Search

We present the Transiting Exoplanet Survey Satellite (TESS) light curve analysis of HX Velorum, located in the Southern Hemisphere, where one of the components is found for the first time to be a β$$ \beta $$ Cep (BCEP) type pulsator. The TESS observations of HX Velorum were published in a total of 6 sectors. Fourier analysis of the observations reveals that the frequencies can be divided into two categories, one of which is related to the orbital period and the other related to the β$$ \beta $$ Cep‐type pulsation. Its non‐eclipsing light curve was analyzed with the well‐known Wilson–Devinney code, and we obtained the geometric and physical parameters of the components using published radial velocity and light curve data by making some assumptions. We obtained plausible masses and radii of the primary and secondary components as M1=9.48±0.27M⊙$$ {M}_1=9.48\pm 0.27{M}_{\odot } $$, M2=5.92±0.17M⊙$$ {M}_2=5.92\pm 0.17{M}_{\odot } $$ and R1=3.93±0.04R⊙$$ {R}_1=3.93\pm 0.04{R}_{\odot } $$, R2=3.59±0.03R⊙$$ {R}_2=3.59\pm 0.03{R}_{\odot } $$, respectively. The obtained system's distance of ∼400$$ \sim 400 $$ pc is smaller than the Gaia distances found in the literature. [ABSTRACT FROM AUTHOR]

We present an analysis of nine bright spectroscopic binaries (HD 1585, HD 6613, HD 12390, HD 39923, HD 55201, HD 147430, HD 195543, HD 202699, HD 221643), which have orbital periods of P > 500 days. These well-separated binaries are the last stars of our sample that we observed with the TIGRE telescope obtaining intermediate-resolution spectra of R > 20,000. We applied the same method as described in our previous publication of this series. For the analysis of the radial velocity curves, we used the toolkit RadVel, which allowed us to determine all orbital parameters. Recently published orbital solutions of some systems from Gaia DR3 agree with our results. However, our solutions have much smaller uncertainties. We determined the basic stellar parameters of the primary stars with our automatic script using iSpec. The parameter determination allowed us to place all nine stars in the Hertzsprung-Russell diagram. We found that all stars have already evolved to the giant phase. A comparison with stellar evolution tracks of the Eggleton code was applied to determine the stellar masses and ages. As a result of our analysis, we were able to estimate themasses of the secondary stars and the orbital inclinations of the binary systems. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of five bright spectroscopic binary systems (HD 18665, HD 27131, HD 171852, HD 215550, and HD 217427) that have orbital periods of P≲500 days. We determined the complete set of orbital parameters using the toolkit RadVel by analyzing the observed radial velocity curves. To study the properties of the five systems, we also analyzed the intermediate resolution spectra (R≈20,000) observed with the Telescopio Internacional de Guanajuato Robótico Espectroscópico (TIGRE) telescope and determined the stellar parameters of the primary stars using the toolkit iSpec. With Gaia Early Data Release 3 parallaxes, a correction for interstellar extinction using the 3D dust map, and bolometric corrections, we placed the stars in the Hertzsprung‐Russell diagram and compared the positions with stellar evolution tracks calculated with the Eggleton code to determine the masses and ages of the primary stars. They have all evolved to the giant phase. Finally, we were able to determine the masses of the secondary stars and to estimate the orbital inclinations i of the binary systems. [ABSTRACT FROM AUTHOR]

Runaway stars can result from core-collapse supernovae in multiple stellar systems. If the supernova disrupts the system, the companion is ejected with its former orbital velocity. A clear identification of a runaway star can yield the time and place of the explosion, as well as orbital parameters of the pre-supernova binary system. Previous searches have mostly considered O- and B-type stars as runaway stars because they are always young in absolute terms (not much older than the lifetime of the progenitor) and can be detected up to larger distances. Here, we present a search for runaway stars of all spectral types. For late-type stars, a young age can be inferred from the lithium test. We used Gaia data to identify and characterize runaway star candidates in nearby supernova remnants, obtained spectra of 39 stars with UVES at the VLT and HDS at the Subaru telescope, and found a significant amount of lithium in the spectra of six dwarf stars. We present the spectral analysis, including measurements of radial velocities, atmospheric parameters, and lithium abundances. Then, we estimate the ages of our targets from the Hertzsprung-Russell diagram and, using the lithium test, present a selection of promising runaway star candidates and drawconstraints on the number of ejected runaway stars compared tomodel expectations. [ABSTRACT FROM AUTHOR]

For nine bright K giants within 100 pc of the sun, the fundamental parameters and the non-local thermodynamic equilibrium (LTE) abundances of three key light elements (Li, C, and O) are accurately determined. These stars are of special interest due to the planets detected around them. Their fundamental parameters are found to be typical for K giants; in particular, these stars have effective temperatures Teff =3,920-4,830 K, surface gravities log g =1.20-2.85, masses M =1.2-2.8 M, and ages t =0.4-5.4 Gyr (the pronounced anticorrelation between ages t and masses M exists). The microturbulent parameter Vt derived from Fe I lines varies between 1.2 and 1.9 kms-1; the metallicity index [Fe/H] forfive stars is close to the normal (zero) value, for other four stars it varies between -0.3 and -0.4 dex. All the giants are on the red giant branch stage and passed the first-dredge-up (FDU) phase. This conclusion is confirmed by the published low isotope ratios 12C/13C and 16O/17O. Basing on the non-LTE analysis of Li I, C I, and O I lines, we determined abundances of lithium, carbon, and oxygen, three tracers of stellar evolution. The carbon deficiency -0.3 dex is found for the giants, which is quite expectable for these post-FDU objects. The oxygen abundance is likely to be unchanged, whereas for the C/O ratio we obtained (after correction due to galactic chemical evolution) the mean value [C/O]cor =-0.22±0.10 that is in very good agreement with the theory. The lithium abundance is not detected for seven of nine program giants; this result is quite expectable for the post-FDU stars. We determined the Li abundance with the confidence only for two giants, namely, log ϵ(Li) = 0.92 for β Gem and log ϵ(Li) = 0.45 for μ Leo; this result contradicts the standard theory. Hypothetical engulfment by a star of a giant planet could solve the problem. [ABSTRACT FROM AUTHOR]

