Folatelli,
A Goobar,
W. Hillebrandt,
R. M. McMahon,
M. Mouchet,
A. Mourao,
S. Nobili,
R Pain,
V. Stanishev,
N. A. Walton
[show abstract]
[hide abstract]
ABSTRACT: We study intermediate--z SNe Ia using the empirical physical diagrams which
enable to learn about those SNe explosions. This information can be very useful
to reduce systematic uncertainties of the Hubble diagram of SNe Ia up to high
z. The study of the expansion velocities and the measurement of the ratio
$\mathcal{R}$(\SiII) allow to subtype those SNe Ia as done for nearby samples.
The evolution of this ratio as seen in the diagram $\mathcal{R}$(\SiII)--(t)
together with $\mathcal{R}$(\SiII)$_{max}$ versus (B-V)$_{0}$ indicate
consistency of the properties at intermediate z compared with local SNe. At
intermediate--z, the expansion velocities of Ca II and Si II are similar to the
nearby counterparts. This is found in a sample of 6 SNe Ia in the range
0.033$\leq z \leq$0.329 discovered within the {\it International Time
Programme} (ITP) of {\it Cosmology and Physics with SNe Ia} during the spring
of 2002. Those supernovae were identified using the 4.2m William Herschel
Telescope. Two SNe Ia at intermediate z were of the cool FAINT type, one being
a SN1986G--like object highly reddened. The $\mathcal{R}$(\SiII) ratio as well
as subclassification of the SNe Ia beyond templates help to place SNe Ia in
their sequence of brightness and to distinguish between reddened and
intrinsically red supernovae. This test can be done with very high z SNe Ia and
it will help to reduce systematic uncertainties due to extinction by dust. It
should allow to map the high-z sample into the nearby one.
The Astrophysical Journal 10/2006; 695(1). · 6.02 Impact Factor
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S. Taubenberger,
A. Pastorello,
P. A. Mazzali,
S. Valenti,
G. Pignata,
D. N. Sauer,
A. Arbey,
O. Bärnbantner,
S. Benetti,
A. Della Valle, [......],
P. Meikle, J. Mendez,
F. Patat,
E. Pian,
C. Ries,
P. Ruiz-Lapuente,
M. Salvo,
V. Stanishev,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: Optical and near-infrared observations of the Type Ic supernova (SN) 2004aw are presented, obtained from day -3 to day +413 with respect to the B-band maximum. The photometric evolution is characterised by a comparatively slow post-maximum decline of the light curves. The peaks in redder bands are significantly delayed relative to the bluer bands, the I-band maximum occurring 8.4 days later than that in B. With an absolute peak magnitude of -18.02 in the V band the SN can be considered fairly bright, but not exceptional. This also holds for the U through I bolometric light curve, where SN 2004aw has a position intermediate between SNe 2002ap and 1998bw. Spectroscopically SN 2004aw provides a link between a normal Type Ic supernova like SN 1994I and the group of broad-lined SNe Ic. The spectral evolution is rather slow, with a spectrum at day +64 being still predominantly photospheric. The shape of the nebular [O I] 6300,6364 line indicates a highly aspherical explosion. Helium cannot be unambiguously identified in the spectra, even in the near-infrared. Using an analytical description of the light curve peak we find that the total mass of the ejecta in SN 2004aw is 3.5-8.0 M_Sun, significantly larger than in SN 1994I, although not as large as in SN 1998bw. The same model suggests that about 0.3 M_Sun of {56}Ni has been synthesised in the explosion. No connection to a GRB can be firmly established.
08/2006;
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B. Dilday,
J. Barentine,
B. Bassett,
A. Becker,
R. Bendar,
M. Bremer,
H. Brewington,
F. DeJongh,
J. Dembicky,
D. L. DePoy, [......],
P. Ruiz-Lapuente,
M. Sako,
D. Schneider,
M. Smith,
S. Snedden,
M. Subbarao,
N. Takanashi,
K. van der Heyden,
C. Wheeler,
N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: As one of its core programs, the SDSS II is conducting a Supernova
survey over 3 Fall seasons (2005-8) with the primary goal of obtaining
well measured multi-band light curves of 200 type Ia supernovae (SNe)
for the study of cosmology and supernova systematics. The survey is
conducted by repeat scanning of a 300 square degree region ( 150 square
degrees every other night) with the SDSS 2.5 meter telescope. The SDSS
will primarily measure SNe Ia in the redshift range z=0.05-0.35, a
'redshift desert' where relatively few SNe have been measured by
previous searches. Follow-up spectroscopy and additional imaging is
provided by a variety of telescopes, including the ARC, HET, Subaru,
WHT, MDM, UH88, NMSU 1m, WIYN, VATT, and the INT. The Carnegie Supernova
Project is carrying out NIR imaging on a subsample of the confirmed SNe.
From early Sept. to mid-October (the time of submission of this
abstract), 52 spectroscopically confirmed SNe Ia were found. We describe
the SN survey and present highlights from the Fall 2005 campaign.
11/2005; 37:1459.
