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A research on stellar magnetism in Crimea was initiated by pioneer works of A.B. Severny, V.E. Stepanov, and D.N. Rachkovsky. Today, the study of stellar magnetic fields is a key field of research at the Crimean Astrophysical Observatory (CrAO). The 2.6 m Shajn telescope equipped with the echelle spectrograph ESPL, CCD, and Stokesmeter (a circular polarization analyzer) allows us to study the magnetic field of bright stars up to 5m–6m. The Single Line (SL) technique is developed for measuring magnetic fields at CrAO. This technique is based on the calculation of the Zeeman effect in individual spectral lines. A key advantage of the SL technique is its ability to detect local magnetic fields on the surface of stars. Many results in the field of direct measurements of stellar magnetic fields were obtained at CrAO for the first time. In particular, the magnetic field on supergiants (ǫ Gem), as well as on a number of subgiants, giants, and bright giants was first detected. This, and investigations of other authors, confirmed the hypothesis that a magnetic field is generated at all the stages of evolution of late-type stars, including the stage of star formation. The emergence of large magnetic flux tubes at the surface of stars of V-IV-III luminosity classes (61 Cyg A, β Gem, β Aql) was first registered. In subgiants, the magnetic field behavior with the activity cycle was first established for β Aql. Using the long-term Crimean spectroscopic and spectropolarimetric observations of α Lyr, the 22-year variability cycle of the star, supposedly associated with meridional flows, is confirmed. Magnetic field variability with the pulsation period was first detected for different types of pulsating variables: the classical Cepheid β Aql, the low-amplitude β Cep-type variable γ Peg, and others. In this review we cover more than a half-century history of the formation of the Crimean scientific school for high-precision direct measurements of stellar magnetic fields.

The research on stellar magnetism in the Crimea was initiated by pioneer works of A.B. Severny, V.E. Stepanov, and D.N. Rachkovsky. Today, the study of stellar magnetic fields is a key field of research at the Crimean Astrophysical Observatory (CrAO). The 2.6 m Shajn telescope equipped with the echelle spectrograph ESPL, CCD, and Stokesmeter (a circular polarization analyzer) allows us to study the magnetic field of bright stars up to 5m–6m. The Single Line (SL) technique is developed for measuring magnetic fields at СrAO. This technique is based on the calculation of Zeeman effect in individual spectral lines. A key advantage of the SL technique is its ability to detect local magnetic fields on the surface of stars. Many results in the field of direct measurements of stellar magnetic fields were obtained at CrAO for the first time. In particular, the magnetic field on supergiants (e Gem), as well as a number of subgiants, giants, and bright giants was first detected. This, and investigations of other authors, confirmed the hypothesis that a magnetic field is generated at all stages of the evolution of late-type stars, including the stage of star formation. The emergence of large magnetic flux tubes at the surface of stars of V-IV-III luminosity classes (61 Cyg A, β Gem, β Aql) was first registered. For β Aql, the behavior of a magnetic field with an activity cycle in subgiants was first established. Using long-term Crimean spectroscopic and spectropolarimetric observations of α Lyr, the 22-year variability cycle of the star, supposedly associated with meridional flows, is confirmed. Magnetic field variability with the pulsation period was first detected for different types of pulsating variables: the classical Cepheid β Aql, the low-amplitude β Cep-type variable γ Peg, and others. In this review we cover more than a half-century history of the formation of the Crimean scientific school for high-precision direct measurements of stellar magnetic fields.

We have revisited and updated the $uvby$ Str\"omgren colour and colour-index distributions of A, F and early G-type main sequence stars. For this aim, we selected 7054 dwarf stars along with 65 MK standard stars within the same spectral range but covering all luminosity classes. The standard stars were selected following the MK mandate strictly, using spectra taken at classification resolution recorded on photographic plates. We used the colours of these stars to determine the effective temperature and surface gravity. After correcting for systematic offsets using fundamental parameters and considering a few exceptions, we find an one-to-one correspondence, among MK spectral types, Str\"omgren photometry, and their associated physical properties. We have applied a principal component analysis to the mean Str\"omgren indices for dwarf stars complemented by MK standards for higher luminosity classes. We have used the projections to introduce three new photometric metaindices, namely SM1, SM2, and SM3. We have defined a 3D-box, which allowed us to segregate dwarf stars from bright giants and supergiant stars, with the aid of the metaindices. Two of the planes show that the projections of dwarfs and supergiants are ordered by temperature; however, the temperature dependence for the supergiants is not as well defined as for the dwarfs. Following the MK Process, we were able to form an automatic classifier. We present some applications and assigned synthetical spectral types. We suggest that our metaindices formalism allows the extension of Str\"omgren photometric outside its original mandate (i.e., later types), without requiring the introduction of additional photometric filters., Comment: 20 pages, 22 figures, 9 tables, accepted for publication in MNRAS

Fundamental astrophysical parameters have been derived for Berkeley 55 (Be 55) open cluster based on the UBVI charge-coupled device (CCD) photometric data observed using a AZT-22 1.5 m telescope at Maidanak Astronomical Observatory (MAO) in Uzbekistan. The mean reddening is obtained as $$E(B-V)=1.77\pm 0.10\,\mathrm {mag}$$ from early-type members. The zero-age main sequence fitting in the $$Q_{V\lambda }$$ – $$Q'$$ diagrams indicates the distance modulus, $$(V_{0}-M_{V})=12.4\pm 0.20\,\mathrm {mag}\,(d=3.02\pm 0.28\,\mathrm {kpc}$$ ). This photometric distance is consistent with the distances of Gaia EDR3 ( $$d = 3.09 \pm 0.16\,\mathrm {kpc}$$ ) and period–luminosity relation ( $$d =$$ 2.78 ± 0.32 kpc) of its Cepheid S5 within the uncertainties. This distance also locates the cluster near the Perseus spiral arm. The Geneva isochrone fittings to the Hertzsprung–Russell diagram and observational colour–magnitude diagrams derive turn-off age, 85 ± 13 Myr, by taking care of five red supergiants/bright giants. The possible inconsistencies in the locations of the bright giants with the rotating/non-rotating isochrones may be due to both the age spread of stars in young open clusters and the diversity in rotational velocities.