We present our final orbit for the late‐type spectroscopic binary Henry Draper one (HD 1). area total of 553 spectra from 13 years of observations are used with our robotic STELLA facility and its high‐resolution echelle spectrograph SES. Its long‐term radial velocity stability is ≈50 m s−1. A single radial velocity of HD 1 reached an rms residual of 63 m s−1, close to the expected precision. Spectral lines of HD 1 are rotationally broadened with a v sin i of 9.1 ± 0.1 km s−1. The overall spectrum appears single‐lined and yielded an orbit with an eccentricity of 0.5056 ± 0.0005 and a semiamplitude of 4.44 km s−1. We constrain and refine the orbital period based on the SES data alone to 2, 318.70 ± 0.32 days, compared to 2, 317.8 ± 1.1 days when including the older dataset published by DAO and Cambridge/Coravel. Owing to the higher precision of the SES data, we base the orbit calculation only on the STELLA/SES velocities so as to not degrade its solution. We redetermine astrophysical parameters for HD 1 from spectrum synthesis and, together with the new Gaia DR‐2 parallax, suggest a higher luminosity than published previously. We conclude that HD 1 is a slightly metal‐deficient K0 III‐II giant 217 times more luminous than the Sun. The secondary remains invisible at optical wavelengths. We present evidence for the existence of a third component. [ABSTRACT FROM AUTHOR]

An original method of estimating the projected rotational velocity, vsini, and the macroturbulent velocity, vmac, of evolved M giant stars is presented. It is based on the use of spectrum synthesis and multiline analysis tools. The goal is to fit the mean line profile of observations with that of synthetic spectra. The method is applied to the red giant star RZ Ari, and the results vsini = 6.0 ± 0.5 km s−1 and vmac = 2.0 ± 1.0 km s−1 are obtained. [ABSTRACT FROM AUTHOR]

We present an analysis of medium‐resolution optical spectra and long‐term V band photometry of four cool stars, BD+13 5000, BD+11 3024, TYC 3557‐919‐1, and TYC 5163‐1764‐1. Our spectroscopic analysis demonstrates that the stars are giant or subgiant from K0 or K1 spectral type, and all of them exhibit emission features in their Ca ii H& K lines. These features appear to be modulated with the rotation of the stars. Except for BD+11 3024, we observe that the radial velocities of the target stars are not stable, which suggests that each of them might be a member of a binary system. Global analysis of photometric data indicates a clear cyclic variation for BD+13 5000 and TYC 5163‐1764‐1, with a period of 8.0 ± 0.3 and 5.04 ± 0.04 year, respectively. Besides that, we observe a dramatic increase (∼0 . m7) in the mean brightness of BD+11 3024, accompanied with a 2.87 ± 0.12 cyclic variation, embedded into the global brightening trend, which indicates possible multiple cycles on this star. [ABSTRACT FROM AUTHOR]

The accuracy of stellar masses and radii determined from asteroseismology is not known! We examine this issue for giant stars by comparing classical measurements of detached eclipsing binary systems (dEBs) with asteroseismic measurements from the Kepler mission. For star clusters, we extrapolate measurements of dEBs in the turn-off region to the red giant branch and the red clump where we investigate the giants as an ensemble. For the field stars, we measure dEBs with an oscillating giant component. These measurements allow a comparison of masses and radii calculated from a classical eclipsing binary analysis to those calculated from asteroseismic scaling relations and/or other asteroseismic methods. Our first results indicate small but significant systematic differences between the classical and asteroseismic measurements. In this contribution we show our latest results and summarize the current status and future plans. We also stress the importance of realizing that for giant stars mass cannot always be translated to age, since an unknown fraction of these evolved through a blue straggler phase with mass transfer in a binary system. Rough estimates of how many such stars to expect are given based on our findings in the open clusters NGC 6819 and NGC 6791. [ABSTRACT FROM AUTHOR]

Here we report on an extensive peakbagging effort on the evolved red giant stars of the open cluster NGC 6819. This consists of around 50 stars spanning all the way up the red giant branch (RGB) and down to and including the red clump (RC). These stars represent a unique sample because of their common distance, metallicity and age. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo (MCMC) techniques, we have extracted individual frequencies, heights, and line widths for hundreds of individual oscillation modes in the sample of stars. We show that average asteroseismic parameters derived from these can be used to distinguish the stellar evolutionary state between RGB and RC stars without having to measure the often difficult dipole modes. Furthermore, we show how the fitting of some of these dipole modes can improve the detectability of acoustic glitches arising from the helium II ionization zone and how this can potentially be used to constrain the helium content in the cluster. We also discuss some of the difficulties facing similar studies in the future, where it seems that detailed studies of star clusters are facing some difficult times ahead. [ABSTRACT FROM AUTHOR]

