We present optical/near-infrared photometry and spectra of the type Ia SN 2002bo spanning epochs from −13 d before maximum B-band light to +102 d after. The pre-maximum optical coverage is ...particularly complete. The extinction deduced from the observed colour evolution and from interstellar Na i D absorption is quite high, namely E(B−V) = 0.43 ± 0.10. On the other hand, model matches to the observed spectra point to a lower reddening E(B−V) ∼ 0.30. In some respects, SN 2002bo behaves as a typical ‘Branch normal’ type Ia supernova (SN Ia) at optical and infrared wavelengths. We find a B-band risetime of 17.9 ± 0.5 d, a Δm15(B) of 1.13 ± 0.05, and a dereddened MB=−19.41 ± 0.42. However, comparison with other type Ia supernovae having similar Δm15(B) values indicates that in other respects SN 2002bo is unusual. While the optical spectra of SN 2002bo are very similar to those of SN 1984A Δm15(B) = 1.19, lower velocities and a generally more structured appearance are found in SNe 1990N, 1994D and 1998bu. For supernovae having Δm15(B) > 1.2, we confirm the variation of with Δm15(B). However, for supernovae such as SN 2002bo, with lower values of Δm15(B) the relation breaks down. Moreover, the evolution of for SN 2002bo is strikingly different from that shown by other type Ia supernovae. The velocities of SN 2002bo and 1984A derived from S ii 5640 Å, Si ii 6355 Å and Ca ii H and K lines are either much higher and/or evolve differently from those seen in other normal SNe Ia events. Thus, while SN 2002bo and SN 1984A appear to be highly similar, they exhibit behaviour which is distinctly different from other SNe Ia having similar Δm15(B) values. We suggest that the unusually low temperature, the presence of high-velocity intermediate-mass elements and the low abundance of carbon at early times indicates that burning to Si penetrated to much higher layers than in more normal type Ia supernovae. This may be indicative of a delayed detonation explosion.
With archival and new Hubble Space Telescope observations, we have refined the space-velocity measurements of the stars in the central region of the remnant of Tycho's supernova (SN) 1572, one of the ...historical Galactic Type Ia supernova remnants (SNRs). We derived a proper motion for Tycho-G of (μαcos δ; μδ)J2000.0 = (−2.63; −3.98) ± (0.06; 0.04) formal errors ± (0.18; 0.10) expected errors mas yr−1. If the star were at the distance of the SNR (taken here to be 2.83 kpc), its velocity would be v
b = −51 ± 1.5 km s−1. We also reconstruct the binary orbit that Tycho-G should have followed if it were the surviving companion of SN 1572. We redetermine the Ni abundance of this star and compare it with new abundance data from stars of the Galactic disc, finding that Ni/Fe is about 1.7σ above the Galactic trend. From the high velocity of Tycho-G perpendicular to the Galactic plane ( − 90 ± 3 km s−1 ≤ v
b ≤ −45 ± 1 km s−1, for the allowed range of distances to the star), its metallicity and its Ni excess, we find the probability of it being a chance interloper to be P 0.000 37 at most. The projected rotational velocity of the star should be below current observational limits. The projected position of Tycho-G is, within the uncertainties, consistent with the centroid of the X-ray emission of Tycho's SNR; moreover, its brightness is generally consistent with the post-explosion evolution of the luminosity of an SN companion. Among the other 23 stars having V < 22 mag and located within 42 arcsec from the X-ray centroid, only 4 are at distances compatible with that of the SNR, and none of them shows any peculiarity. Therefore, if even Tycho-G is not the surviving companion of SN 1572, the absence of other viable candidates does favour the merging of two white dwarfs as the producer of the SN.
The early spectral evolution of SN 2004dt Altavilla, G.; Stehle, M.; Ruiz–Lapuente, P. ...
Astronomy & astrophysics,
11/2007, Letnik:
475, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Aims.We study the optical spectroscopic properties of Type Ia Supernova (SN Ia) 2004dt, focusing our attention on the early epochs. Methods.Observation triggered soon after the SN 2004dt discovery ...allowed us to obtain a spectrophotometric coverage from day –10 to almost one year (~353 days) after the B band maximum. Observations carried out on an almost daily basis allowed us a good sampling of the fast spectroscopic evolution of SN 2004dt in the early stages. To obtain this result, low–resolution, long–slit spectroscopy was obtained using a number of facilities. Results.This supernova, which in some absorption lines of its early spectra showed the highest degree of polarization ever measured in any SN Ia, has a complex velocity structure in the outer layers of its ejecta. Unburnt oxygen is present, moving at velocities as high as ~16 700 km s-1, with some intermediate–mass elements (Mg, Si, Ca) moving equally fast. Modeling of the spectra based on standard density profiles of the ejecta fails to reproduce the observed features, whereas enhancing the density of outer layers significantly improves the fit. Our analysis indicates the presence of clumps of high–velocity, intermediate–mass elements in the outermost layers, which is also suggested by the spectropolarimetric data.