We model the effects of collisions and close encounters on the stellar populations observed in the Milky Way nuclear stellar cluster (NSC). Our analysis is based on $N$-body simulations in which the NSC forms by accretion of massive stellar clusters around a supermassive black hole. We attach stellar populations to our $N$-body particles and follow the evolution of their stars, and the rate of collisions and close encounters. The most common encounters are collisions between pairs of main-sequence stars, which lead to mergers: destructive collisions between main-sequence stars and compact objects are rare. We find that the effects of collisions on the stellar populations are small for three reasons. First, our models possess a core which limits the maximum stellar density. Secondly, the velocity dispersion in the NSC is similar to the surface escape velocities of the stars, which minimises the collision rate. Finally, whilst collisions between main-sequence stars destroy bright giants by accelerating their evolution, they also create them by accelerating the evolution of lower-mass stars. These two effects approximately cancel out. We also investigate whether the G2 cloud could be a fuzzball: a compact stellar core which has accreted a tenuous envelope in a close encounter with a red giant. We conclude that fuzzballs with cores below $2\,M_\odot$ have thermal times-scales too short to reproduce G2. A fuzzball with a black-hole core could reproduce the surface properties of G2 but the production rate of such objects in our model is low., 17 pages, 15 figures, 4 tables. Accepted for publication in MNRAS

Non-LTE analysis (where LTE is local thermodynamic equilibrium) of the oxygen abundances for 51 Galactic A-, F- and G-type supergiants and bright giants is performed. In contrast with carbon and nitrogen, oxygen does not show any significant systematic anomalies in its abundances log ε(O). There is no marked difference from the initial oxygen abundance, within the errors, for the log ε(O) determination across the Teff interval from 4500–8500 K and the $\log \, g$ interval from 1.2–2.9 dex. This result agrees well with theoretical predictions for stellar models with rotation. With our new data for oxygen and our earlier non-LTE determinations of the N and C abundances for stars from the same sample, we constructed the [N/C] versus [N/O] relation for 17 stars. This relation is known to be a sensitive indicator of stellar evolution. A pronounced correlation between [N/C] versus [N/O] is found; the observed [N/C] increase from 0 to 1.6 dex is accompanied by a [N/O] increase from 0 to 0.9 dex. When comparing the observed [N/C] versus [N/O] relation with the theoretical one, we show that this relation reflects a strong dependence of the evolutionary changes in CNO abundances on the initial rotation velocities of stars. Given that the initial rotational velocities of these stars are expected to satisfy V0 < 150 km s−1, it is found that they are mostly post-first-dredge-up (post-FDU) objects. It is important that such initial velocities V0 are typical for about 80 per cent of the stars in question (i.e. stars with masses 4–19 M$\odot$). A constancy of the total C+N+O abundance during stellar evolution is confirmed. The mean value of log ε(C+N + O) = 8.97 ± 0.08 found for AFG supergiants and bright giants seems to be very close to the initial values of 8.92 (the Sun) or 8.94 (unevolved B-type main-sequence stars).

In the search of a sample of metal-poor bright giants using Str{\"o}mgren photometry, we serendipitously found a sample of 26 young (ages younger than 1 Gyr) metal-rich giants, some of which have high rotational velocities.We determined the chemical composition and rotational velocities of these stars in order to compare them with predictions from stellar evolution models. These stars where of spectral type A to B when on the main sequence, and we therefore wished to compare their abundance pattern to that of main-sequence A and B stars.Stellar masses were derived by comparison of the position of the stars in the colour-magnitude diagram with theoretical evolutionary tracks. These masses, together with Gaia photometry and parallaxes, were used to derive the stellar parameters. We used spectrum synthesis and model atmospheres to determine chemical abundances for 16 elements (C, N, O, Mg, Al, Ca, Fe, Sr, Y, Ba, La, Ce, Pr, Nd, Sm, and Eu) and rotational velocities.The age-metallicity degeneracy can affect photometric metallicity calibrations. We identify 15 stars as likely binary stars. All stars are in prograde motion around the Galactic centre and belong to the thin-disc population. All but one of the sample stars present low [C/Fe] and high [N/Fe] ratios together with constant [(C+N+O)/Fe], suggesting that they have undergone CNO processing and first dredge-up. The observed rotational velocities are in line with theoretical predictions of the evolution of rotating stars., Comment: Astronomy and Astrophysics - A\&A, EDP Sciences, 2021

A five-dimensional interpolation method and corresponding computer program are developed for using published calculations to determine the non-LTE correction {\Delta\}NLTE to the lithium abundance log{\epsilon}(Li) derived from the Li I 6707.8 {\AA} line. The {\Delta\}NLTE values is determined from the following five parameters: {\Delta\}NLTE the effective temperature Teff, the acceleration of gravity logg, the metallicity index [Fe/H], the microturbulent velocity Vt, and the LTE Li abundance log {\epsilon}(Li). The program is used to calculate values of {\Delta\}NLTE and the non-LTE Li abundance for 91 single bright giants from the list of Lebre, et al. By combining these results with data for 55 stars, we obtain the non-LTE values of log {\epsilon}(Li) for 146 FGK-giants and supergiants. We confirm that, in the spectra of most of these stars, it is only possible to estimate for them an upper limit for the Li abundance. A large spread is confirmed in log {\epsilon}(Li) for stars with masses M2 and nearly up to the initial value of log {\epsilon}(Li) = 3.2 +- 0.1 are examined. It is shown that the fraction of Li-rich giants with V0 = 0 - 50 km/s is consistent with current evolutionary models. The other stars of this type, as well as all of the "super Li-rich" giants, for which the standard theory is untenable, can be explained by invoking the hypothesis of recent lithium synthesis in the star or an alternative hypothesis according to which a giant planet is engulfed by the star., Comment: 15 pages, 5 figures, 2 tables

Analysis of late O-type stars observed in the Large Magellanic Cloud (LMC) by the VLT-FLAMES Tarantula Survey (VFTS) revealed a discrepancy between the physical properties estimated from model-atmosphere analysis and those expected from their morphological classifications. Here we revisit the analysis of 32 of these puzzling objects using new hydrogen-helium-silicon FASTWIND models and a different fitting approach to re-evaluate their physical properties. Our new analysis confirms that these stars indeed have properties that are typical of late O-type dwarfs. We also present the first estimates of silicon abundances for O-type stars in the 30 Dor clusters NGC 2060 and NGC 2070, with a weighted mean abundance for our sample of 7.05 +/- 0.03. Our values are about 0.20 dex lower than those previously derived for B-type stars in the LMC clusters N 11 and NGC 2004 using TLUSTY models. Various possibilities (e.g. differences in the analysis methods, effects of microturbulence, and real differences between stars in different clusters) were considered to account for these results. We also used our grid of FASTWIND models to reassess the impact of using the Galactic classification criteria for late O-type stars in the LMC by scrutinising their sensitivity to different stellar properties. At the cool edge of the O star regime the HeII 4686/HeI 4713 ratio used to assign luminosity class for Galactic stars can mimic giants or bright giants in the LMC, even for objects with high gravities (log_g > 4.0 dex). We argue that this line ratio is not a reliable luminosity diagnostic for late O-type stars in the LMC, and that the SiIV 4989/HeI4026 ratio is more robust for these types., 18 pages, 10 figures accepted for publication in A&A

We recently used archival and newly obtained data from the Navy Precision Optical Interferometer to measure the fundamental properties of 87 stars. The sample consisted of 5 dwarfs, 3 subgiants, 69 giants, 3 bright giants, and 7 supergiants, and spanned a wide range of spectral classes from B to M. We combined our angular diameters with photometric and distance information from the literature to determine each star’s physical radius, effective temperature, bolometric flux, luminosity, mass, and age. Several dozen of the stars have visibility curves sampled down to the first null, where the visibilities drop to zero. Here we present preliminary results showing limb-darkening fits for the five zero crossing stars that have the best coverage of the second lobe.