We performed a detailed analysis of the main theoretical uncertainties affecting the age at the lithium depletion boundary (LDB). We computed almost 12 000 pre-main sequence models with mass in the range [0.06, 0.4] M⊙ by varying input physics (nuclear reaction cross sections, outer boundary conditions, equation of state, and radiative opacity), initial chemical abundances (total metallicity, helium and deuterium abundances, and heavy element mixture), and convection efficiency (mixing length parameter, αML). As a first step, we investigated the effect of varying all these quantities individually within their extreme values. Then, we analysed the impact of simultaneously perturbing the main input physics/chemical abundances/parameters that affect the LDB age, without making any a priori assumption of independence among each other. Such an approach allowed us to build the cumulative error stripe which defines the edges of the maximum uncertainty region in the theoretical LDB age. The error stripe ranges from about 5-15 % for αML = 1.00, and it slightly reduces to about 5-10 % for a solar calibrated αML. About 40 % of the total error stripe is due to the uncertainty in the adopted initial chemical composition. [ABSTRACT FROM AUTHOR]

The determination of the age of single stars by means of grid-based techniques is a well established method. We discuss the impact on these estimates of the uncertainties in several ingredients routinely adopted in stellar computations. The systematic bias on age determination caused by varying the assumed initial helium abundance, the mixing-length and convective core overshooting parameters, and the microscopic diffusion are quantified and compared with the statistical error owing to the current uncertainty in the observations. The typical uncertainty in the observations accounts for 1 ω statistical relative error in age determination ranging on average from about -35 % to +42 %, depending on the mass. However, the age's relative error strongly depends on the evolutionary phase and can be higher than 120 % for stars near the zero-age main-sequence, while it is typically about 20 % or lower in the advanced main-sequence phase. A variation of ±1 in the helium-to-metal enrichment ratio induces a quite modest systematic bias on age estimates. The maximum bias due to the presence of the convective core overshooting is -7% for β = 0.2 and -13% for β = 0.4. The main sources of bias are the uncertainty in the mixing-length value and the neglect of microscopic diffusion, which account each for a bias comparable to the random error uncertainty. [ABSTRACT FROM AUTHOR]

Asteroseismology can make a substantial contribution to our understanding of the formation history and evolution of our Galaxy by providing precisely determined stellar properties for thousands of stars in different regions of the Milky Way. We present here the different sets of observables used in determining asteroseismic stellar properties, the typical level of precision obtained, the current status of results for ages of dwarfs and giants, and the improvements than can be expected in the near future in the context of Galactic archaeology. [ABSTRACT FROM AUTHOR]

The Gaia benchmark stars are stars with very precise stellar parameters that cover a wide range in the HR diagram at various metallicities. They are meant to be good representative of typical FGK stars in the Milky Way. Currently, they are used by several spectroscopic surveys to validate and calibrate the methods that analyse the data. I review our recent activities done for these stars. Additionally, by applying our new method to find stellar twins on the Gaia-ESO Survey, I discuss how good representatives of Milky Way stars the benchmark stars are and how they distribute in space. [ABSTRACT FROM AUTHOR]

SP_Ace is a FORTRAN95 code that derives stellar parameters and elemental abundances from stellar spectra. To derive these parameters, SP_Ace does not measure equivalent widths of lines nor it uses templates of synthetic spectra, but it employs a new method based on a library of General Curve-Of-Growths. To date SP_Ace works on the wavelength range 5212-6860 Å and 8400-8921 Å, and at the spectral resolution R = 2000-20000. Extensions of these limits are possible. SP_Ace is a highly automated code suitable for application to large spectroscopic surveys. A web front end to this service is publicly available at together with the library and the binary code. [ABSTRACT FROM AUTHOR]

In a companion paper, we have presented the combined asteroseismic-spectroscopic dataset obtained from CoRoT light curves and APOGEE infra-red spectra for 606 solar-like oscillating red giants in two fields of the Galactic disc (CoRoGEE). We have measured chemical abundance patterns, distances, and ages of these field stars which are spread over a large radial range of the Milky Way's disc. Here we show how to simulate this dataset using a chemodynamical Galaxy model. We also demonstrate how the observation procedure influences the accuracy of our estimated ages. [ABSTRACT FROM AUTHOR]

4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the areas of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO. 4MOST will have an unique operations concept in which 5-years public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the southern sky. As a dedicated spectroscopic survey facility with a large field-of-view, a high multiplex that can be reconfigured quickly, and with a broad wavelength coverage, 4MOST is particularly well suited to complement the upcoming asteroseismology space missions like TESS and PLATO. Here we show that, by dedicating the observing time during twilight and poor observing conditions to bright stars, 4MOST will obtain resolution R > 18000 spectra of nearly all stars brighter than 12th magnitude at Dec <30° every 2 years. 4MOST is also expected to spectroscopically complement any fainter asteroseismology target tobe observed with PLATO. These observations will provide a chemical characterization of nearly all stars tobe observed with the TESS and PLATO missions and place any planets found in a full chemo-dynamical context of the star formation history of the Galaxy, yield very accurate ages and masses for all stars that can be characterized with asteroseismology, and allow removal of contaminants from target samples (e.g., spectroscopic binaries). [ABSTRACT FROM AUTHOR]

