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See detailGRB 070920A: deep optical observations at the NOT.
Jaunsen, A. O.; Gorosabel, J.; Fynbo, J. P. U. et al

in GRB Coordinates Network (2007), 6921

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See detailAbundance analysis of prime B-type targets for asteroseismology. I. Nitrogen excess in slowly-rotating beta Cephei stars
Morel, Thierry ULg; Butler, K.; Aerts, C. et al

in Astronomy and Astrophysics (2006), 457

Seismic modelling of the β Cephei stars promises major advances in our understanding of the physics of early B-type stars on (or close to) the main sequence. However, a precise knowledge of their ... [more ▼]

Seismic modelling of the β Cephei stars promises major advances in our understanding of the physics of early B-type stars on (or close to) the main sequence. However, a precise knowledge of their physical parameters and metallicity is a prerequisite for correct mode identification and inferences regarding their internal structure. Here we present the results of a detailed NLTE abundance study of nine prime targets for theoretical modelling: <ASTROBJ>γ Peg</ASTROBJ>, <ASTROBJ>δ Cet</ASTROBJ>, <ASTROBJ>ν Eri</ASTROBJ>, <ASTROBJ>β CMa</ASTROBJ>, <ASTROBJ>ξ1 CMa</ASTROBJ>, <ASTROBJ>V836 Cen</ASTROBJ>, <ASTROBJ>V2052 Oph</ASTROBJ>, <ASTROBJ>β Cep</ASTROBJ> and DD (12) Lac (hereafter <ASTROBJ>12 Lac</ASTROBJ>). The following chemical elements are considered: He, C, N, O, Mg, Al, Si, S and Fe. Our curve-of-growth abundance analysis is based on a large number of time-resolved, high-resolution optical spectra covering in most cases the entire oscillation cycle of the stars. Nitrogen is found to be enhanced by up to 0.6 dex in four stars, three of which have severe constraints on their equatorial rotational velocity, Ω R, from seismic or line-profile variation studies: <ASTROBJ>β Cep</ASTROBJ> (Ω R ~ 26 km s[SUP]-1[/SUP]), <ASTROBJ>V2052 Oph</ASTROBJ> (Ω R ~ 56 km s[SUP]-1[/SUP]), <ASTROBJ>δ Cet</ASTROBJ> (Ω R < 28 km s[SUP]-1[/SUP]) and <ASTROBJ>ξ1 CMa</ASTROBJ> (Ω R sin i ⪠10 km s[SUP]-1[/SUP]). The existence of core-processed material at the surface of such largely unevolved, slowly-rotating objects is not predicted by current evolutionary models including rotation. We draw attention to the fact that three stars in this subsample have a detected magnetic field and briefly discuss recent theoretical work pointing to the occurrence of diffusion effects in β Cephei stars possibly capable of altering the nitrogen surface abundance. On the other hand, the abundances of all the other chemical elements considered are, within the errors, indistinguishable from the values found for OB dwarfs in the solar neighbourhood. Despite the mild nitrogen excess observed in some objects, we thus find no evidence for a significantly higher photospheric metal content in the studied β Cephei stars compared to non-pulsating B-type stars of similar characteristics. [less ▲]

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See detailPhotospheric Abundance Peculiarities in RS CVn Binaries
Morel, Thierry ULg; Micela, Giuseppina; Favata, Fabio

in Astrophysics & Space Science (2006), 304

We discuss the results of a LTE abundance study of 14 single-lined RS CVn binaries. Increasingly peculiar abundance ratios are observed for the cooler and more active stars in this sample (this is best ... [more ▼]

We discuss the results of a LTE abundance study of 14 single-lined RS CVn binaries. Increasingly peculiar abundance ratios are observed for the cooler and more active stars in this sample (this is best illustrated in the case of oxygen). This may arise from the existence of large spot groups, departures from LTE much larger than anticipated and/or inadequacies in the Kurucz model atmospheres for these objects. [less ▲]

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See detailX1908+075: A Late O-Type Supergiant with a Neutron Star Companion
Morel, Thierry ULg; Grosdidier, Yves

in Astrophysics & Space Science (2006), 304

X1908 + 075 is a highly-absorbed Galactic X-ray source likely made up of a pulsar accreting wind material from a massive companion. We have used near-IR photometric data complemented by follow-up ... [more ▼]

X1908 + 075 is a highly-absorbed Galactic X-ray source likely made up of a pulsar accreting wind material from a massive companion. We have used near-IR photometric data complemented by follow-up spectroscopy to identify the likely counterpart to this X-ray source and to assign a spectral type O7.5 9.5 If to the primary. Further details can be found in Morel and Grosdidier (2005). [less ▲]

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See detailA Comparison of Methods for Photospheric Abundance Determinations in K-Type Stars
Affer, L.; Micela, G.; Morel, Thierry ULg et al

in Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites, ESO ASTROPHYSICS SYMPOSIA. ISBN 978-3-540-34135-2. Springer-Verlag, 2006, p. 31 (2006)

