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The present study is the first of a series of three papers where we characterise the type II supernovae (SNe~II) from the Carnegie Supernova Project-I to understand their diversity in terms of progenitor and explosion properties. In this first paper, we present bolometric light curves of 74 SNe~II. We outline our methodology to calculate the bolometric luminosity, which consists of the integration of the observed fluxes in numerous photometric bands ($uBgVriYJH$) and black-body (BB) extrapolations to account for the unobserved flux at shorter and longer wavelengths. BB fits were performed using all available broadband data except when line blanketing effects appeared. Photometric bands bluer than $r$ that are affected by line blanketing were removed from the fit, which makes near-infrared (NIR) observations highly important to estimate reliable BB extrapolations to the infrared. BB fits without NIR data produce notably different bolometric light curves, and therefore different estimates of SN~II progenitor and explosion properties when data are modelled. We present two methods to address the absence of NIR observations: (a) colour-colour relationships from which NIR magnitudes can be estimated using optical colours, and (b) new prescriptions for bolometric corrections as a function of observed SN~II colours. Using our 74 SN~II bolometric light curves, we provide a full characterisation of their properties based on several observed parameters. We measured magnitudes at different epochs, as well as durations and decline rates of different phases of the evolution. An analysis of the light-curve parameter distributions was performed, finding a wide range and a continuous sequence of observed parameters which is consistent with previous analyses using optical light curves., Comment: Accepted for publication in A&A

A small fraction of the radiative flux emitted by hot stars is absorbed by their winds and redistributed towards longer wavelengths. This effect, which leads also to the heating of the stellar photosphere, is termed wind blanketing. For stars with variable winds, the effect of wind blanketing may lead to the photometric variability. We have studied the consequences of line driven wind instability and wind blanketing for the light variability of O stars. We combined the results of wind hydrodynamic simulations and of global wind models to predict the light variability of hot stars due to the wind blanketing and instability. The wind instability causes stochastic light variability with amplitude of the order of tens of millimagnitudes and a typical timescale of the order of hours for spatially coherent wind structure. The amplitude is of the order of millimagnitudes when assuming that the wind consists of large number of independent concentric cones. The variability with such amplitude is observable using present space borne photometers. We show that the simulated light curve is similar to the light curves of O stars obtained using BRITE and CoRoT satellites., Comment: 7 pages, accepted for publication in Astronomy & Astrophysics

Aims. The fast improvement of spectroscopic observations makes mandatory a strong effort on the theoretical side to better reproduce the spectral energy distribution (SED) of stars at high spectral resolution. In this regard, relying on the Kurucz Atlas/Synthe original codes we computed the Bluered library, consisting of 832 synthetic SED of stars, that cover a large parameter space at very high spectral resolution (R = 500 000) along the 3500−7000 A wavelength range. Methods. Bluered synthetic spectra have been used to assess in finer detail the intrinsic reliability and the performance limits of the Atlas theoretical framework. The continuum-normalized spectra of the Sun, Arcturus, and Vega, plus a selected list of 45 bright stars with high-quality SEDs from the Prugniel & Soubiran Elodie catalog, form our sample designed to probe the global properties of synthetic spectra across the entire range of H-R parameters. Results. Atlas models display a better fitting performance with increasing stellar temperature. High-resolution spectra of Vega, the Sun, and Arcturus have been reproduced at R = 100 000, respectively, within a 0.7%, 4.5%, and 8.8% relative scatter in residual flux. In all the three cases, the residual flux distribution shows a significant asymmetry (skewness parameter γ = −2.21, −0.98, −0.67, respectively), which neatly confirms an overall “excess” of theoretical line blanketing. For the Sun, this apparent discrepancy is alleviated, but not recovered, by a systematic decrease (−40%) of the line oscillator strengths, log(gf ), especially referring to iron transitions. Definitely, a straight “astrophysical” determination of log(gf ) for each individual atomic transition has to be devised to overcome the problem. By neglecting overblanketing effects in theoretical models when fitting high-resolution continuum-normalized spectra of real stars, we lead to a systematically warmer effective temperature (between +80 and +300 K for the solar fit) and a slightly poorer metal content.