We present results of the analysis of a sample of 22 stars of spectral types from O7 to B5 and luminosity classes I-V for which Spitzer/IRS spectra are available. The IRS spectra of these stars are examined for signs of excess infrared (IR) emission by comparison with stellar atmospheric spectra. We find that the spectra of half of the studied stars are dominated by excess emission in the far-IR, including all six super- and bright giants. In order to examine the origin of the far-IR excess, we supplement the Spitzer data with optical high-resolution echelle spectroscopy ($\lambda/\Delta \lambda \sim 10^5$), near-IR high-contrast coronagraphic imaging taken with the SPHERE instrument at VLT with a spatial resolution of 0.05", and WISE and Herschel photometry. In the optical region, we detect various absorption and emission lines (H$\alpha$, CIII, and NIII) irrespective of the far-IR excess. Pfund($\alpha$) and Humphrey($\alpha$) lines are observed at the same time as the far-IR excess. These lines are stronger in stars with far-IR excess than in stars without excess. A scattered-light disk in the central r < 2.5" region of the far-IR excess stars HD149404, HD151804, and HD154368 can be excluded from H band imaging down to a 1$\sigma$ contrast of $F(r)/F_{*} \sim 10^{-6}$. The far-IR excess is fit either by a free-free component from ionized gas as for the winds of hot stars or a large (1pc) circumstellar dust shell. The putative dust envelopes required to explain the excess have a visual extinction as low as a few hundred $\mu$-mag., Comment: A&A accepted, 10 pages, 6 Figures, HR spectra availabe at CDS

We present the fundamental properties of 87 stars based on angular diameter measurements from the Navy Precision Optical Interferometer, 36 of which have not been measured previously using interferometry. Our sample consists of 5 dwarfs, 3 subgiants, 69 giants, 3 bright giants, and 7 supergiants, and span a wide range of spectral classes from B to M. We combined our angular diameters with photometric and distance information from the literature to determine each star's physical radius, effective temperature, bolometric flux, luminosity, mass, and age., 7 tables, 4 figures

With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H] = -0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5 Msun with a tail at higher masses up to 4.5 Msun. This peak is also seen in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1 - 2 Msun) barium giants. This is probably because low-mass stars reach large radii at the tip of the red giant branch, which may have resulted in an early binary interaction. Among barium giants, the high-mass tail is however dominated by stars with barium indices of less than unity, based on a visual inspection of the barium spectral line; that is, these stars have a very moderate barium line strength. We believe that these stars are not genuine barium giants, but rather bright giants, or supergiants, where the barium lines are strengthened because of a positive luminosity effect. Moreover, contrary to previous claims, we do not see differences between the mass distributions of mild and strong barium giants., 14 pages, 17 figures

When a star reaches the red giant stage in the course of its evolution, its closest planets are in its atmosphere. Numerical gas dynamic models are constructed for hypersonic flow around planets by matter in the atmosphere of a red giant. The results are compared with analytic models for the motion of planets in the atmospheres of stars.

Early observations of supernovae (SNe) indicate that enhanced mass loss and pre-SN outbursts may occur in progenitors of many types of SNe. We investigate the role of energy transport via waves driven by vigorous convection during late-stage nuclear burning of otherwise typical $15 \, M_\odot$ red supergiant SNe progenitors. Using MESA stellar evolution models including 1D hydrodynamics, we find that waves carry $\sim \! 10^7 \, L_\odot$ of power from the core to the envelope during core neon/oxygen burning in the final years before core collapse. The waves damp via shocks and radiative diffusion at the base of the hydrogen envelope, which heats up fast enough to launch a pressure wave into the overlying envelope that steepens into a weak shock near the stellar surface, causing a mild stellar outburst and ejecting a small ($\lesssim 1 \, M_\odot$) amount of mass at low speed ($\lesssim \! 50 \, {\rm km}/{\rm s}$) roughly one year before the SN. The wave heating inflates the stellar envelope but does not completely unbind it, producing a non-hydrostatic pre-SN envelope density structure different from prior expectations. In our models, wave heating is unlikely to lead to luminous type IIn SNe, but it may contribute to flash-ionized SNe and some of the diversity seen in II-P/II-L SNe., Comment: Published in MNRAS

The Tarantula region in the Large Magellanic Cloud contains the richest population of spatially resolved massive O-type stars known so far. This unmatched sample offers an opportunity to test models describing their main-sequence evolution and mass-loss properties. Using ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to determine stellar, photospheric and wind properties of 72 presumably single O-type giants, bright giants and supergiants and to confront them with predictions of stellar evolution and of line-driven mass-loss theories. We apply an automated method for quantitative spectroscopic analysis of O stars combining the non-LTE stellar atmosphere model {{\sc fastwind}} with the genetic fitting algorithm {{\sc pikaia}} to determine the following stellar properties: effective temperature, surface gravity, mass-loss rate, helium abundance, and projected rotational velocity. We present empirical effective temperature versus spectral subtype calibrations at LMC-metallicity for giants and supergiants. In the spectroscopic and classical Hertzsprung-Russell diagrams, our sample O stars are found to occupy the region predicted to be the core hydrogen-burning phase by Brott et al. (2011) and K\"{o}hler et al. (2015). Except for five stars, the helium abundance of our sample stars is in agreement with the initial LMC composition. The aforementioned five stars present moderate projected rotational velocities (i.e., $v_{\mathrm{e}}\,\sin\,i\, Comment: 39 pages, 12 figures in the main text, 12 figures in the appendix. Accepted for publication in A&A. Tables C1-C5 will be available at the CDS. Appendix E has been truncated due to size limitations, the full version will be available on A&A

