Publications (6)0 Total impact
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Keren Sharon,
A. Gal-Yam,
D. Maoz,
M. Donahue,
H. Ebeling,
R Ellis, A. Filippenko,
R Foley,
W. Freedman,
R. Kirshner,
J. -P. Kneib,
T. Matheson,
J. Mulchaey,
V. Sarajedini,
M. Voit
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ABSTRACT: We describe our ongoing program designed to measure the SN-Ia rate in a sample of massive z=0.5-0.9 galaxy clusters. The SN-Ia rate is a poorly known observable, especially at high z, and in cluster environments. The SN rate and its redshift dependence can serve as powerful discrimiminants for a number of key issues in astrophysics and cosmology. Our observations will put clear constraints on the characteristic SN-Ia ``delay time'', the typical time between the formation of a stellar population and the explosion of some of its members as SNe-Ia. Such constraints can exclude entire categories of SN-Ia progenitor models, since different models predict different delays. These data will also help to resolve the question of the dominant source of the high metallicity in the intracluster medium (ICM) - SNe-Ia, or core-collapse SNe from an early stellar population with a top-heavy IMF, perhaps those population III stars responsible for the early re-ionization of the Universe. Since clusters are excellent laboratories for studying enrichment (they generally have a simple star-formation history, and matter cannot leave their deep potentials), the results will be relevant for understanding metal enrichment in general, and the possible role of first generation stars in early Universal enrichment. Observations obtained so far during cycles 14 and 15 yield many SNe in our cluster fields, but our follow-up campaign reveals most are not in cluster galaxies.
12/2006;
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A. Clocchiatti,
B Schmidt, A. Filippenko,
P. Challis,
A. Coil,
R. Covarrubias,
A. Diercks,
P. Garnavich,
L. Germany,
R. Gilliland, [......],
A. Riess,
R. Schommer,
R Smith,
A. Soderberg,
J. Spyromilio,
C. Stubbs,
N. Suntzeff,
J. Tonry,
P. Woudt,
for the High Z SN Search Collaboration
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ABSTRACT: We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z~0.5. They were discovered in early 1999 with the 4.0~m Blanco telescope at Cerro Tololo Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U were also observed with the Hubble Space Telescope. We computed luminosity distances to the new SNe using two methods, and added them to the high-z Hubble diagram that the HZT has been constructing since 1995. The new distance moduli confirm the results of previous work. At z~0.5, luminosity distances are larger than those expected for an empty universe, implying that a ``Cosmological Constant,'' or another form of ``dark energy,'' has been increasing the expansion rate of the Universe during the last few billion years.
11/2005;
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ABSTRACT: The robotic Lick Observatory Supernova Search (LOSS), conducted with the
the 0.76-m Katzman Automatic Imaging Telescope (KAIT) equipped with a
CCD imaging camera, has discovered over 400 supernovae in the past 7
years. This makes KAIT the world's most successful search engine for
nearby supernovae. The LOSS sample has about 14,000 galaxies, roughly
half of which are available at any given season, and these are imaged
with temporal frequencies that typically range from 2 to 10 days.
Detailed log files of the search information are automatically created
during the process. With this uniform database we expect to determine
the most accurate supernova rate in the local universe to date.
11/2004; 36:1464.