Nowadays large spectroscopic surveys, like the Gaia-ESO Survey (GES), provide unique stellar databases for better investigating the formation and evolution of our Galaxy. Great attention must be paid to the accuracy of the basic stellar properties derived: large uncertainties in stellar parameters lead to large uncertainties in abundances, distances and ages. Asteroseismology has a key role in this context: when seismic information is combined with information derived from spectroscopic analysis, highly precise constraints on distances, masses, extinction and ages of red giants can be obtained. In the light of this promising joint action, we started the CoRoT-GES collaboration. We present a set of 1111 CoRoT stars, observed by GES from December 2011 to July 2014, these stars belong to the CoRoT field LRc01, pointing at the inner Galactic disk. Among these stars, 534 have reliable global seismic parameters. By combining seismic informations and spectroscopy, we derived precise stellar parameters, ages, kinematic and orbital parameters and detailed element abundances for this sample of stars. We also show that, thanks to asteroseismology, we are able to obtain a higher precision than what can be achieved by the standard spectroscopic means. This sample of CoRoT red giants, spanning Galactocentric distances from 5 to 8 kpc and a wide age interval (1-13 Gyr), provides us a representative sample for the inner disk population. [ABSTRACT FROM AUTHOR]

Asteroseismology has started to provide constraints on stellar properties that will be essential to accurately reconstruct the history of the Milky Way. Here we look at the information content in data sets representing current and future space missions (CoRoT, Kepler, K2, TESS, and PLATO) for red giant stars. We describe techniques for extracting the information in the frequency power spectrum and apply these techniques to Kepler data sets of different observing length to represent the different space missions. We demonstrate that for KIC 12008916, a low-luminosity red giant branch star, we can extract useful information from all data sets, and for all but the shortest data set we obtain good constraint on the g-mode period spacing and core rotation rates. We discuss how the high precision in these parameters will constrain the stellar properties of stellar radius, distance, mass and age. We show that high precision can be achieved in mass and hence age when values of the g-mode period spacing are available. We caution that tests to establish the accuracy of asteroseismic masses and ages are still 'work in progress'. [ABSTRACT FROM AUTHOR]

We carried out light curve solutions of the Kepler light curves of twenty detached eclipsing binaries with circular orbits and determined the orbital inclinations, temperatures. relative radii and luminosities of their components. We studied the quality of the solutions with respect to the adopted limb-darkening law and its coefficients. The detailed tracing of the numerous and uninterrupted data of our targets gave us an unique possibility to detect and learn their spot and flare activity. We established that the out-of-eclipse variability of the most targets gradually changes from small-amplitude two-waved type to big-amplitude one-waved type and vice versa, i.e. their spot activity cycles pass through phase of two almost diametrically opposite spots and phase of big polar cool spot. We found that the low-temperature targets show flare activity of UV Cet-type with amplitudes of 0.002-0.22 mag and duration of up to several hours. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a detailed analysis of seven young stars observed with the spectrograph SOPHIE at the Observatoire de Haute-Provence for which the chemical composition was incomplete or absent in the literature. For five stars, we derived the stellar parameters and chemical compositions using our automatic pipeline optimized for F, G, and K stars, while for the other two stars with high rotational velocity, we derived the stellar parameters by using other information (parallax), and performed a line-by-line analysis. Chromospheric emission-line fluxes from Caii are obtained for all targets. The stellar parameters we derive are generally in good agreement with what is available in the literature. We provide a chemical analysis of two of the stars for the first time. The star HIP 80124 shows a strong Li feature at 670.8 nm implying a high lithium abundance. Its chemical pattern is not consistent with it being a solar sibling, as has been suggested. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

