The ESC-RTN optical spectroscopy data set for SN 2005cf is presented and analyzed. The observations range from -11.6 and +77.3 days with respect to B-band maximum light. The evolution of the spectral energy distribution of SN 2005cf is characterized by the presence of high velocity Si II and Ca II features. SYNOW synthetic spectra are used to investigate the ejecta geometry of silicon. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
Using the largest spectroscopic data set of stripped-envelope core-collapse supernovae (stripped SNe), we present a systematic investigation of spectral properties of Type IIb SNe (SNe IIb), Type Ib SNe (SNe Ib), and Type Ic SNe (SNe Ic). Prior studies have been based on individual objects or small samples. Here, we analyze 242 spectra of 14 SNe IIb, 262 spectra of 21 SNe Ib, and 207 spectra of 17 SNe Ic based on the stripped SN data set of Modjaz et al. (2016ApJ...832..108M) and other published spectra of individual SNe. Each SN in our sample has a secure spectroscopic ID, a date of V-band maximum light, and most have multiple spectra at different phases. We analyze these spectra as a function of subtype and phase in order to improve the SN identification scheme and constrain the progenitors of different kinds of stripped SNe. By comparing spectra of SNe IIb with those of SNe Ib, we find that the strength of H{alpha} can be used to quantitatively differentiate between these two subtypes at all epochs. Moreover, we find a continuum in observational properties between SNe IIb and Ib. We address the question of hidden He in SNe Ic by comparing our observations with predictions from various models that either include hidden He or in which He has been burnt. Our results favor the He-free progenitor models for SNe Ic. Finally, we construct continuum-divided average spectra as a function of subtype and phase to quantify the spectral diversity of the different types of stripped SNe.
Many large stellar surveys have been and are still being carried out, providing huge amounts of data, for which stellar physical parameters will be derived. Solar twins and analogues provide a means to test the calibration of these stellar catalogues because the Sun is the best-studied star and provides precise fundamental parameters. Solar twins should be centred on the solar values. This spectroscopic study of solar analogues selected from the Geneva-Copenhagen Survey (GCS) at a resolution of 48000 provides effective temperatures and metallicities for these stars. We test whether our spectroscopic parameters, as well as the previous photometric calibrations, are properly centred on the Sun. In addition, we search for more solar twins in our sample. The methods used in this work are based on literature methods for solar twin searches and on methods we developed in previous work to distinguish the metallicity-temperature degeneracies in the differential comparison of spectra of solar analogues versus a reference solar reflection spectrum.
A sample of 112 sources with flux densities higher than 200mJy at the 4.85GHz and with the range of declinations from +3 till +5 degrees from the Green Bank survey catalog 87GB <VIII/14> was observed at three frequencies: 0.96, 3.95, and 11.1GHz. The observations were performed in January and February 1992, in the Northern sector of the RATAN-600 radio telescope. The accuracy of the source right ascensions was improved by a factor of 5-10 (for 70% of the sources the accuracy of the right ascension is 0.1arcsec). About 80% of the objects studied were identified with sources from the Texas survey.
In this paper, we present high-resolution optical spectra and optical classifications from our large sample of 285 warm infrared galaxies 10^8^<L_IR_<10^12.5^L_{sun}_. We have classified these galaxies using new theoretical lines on the standard optical diagnostic diagrams. We use a theoretical extreme mixing line between the starburst and AGN regions to classify LINER galaxies and we define a theoretical boundary separating AGNs from starbursts. We find that many galaxies previously classified as LINERs appear to lie on a mixing sequence between starburst and AGN type galaxies.
The present knowledge of stellar properties and dynamical structure of early-type multiple stellar systems is insufficient to offer useful statistical constraints for stellar formation models. To increase the amount of observational information about the characteristics of early-type multiples, we carried out a spectroscopic monitoring to search for new spectroscopic components and to determine their orbits. We observed 30 early-type multiple systems using the 2.15m telescope and REOSC echelle spectrograph at the Complejo Astronomico El Leoncito (CASLEO) during 10 observing runs between 2008 and 2013. We measured radial velocities by cross-correlations and applied a spectral disentangling method to double-lined systems. We calculated orbital elements for the inner subsystem of each analysed multiple. In this first paper we present calculated orbits for six previously catalogued subsystems. Three subsystems had no previously published parameters, while we obtained more accurate orbits for the other three. In one case we found absolute masses and radii for the components by using available photometric data. The long-term spectroscopic monitoring of multiple systems is a useful method of investigating the companions in intermediate hierarchical levels, particularly those that could affect the dynamical evolution of a close inner binary subsystem.