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J. Millard,
D. Branch,
E. Baron,
K. Hatano,
A. Fisher, A. Filippenko,
R. Kirshner,
P. Challis,
C. Fransson,
N. Panagia,
M. Phillips,
G. Sonneborn,
N. Suntzeff,
R. Wagoner,
J. Wheeler
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ABSTRACT: Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to observed photospheric-phase spectra of the Type Ic supernova 1994I. The observed optical spectra can be well matched by synthetic spectra that are based on the assumption of spherical symmetry. We consider the identification of the infrared absorption feature observed near 10,250 \AA, which previously has been attributed to He I $\lambda10830$ and regarded as strong evidence that SN 1994I ejected some helium. We have difficulty accounting for the infrared absorption with He I alone. It could be a blend of He I and C I lines. Alternatively, we find that it can be fit by Si I lines without compromising the fit in the optical region. In synthetic spectra that match the observed spectra, from 4 days before to 26 days after the time of maximum brightness, the adopted velocity at the photosphere decreases from 17,500 to 7000 \kms. Simple estimates of the kinetic energy carried by the ejected mass give values that are near the canonical supernova energy of $10^{51}$ ergs. The velocities and kinetic energies that we find for SN 1994I in this way are much lower than those that we find elsewhere for the peculiar Type Ic SNe 1997ef and 1998bw, which therefore appear to have been hyper-energetic. Comment: 18 pages, 12 figures, ApJ, in press
06/1999;
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S. Jha,
P. Garnavich,
R. Kirshner,
P. Challis,
A. Soderberg,
L. Macri,
J. Huchra,
P. Barmby,
E. Barton,
P. Berlind, [......],
P. Benson,
A. Rizvi,
L. Marschall,
J. Goldader,
M. Beasley,
W. Vacca,
B. Leibundgut,
J. Spyromilio,
B Schmidt,
P. Wood
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ABSTRACT: We present optical and near-infrared photometry and spectroscopy of the type Ia SN 1998bu in the Leo I Group galaxy M96 (NGC 3368). The data set consists of 356 photometric measurements and 29 spectra of SN 1998bu between UT 1998 May 11 and July 15. The well-sampled light curve indicates the supernova reached maximum light in B on UT 1998 May 19.3 (JD 2450952.8 +/- 0.8) with B = 12.22 +/- 0.03 and V = 11.88 +/- 0.02. Application of a revised version of the Multicolor Light Curve Shape (MLCS) method yields an extinction toward the supernova of A_V = 0.94 +/- 0.15 mag, and indicates the supernova was of average luminosity compared to other normal type Ia supernovae. Using the HST Cepheid distance modulus to M96 (Tanvir et al. 1995) and the MLCS fit parameters for the supernova, we derive an extinction-corrected absolute magnitude for SN 1998bu at maximum, M_V = -19.42 +/- 0.22. Our independent results for this supernova are consistent with those of Suntzeff et al. (1999). Combining SN 1998bu with three other well-observed local calibrators and 42 supernovae in the Hubble flow yields a Hubble constant, H_0 = 64^{+8}_{-6} km/s/Mpc, where the error estimate incorporates possible sources of systematic uncertainty including the calibration of the Cepheid period-luminosity relation, the metallicity dependence of the Cepheid distance scale, and the distance to the LMC. Comment: 34 pages, 13 figures, to appear in ApJS
06/1999;
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B. P. Schmidt,
N. B. Suntzeff,
M. Phillips,
R. Schommer,
A. Clocchiatti,
R. P. Kirshner,
P. Garnavich,
P. Challis,
B. Leibundgut,
J. Spyromilio,
C. Hogan,
C. Stubbs,
D. Reiss,
A. Diercks, A. Filippenko,
A. Reiss,
C. Smith,
M. Hamuy,
R. Gilliland,
J. Tonry
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ABSTRACT: The High-Z SN Search is an international collaboration to discover and
follow SNe Ia at z > 0.2 with the aim of tracing out cosmic
deceleration and global curvature. This project has discovered 37
supernovae (0.09 <z< 0.84) using the Blanco 4-meter telescope at
CTIO over the past two years. We have obtained spectra and two color
photometry for most of these supernovae and find that 25 of the objects
are SNe Ia useful for measuring distances. Using the extensive nearby
set of supernovae gathered by members of our group, we demonstrate that
it is possible to overcome problems associated with K-corrections,
Malmquist Bias, extinction, and evolution which could affect the
distances derived from SNe Ia. In addition to the SNe Ia, the search has
uncovered several normal Type II supernovae on which the Expanding
Photosphere can be applied, several Kuiper Belt asteroids, and a few
short duration events of unknown origin.
11/1996; 28:1420.