We have performed a detailed abundance analysis of six inactive K-type stars using high-resolution optical spectra. We have used three different techniques and compared the results obtained in order to ... [more ▼]

We have performed a detailed abundance analysis of six inactive K-type stars using high-resolution optical spectra. We have used three different techniques and compared the results obtained in order to establish their respective merits and faults. The two spectroscopic methods give consistent results suggesting that non- LTE effects are small, whereas the â mixedâ spectroscopic-photometric method leads to photospheric parameters and abundances systematically lower than those obtained with the other two. We have also determined the starsâ positions in H-R diagrams and made a comparison between the gravities derived from the ionization equilibrium of the iron lines and from the evolutionary tracks: the agreement is reasonably good. [less ▲]

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See detailSome Concerns About the Reliability of LTE Abundance Analyses in Cool, Active Stars
Morel, Thierry ULg; Micela, G.; Favata, F.

in Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites, ESO ASTROPHYSICS SYMPOSIA. ISBN 978-3-540-34135-2. Springer-Verlag, 2006, p. 64 (2006)

We discuss recent observational evidence illustrating the current limitations plaguing classical LTE abundance analyses of cool (T [SUB]eff[/SUB] < 5500 K), chromospherically active stars. Although ... [more ▼]

We discuss recent observational evidence illustrating the current limitations plaguing classical LTE abundance analyses of cool (T [SUB]eff[/SUB] < 5500 K), chromospherically active stars. Although significant progress on this issue can be evidently expected from a more realistic atmospheric modelling and treatment of NLTE line formation, a homogeneous abundance study of a large sample of inactive K-type stars may also prove valuable in disentangling temperature and activity effects. [less ▲]

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See detailSpectroscopic determination of photospheric parameters and chemical abundances of 6 K-type stars
Affer, L.; Micela, G.; Morel, Thierry ULg et al

in Astronomy and Astrophysics (2005), 433

High resolution, high -S/N- ratio optical spectra have been obtained for a sample of 6 K-type dwarf and subgiant stars, and have been analysed with three different LTE methods in order to derive detailed ... [more ▼]

High resolution, high -S/N- ratio optical spectra have been obtained for a sample of 6 K-type dwarf and subgiant stars, and have been analysed with three different LTE methods in order to derive detailed photospheric parameters and abundances and to compare the characteristics of analysis techniques. The results have been compared with the aim of determining the most robust method to perform complete spectroscopic analyses of K-type stars, and in this perspective the present work must be considered as a pilot study. In this context we have determined the abundance ratios with respect to iron of several elements. In the first method the photospheric parameters (T_eff, log g, and ξ) and metal abundances are derived using measured equivalent widths and Kurucz LTE model atmospheres as input for the MOOG software code. The analysis proceeds in an iterative way, and relies on the excitation equilibrium of the ion{Fe}{i} lines for determining the effective temperature and microturbulence, and on the ionization equilibrium of the ion{Fe}{i} and ion{Fe}{ii} lines for determining the surface gravity and the metallicity. The second method follows a similar approach, but discards the ion{Fe}{i} low excitation potential transitions (which are potentially affected by non-LTE effects) from the initial line list, and relies on the B-V colour index to determine the temperature. The third method relies on the detailed fitting of the 6162 à ion{Ca}{i} line to derive the surface gravity, using the same restricted line list as the second method. Methods 1 and 3 give consistent results for the program stars; in particular the comparison between the results obtained shows that the ion{Fe}{i} low-excitation potential transitions do not appear significantly affected by non-LTE effects (at least for the subgiant stars), as suggested by the good agreement of the atmospheric parameters and chemical abundances derived. The second method leads to systematically lower T_eff and log g values with respect to the first one, and a similar trend is shown by the chemical abundances (with the exception of the oxygen abundance). These differences, apart from residual non-LTE effects, may be a consequence of the colour-T_eff scale used. The α-elements have abundance ratios consistent with the solar values for all the program stars, as expected for â normalâ disk stars. The first method appears to be the most reliable one, as it is self-consistent, it always leads to convergent solutions and the results obtained are in good agreement with previous determinations in the literature. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roche de los Muchachos of the Instituto de Astrofisica de Canarias. Table 6 is only available in electronic form at http://www.edpsciences.org [less ▲]

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See detailPhotospheric abundance peculiarities in chromospherically active stars
Morel, Thierry ULg; Micela, G.; Favata, F.

in 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun (2005, March 01)

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See detailNear-infrared identification of the counterpart to X1908+075: a new OB-supergiant X-ray binary
Morel, Thierry ULg; Grosdidier, Y.

in Monthly Notices of the Royal Astronomical Society (2005), 356

We report the near-infrared (near-IR) identification of the likely counterpart to X1908+075, a highly absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron ... [more ▼]