We present chemical abundances for 17 elements in a sample of 11 red giant branch stars in NGC 6362 from UVES spectra. NGC 6362 is one of the least massive globulars where multiple populations have been detected, yet its detailed chemical composition has not been investigated so far. NGC 6362 turns out to be a metal-intermediate ([Fe/H]=-1.07\pm0.01 dex) cluster, with its \alpha- and Fe-peak elements content compatible with that observed in clusters with similar metallicity. It also displays an enhancement in its s-process element abundances. Among the light elements involved in the multiple populations phenomenon, only [Na/Fe] shows star-to-star variations, while [Al/Fe] and [Mg/Fe] do not show any evidence for abundance spreads. A differential comparison with M4, a globular cluster with similar mass and metallicity, reveals that the two clusters share the same chemical composition. This finding suggests that NGC 6362 is indeed a regular cluster, formed from gas that has experienced the same chemical enrichment of other clusters with similar metallicity., Comment: 14 pages, 8 figures, 6 tables, accepted for publication by MNRAS

Massive stars are the cosmic engines that shape and drive our Universe. Many issues such as their formation, their stability and the mass loss effects, are far from being completely understood. Recent ground-based and space observations have shown pulsations in massive MS and post-MS stars, such as acoustic and gravity modes excited by the κ-mechanism and even solar-like oscillations. Theoretical studies emphasized the presence of strange modes in massive models, and recent theoretical analyses have shown that hot supergiants can pulsate in oscillatory convective modes. We review the instability domains of massive stars as well as their excitation mechanisms and present the latest results.

We present a non-local thermodynamic equilibrium abundance analysis of the resonance doublet Li I at 6707.8 A for 55 Galactic F and G supergiants and bright giants. The derived lithium abundances log \epsilon(Li) may be considered in three groups, namely: (i) 10 Li-rich giants with log \epsilon(Li) = 2.0-3.2 (all 10 are F-type or A9 stars); (ii) 13 G- to K0-type stars with Li abundances in the narrow range log \epsilon(Li) = 1.1-1.8; (iii) all other stars provide just upper limits to the Li abundance. The derived Li abundances are compared with theoretical predictions of 2-15 Msun stars. Our results are generally in good agreement with theory. In particular, the absence of detectable lithium for the majority of programme stars is explainable. The comparison suggests that the stars may be separated by mass M into two groups, namely M 6 Msun. All Li-rich giants and supergiants with log \epsilon(Li) > 2.0 have masses M 6 Msun agrees with the theoretical prediction that F and G supergiants and giants with M > 6 Msun cannot show detectable lithium. We note that present theory appears unable to account for the derived Li abundances for some stars, namely for (i) a few relatively low-mass Li-rich giants (M 6 Msun) with the detected abundances log \epsilon = 1.3-1.5. It is possible that the lithium in such stars was synthesized recently.

We discuss the stellar and wind properties of 72 presumably single O-type giants, bright giants, and supergiants in the 30 Doradus region. This sample constitutes the largest and most homogeneous sample of such stars ever analyzed and offers the opportunity to test models describing their main-sequence evolution.

Red giant stars are perhaps the most important type of stars for Galactic and extra-galactic archaeology: they are luminous, occur in all stellar populations, and their surface temperatures allow precise abundance determinations for many different chemical elements. Yet, the full star formation and enrichment history of a galaxy can be traced directly only if two key observables can be determined for large stellar samples - age and chemical composition. While spectroscopy is a powerful method to analyse the detailed abundances of stars, stellar ages are the "missing link in the chain", since they are not a direct observable. However, spectroscopy should be able to estimate stellar masses, which for red giants directly infer ages provided their chemical composition is known. Here we establish a new empirical relation between the shape of the hydrogen line in the observed spectra of red giants and stellar mass determined from asteroseismology. The relation allows to determine stellar masses and ages with the accuracy of 10-15%. The method can be used with confidence for stars in the following range of stellar parameters: 4000 < Teff < 5000 K, 0.5 < log g < 3.5, -2.0 < [Fe/H] < 0.3, and luminosities log L/LSun < 2.5. Our analysis provides observational evidence that the Halpha spectral characteristics of red giant stars are tightly correlated with their mass and therefore their age. We also show that the method samples well all stellar populations with ages above 1 Gyr. Targeting bright giants, the method allows to obtain simultaneous age and chemical abundance information far deeper than would be possible with asteroseismology, extending the possible survey volume to remote regions of the Milky Way and even to neighbouring galaxies like Andromeda or the Magellanic Clouds already with present instrumentation, like VLT and Keck facilities., 18 pages, accepted for publication in A&A

The discovery of lithium-rich giants contradicts expectations from canonical stellar evolution. Here we report on the serendipitous discovery of 20 Li-rich giants observed during the Gaia-ESO Survey, which includes the first nine Li-rich giant stars known towards the CoRoT fields. Most of our Li-rich giants have near-solar metallicities, and stellar parameters consistent with being before the luminosity bump. This is difficult to reconcile with deep mixing models proposed to explain lithium enrichment, because these models can only operate at later evolutionary stages: at or past the luminosity bump. In an effort to shed light on the Li-rich phenomenon, we highlight recent evidence of the tidal destruction of close-in hot Jupiters at the sub-giant phase. We note that when coupled with models of planet accretion, the observed destruction of hot Jupiters actually predicts the existence of Li-rich giant stars, and suggests Li-rich stars should be found early on the giant branch and occur more frequently with increasing metallicity. A comprehensive review of all known Li-rich giant stars reveals that this scenario is consistent with the data. However more evolved or metal-poor stars are less likely to host close-in giant planets, implying that their Li-rich origin requires an alternative explanation, likely related to mixing scenarios rather than external phenomena., This work is based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.B-3002. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the $\textit{Gaia}$-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council. This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and the Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR) in the form of the grant Premiale VLT 2012 and the Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies (prot. 2010LY5N2T). The results presented here benefit from discussions held during the $\textit{Gaia}$-ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. GR acknowledges support from the project grant ‘The New Milky Way’ from the Knut and Alice Wallenberg Foundation. GMK is supported by the Royal Society as a Royal Society University Research Fellow. LS acknowledges support provided by the Chilean Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to the Millennium Institute of Astrophysics, MAS. Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation. The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (Grant agreement no. 267864). VSA acknowledges support from VILLUM FONDEN (research grant 10118). SLM acknowledges support from the Australian Research Council through DECRA fellowship DE140100598. TM acknowledges financial support from Belspo for contract PRODEX Gaia-DPAC. JM acknowledges the support from the European Research Council Consolidator Grant funding scheme (project STARKEY, G.A. no. 615604). This research has made use of the ExoDat Database, operated at LAM-OAMP, Marseille, France, on behalf of the CoRoT/Exoplanet programme. This research made use of astropy, a community-developed core python package for Astronomy (Astropy Collaboration et al. 2013). This research has made use of NASA's Astrophysics Data System Bibliographic Services., This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stw1512

The supergiant star Alpha Orionis (Betelgeuse) is the only star other than the Sun to be spatially resolved either through direct imaging or through reconstruction of interferometric observations. Centimeter-radio wavelength, infrared and ultraviolet images reveal a few bright hot spots in the photosphere and chromosphere that possess characteristics different from sunspots. Large photospheric spots on Betelgeuse appear to result from convective motions, consistent with radiative hydrodynamic modeling; the chromospheric hot spots may be produced by shock waves in the chromosphere excited by the convective motions or pulsation in the photosphere. Bright chromospheric spots that cluster around the pole of Betelgeuse could be a natural result of shock breakout in a rotating star.

