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 similar to 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.
Cosmology with Supernovae Ruiz-Lapuente, P
Astrophysics and space science,
2004, Letnik:
290, Številka:
1
Journal Article
Recenzirano
This review gives an update of the cosmological use of SNe Ia and the progress made in testing their properties from the local universe to high-z. The cosmological road from high-z supernovae down to ...Galactic SNe Ia is followed in search of the answer to standing questions on their nature and their validity as cosmological indicators.
We present spectra of twelve type Ia supernovae obtained in 1999 at the William Herschel Telescope and the Nordic Optical Telescope during a search for type Ia supernovae (SN Ia) at intermediate ...redshift. The spectra range from $z=0.178$ to $z=0.493$, including five high signal-to-noise ratio SN Ia spectra in the still largely unexplored range $0.15\leq z \leq 0.3$. Most of the spectra were obtained before or around restframe B-band maximum light. None of them shows the peculiar spectral features found in low-redshift over- or under-luminous SN Ia. Expansion velocities of characteristic spectral absorption features such as Si ii at 6355 Å, S ii at 5640 Å and Ca ii at 3945 Å are found to be consistent with those of their low-z SN Ia counterparts.
The Quest for a Supernova Companion Ruiz-Lapuente, Pilar
Science (American Association for the Advancement of Science),
06/1997, Letnik:
276, Številka:
5320
Journal Article
Recenzirano
The link between supernovae and white drawf stars is examined.
Aims.We present a study of the optical and near-infrared (NIR) properties of the Type Ia Supernova (SN Ia) 2003du. Methods. An extensive set of optical and NIR photometry and low-resolution long-slit ...spectra 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. Results. The ${\it UBVRIJHK}$ 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 JD2 452 766.38 ± 0.5. We derive a B-band stretch parameter of $0.988 \pm0.003$, which corresponds to $\Delta m_{15}=1.02\,\pm0.05$, 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. Using an updated calibration of the V and ${\it JHK}$ absolute magnitudes of SNe Ia, we find a distance modulus $\mu=32.79\pm0.15$ mag to the host galaxy, UGC 9391. We measure a peak ${\it uvoir}$ bolometric luminosity of $1.35(\pm0.20)\times10^{43}$ erg s-1 and Arnett's rule implies that $M_{^{56}{\rm Ni}}\simeq0.68 \pm0.14\,M_{\odot}$ of $\element56{Ni}$ was synthesized during the explosion. Modeling of the ${\it uvoir}$ bolometric light curve also indicates $M_{^{56}{\rm Ni}}$ in the range $0.6{-}0.8\,M_{\odot}$. The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the $\ion{Si}{ii}$ ratio at maximum $\mathcal{R}$($\ion{Si}{ii}$) = $0.22\,\pm0.02$ 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 $\ion{Ca}{ii}$ H&K doublet and infrared triplet, and possibly in $\ion{Si}{ii}$ λ6355, 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 $\ion{Si}{ii}$ λ6355 line in many SNe Ia is due to the presence of two blended absorption components.
Reclassification of gamma-ray bursts Balastegui, Andreu; Ruiz-Lapuente, Pilar; Canal, Ramon
Monthly Notices of the Royal Astronomical Society,
11/2001, Letnik:
328, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We have applied two different automatic classifier algorithms to the BATSE Current GRB Catalog data and we obtain three different classes of gamma-ray bursts (GRBs). Our results confirm the existence ...of a third, intermediate class of GRBs, with mean duration ∼, as deduced from a cluster analysis and from a neural network algorithm. Our analyses imply longer durations than those found by Mukherjee et al. and Horváth, whose intermediate class had durations ∼. From the neural network analysis no difference in hardness between the two longest classes is found, and from both methods we find that the intermediate-duration class constitutes the most homogeneous sample of GRBs in its space distribution, while the longest-duration class constitutes the most inhomogeneous one with , being thus the deepest population of GRBs with . The trend previously found in long bursts, of spatial inhomogeneity increasing with hardness, only holds for this new longest-duration class.
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