We present synthetic spectra around maximum for the type II supernova SN 2003Z, which was first detected on January 29.7 2003. Comparison with observed spectra aim at the determination of physical parameters for SN 2003Z. Synthetic spectra are calculated with our stellar atmosphere code PHOENIX. It solves the special relativistic equation of radiative transfer, including large NLTE-calculations and line blanketing by design, in 1-dimensional spherical symmetry. The observed spectra were obtained at the 3.5 meter telescope at Calar Alto. The TWIN instrument was used so that a spectral range from about 3600 to 7500 Angstroem was covered. The spectra were taken on Feb. 4, 5, 9, and 11, 2003. The physical parameters of the models give the luminosities, a range of possible velocity profiles for the SN, an estimate of the colour excess, and the observed metalicity., 8 figures

Model atmospheres of A and B stars are computed taking into account magnetic line blanketing. These calculations are based on the new stellar model atmosphere code LLModels which implements direct treatment of the opacities due to the bound-bound transitions and ensures an accurate and detailed description of the line absorption. The anomalous Zeeman effect was calculated for the field strengths between 1 and 40 kG and a field vector perpendicular to the line of sight. The model structure, high-resolution energy distribution, photometric colors, metallic line spectra and the hydrogen Balmer line profiles are computed for magnetic stars with different metallicities and are discussed with respect to those of non-magnetic reference models. The magnetically enhanced line blanketing changes the atmospheric structure and leads to a redistribution of energy in the stellar spectrum. The most noticeable feature in the optical region is the appearance of the 5200 A depression. However, this effect is prominent only in cool A stars and disappears for higher effective temperatures. The presence of a magnetic field produces opposite variation of the flux distribution in the optical and UV region. A deficiency of the UV flux is found for the whole range of considered effective temperatures, whereas the ``null wavelength'' where flux remains unchanged shifts towards the shorter wavelengths for higher temperatures., Comment: accepted by Astronomy & Astrophysics

This work is part of a larger project on the study of activity in stars of spectral type similar to, or later than the Sun, from PMS to ZAMS, based on the analysis of the high resolution Call InfraRed Triplet (Ca II IRT: λ = 8498, 8542, 8662 A) observed profiles. Here, a preliminary study on the diagnostic power of these calcium lines has been performed by means of NLTE calculations of the line profiles with an approximate treatment of UV line-blanketing, for a grid of photospheric models with Ten = 4200, 5200, 6200 K, log g = 4.0, 4.5, 5.0 and [A/H] = 0.0, -1.0, -2.0. We used these calculations to estimate the sensitivity of the profiles to changes in stellar parameters and the effect of departures from LTE. As found by other authors, the Ca II triplet NLTE EQWs (equivalent widths) are quite sensitive to photospheric parameters, in particular to T eff and [A/H]. On the other hand, we find that the dependence of the Call triplet lines central depression (CD = 1-central relative flux) on log g and T eff , and to a lesser extent to [A/H], is very weak. The departure from LTE is negligible when we consider EQWs, unless very metal-poor atmospheres are considered, while CDs can be affected by NLTE by more than 20%. This analysis indicates that in the use of these lines as activity indicators (where the details of the line profile in the core are important), a NLTE treatment is required. Furthermore, we show that a new chromospheric indicator, which we denote R IRT , can he derived from measurements of Ca II IRT line central depressions, provided that rotational broadening is taken into proper account. In order to facilitate the use of the Ca II IRT lines as activity diagnostics, we give interpolation formulae for estimating line CDs within the range of stellar parameters of our NLTE calculations.

We present a recently developed code for detailed NLTE calculations of accretion disc spectra of cataclysmic variables and compact X-ray binaries. Assuming a radial structure of a standard alpha-disc, the disc is divided into concentric rings. For each disc ring the solution of the radiation transfer equation and the structure equations, comprising the hydrostatic and radiative equilibrium, the population of the atomic levels as well as charge and particle conservation, is done self-consistently. Metal-line blanketing and irradiation by the central object are taken into account. As a first application, we show the influence of different disc parameters on the disc spectrum for the helium cataclysmic variable AM CVn., 7 pages, 11 figures to be published in A&A