-
M. Sako,
J. Barentine,
J. Bassett,
A. Becker,
R. Bender,
M. Bremer,
H. Brewington,
F. DeJongh,
J. Dembicky,
D. L. DePoy, [......],
K. Romer,
P. Ruiz-Lapuente,
D. Schneider,
M. Smith,
S. Snedden,
M. Subbarao,
N. Takanashi,
K. van der Heyden,
C. Wheeler,
N. Yasuda
[show abstract]
[hide abstract]
ABSTRACT: The Sloan Digital Sky Survey II is currently conducting a supernova
(SNe) search, where approximately 300 square degrees of the sky are
scheduled for multi-band imaging on a cadence of two days with the
primary goal of studying type Ia SNe as cosmological distance
indicators. The first of the three-year program began in early September
and will continue until the end of November 2005. During the first
month, the survey has discovered and obtained multi-band light curves
and spectroscopic data of 50 SN Ia from z = 0.05 - 0.4, a redshift
"desert" that is poorly sampled in other local and high-redshift
searches. We present some early results from the first year of the
survey and discuss future prospects.
11/2005; 37:1408.
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[show abstract]
[hide abstract]
ABSTRACT: We discuss the host galaxy morphology of the 8 SNe discovered as a part of the International Time Programme (ITP) project ``Omega and Lambda from Supernovae, and the Physics of Supernovae Explosions'' at the European Northern Observatory (ENO). Identification of the SN host galaxy types was done exploiting both imaging and spectroscopy. A peculiar SNIa at z= 0.033 is found in a spiral galaxy, as most other SNeIa with z between 0.1 and 0.4. A complete account of these studies will be given elsewhere.
03/2005;
-
[show abstract]
[hide abstract]
ABSTRACT: We discuss the expansion velocities of different elements in the ejecta of the intermediate-z SNe Ia discovered as a part of the International Time Programme (ITP) project ``Omega and Lambda from Supernovae and the Physics of Supernova Explosions'' at the European Northern Observatory (ENO). The expansion velocities measured for each normal SNIa are found to be within the typical velocity dispersion for their epoch. Meanwhile, the subluminous SN 2002lk SiII expansion velocity is significantly higher than that of SN 1991bg shortly after maximum. The observed phase was younger in SN2002lk than in the local subluminous SNIa SN1991bg.
03/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We study 8 supernovae discovered as part of the International Time Programme (ITP) project ``Omega and Lambda from Supernovae and the Physics of Supernova Explosions'' at the European Northern Observatory (ENO). The goal of the project is to increase the sample of intermediate redshift (0.1<z<0.4) SNe Ia for testing properties of SNe Ia along z and for enlarging the sample in the Hubble diagram up to large z.
03/2005;
-
P. A. Mazzali,
S. Benetti,
G. Altavilla,
G. Blanc,
E. Cappellaro,
N. Elias-Rosa,
G. Garavini,
A Goobar,
A. Harutyunyan,
R. Kotak, [......],
Ph. Podsiadlowski,
P. Ruiz-Lapuente,
M. Salvo,
B. P. Schmidt,
J. Sollerman,
V. Stanishev,
M. Stehle,
C. Tout,
M. Turatto,
W. Hillebrandt
[show abstract]
[hide abstract]
ABSTRACT: Evidence of high-velocity features such as those seen in the near-maximum spectra of some Type Ia Supernovae (eg SN 2000cx) has been searched for in the available SNIa spectra observed earlier than one week before B maximum. Recent observational efforts have doubled the number of SNeIa with very early spectra. Remarkably, all SNeIa with early data (7 in our RTN sample and 10 from other programmes) show signs of such features, to a greater or lesser degree, in CaII IR, and some also in SiII 6255A line. High-velocity features may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disc and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in Single Degenerate systems. Large-scale angular fluctuations in the radial density and abundance distribution may also be responsible: this could originate in the explosion, and would suggest a deflagration as the more likely explosion mechanism. CSM-interaction and surface fluctuations may coexist, possibly leaving different signatures on the spectrum. In some SNe the HVFs are narrowly confined in velocity, suggesting the ejection of blobs of burned material. Comment: 12 pages, 2 figures, ApJ Letters in press
02/2005;
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M. Kowalski,
G. Aldering,
A. Conley,
B. Farris,
V. Fadeyev,
B. Frye,
R. Gibbons,
G. Goldhaber,
D. E. Groom,
D. A. Howell, [......],
E. Smith,
C. Lidman, J. Mendez,
G. J. Miller,
H. Newberg,
J. Rich,
G. T. Richards,
B. E. Schaefer,
P. Ruiz-Lapuente,
N. A. Walton
[show abstract]
[hide abstract]
ABSTRACT: Type Ia SNe represent the best distance indicators for cosmology, having
established the presence of dark energy through measurement of the
expansion history of the universe. While high-z SNe are used to study
the change in the expansion rate, low-z SNe establish a baseline for
brightness comparisons and provide the important calibration used for
standardization. Besides the statistical gain in precision from a large
number of SNe, a good understanding of their systematic variations is
essential. We present the B, V, R, I lightcurves for a new sample of
nearby supernova, obtained by the Supernova Cosmology Project in
collaboration with several other supernova groups. A unique challenge of
this dataset is that seventeen different instruments were used to obtain
the follow-up photometry. Therefore, we focus in particular on the
analysis procedure developed for handling and cross-calibrating the data
from various instruments.
This work was supported in part by the U.S. Department of Energy under
Contract No. DE-AC03-76SF00098.
11/2004; 36:1466.