525 measures of 213 visual double stars have been made using the 26.5-inch (67-cm) Innes telescope in Johannesburg and the Repsold micrometer between 2008.375 and 2008.419, 2010.608 and 2010.652, and 2013.663 and 2013.712. A comparison with known orbits is made. Revised orbits are presented for WDS 01061-4643 (SLR 1), WDS 12415-4858 (HJ 4539), WDS 16253-4909 (COO 197) and WDS 16425-3705 (R 283). (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Planetary transits detected by the CoRoT mission can be mimicked by a low-mass star in orbit around a giant star. Spectral classification helps to identify the giant stars and also early-type stars which are often excluded from further follow-up. We study the potential and the limitations of low-resolution spectroscopy to improve the photometric spectral types of CoRoT candidates. In particular, we want to study the influence of the signal-to-noise ratio (SNR) of the target spectrum in a quantitative way. We built an own template library and investigate whether a template library from the literature is able to reproduce the classifications. Including previous photometric estimates, we show how the additional spectroscopic information improves the constraints on spectral type. Low-resolution spectroscopy ( R ≈ 1000) of 42 CoRoT targets covering a wide range in SNR (1-437) and of 149 templates was obtained in 2012-2013 with the Nasmyth spectrograph at the Tautenburg 2 m telescope. Spectral types have been derived automatically by comparing with the observed template spectra. The classification has been repeated with the external CFLIB library. The spectral class obtained with the external library agrees within a few sub-classes when the target spectrum has a SNR of about 100 at least. While the photometric spectral type can deviate by an entire spectral class, the photometric luminosity classification is as close as a spectroscopic classification with the external library. A low SNR of the target spectrum limits the attainable accuracy of classification more strongly than the use of external templates or photometry. Furthermore we found that low-resolution reconnaissance spectroscopy ensures that good planet candidates are kept that would otherwise be discarded based on photometric spectral type alone. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We carried out light-curve solutions of the ultrashort-period binaries with MS components observed by Kepler. All six targets turned out almost in thermal contact with contact or slightly overcontact configurations. Two of them, KID 4921906 and KID 6309193, are not eclipsing but reveal ellipsoidal and spot variability. One of the components of KID 8108785 exhibits inherent, quasi-sinusoidal, small-amplitude variability. KID 12055255 turned out tobe a very rare case of ultrashort-period overcontact binary consisting of two M dwarfs. Our modeling indicated that the variability of KID 9532219 is due to eclipses but not to δ Sct pulsations as it was previously supposed. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This paper is based on 2MASS photometry ( J H Ks magnitudes) of 1172 Be stars. The observed mean intrinsic colours have been derived with aid of two-colour diagrams for Be stars of luminosity classes Ie-IIe, IIIe and IVe-Ve. The obtained results are the first determinations of their intrinsic colours in the astronomical literature. The smoothed infrared colours are compared with those obtained for 'normal' B stars. Several two-colour diagrams and plots of observed and smoothed intrinsic colour versus spectral type of luminosity classes Ie-IIe, IIIe and IVe-Ve are presented. Generally the determined infrared intrinsic colours of Be stars ( V - J)0, ( V - H)0, and ( V - Ks) o differ substantially from those of 'normal' B stars. It is found that the intrinsic colours of B stars are generally bluer than Be stars of corresponding spectral type and luminosity class. The mean absolute visual magnitude M v of 528 Be stars for luminosity classes Iae, Ibe-Iabe, IIe, IIIe and IVe-Ve is derived from HIPPARCOS parallaxes. The M v calibration is compared with the existing ones. The Be stars are generally brighter than 'normal' B stars of corresponding spectral types. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We spatially and temporally resolve the future Supernova (SN) rate in the Solar vicinity and the whole Galaxy by comparing observational parameters of massive stars with theoretical models for estimating age and mass and, hence, the remaining lifetime until the SN explosion. Our SN rate derived in time and space for the future (few Myr) should be the same as in the last few Myr by assuming a constant rate. From BVRIJHK photometry, parallax, spectral type, and luminosity class we compile a Hertzsprung-Russell diagram (HRD) for 25027 massive stars and derive extinction, and luminosity, then mass, age, and remaining lifetime from evolutionary models. Within 600 pc our sample of SN progenitors and, hence, SN prediction, is complete, and all future SN events of our sample stars take place in 8 % of the area of the sky, whereas 90 % of the events take place in 7 % of the area of the sky. The current SN rate within 600 pc is increased by a factor of 5-6 compared with the Galactic rate. For a distance of 5 kpc our sample is incomplete, nevertheless 90 % of those SN events take place in only 12 % of the area of the projected sky. If the SN rate in the near future is the same as the recent past, there should be unknown young neutron stars concentrated in those areas. Our distribution can be used as input for constraints of gravitational waves detection and for neutron star searches. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present continuous and time-resolved R = 55 000 optical échelle spectroscopy of ε Aurigae from 2006-2013. Data were taken with the STELLA Echelle Spectrograph of the robotic STELLA facility at the Observatorio del Teide in Tenerife. Contemporaneous photometry with the Automatic Photoelectric Telescopes at Fairborn Observatory in Arizona is presented for the years 1996-2013. Spectroscopic observations started three years prior to the photometric eclipse and are still ongoing. A total of 474 high-resolution échelle spectra are analyzed and made available in this paper. We identify 368 absorption lines of which 161 lines show the characteristic sharp disk lines during eclipse. Another 207 spectral lines appeared nearly unaffected by the eclipse. From spectrum synthesis, we obtained the supergiant atmospheric parameters Teff = 7395 ± 70 K, log g ≈ 1, and [Fe/H] = +0.02 ± 0.2 with ξt = 9 km s-1, ζRT = 13 km s-1, and v sin i = 28 ± 3 km s-1. The residual average line broadening expressed in km s-1 varies with a period of 62.6 ± 0.7 d, in particular at egress and after the eclipse. Two-dimensional line-profile periodograms show several periods, the strongest with ≈110 d evident in optically thin lines as well as in the Balmer lines. Center-of-intensity weighted radial velocities of individual spectral lines also show the 110-d period but, again, additional shorter and longer periods are evident and are different in the Balmer lines. The two main spectroscopic H α periods, ≈ 116 d from the line core and ≈ 150 d from the center-of-intensity radial velocities, appear at 102 d and 139 d in the photometry. The H β and Johnson V I photometry on the other hand shows two well-defined and phase-coherent periods of 77 d and 132 d. We conclude that H α is contaminated by changes in the circumstellar environment while the H β and V I photometry stems predominantly from the non radial pulsations of the F0 supergiant. We isolate the disk-rotation profile from 61 absorption lines and found that low disk eccentricity generally relates to low disk rotational velocity (but not always) while high disk eccentricity always relates to high velocity. There is also the general trend that the disk-absorption in spectral lines with higher excitation potential comes from disk regions with higher eccentricity and thus also with higher rotational velocity. The dependency on transition probability is more complex and shows a bi-modal trend. The outskirts of the disk is distributed asymmetrically around the disk and appears to have been built up mostly in a tail along the orbit behind the secondary. Our data show that this tail continues to eclipse the F0 Iab primary star even two years after the end of the photometric eclipse. High-resolution spectra were also taken of the other, bona-fide, visual-binary components of ε Aur (ADS 3605BCDE). Only the C-component, a K3-4-giant, appears at the same distance than ε Aur but its radial velocity is in disagreement with a bound orbit. The other components are a nearby (≈ 7 pc) cool DA white dwarf, a G8 dwarf, and a B9 supergiant, and not related to ε Aur. The cool white dwarf shows strong DIB lines that suggest the existence of a debris disk around this star. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We considered some selected published stellar catalogues with B - V and V values for the open cluster NGC 188 and estimated the errors from data comparisons. The results are used to homogenize the data by averaging with weights inversely proportional to the errors squared. A recent calibration by Casagrande et al. (2010) of B - V versus effective temperatures for F, G, and K dwarfs and subgiants is used to produce the homogenized effective temperatures for the cluster stars. A homogenized Hertzsprung-Russell diagram (relationship between the effective temperatures and the absolute magnitudes) is presented and analysed. [ABSTRACT FROM AUTHOR]