We present N abundances for 21 bright giants in the globular cluster NGC 6752 based on high-resolution UVES spectra of the 3360A NH lines. We confirm that the Stromgren c1 index traces the N abundance and find that the star-to-star N abundance variation is 1.95 dex, at the sample's luminosity. We find statistically significant correlations, but small amplitude variations, between the abundances of N and alpha-, Fe-peak, and s-process elements. Analyses using model atmospheres with appropriate N, O, Na, and Al abundances would strengthen, rather than mute, these correlations. If the small variations of heavy elements are real, then the synthesis of the N anomalies must take place in stars which also synthesize alpha-, Fe-peak, and s-process elements. These correlations offer support for contributions from both AGB and massive stars to the globular cluster abundance anomalies., Accepted for publication in ApJ

Being fully radiative, stars of spectral type A are not expected to harbor magnetic dynamos and hence such stars are not expected to produce X-ray emission. Indeed, while the X-ray detection rate of such stars in X-ray surveys is low, it is not zero and some of the brighter A-type stars have been detected on different occasions and with different instruments. To study systematically the puzzle of the X-ray emitting A-type stars, we carried out an X-ray study of all A-type stars listed in the Bright Star Catalogue using the ROSAT public data archive. We found a total of 312 bright A-type stars positionally associated with ROSAT X-ray sources; we analyzed the X-ray light curves as well as searched for evidence of RV variations to identify possible late-type companions producing the X-ray emission. In this paper we present a list of X-ray active A-type stars, including the collected data about multiplicity, X-ray luminosity and spectral peculiarities.

We present Washington photometry of the giant branches of the relatively metal-rich globular cluster NGC 6388 and compare it with 47 Tuc. By examining the spatial distribution of stellar colors across the red giant branch and using spectroscopic data on several bright giants, we found that NGC 6388's center is affected by differential reddening of at least ΔE(B - V) ~ 0.1. Most of the width of the red giant branch is caused by that differential reddening. The southeastern outer regions of the cluster seem to be less affected by variable dust extinction, and we find that NGC 6388 is slightly more metal-rich than 47 Tuc, with a distinct asymptotic giant branch. We have put an upper limit on possible variations in [Fe/H] for NGC 6388, finding that it must be less than ~0.2 dex. It is unlikely that such a small range in metallicity could be responsible for the blue horizontal branch and blue tail stars in a cluster with a metallicity similar to the more massive 47 Tuc, which only exhibits a red horizontal branch.

We have studied the optical spectra of a sample of 28 O- and early B-type stars in the Large Magellanic Cloud, 22 of which are associated with the young star forming region N11. Our observations sample the central associations of LH9 and LH10, and the surrounding regions. Stellar parameters are determined using an automated fitting method (Mokiem et al. 2005), which combines the stellar atmosphere code fastwind (Puls et al. 2005) with the genetic algorithm based optimisation routine pikaia (Charbonneau 1995). We derive an age of 7.0 ± 1.0 and 3.0 ± 1.0 Myr for LH9 and LH10, respectively. The age difference and relative distance of the associations are consistent with a sequential star formation scenario in which stellar activity in LH9 triggered the formation of LH10. Our sample contains four stars of spectral type O2. From helium and hydrogen line fitting we find the hottest three of these stars to be 49{-}54 kK (compared to 45{-}46 kK for O3 stars). Detailed determination of the helium mass fraction reveals that the masses of helium enriched dwarfs and giants derived in our spectroscopic analysis are systematically lower than those implied by non-rotating evolutionary tracks. We interpret this as evidence for efficient rotationally enhanced mixing leading to the surfacing of primary helium and to an increase of the stellar luminosity. This result is consistent with findings for SMC stars by Mokiem et al. (2006). For bright giants and supergiants no such mass discrepancy is found; these stars therefore appear to follow tracks of modestly or non-rotating objects. The set of programme stars was sufficiently large to establish the mass loss rates of OB stars in this Z Ëœ 1/2 Zo environment sufficiently accurate to allow for a quantitative comparison with similar objects in the Galaxy and the SMC. The mass loss properties are found to be intermediate to massive stars in the Galaxy and SMC. Comparing the derived modified wind momenta D_mom as a function of luminosity with predictions for LMC metallicities by Vink et al. (2001) yields good agreement in the entire luminosity range that was investigated, i.e. 5.0 < log L/Lo< 6.1. Appendix A is only available in electronic form at http://www.aanda.org

We investigate the magnetic field at the surface of 48 red giants selected as promising for detection of Stokes V Zeeman signatures in their spectral lines. We use the spectropolarimeters Narval and ESPaDOnS to detect circular polarization within the photospheric absorption lines of our targets and use the least-squares deconvolution (LSD) method. We also measure the classical S-index activity indicator, and the stellar radial velocity. To infer the evolutionary status of our giants and to interpret our results, we use state-of-the-art stellar evolutionary models with predictions of convective turnover times. We unambiguously detect magnetic fields via Zeeman signatures in 29 of the 48 red giants in our sample. Zeeman signatures are found in all but one of the 24 red giants exhibiting signs of activity, as well as 6 out of 17 bright giant stars.The majority of the magnetically detected giants are either in the first dredge up phase or at the beginning of core He burning, i.e. phases when the convective turnover time is at a maximum: this corresponds to a 'magnetic strip' for red giants in the Hertzsprung-Russell diagram. A close study of the 16 giants with known rotational periods shows that the measured magnetic field strength is tightly correlated with the rotational properties, namely to the rotational period and to the Rossby number Ro. Our results show that the magnetic fields of these giants are produced by a dynamo. Four stars for which the magnetic field is measured to be outstandingly strong with respect to that expected from the rotational period/magnetic field relation or their evolutionary status are interpreted as being probable descendants of magnetic Ap stars. In addition to the weak-field giant Pollux, 4 bright giants (Aldebaran, Alphard, Arcturus, eta Psc) are detected with magnetic field strength at the sub-gauss level., Comment: 34 pages, 22 Figures, accepted for publication in Astronomy & Astrophysics