We study mass-loss and wind momentum rates of 29 Galactic O-type stars with luminosity classes I, III and V by means of a pure Hα profile analysis and investigate to what extent the results compare to those originating from a state-of- the-art, complete spectral analysis. Our investigation relies on the approximate method developed by Puls et al. (1996) which we have modified to account for the effects of line-blanketing. Effective temperatures and gravities needed to obtain quanti- tative results from such a simplified approach have been derived by means of calibrations based on most recent spectroscopic NLTE analyses and models of Galactic stars by Repolust et al. (2003) and Martins et al. (2002). Comparing (i) the derived wind- densities to those determined by Repolust et al. (2003) for eleven stars in common and (ii) the Wind-momentum Luminosity Relationship (WLR) for our sample stars to those derived by other investigations, we conclude that our approximate approach is actually able to provide consistent results. Additionally, we studied the consequences of "fine tuning" some of the direct and indirect parameters entering the WLR, especially by accounting for different possible values of stellar reddening and distances. Combining our data set with the corresponding data provided by Herrero et al. (2002) and Repolust et al. (2003) we finally study the WLR for the largest sample of Galactic O-type stars gathered so far, including an elaborate error treatment. The established disagreement between the theoretical predictions and the "observed" WLRs being a function of luminosity class is suggested to be a result of wind clumping. Different strategies to check this hypothesis are discussed, particularly by comparing the Hα mass-loss rates with the ones derived from radio observations.

We describe the treatment of iron group line-blanketing in non-LTE model atmospheres for WR stars. As an example, a blanketed model for the early-type WC star WR 111 is compared to its un-blanketed counter- part. Blanketing aects the ionization structure and the emergent flux distribution of our models. The radiation pressure, as computed within our models, falls short by only a factor of two to provide the mechanical power of the WR wind.

We rediscuss the temperature of O dwarfs based on new non-LTE line blanketed atmosphere models including stellar winds computed with the CMFGEN code of Hillier & Miller (1998). Compared to the latest calibration of Vacca et al. (1996), the inclusion of line blanketing leads to lower effective temperatures, typically by 4000 to 1500 K for O3 to O9.5 dwarf stars. The dependence of the Teff-scale on stellar and model parameters - such as mass loss, microturbulence, and metallicity - is explored, and model predictions are compared to optical observations of O stars. Even for an SMC metallicity we find a non-negligible effect of line blanketing on the Teff-scale. The temperature reduction implies downward revisions of luminosities by 0.1 dex and Lyman continuum fluxes Q0 by approximately 40% for dwarfs of a given spectral type., 6 pages, 4 figures. To be published in A&A

We present a method to estimate the contribution of line opacity to the total opacity as a function of wavelength. The estimated line-opacity function can then be used to simulate line-blanketing in NLTE radiative transfer calculations. Given a reference flux distribution (either observed or theoretical), our method allows to ob- tain a good estimate of the spectrum without the need for considering in detail all the millions of lines contributing to line blanketing. We applied the method to the spectra computed from a sample of photospheric models with eective temperatures Te = 4200, 5200 and 6200 K, logg =4 :0, 4.5, 5.0 and (A/H) = 0:0, 1:0, 2:0, taken from the NextGen database (Allard & Hauschildt 1995). The computed flux distributions agree quite well with the corresponding LTE line-blanketed NextGen fluxes when we introduce the estimated line-opacity contribution as a multiplicative factor of the continuum opacity in the radiative transfer calculations. In particular we discuss the importance of a correct estimate of the continuum flux, mainly in the UV, in the NLTE formation of the Ca ii H & K, the Ca ii InfraRed Triplet (IRT: = 8498, 8542, 8662), Na i D, Li i and K i resonance lines.