R-band intensity measurements along the light curve of Type Ia supernovae discovered by the Supernova Cosmology Project (SCP) are fitted in brightness to templates allowing a free parameter the ...time-axis width factor w = s(1+z). The data points are then individually aligned in the time-axis, normalized and K-corrected back to the rest frame, after which the nearly 1300 normalized intensity measurements are found to lie on a well-determined common rest-frame B-band curve which we call the ``composite curve''. The same procedure is applied to 18 low-redshift Calan/Tololo SNe with z < 0.11; these nearly 300 B-band photometry points are found to lie on the composite curve equally well. The SCP search technique produces several measurements before maximum light for each supernova. We demonstrate that the linear stretch factor, s, which parameterizes the light-curve timescale appears independent of z,and applies equally well to the declining and rising parts of the light curve. In fact, the B-band template that best fits this composite curve fits the individual supernova photometry data when stretched by a factor s with chi^2/DoF approx = 1, thus as well as any parameterization can, given the current data sets. The measurement of the date of explosion, however, is model dependent and not tightly constrained by the current data. We also demonstrate the 1+z light-curve time-axis broadening expected from cosmological expansion. This argues strongly against alternative explanations, such as tired light, for the redshift of distant objects.
We present the intensive spectroscopic follow up of the Type Ia supernova (SN Ia) 2014J in the starburst galaxy M82. Twenty-seven optical spectra have been acquired from 2014 January 22 to September ...1 with the Isaac Newton and William Herschel Telescopes. After correcting the observations for the recession velocity of M82 and for Milky Way and host galaxy extinction, we measured expansion velocities from spectral line blueshifts and pseudo-equivalent width of the strongest features in the spectra, which gives an idea on how elements are distributed within the ejecta. We position SN 2014J in the Benetti, Branch et al. and Wang et al. diagrams. These diagrams are based on properties of the Si ii features and provide dynamical and chemical information about the SN ejecta. The nearby SN 2011fe, which showed little evidence for reddening in its host galaxy, is shown as a reference for comparisons. SN 2014J is a border-line object between the Core-normal and Broad-line groups, which corresponds to an intermediate position between low-velocity gradient and high-velocity gradient objects. SN 2014J follows the $R({\rm Si\,{\small {II}}})$–Δm15 correlation, which confirms its classification as a relatively normal SN Ia. Our description of the SN Ia in terms of the evolution of the pseudo-equivalent width of various ions as well as the position in the various diagrams put this specific SN Ia into the overall sample of SN Ia.
The ultimate fate of the Universe, infinite expansion or a big crunch,
can be determined by using the redshifts and distances of very distant supernovae
to monitor changes in the expansion rate. We ...can now find large
numbers of these distant supernovae, and measure their redshifts and apparent
brightnesses; moreover, recent studies of nearby type Ia supernovae have shown
how to determine their intrinsic luminosities-and
therefore with their apparent brightnesses obtain their distances. The >50
distant supernovae discovered so far provide a record of changes in the expansion
rate over the past several billion years. However, it
is necessary to extend this expansion history still farther away (hence further
back in time) in order to begin to distinguish the causes of the expansion-rate
changes-such as the slowing caused by the gravitational attraction of
the Universe's mass density, and the possibly counteracting effect of the
cosmological constant. Here we report the most distant spectroscopically
confirmed supernova. Spectra and photometry from the largest telescopes on
the ground and in space show that this ancient supernova is strikingly similar
to nearby, recent type Ia supernovae. When combined with previous measurements
of nearer supernovae,, these new measurements
suggest that we may live in a low-mass-density universe.
'Dark energy' is the name given to the unknown cause of the Universe's accelerating expansion, which is one of the most significant and surprising discoveries in recent cosmology. Understanding this ...enigmatic ingredient of the Universe and its gravitational effects is a very active, and growing, field of research. In this volume, twelve world-leading authorities on the subject present the basic theoretical models that could explain dark energy, and the observational and experimental techniques employed to measure it. Covering the topic from its origin, through recent developments, to its future perspectives, this book provides a complete and comprehensive introduction to dark energy for a range of readers. It is ideal for physics graduate students who have just entered the field and researchers seeking an authoritative reference on the topic.
ABSTRACT
Extensive light and colour curves for the Type Ia supernova (SN Ia) SN 2002er are presented as part of the European Supernova Collaboration. We have collected UBVRI photometry from 11 ...different telescopes covering the phases from 7 d before until 619 d after maximum light. Corrections for the different instrumental systems and the non‐thermal spectrum of the supernova (S‐corrections) have been applied. With the densely sampled light curves we can make detailed comparisons to other well‐observed objects. SN 2002er most closely resembles SN 1996X after maximum, but clearly shows a different colour evolution before peak light and a stronger shoulder in V and R bands compared to other well‐observed SNe Ia. In particular, the rise time appears to be longer than what is expected from the rise time versus decline rate relation. We use several methods to determine the reddening towards SN 2002er based on the colour evolution at near peak and at late phases. The uvoir (bolometric) light curve shows great similarity with SN 1996X, but also indications of a higher luminosity, longer rise time and a more pronounced shoulder 25 d past maximum. The interpretation of the light curves was carried out with two independent light curve codes. Both find that given the luminosity of SN 2002er the 56Ni mass exceeds 0.6 M⊙ with preferred values near 0.7 M⊙. Uncertainties in the exact distance to SN 2002er are the most serious limitation of this measurement. The light‐curve modelling also indicates a high level of mixing of the nickel in the explosion of SN 2002er.
The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data-provides a powerful tool for ...constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant . Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over cold dark matter. Dark energy described by two equation-of-state parameters has considerable phase space to avoid and next-generation data will be required to constrain such physics, with the level of complementarity between probes varying with cosmology.
PDF