Massive stars show a variety of spectral variability: presence of discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, radial velocity modulations. Our goal is to study the spectral variability of single OB stars to better understand the relation between photospheric and wind variability. For that, we rely on high spectral resolution, high signal-to-noise ratio optical spectra collected with the spectrograph NARVAL on the Telescope Bernard Lyot at Pic du Midi. We investigate the variability of twelve spectral lines by means of the Temporal Variance Spectrum (TVS). The selected lines probe the radial structure of the atmosphere, from the photosphere to the outer wind. We also perform a spectroscopic analysis with atmosphere models to derive the stellar and wind properties, and to constrain the formation region of the selected lines. We show that variability is observed in the wind lines of all bright giants and supergiants, on a daily timescale. Lines formed in the photosphere are sometimes variable, sometimes not. The dwarf stars do not show any sign of variability. If variability is observed on a daily timescale, it can also (but not always) be observed on hourly timescales, albeit with lower amplitude. There is a very clear correlation between amplitude of the variability and fraction of the line formed in the wind. Strong anti-correlations between the different part of the temporal variance spectrum are observed. Our results indicate that variability is stronger in lines formed in the wind. A link between photospheric and wind variability is not obvious from our study, since wind variability is observed whatever the level of photospheric variability. Different photospheric lines also show different degrees of variability., Comment: 13 pages, 9 figures + appendix. A&A accepted. Figures degraded for arxiv submission

Planets are known to orbit giant stars, yet there is a shortage of planets orbiting within ~0.5 AU (P, Accepted for publication in PASP

We investigate the light-element behavior of red giant stars in Northern globular clusters (GCs) observed by the SDSS-III Apache Point Observatory Galactic Evolution Experiment (APOGEE). We derive abundances of nine elements (Fe, C, N, O, Mg, Al, Si, Ca, and Ti) for 428 red giant stars in 10 globular clusters. The intrinsic abundance range relative to measurement errors is examined, and the well-known C-N and Mg-Al anticorrelations are explored using an extreme-deconvolution code for the first time in a consistent way. We find that Mg and Al drive the population membership in most clusters, except in M107 and M71, the two most metal-rich clusters in our study, where the grouping is most sensitive to N. We also find a diversity in the abundance distributions, with some clusters exhibiting clear abundance bimodalities (for example M3 and M53) while others show extended distributions. The spread of Al abundances increases significantly as cluster average metallicity decreases as previously found by other works, which we take as evidence that low metallicity, intermediate mass AGB polluters were more common in the more metal poor clusters. The statistically significant correlation of [Al/Fe] with [Si/Fe] in M15 suggests that $^{28}$Si leakage has occurred in this cluster. We also present C, N and O abundances for stars cooler than 4500 K and examine the behavior of A(C+N+O) in each cluster as a function of temperature and [Al/Fe]. The scatter of A(C+N+O) is close to its estimated uncertainty in all clusters and independent on stellar temperature. A(C+N+O) exhibits small correlations and anticorrelations with [Al/Fe] in M3 and M13, but we cannot be certain about these relations given the size of our abundance uncertainties. Star-to-star variations of $\alpha-$elements (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters., Comment: 22 pages, 13 figures, 8 tables, accepted to AJ, fixed some typos in text

We describe a new method for robustly testing theoretical predictions of red giant evolution near the tip of the giant branch. When theoretical cumulative luminosity functions are shifted to align the tip in I-band and normalized at a luminosity level slightly brighter than the red giant bump, virtually all dependence on age and composition (heavy elements and helium abundance) is eliminated. While significant comparisons with observations require large samples of giant stars, such samples are available for some of the most massive Milky Way globular clusters. We present comparisons with the clusters NGC 2808 and M5, and find that NGC 2808 has a deficiency of bright giants (with a probability of less than about 3% that a more extreme distribution of giant stars would have happened by chance). We discuss the possibilities that underestimated neutrino losses or strong mass loss could be responsible for the deficit of giants. While we cannot rule out the neutrino hypothesis, it cannot explain the apparent agreement between the M5 observations and models. On the other hand, strong mass loss provides a potential link between the giant star observations and NGC 2808's unusually blue horizontal branch. If the mass loss hypothesis is true, there is likely a significant population of He white dwarfs that could be uncovered with slightly deeper UV observations of the cluster., 6 pages, 2 figures, uses emulateapj, accepted for ApJ Letters

We analyze the Na, Mg, Al, and Si abundances in the atmospheres of more than 40 stars, includingred giants of different spectral subgroups (normal red giants, mild and classical barium stars) and several supergiants. All these elements exhibit abundance excesses, with the overabundance increasing with the star’s luminosity. The dependence of the overabundances for each of these elements on the luminosity (or log g) is the same for all the spectral subgroups, testifying to a common origin: they are all products of hydrogen burning in the NeNa and MgAl cycles that have been dredged up from the stellar interiors to the outer atmospheric layers by convection that gradually develops during the star’s evolution from the main sequence to the red-giant stage. The sodium abundances derived for several stars are lower than for other stars with similar atmospheric parameters. The ages and kinematic characteristics of these two groups of stars suggest that they probably belong to different stellar generations.

CN and CH band strengths for fourteen bright giants in the globular cluster M71 have been measured from archival spectra obtained with the Multiple Mirror Telescope. Adding the collected. data from the literature we confirm a bimodality of CN distribution on the red giant branch and the honzontal branch, and CN-CH anti-correlations on the lower giant branch and horizontal branch. However a CN-CH anti-correlation on the upper red giant branch is not quite clear as those of other branches. The small number If statistics could not be excluded as a possible cause. To confirm this, a greater number of sample stars are needed. We also confirm that the ratio of CN-strong to CN-weak stars is quite different from that in 47 Tuc, although the anti-correlation between CN and CH bands, the bimodality of the CN distribution, and the spatial distribution of CN stars in M71 are found to be similar to those III 47 Tuc.

