KIC 10661783 is an eclipsing binary that shows delta Sct-like oscillations. More than 60 pulsation frequencies have been detected in its light curve as observed by the Kepler satellite. We want to determine the fundamental stellar and system parameters of the eclipsing binary as a precondition for asteroseismic modelling of the pulsating component and to establish whether the star is a semi-detached Algol-type system. We measured the radial velocities of both components from new high-resolution spectra using TODCOR and compute the orbit using PHOEBE. We used the KOREL program to decompose the observed spectra into its components, and analysed the decomposed spectra to determine the atmospheric parameters. For this, we developed a new computer program for the normalisation of the KOREL output spectra. Fundamental stellar parameters are determined by combining the spectroscopic results with those from the analysis of the Kepler light curve. We obtain Teff, logg, vsini, and the absolute masses and radii of the components, together with their flux ratio and separation. Whereas the secondary star rotates synchronously with the orbital motion, the primary star rotates subsynchronously by a factor of 0.75. The newly determined mass ratio of 0.0911 is higher than previously thought and means a detached configuration is required to fit the light curve. With its low orbital period and very low mass ratio, the system shows characteristics of the R CMa-type stars but differs from this group by being detached. Its current state is assumed to be that of a detached post-Algol binary system with a pulsating primary component.
This catalog contains a collection of K-band spectra for 26 stars with near-solar abundances, ranging in spectral class from F8 to M7 and in luminosity from dwarfs to supergiants. The spectra cover the wavelength region from 4150 to 4950 /cm and generally exhibit a signal to noise ratio above 400. Five stars here are supergiants, 15 are giants, and six are dwarfs. Data included: observation date, starting wavenumber, wavenumber increment, scale factor of relative intensity, and offset of relative intensity.
We present optical spectra of 21 stars from 4800 to 8920A, covering essentially the late spectral types, G, K, M and the luminosity classes I and III. Half of the stars are super metal rich (SMR) ones. The spectra were obtained at a resolution of 1.25A using the Aurelie spectrograph, equipped with a linear array CCD-like detector, attached to the OHP 1.52m telescope. Also presented are the spectra of 7 stars, covering the region 5000-9783A at a resolution of 8.5A, observed at the CFHT with the Herzberg spectrograph. The spectral types are F, G, K, M and the luminosity classes III and V. Five stars are SMR. These spectra have been obtained with the aim of extending existing libraries used for population synthesis purposes. The inclusion of SMR stars in a stellar library dedicated to the study of stellar populations in the central part of galaxies is crucial as abundance gradients have been observed in the optical range.
The gravitational lensing time delay method provides a one-step determination of the Hubble constant (H0) with an uncertainty level on par with the cosmic distance ladder method. However, to further investigate the nature of the dark energy, a H0 estimate down to 1% level is greatly needed. This requires dozens of strongly lensed quasars that are yet to be delivered by ongoing and forthcoming all-sky surveys. In this work we aim to determine the spectroscopic redshift of PSOJ0147, the first strongly lensed quasar candidate found in the Pan-STARRS survey. The main goal of our work is to derive an accurate redshift estimate of the background quasar for cosmography. To obtain timely spectroscopically follow-up, we took advantage of the fast-track service programme that is carried out by the Nordic Optical Telescope. Using a grism covering 3200-9600{AA}, we identified prominent emission line features, such as Ly{alpha}, NV, OI, CII, SiIV, CIV, and [CIII] in the spectra of the background quasar of the PSOJ0147 lens system. This enables us to determine accurately the redshift of the background quasar. The spectrum of the background quasar exhibits prominent absorption features bluewards of the strong emission lines, such as Ly{alpha}, NV, and CIV. These blue absorption lines indicate that the background source is a broad absorption line (BAL) quasar. Unfortunately, the BAL features hamper an accurate determination of redshift using the above-mentioned strong emission lines. Nevertheless, we are able to determine a redshift of 2.341+/-0.001 from three of the four lensed quasar images with the clean forbidden line [CIII]. In addition, we also derive a maximum outflow velocity of ~9800km/s with the broad absorption features bluewards of the CIV emission line. This value of maximum outflow velocity is in good agreement with other BAL quasars.
We provide single-epoch spectroscopic data for a sample of 13 lensed quasars. The sources have bolometric luminosities between 10^44.7-47.4^erg/s and black hole masses 10^7.6-9.8^M_{sun}. These spectra have been used to perform a systematic search for microlensing in the broad line region. The spectra have been deblended using the MCS advanced deconvolution technique. We provide the extracted and flux calibrated spectra, and the 2D deconvolved frames, separating the point-like emission from the extended emission (from the residual sky and from the lensing galaxy).
