We present a novel technique for fitting restframe I-band light curves on a
data set of 42 Type Ia supernovae (SNe Ia). Using the result of the fit, we
construct a Hubble diagram with 26 SNe from the ...subset at 0.01< z<0.1. Adding
two SNe at z~0.5 yields results consistent with a flat
Lambda-dominated``concordance universe''
($\Omega_M,\Omega_\Lambda$)=(0.25,0.75). For one of these, SN 2000fr, new near
infrared data are presented. The high redshift supernova NIR data are also used
to test for systematic effects in the use of SNe Ia as distance estimators. A
flat, Lambda=0, universe where the faintness of supernovae at z~0.5 is due to
grey dust homogeneously distributed in the intergalactic medium is disfavoured
based on the high-z Hubble diagram using this small data-set. However, the
uncertainties are large and no firm conclusion may be drawn. We explore the
possibility of setting limits on intergalactic dust based on B-I and B-V colour
measurements, and conclude that about 20 well measured SNe are needed to give
statistically significant results. We also show that the high redshift
restframe I-band data points are better fit by light curve templates that show
a prominent second peak, suggesting that they are not intrinsically
underluminous.
We present VLT FORS1 and FORS2 spectra of 39 candidate high-redshift
supernovae that were discovered as part of a cosmological study using Type Ia
supernovae (SNe Ia) over a wide range of redshifts. ...From the spectra alone, 20
candidates are spectrally classified as SNe Ia with redshifts ranging from
z=0.212 to z=1.181. Of the remaining 19 candidates, 1 might be a Type II
supernova and 11 exhibit broad supernova-like spectral features and/or have
supernova-like light curves. The candidates were discovered in 8 separate
ground-based searches. In those searches in which SNe Ia at z ~ 0.5 were
targeted, over 80% of the observed candidates were spectrally classified as SNe
Ia. In those searches in which SNe Ia with z > 1 were targeted, 4 candidates
with z > 1 were spectrally classified as SNe Ia and later followed with ground
and space based observatories. We present the spectra of all candidates,
including those that could not be spectrally classified as supernova.
Quels scénarios de péage urbain sont acceptables aux yeux des citadins ? Comment peut-on simuler les réactions comportementales à de tels scénarios ? Quels types d'adaptation sont à prévoir ? Les ...réponses à ces questions se dégagent d'une série d'entretiens du type jeu simulation, menés auprès d'une quinzaine d'automobilistes de la région lyonnaise. Il en ressort que le transfert vers les transports collectifs ne se fait souvent qu'en dernier recours.---Cet article vous est proposé avec l'aimable autorisation des auteurs et de l'éditeur, EDITECOM. La présente version en PDF est sous le copyright d'EDITECOM (http://www.editecom.com/) - 1995. Ce document est protégé en vertu de la loi du droit d'auteur.
Quels scénarios de péage urbain sont acceptables aux yeux des citadins ? Comment peut-on simuler les réactions comportementales à de tels scénarios ? Quels types d'adaptation sont à prévoir ? Les ...réponses à ces questions se dégagent d'une série d'entretiens du type jeu simulation, menés auprès d'une quinzaine d'automobilistes de la région lyonnaise. Il en ressort que le transfert vers les transports collectifs ne se fait souvent qu'en dernier recours.---Cet article vous est proposé avec l'aimable autorisation des auteurs et de l'éditeur, EDITECOM. La présente version en PDF est sous le copyright d'EDITECOM (http://www.editecom.com/) - 1995. Ce document est protégé en vertu de la loi du droit d'auteur.
Astron.J.128:387-404,2004 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 a SN 1991T-like object but
with a relatively strong Ca H&K absorption feature. The first clear sign of Si
II 6355, 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 which could be identified as high
velocity C II 6580 or H-alpha. At the same epoch C III 4648.8 at photospheric
velocity is probably responsible for the absorption feature at 4500 A. 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 hydrodynamical models are briefly discussed.