Carbon and nitrogen abundances have been derived for red giants in the globular clusters M13, M10, and NGC 7006. These constitute a "second-parameter" trio of clusters having very similar metallicities ([Fe/H] ≈ -1.55) but different horizontal-branch (HB) morphologies, with NGC 7006 having a much higher fraction of red HB stars than either M13 or M10. The red giants observed have absolute magnitudes in the range -2.5 < MV < 0.7 in the case of M13, -1.8 < MV < 0.4 for M10, and -2.1 < MV < -1.2 for the more distant NGC 7006. Most of the spectra were obtained with the Lick Observatory 3 m Shane reflector, supplemented by observations of M10 with the McDonald Observatory 2.7 m telescope. These data were reduced in a homogeneous manner and compared with synthetic spectra computed from model atmospheres in order to derive [C/Fe] abundances from the λ4300 G band and [N/Fe] abundances from the λ3883 CN band. The giants in all three clusters appear to exhibit a common relationship between [C/Fe] and MV in which the carbon abundance becomes increasingly diminished with increasing luminosity on the giant branch. Such behavior was previously discovered for M13 by Suntzeff and is known to occur in other low-metallicity globular clusters, such as M3, M92, and M15, as well as among halo field red giants. The phenomenon is widely recognized as indicating a progressive dredge-up of CNO-processed material from regions close to the H-burning shell within Population II giants. The similarities between the [C/Fe]-MV trends in the three second-parameter clusters indicates that the deep-mixing mechanism is relatively uncorrelated with cluster HB type. This result may be inconsistent with scenarios that rely on rotation to both drive deep mixing within metal-poor red giants and to set the eventual zero-age HB position of these stars, unless there is a threshold for rotation-induced mixing that is well below that needed to delay the He-flash. The nitrogen abundance is found to differ by as much as 1.0 dex between giants in the program clusters and to be anticorrelated with the carbon abundance. It is speculated that the behavior of [N/Fe] with respect to MV can be interpreted as a combination of deep mixing and primordial contributions.

We present the results of a search for near-IR chromospheric He i absorption in 10 metal-poor red giants using high-resolution spectra obtained with NIRSPEC on Keck II. Four of these red giants are in the field, and six are in the globular cluster M13. Two of the field stars and one of the cluster stars show evidence for He i absorption that is consistent with chromospheric outflow velocities ranging from 30 to 140 km s–1. If identified with a wind, the velocity found in the M13 red giant IV-15 (30 km s–1) is comparable to the escape velocity of the cluster core, suggesting that such winds may be effective in clearing out the interstellar medium of globular clusters. Absorption is confined to stars with Teff 4600 K and MV fainter than –1.5. Since previous studies have found Hα and Ca ii K2 emission line profiles indicative of winds in metal-poor giants brighter than this limit, the mechanism responsible for He i absorption in metal-poor red giants apparently operates less effectively in the cooler and brighter stars. On the other hand, the He i line extends the detection of mass outflows further down the giant branch of metal-poor stars than the Hα observations.

Rotation is one of the most important observable in stellar astrophysics driving strongly the evolution of stars. This review presents the main observational results on the rotation of Red Giant and Horizontal-Branch stars carried out along the past 50 years. The review brings, in particular, the most recent results based on very accurate measurements of rotational velocity obtained mostly along the last decade.

The behavior of carbon abundance as a function of luminosity is used to compare the rates of deep mixing within red giants of four globular clusters and the Galactic halo field population. Measurements of [C/Fe] for the clusters M92, NGC 6397, M3, and M13 have been compiled from the literature, together with the Gratton et al. data for halo field stars. Plots of [C/Fe] versus absolute visual magnitude show that for MV < +1.6 the rate of decline of carbon abundance with increasing luminosity on the red giant branch is d[C/Fe]/dMV ≈ 0.22 ± 0.03 among the field stars, as well as in M92, NGC 6397, and M3. Among giants fainter than MV = +1.6 the variation of [C/Fe] with absolute magnitude is much less. The data indicate that the rate at which deep mixing introduces carbon-depleted material into the convective envelopes of field halo stars during the upper red giant branch phase of evolution is similar to that of many globular cluster giants. The notable exception appears to be M13, in which stars exhibit deep mixing at a greater rate; this may account for the high incidence of very low oxygen abundances among the most luminous giants in M13 in comparison to M3.

We reduce the published measurements of the equivalent width of the oxygen triplet (Oiλ7774Å) to a single system and combine the resulting homogenized indices with revised Hipparcos parallaxes to derive the MK versus log[W(Oiλ7774Å)] absolute-magnitude calibration for bright F-type giants and supergiants and use the resulting calibration to estimate both the distance to the Large Magellanic Cloud and the parameters of the Galactic rotation curve.

Measurements of the l3883 CN band absorption strength in spectra of red giant members of the globular cluster M3 have been compiled from several sources in the literature, including the pioneering survey of N. B. Suntzeff, and transformed onto a common system. The homogenized indices give a picture of the behavior of the CN band strength over a range in stellar magnitude of ∼3.6 mag, from the tip of the red giant branch (RGB) to . As with other well-studied globular clusters, the red giant branch stars of M3 exhibit M ∼ 1.0 V a bimodal distribution of CN band strengths that extends to the limit of the available survey. The asymptotic giant branch stars also show evidence of an intrinsic spread in CN content. Anticorrelations exist between the CN band strength and both carbon and oxygen abundances, suggesting that the high nitrogen abundances of the CN-strong giants have derived from a conversion of C and/or O into nitrogen, either within the cluster stars themselves or in some primordial site. Among both CN-strong and CN-weak stars, the (C/Fe) abundance decreases with increasing luminosity on the RGB. Stellar atmosphere models indicate that in the magnitude range , the C # N abundance product is roughly constant among the CN-weak giants, while it decreases 1.5 ! M ! 0 V toward the upper RGB among CN-strong stars. This decrease in the product of C # N may indicate that carbon- to-nitrogen conversion plus deep mixing is occurring within the CN-strong giants to a greater degree than in the CN-weak giants. These results, when interpreted with additional constraints from the giant branch luminosity function of M3, suggest that the C and N abundance pattern requires a hybrid scenario involving interior mixing within red giants as well as primordial abundance inhomogeneities that precede the RGB phase of evolution.