We define an H{alpha} photometric system that is designed as a companion to the well established H{beta} index. The new system is built on spectrophotometric observations of field stars as well as stars in benchmark open clusters. We present data for 75 field stars, 12 stars from the Coma star cluster, 24 stars from the Hyades, 17 stars from the Pleiades, and 8 stars from NGC 752 to be used as primary standard stars in the new systems. We show that the system transformations are relatively insensitive to the shape of the filter functions. We make comparisons of the H{alpha} index to the H{beta} index and illustrate the relationship between the two systems. In addition, we present relations that relate both hydrogen indices to equivalent width and effective temperature. We derive equations to calibrate both systems for Main Sequence stars with spectral types in the range O9 to K2 for equivalent width and A2 to K2 for effective temperature.
We report the results of long-slit spectroscopy at position angles 68{deg}, 131{deg}, and 164{deg} for the minor-merger NGC 4194, a luminous infrared starburst galaxy. The mass within 1.2kpc of the dynamical center is estimated to be 4.8*109 to 1.7*1010 M{sun}, depending on the assumed inclination to the plane of the sky. The star formation rate (SFR) in the areas sampled is 8 M{sun}/yr. The metallicity, log(O/H)+12, ranges from ~8.8 to >9.0 in regions of significant star formation, suggesting that the metallicity has been enhanced by the current star formation. The star-forming regions range in age from 5 to 9Myr, with the youngest ages occurring in the regions of high SFR. Electron temperatures and the location of the spectra in emission line diagnostic diagrams suggest the presence of shock waves, presumably due to the presence of supernovae, winds from massive stars, and/or collisions of clouds due to the merger. The presence of massive stars and supernovae is consistent with the ages determined for the star-forming regions. The ages of the continua produced by the stellar population are estimated to range from 10Myr to 5Gyr. Much of the stellar population represented in the continua was probably formed before the merger and represents the progenitor galaxies.
Intermediate resolution spectra at the CaII triplet have been obtained for 55 candidate red giants in the field of the globular cluster M22 with the VLT/FORS2 instrument. Spectra were also obtained for a number of red giants in standard globular clusters to provide a calibration of the observed line strengths with overall abundance [Fe/H]. For the 41 M22 member stars that lie within the V-V_HB_ bounds of the calibration, we find an abundance distribution that is substantially broader than that expected from the observed errors alone. We argue that this broad distribution cannot be the result of differential reddening. Instead, we conclude that, as has long been suspected, M22 is similar to {omega} Cen in having an intrinsic dispersion in heavy element abundance. The observed M22 abundance distribution rises sharply to a peak at [Fe/H]~-1.9 with a broad tail to higher abundances: the highest abundance star in our sample has [Fe/H] ~-1.45dex. If the unusual properties of {omega} Cen have their origin in a scenario in which the cluster is the remnant nucleus of a disrupted dwarf galaxy, then such a scenario likely also applies to M22.
In this paper, we present a detailed high-resolution spectroscopic study of post main sequence stars in the globular cluster (GC) M68. Our sample, which covers a range of 4000K in T_eff_, and 3.5dex in log(g), is comprised of members from the red giant, red horizontal, and blue horizontal branch, making this the first high-resolution GC study covering such a large evolutionary and parameter space. Initially, atmospheric parameters were determined using photometric as well as spectroscopic methods, both of which resulted in unphysical and unexpected T_eff_, log(g), {xi}_t_, and [Fe/H] combinations. We therefore developed a hybrid approach that addresses most of these problems, and yields atmospheric parameters that agree well with other measurements in the literature. Furthermore, our derived stellar metallicities are consistent across all evolutionary stages, with <[Fe/H]>=-2.42 ({sigma}=0.14) from 25 stars. Chemical abundances obtained using our methodology also agree with previous studies and bear all the hallmarks of GCs, such as a Na-O anti-correlation, constant Ca abundances, and mild r-process enrichment.