Un-evolved, very metal-poor stars are the most important tracers of the cosmic abundance of lithium in the early universe. Combining the standard Big Bang nucleosynthesis model with Galactic production through cosmic ray spallation, these stars at [Fe/H]<-2 are expected to show an undetectably small ^6^Li/^7^Li isotopic signature. Evidence to the contrary may necessitate an additional pre-galactic production source or a revision of the standard model of Big Bang nucleosynthesis. It would also cast doubts on Li depletion from stellar atmospheres as an explanation for the factor 3-5 discrepancy between the predicted primordial ^7^Li from the Big Bang and the observed value in metal-poor dwarf/turn-off stars. We revisit the isotopic analysis of four halo stars, two with claimed ^6^Li-detections in the literature, to investigate the influence of improved model atmospheres and line formation treatment. For the first time, a combined 3D, non-local thermodynamic equilibrium (NLTE) modelling technique for Li, Na, and Ca lines is utilised to constrain the intrinsic line-broadening and to determine the Li isotopic ratio. We discuss the influence of 3D NLTE effects on line profile shapes and assess the realism of our modelling using the Ca excitation and ionisation balance. By accounting for NLTE line formation in realistic 3D hydrodynamical model atmospheres, we can model the Li resonance line and other neutral lines with a consistency that is superior to LTE, with no need for additional line asymmetry caused by the presence of ^6^Li. Contrary to the results from 1D and 3D LTE modelling, no star in our sample has a significant (2 sigma) detection of the lighter isotope in NLTE. Over a large parameter space, NLTE modelling systematically reduces the best-fit Li isotopic ratios by up to five percentage points. As a bi-product, we also present the first ever 3D NLTE Ca and Na abundances of halo stars, which reveal significant departures from LTE. The observational support for a significant and non-standard 6Li production source in the early universe is substantially weakened by our findings.
We have obtained multi-fibre intermediate-resolution optical spectroscopy of 94 photometric and proper motion selected low-mass star and brown dwarf candidates in Upper Sco with the AAOmega spectrograph on the Anglo-Australian Telescope. We have estimated the spectral types and measured the equivalent widths of youth and gravity diagnostic features to confirm the spectroscopic membership of about 95% of the photometric and proper motion candidates extracted from 6.5 square degrees surveyed in Upper Sco by the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS). We have estimated the effective temperatures and masses for each new spectroscopic member using the latest evolutionary models available for low-mass stars and brown dwarfs. Combining the current optical spectroscopy presented here with near-infrared spectroscopy obtained for the faintest photometric candidates, we confirm the shape and slope of our earlier photometric mass function. The luminosity function drawn from the spectroscopic sample of 113 USco members peaks at around M6 and is flat at later spectral type. The mass function may peak at 0.2M_{sun}_ and is quite flat in the substellar regime. We observe a possible excess of cool low-mass brown dwarfs compared to IC 348 and the extrapolation of the field mass functions, supporting the original hypothesis that Upper Sco may possess an excess of brown dwarfs compared.
We obtained new spectra of fourteen Magellanic Cloud planetary nebulae with the South African Large Telescope to determine heating rates of their central stars and to verify evolutionary models of post asymptotic giant branch stars. We compared new spectra with observations made in previous years. Five planetary nebulae showed an increase of the excitation with time. Four of their central stars exhibit [WC] features in their spectra, including three new detections. This raises the total number of [WC] central stars of PNe in the Magellanic Clouds to ten. We compared determined heating rates of the four [WC] central stars with the He burning post asymptotic giant branch evolutionary tracks and the remaining star with the H-burning tracks. Determined heating rates are consistent with the evolutionary models for both H and He-burning post asymptotic giant branch stars. The central stars of the PNe which show the fastest increase of excitation are also the most luminous in the sample. This indicates that [WC] central stars in the Magellanic Clouds evolve faster than H-burning central stars and originate from more massive progenitors.
We use moderate-resolution spectra of nearby late K and M dwarf stars with parallaxes and interferometrically determined radii to refine their effective temperatures, luminosities, and metallicities. We use these revised values to calibrate spectroscopic techniques to infer the fundamental parameters of more distant late-type dwarf stars. We demonstrate that, after masking out poorly modeled regions, the newest version of the PHOENIX atmosphere models accurately reproduce temperatures derived bolometrically. We apply methods to late-type hosts of transiting planet candidates in the Kepler field, and calculate effective temperature, radius, mass, and luminosity with typical errors of 57K, 7%, 11%, and 13%, respectively. We find systematic offsets between our values and those from previous analyses of the same stars, which we attribute to differences in atmospheric models utilized for each study. We investigate which of the planets in this sample are likely to orbit in the circumstellar habitable zone. We determine that four candidate planets (KOI 854.01, 1298.02, 1686.01, and 2992.01) are inside of or within 1{sigma} of a conservative definition of the habitable zone, but that several planets identified by previous analyses are not (e.g., KOI 1422.02 and KOI 2626.01). Only one of the four habitable-zone planets is Earth sized, suggesting a downward revision in the occurrence of such planets around M dwarfs. These findings highlight the importance of measuring accurate stellar parameters when deriving parameters of their orbiting planets.
Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs that is difficult to disentangle due to the lack of constraints on their age, such as trigonometric parallax, lithium detection, and space velocity. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Based on theoretical models, we used the color I-J, the J-band absolute magnitude, and the detection of the LiI 6708{AA} doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850um. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates, and one is a young very low-mass star. The closest young field brown dwarf in our sample at only ~15pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100-150Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.