We present the first long-term Johnson UBVR observations and comprehensive photometric analysis of the W UMa-type eclipsing binary V2612 Oph. Observations in the time interval between 2003 and 2009 enabled us to reveal the seasonal and long-term variations of the light curve. Hence, we found that the mean brightness level of the light curve shows a variation with a period of 6.7 years. Maximum and minimum brightness levels of the light curve exhibit a variation from year to year which we attribute to a solar-like activity. The O - C variation of eclipse timings of the system shows a decreasing parabolic trend and reveals a period decrease at a rate of P = 6.27×10-7 day yr-1 with an additional low-amplitude sinusoidal variation that has a similar period as the long-term brightness variations. Our light curve analysis shows that the system is a W-subtype WUMa eclipsing binary. We calculated masses and radii of the primary and secondary components as M1 = 1.28M☉,M2 = 0.37M☉ and R1 = 1.31 R☉, R2 = 0.75 R☉, respectively. The derived absolute photometric parameters allow us to calculate a distance of 140 pc, which confirms that the system is a foreground star in the sky field of the Galactic open cluster NGC 6633. [ABSTRACT FROM AUTHOR]

We report our investigation of the first transiting planet candidate from the YETI project in the young (∼4 Myr old) open cluster Trumpler 37. The transit-like signal detected in the lightcurve of F8V star 2M21385603+5711345 repeats every 1.364894 + 0.000015 days, and has a depth of 54.5 + 0.8 mmag in R. Membership in the cluster is supported by its mean radial velocity and location in the color-magnitude diagram, while the Li diagnostic and proper motion are inconclusive in this regard. Follow-up photometric monitoring and adaptive optics imaging allow us to rule out many possible blend scenarios, but our radial-velocity measurements show it to be an eclipsing single-lined spectroscopic binary with a late-type (mid-M) stellar companion, rather than one of planetary nature. The estimated mass of the companion is 0.15-0.44 M⊙. The search for planets around very young stars such as those targeted by the YETI survey remains of critical importance to understand the early stages of planet formation and evolution. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The principal idea of the Virtual Observatory is to achieve real transparency for astronomical data, similar to transparency for all the world's documents in the World Wide Web. In the Virtual Observatory, all the world's astronomical data is available from one's desktop. All archives understand the same query language, can be accessed through a uniform interface, and diverse data can be analyzed with the same tools. In particular, facilities of the Virtual Observatory allow users to make a fast and correct analysis of objects from various surveys. It yields multi-photometry data on registered objects and makes it possible to determine stellar parameters. Methods of astronomical data analysis as well as their application to various areas of stellar astronomy are discussed in this paper. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The purpose of the LYRA mission is a multi-color all-sky survey of objects from 3m to 16m from the International Space Station, to result in a high-precision photometric catalog (Zakharov et al. 2013b). The expected error of the catalog will be 0.001-0.003m for stars brighter than 12m and 0.01m for the stars down to 16m. The estimated duration of the survey is about 5 years. This paper describes the characteristics of data to be received in the course of the LYRA experiment for future users. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The 10-color photometric system for the Russian space photometric experiment LYRA is described. It is shown that the system is effective for the determination of interstellar extinction, separation of supergiants, and evaluation of metallicity. The creation of a large grid of high-precision photometric standards is one of the most important tasks of the LYRA experiment. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Homogeneous independent subsamples from selected catalogues and libraries of effective temperatures for metal deficient F-G stars are treated here by combining them in triples and pairs for the stars in common to determine their external errors from data intercomparisons. The effective temperatures are then averaged (with the weights inversely proportional to the squared errors) to produce mean homogenized catalogues which may be used for calibration of spectral and photometric data in large Galactic surveys. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We separate and analyse the component spectra of the composite-spectrum binary HD 208253. We find that the cool primary is an evolving star of spectral type G7 III, while its hot secondary is an early-A dwarf. The giant is currently near the lowest point of the red-giant branch and is slightly less luminous than its dwarf companion. We provide a set of precise radial-velocity measurements for both stars. The double-lined orbit which we derive from them shows that the component mass ratio is close to unity (q = 1.05 ± 0.01). We deduce the physical properties of both stars, determine their respective masses to be 2.75 ± 0.07 Me (giant) and 2.62 ± 0.07 Me (dwarf), and show that the orbit's inclination is within a degree or two of 68°. The spectrum of the A-type component has quite component has quite narrow lines (we infer a rotational velocity of 18 km s-1), though since the period of the orbit is well over 1 year that component cannot be in synchronous rotation. An intriguing property of the dwarf is its enhanced Sr and Ba, though it does not exhibit the other spectral peculiarities that would signal a classical Am star. While by no means unique amongst the multitude of oddities exhibited by A and early-F stars, this dwarf which we have uncovered in a long-period binary offers valuable constraints and challenges to stellar-evolution theory. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present and analyze long-term optical photometric measurements of the three active stars V2253 Oph, IT Com and IS Vir. All three systems are single-lined spectroscopic binaries with an early K giant as primary component but in different stages of orbital-rotational synchronization. Our photometry is supplemented by 2MASS and WISE near-IR and mid-IR magnitudes and then used to obtain more accurate effective temperatures and extinctions. For V2253 Oph and IT Com, we found their spectral energy distributions consistent with pure photospheric emission. For IS Vir, we detect a marginal mid-IR excess which hints towards a dust disk. The orbital and rotational planes of IT Com appear tobe coplanar, contrary to previous findings in the literature. We apply a multiple frequency analysis technique to determine photometric periods, and possibly changes of periods, ranging from days to decades. New rotational periods of 21.55±0.03 d, 65.1±0.3 d, and 23.50±0.04 d were determined for V2253 Oph, IT Com, and IS Vir, respectively. Splitting of these periods led to tentative detections of differential surface rotations of δP/P ≈ 0.02 for V2253 Oph and 0.07 for IT Com. Using a time-frequency technique based on short-term Fourier transforms we present evidence of cyclic light variations of length ≈ 10 yr for V2253 Oph and 5-6 yr for IS Vir. A single flip-flop event has been observed for IT Com of duration 2-3 yr. Its exchange of the dominant active longitude had happened close to a time of periastron passage, suggesting some response of the magnetic activity from the orbital dynamics. The 21.55-d rotational modulation of V2253 Oph showed phase coherence also with the orbital period, which is 15 times longer than the rotational period, thus also indicating a tidal feedback with the stellar magnetic activity. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We review the classification of the variable star SW Equulei, formerly classified as a close binary of the W UMa type with a period of 0.83632 d and components of spectral types O-A or F-G and later. New observations indicate that the light curve is not that of an eclipsing binary but of a pulsating star with a period half of the old value. Further examination shows that SW Equulei is a double mode star of the RRd Lyrae type with a fundamental period of P = 0.560727 d and an overtone of P = 0.4181777 d at a distance of ≈ 7.1 kpc. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Age is among the most elusive, yet important, fundamental properties of low-mass stars and brown dwarfs. M dwarfs have main-sequence lifetimes that are estimated to be trillions of years, with little change in luminosity. In contrast, brown dwarfs cool and dim with time, resulting in a significant degeneracy between mass, age, and luminosity. Despite these inherent challenges, there have been recent efforts on both observational and theoretical fronts that may yield precise ages for low-mass stars and brown dwarfs. We feature some current observational efforts focused on estimating ages of these objects as presented in our Cool Stars 17 splinter session. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Asteroseismology has been extremely successful in determining the properties of stars in different evolutionary stages with a remarkable level of precision. However, to fully exploit its potential, robust methods for estimating stellar parameters are required and independent verification of the results is needed. In this talk, I present a new technique developed to obtain stellar properties by coupling asteroseismic analysis with the infrared flux method. Using two global seismic observables and multi-band photometry, the technique determines masses, radii, effective temperatures, bolometric fluxes, and thus distances for field stars in a self-consistent manner. Applying our method to a sample of solar-like oscillators in the Kepler field that have accurate Hipparcos parallaxes, we find agreement in our distance determinations to better than 5 %. Comparison with measurements of spectroscopic effective temperatures and interferometric radii also validate our results, and show that our technique can be applied to stars evolved beyond the main-sequence phase. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This proceeding reviews the results of our survey to measure the fundamental properties of nearby, main-sequence, K- and M-type stars, specifically reported in Boyajian et al. (2012a). The results presented double the number of precise measurements obtained for stars of this type. We use observations of the stellar angular diameter obtained through interferometry coupled with the distance and bolometric flux to determine the stellar linear radius, effective temperature, and luminosity. These data are used to derive empirical relations to the fundamental properties of stars. We highlight the challenges these data bring to current stellar atmospheric and evolutionary models. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