The luminosity function (LF) of nearly 300 Galactic carbon giants is derived. Adding BaII giants and various related objects, about 370 objects are located in the RGB and AGB portions of the theoretical HR diagram. As intermediate steps, (1) bolometric corrections are calibrated against selected intrinsic color indices; (2) the diagram of photometric coecients hki 1=2 vs. astrometric true parallaxes$ are interpreted in terms of ranges of photospheric radii for every photometric group; (3) coecients CR and CL for bias-free evaluation of mean photospheric radii and mean luminosities are computed. The LF of Galactic carbon giants exhibits two maxima corresponding to the HC-stars of the thick disk and to the CV-stars of the old thin disk respectively. It is discussed and compared to those of carbon stars in the Magellanic Clouds and Galactic bulge. The HC-part is similar to the LF of the Galactic bulge, reinforcing the idea that the Bulge and the thick disk are part of the same dynamical component. The CV-part looks similar to the LF of the Large Magellanic Cloud (LMC), but the former is wider due to the substantial errors on HIPPARCOS parallaxes. The obtained mean luminosities increase with increasing radii and decreasing eective temperatures, along the HC-CV se- quence of photometric groups, except for HC0, the earliest one. This trend illustrates the RGB- and AGB-tracks of low- and intermediate-mass stars for a range in metallicities. From a comparison with theoretical tracks in the HR diagram, the initial masses Mi range from about 0.8 to 4:0 M for carbon giants, with possibly larger masses for a few extreme objects. A large range of metallicities is likely, from metal-poor HC-stars classified as CH stars on the grounds of their spectra (a spheroidal component), to near-solar compositions of many CV-stars. Technetium-rich carbon giants are brighter than the lower limit Mbol' 3:6 0:4 and centered athMboli' 4:7 +0:6

48 supergiants and bright giants have been observed in order to investigate the sodium enrichment of their atmospheres and its connection with stellar gravity. We present the equivalent widths of the 6154 A and 6160 ANaI lines measured from the program spectra, the results of effective temperature determinations, the NLTE sodium abundances, and the derived relation between the sodium overabundance and surface gravity.

Bright stars, stars with visual magnitude smaller than 6.5, can be studied using small telescope. In general, if stars are assumed as black body radiator, then the color in infrared (IR) region is usually equal to zero. Infrared data from IRAS observations at 12 and 25μm (micron) with good flux quality are used to search for bright stars (from Bright Stars Catalogues) with infrared excess. In magnitude scale, stars with IR excess is defined as stars with IR color m12−m25>0; where m12−m25 = −2.5log(F12/F25)+1.56, where F12 and F25 are flux density in Jansky at 12 and 25μm, respectively. Stars with similar spectral type are expected to have similar color. The existence of infrared excess in the same spectral type indicates the existence of circum-stellar dust, the origin of which is probably due to the remnant of pre main-sequence evolution during star formation or post AGB evolution or due to physical process such as the rotation of those stars.

With the exception of Terzan 5, all the Galactic globular clusters that possess significant metallicity spreads, such as omega Cen and M22, are preferentially the more luminous clusters with extended horizontal branches. Here we present radial velocities and chemical abundances for seven bright giants in the globular cluster M62, a previously little-studied cluster. With M_V = -9.18, M62 is the ninth most luminous Galactic globular cluster and has an extended horizontal branch. Within our sample, we find (i) no evidence for a dispersion in metallicity, [Fe/H], beyond the measurement uncertainties, (ii) star-to-star abundance variations for C, O, Na and Al with the usual correlations between these elements as seen in other globular clusters, and (iii) a global enrichment for the elements Zr, Ba and La at the level [X/Fe] = +0.4 dex. For elements heavier than La, the abundance ratios are consistent with the scaled-solar $r$-process distribution. Below La, the abundances are anomalous when compared to the scaled-solar s-process or r-process distributions. For these elements, the abundance signature in M62 is in agreement with predictions of the s-process from fast-rotating massive stars, although the high [Rb/Y] ratio we measure may be a challenge to this scenario., Comment: Accepted for publication in MNRAS

Based on our prior accurate determination of fundamental parameters for 36 Galactic A-, F- and G-type supergiants and bright giants (luminosity classes I and II), we undertook a non-LTE analysis of the carbon abundance in their atmospheres. It is shown that the non-LTE corrections to the C abundances derived from C I lines are negative and increase with the effective temperature Teff; the corrections are especially significant for the infrared C I lines with wavelengths 9060-9660 \AA. The carbon underabundance as a general property of the stars in question is confirmed; a majority of the stars studied has the carbon deficiency [C/Fe] between -0.1 and -0.5 dex, with a minimum at -0.7 dex. When comparing the derived C deficiency with the N excess found by us for the same stars earlier, we obtain a pronounced N vs. C anti-correlation, which could be expected from predictions of the theory.We found that the ratio [N/C] spans mostly the range from 0.3 to 1.7 dex. Both these enhanced [N/C] values and the C and N anomalies themselves are an obvious evidence of the presence on a star's surface of mixed material from stellar interiors; so, a majority of programme stars passed through the deep mixing during the main sequence (MS) and/or the first dredge-up (FD) phase. Comparison with theoretical predictions including rotationally-induced mixing shows that the stars are either post-MS objects with the initial rotational velocities V0 = 200-300 km/s or post-FD objects with V0 = 0-300 km/s. The observed N vs. C anti-correlation reflects a dependence of the C and N anomalies on the V0 value: on average the higher V0 the greater the anomalies. It is shown that an absence of detectable lithium in the atmospheres of the stars, which is accompanied with the observed N excess and C deficiency, is quite explainable., Comment: 15 pages, 13 figures, 3 tables

Paper I of this series presented precise MK spectral types for 372 late A-, F-, and early G-type stars with the aim of understanding the nature of luminosity classification on the MK spectral classification system for this range of spectral types. In this paper, a multidimensional downhill simplex technique is introduced to determine the basic parameters of the program stars from fits of synthetic spectra and fluxes with observed spectra and fluxes from Stromgren uvby photometry. This exercise yields useful calibrations of the MK spectral classification system but, most importantly, gives insight into the physical nature of luminosity classification on the MK spectral classification system. In particular, we find that in this range of spectral types, microturbulence appears to be at least as important as gravity in determining the MK luminosity type.

The size of a telescope determines goals and objects of observations. During the latest decades it becomes more and more difficult to get photometric data of bright stars because most of telescopes of small sizes do not operate already. But there are rather interesting questions connected to the properties and evolution ties between different types of massive stars. Multi-wavelength photometric data are needed for solution of some of them. We are presenting our observational plans of bright Massive X-ray binaries, WR and LBV stars using a small size telescope. All these stars, which are presented in the poster are observational targets of Sopia Beradze’s future PhD thesis. We already have got very interesting results on the reddening and possible future eruption of the massive hypergiant star P Cygni. Therefore, we decided to choose some additional interesting massive stars of different type for future observations. All Massive stars play an important role in the chemical evolution of galaxies because of they have very high mass loss - up to 10−4M⊙/a year. Our targets are on different evolutionary stages and three of them are the members of massive binaries. We plan to do UBVRI photometric observations of these stars using the 48 cm Cassegrain telescope of the Abastumani Astrophisical Observatory.

The results of a spectral classification of 257 M stars observed in the Cepheus region are given. Their equatorial coordinates, photographic stellar magnitudes, and spectral subtypes were determined. These stars are giants and supergiants, in all probability. None of them appear in a catalog of variable stars. It is assumed that variability might be detected in many of them upon further study. Fifty-two of the stars have been identified with infrared sources.