New opacity distribution functions (ODF) have been computed for use with the ATLAS9 model atmosphere code of Kurucz. One of the improvements upon the Kurucz (1990) ODFs is the addition to the line blanketing of the Lyman- H{H and H{H + quasi-molecular absorptions near 1600 A and 1400 A. New-ODF fluxes are expected to reproduce the ultraviolet observations of Boo stars and metal-poor A-type stars in a more realistic way than previous computations did. In this paper we compare low- and high-resolution IUE observations of Boo (HD 125162, HR 5351) with fluxes and synthetic spectra based on ATLAS9 models and new-ODFs, which were computed for (M=H) = 2:0 for all the elements, except CNO. For C, N, and O, abundances log(Nelem=Ntot) equal to 3.85, 3.99, and 3.11, respectively, were adopted. We selected Boo in order to compare results from the new-ODFs with those from Allard et al. (1998a, 1998b), who tested their semi-classical computations of the H{H and H{H + quasi-molecular absorptions on this star. The analysis of the IUE high-resolution spectrum has shown that lines of H2 are a very important source of line opacity for Boo shortward 1600 A. When both atomic and molecular lines are considered, the slope of the observed energy distribution is well reproduced in the whole region 1300{3000 A by the new-ODF model, but the H{H quasi-molecular absorption at 1600 A is computed about 10% too strong. The t of the low-resolution IUE image SWP17872 to a small grid of new-ODF models gives parameters Te = 8650 K, log g =4 :0, while the t of the high-resolution image SWP42081, rebinned at the low resolution wavelength step size, gives parameters Te = 8500 K, log g =4 :0. These last parameters are in close agreement with Te = 8550 K, log g =4 :1 obtained by tting the visible energy distribution. The dierent IUE images are discussed.

Physical and phenomenological properties (radius, luminosity, shape of the light curve, etc.) of Cepheids strongly depend on the pulsation period, with the exception of the pulsation amplitude. A possible factor causing a wide range of pulsation amplitudes might be the different atmospheric metallicities of individual Cepheids. We studied the influence exerted by the atmospheric iron content, [Fe/H], on the pulsational amplitude of Galactic Cepheids. We searched for correlations between the [Fe/H] value and both the observed amplitudes and amplitude related parameters. The amplitude of the Cepheid pulsation slightly decreases with increasing iron abundance. This effect is more pronounced for the radial velocity variations and for the shorter pulsation periods. The wavelength dependence of photometric amplitudes is also found to be sensitive to the metallicity. Some of these effects are not consequences of differential line blanketing. Based on the calibrations of the metallicity sensitivity relationships, we derived photometric iron abundance for 21 Galactic Cepheids. The dichotomic behaviour dividing Galactic Cepheids that pulsate in the fundamental mode into short- and long-period groups at the period of 10.47 d can be noticed in some diagrams that show metallicity-related dependences. We confirm that variety in atmospheric metallicity in Cepheids contributes to the finite range of pulsation amplitudes at a given period. Effects of metallicity on the amplitudes revealed from observational data and the occurrence of the dichotomy also derived from phenomenological data have to be confirmed by appropriate theoretical models of stellar structure and pulsation., Comment: 9 pages, 8 figures, accepted for publication in the Astronomy and Astrophysics

Aims. We analyze the photometric properties of SN 2006aj associated with GRB 060218. We also investigate this event in relation to other supernovae. Methods. We determined the color indices from multiband photometry and investigated their time evolution by taking their time stretch factors into account. We used both the ground-based and UVOT/Swift data to ensure a coverage from the cosmic UV region (UVW1 (2510 A), UVM2 (2170 A), UVW2 (1880 A)) to the I band. Results. We find a large difference between the values and time evolution of the color indices of the early phase (t −T0 ≤ 2. 5d ) of the optical afterglow (OA) and the subsequent SN 2006aj. The clustering and small evolution of most color indices in UV in t −T0 ≤ 2. 5d resemble the behavior seen in the ensemble of OAs of long GRBs. In our interpretation, the light of the early OA comes from far above the photosphere of the progenitor and its wind. The outer layers of SN 2006aj underwent the strongest evolution among the considered supernovae of various types. We find that the adjustment of time evolution of various color indices by stretching is very helpful in searching for the proper supernova type. We attribute this evolution of SN 2006aj to the exceptionally low mass of its ejecta and the structural changes of the region producing the GRB. In our interpretation, we observed the different regions simultaneously in the complicated, asymmetric shape of SN 2006aj. The colors in the UV band can be explained if line blanketing undergoes only small variations and the UV emitting area tends to shrink during the evolution of SN 2006aj over the time interval investigated. Our approach is also of general importance for investigating supernovae in OAs.