he determination of metallicities in late-type stars is particularly difficult because their cool atmospheres enable the formation of complex molecules. Instead, most studies use wide binaries that include a solar-type primary and an M dwarf companion. However, most previous studies utilize only a small number (15-25) of binaries, limiting the effective range of their calibrations. We present our observations and analysis of a sample of 105 FGK-M wide binary systems with metallicities of -1.04 < [Fe/H] < +0.56 and companion spectral types from K5.5 to M6. We obtain moderate resolution (1300 < R < 2000) visible and near-infrared spectra for each late-type companion, and high-resolution spectra for the 44 primary stars that lack published metallicities. We use our sample to determine, empirically, which spectral features are best correlated with the metallicity of the primary. We find over 80 features in K and M dwarf visible and near-infrared spectra that are useful for predicting metallicity. We use a subset of these features to derive metallicity calibrations for different wavelength regimes, and show that it is possible to get metallicities reliable to < 0.10 dex using either visible, J, H, or K band spectra, however, when using visible spectra this requires the use of different calibrations for early-type (K5.5 to M2) and late-type (M2 to M6) dwarfs. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a brief overview of a splinter session on M dwarf stars as planet hosts that was organized as part of the Cool Stars 17 conference. The session was devoted to reviewing our current knowledge of M dwarf stars and exoplanets in order to prepare for current and future exoplanet searches focusing in low mass stars. We review the observational and theoretical challenges to characterize M dwarf stars and the importance of accurate fundamental parameters for the proper characterization of their exoplanets and our understanding on planet formation. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Data from the Kepler satellite (Q0-Q11) are used to study HAT-P-7. The satellite's data are extremely valuable for asteroseismic studies of stars and for observing planetary transits; in this work we do both. An asteroseismic study of the host star improves the accuracy of the stellar parameters derived by Christensen-Dalsgaard et al. (2010), who followed largely the same procedure but based the analysis on only one month of Kepler data. The stellar information is combined with transit observations, phase variations and occultations to derive planetary parameters. In particular, we confirm the presence of ellipsoidal variations as discovered by Welsh et al. (2010), but revise their magnitude, and we revise the occultation depth (Borucki et al. 2009), which leads to different planetary temperature estimates. All other stellar and planetary parameters are now more accurately determined (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Seismic modeling of the slowly pulsating B-type star HD182255 yields strong constraints on the radial orders of the two dominant modes. For these frequencies, we derive also the empirical values of the complex nonadiabatic parameter f. These two seismic tools, i.e., pulsational frequencies and the associated values of f, allow to test available opacity data, chemical composition, and overshooting effciency (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We have used two robotic telescopes to obtain time-series high-resolution optical echelle spectroscopy and VI and/or by photometry for a sample of 60 active stars, mostly binaries. Orbital solutions are presented for 26 double-lined systems and for 19 single-lined systems, seven of them for the first time but all of them with unprecedented phase coverage and accuracy. Eighteen systems turned out to be single stars. The total of 6609 R = 55000 échelle spectra are also used to systematically determine effective temperatures, gravities, metallicities, rotational velocities, lithium abundances and absolute Hα-core fluxes as a function of time. The photometry is used to infer unspotted brightness, V - I and/or b - y colors, spot-induced brightness amplitudes and precise rotation periods. An extra 22 radial-velocity standard stars were monitored throughout the science observations and yield a new barycentric zero point for our STELLA/SES robotic system. Our data are complemented by literature data and are used to determine rotation-temperature-activity relations for active binary components. We also relate lithium abundance to rotation and surface temperature. We find that 74% of all known rapidly-rotating active binary stars are synchronized and in circular orbits but 26% (61 systems) are rotating asynchronously of which half have Prot > Porb and e > 0. Because rotational synchronization is predicted to occur before orbital circularization active binaries should undergo an extra spin-down besides tidal dissipation. We suspect this to be due to a magnetically channeled wind with its subsequent braking torque. We find a steep increase of rotation period with decreasing effective temperature for active stars, Prot α T-7eff, for both single and binaries, main sequence and evolved. For inactive, single giants with Prot > 100 d, the relation is much weaker, Prot α T-1.12eff. Our data also indicate a period-activity relation for Hα of the form RHα α P0.24rot for binaries and RHα α P-0.14rot for singles. Its power-law difference is possibly significant. Lithium abundances in our (field-star) sample generally increase with effective temperature and are paralleled with an increase of the dispersion. The dispersion for binaries can be 1-2 orders of magnitude larger than for singles, peaking at an absolute spread of 3 orders of magnitude near Teff ≈ 5000 K. On average, binaries of comparable effective temperature appear to exhibit 0.25 dex less surface lithium than singles, as expected if the depletion mechanism is rotation dependent. We also find a trend of increased Li abundance with rotational period of form log n (Li) α -0.6 log Prot but again with a dispersion of as large as 3-4 orders of magnitude (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a full description of, and parameters for, the component stars in the triple-lined composite-spectrum system HR 6497. Both the outer and the inner orbits have already been computed with fair accuracy, but the improved orbits resulting from this new analysis have precisions that are up to an order of magnitude tighter. By applying the proven technique of spectral subtraction to a large sample of new, high-quality spectra we separate the spectra of the inner pair cleanly for the first time, and show that it has characteristics which cannot be explained at all easily by conventional models. Since the inner pair are separated by only 4 times their own radii, we expect their rotations to be synchronized to their orbital revolution, or close to 28 km/s, but in fact they have almost no visible rotation at all. The Mg II line at λ 4481 Å, itself a close doublet with a separation of 0.2 Å, is clearly resolved in the spectra of both components of the inner system. Such resolution is extremely rare in our experience, and we are unable to suggest a satisfactory explanation for it (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present a method of obtaining the most reliable stellar spectral type based on multi-color photometry. The method also allows us to estimate color excess E B-V and distance to the star. Approbation of the method using bright stars with known spectral classification and WBVR photometry permits to estimate its reliability. Stellar spectra models from Pickles (1998) library and Fluks et al. (1994) interstellar extinction law were used in the application of the method. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We used high-quality Kepler photometry and recent spectroscopic data to investigate the Kepler target KIC 005988140 considering three possible scenario's: (1) binarity, (2) co-existence of δ Scuti- and γ Doradus-type oscillations, and (3) rotational modulation with spots over the stellar surface. Using spectrum synthesis, we derived improved atmospheric parameters from high-resolution, high signal-to-noise spectra. The star is of spectral type A7.5 IV-III with a metallicity slightly lower than that of the Sun. The Fourier analyses of both the photometric and the spectroscopic data reveal two dominant frequencies - with an integer ratio equal to two - in the low frequency regime. Nine more frequencies located in the typical δ Scuti range were also detected. The mean light and radial velocity curves which are not exactly in antiphase, show a similar double-wave shape. We therefore suggest on a preliminary basis that the physical cause of the observed light and radial velocity variations is the simultaneous occurrence of (δ Sct-type) pressure modes and stellar rotation coupled to inhomogeneities on the surface of this late A-type star (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The 131 days long, high-precision light curves observed in the CoRoT exo-field during LRa01 were investigated for γ Dor and δ Sct-γ Dor hybrid stars. In total 418 γ Dor and 274 δ Sct-γ Dor hybrid candidates were identified. For a fraction of these candidates spectra are available obtained at the Anglo-Australian Observatory. Effective temperatures and surface gravity were derived by fitting synthetic spectra of three Balmer lines, i.e. Hα, Hβ, and Hγ, as well as of the Ca K line at 3933 °A. The bona fide γ Dor and hybrid stars were plotted in an Teff- log g diagram that shows the expected concentration of γ Dor stars at the cool border of the δ Sct strip. In contrast, the hybrids fill the whole δ Sct instability strip without a noticeable concentration. Remarkably, the fraction of constant stars, with no signal above 3 times the noise level, is smallest in the same temperature regime (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]