We report the near-infrared (near-IR) identification of the likely counterpart to X1908+075, a highly absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron star binary systems. Our JHK[SUB]s[/SUB]-band imaging of the field reveals the existence within the X-ray error boxes of a near-IR source consistent with an early-type star lying at d~ 7 kpc and suffering A[SUB]V[/SUB]~ 16 mag of extinction, the latter value being in good agreement with the hydrogen column density derived from modelling of the X-ray spectrum. Our follow-up, near-IR spectroscopic observations confirm the nature of this candidate and lead to a late O-type supergiant classification, thereby supporting the identification of a new Galactic OB-supergiant X-ray binary. [less ▲]

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See detailThe photospheric abundances of active binaries. III. Abundance peculiarities at high activity levels
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Astronomy and Astrophysics (2004), 426

We report the determination from high-resolution spectra of the atmospheric parameters and abundances of 13 chemical species (among which lithium) in 8 single-lined active binaries. These data are ... [more ▼]

We report the determination from high-resolution spectra of the atmospheric parameters and abundances of 13 chemical species (among which lithium) in 8 single-lined active binaries. These data are combined with our previous results for 6 other RS CVn systems to examine a possible relationship between the photospheric abundance patterns and the stellar activity level. The stars analyzed are generally found to exhibit peculiar abundance ratios compared to inactive, Galactic disk stars of similar metallicities. We argue that this behaviour is unlikely to be an artefact of errors in the determination of the atmospheric parameters or non-standard mixing processes along the red giant branch, but diagnoses instead the combined action of various physical processes related to activity. The most promising candidates are cool spot groups covering a very substantial fraction of the stellar photosphere or NLTE effects arising from nonthermal excitation. However, we cannot exclude the possibility that more general shortcomings in our understanding of K-type stars (e.g. inadequacies in the atmospheric models) also play a significant role. Lastly, we call attention to the unreliability of the (V-R) and (V-I) colour indices as temperature indicators in chromospherically active stars. Based on observations collected at the European Southern Observatory, Chile (Proposals 64.L-0249 and 071.D-0260). Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/1007 [less ▲]

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See detailThe European Large Area ISO Survey - VIII. 90-microns final analysis and source counts
Heraudeau, P.; Oliver, S.; del Burgo, C. et al

in Monthly Notices of the Royal Astronomical Society (2004), 354

We present a re-analysis of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) 90-μm observations carried out with ISOPHOT, an instrument on board the ISO of the European Space ... [more ▼]

We present a re-analysis of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) 90-μm observations carried out with ISOPHOT, an instrument on board the ISO of the European Space Agency. With more than 12 deg[SUP]2[/SUP], the ELAIS survey is the largest area covered by ISO in a single programme and is about one order of magnitude deeper than the IRAS 100-μm survey. The data analysis is presented and was mainly performed with the PHOT interactive analysis software but using the pairwise method of Stickel et al. for signal processing from edited raw data to signal per chopper plateau. The ELAIS 90-μm catalogue contains 237 reliable sources with fluxes larger than 70 mJy and is available in the electronic version of this article. Number counts are presented and show an excess above the no-evolution model prediction. This confirms the strong evolution detected at shorter (15 μm) and longer (170 μm) wavelengths in other ISO surveys. The ELAIS counts are in agreement with previous works at 90 μm and in particular with the deeper counts extracted from the Lockman hole observations. Comparison with recent evolutionary models show that the models of Franceschini et al. and Guiderdoni et al. (which includes a heavily extinguished population of galaxies) give the best fit to the data. Deeper observations are nevertheless required to discriminate better between the model predictions in the far-infrared, and are scheduled with the Spitzer Space Telescope, which has already started operating, and will also be performed by ASTRO-F. [less ▲]

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See detailHydrogen in the atmosphere of the evolved WN3 Wolf-Rayet star WR 3: defying an evolutionary paradigm?
Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A. et al

in Monthly Notices of the Royal Astronomical Society (2004), 353(1), 153-161

WR 3 is the brightest very early-type WN star in the sky. Based on several years of time-resolved spectroscopy and precision photometry on various time-scales, we deduce that WR 3 is most likely a single ... [more ▼]

WR 3 is the brightest very early-type WN star in the sky. Based on several years of time-resolved spectroscopy and precision photometry on various time-scales, we deduce that WR 3 is most likely a single, weak-lined star of type WN3ha (contrary to its current catalogue-type of WN3 + O4), with H lines occurring both in emission and absorption in its wind. This conclusion is confirmed and strengthened via detailed modelling of the spectrum of WR 3. Given the similarity of WR 3 with numerous H-rich WNE stars in the Large Magellanic Cloud and especially the Small Magellanic Cloud, and its location towards the metal-deficient exterior of the Galaxy, we conclude that rotationally induced meridional circulation probably led to the apparently unusual formation of this hot Galactic WN star with enhanced hydrogen. Although we cannot completely rule out the possibility of a binary with a low orbital inclination and/or long period, we regard this latter possibility as highly unlikely. [less ▲]

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See detailOn the determination of oxygen abundances in chromospherically active stars
Morel, Thierry ULg; Micela, G.

in Astronomy and Astrophysics (2004), 423

We discuss oxygen abundances derived from [O I] λ6300s and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant ... [more ▼]

We discuss oxygen abundances derived from [O I] λ6300s and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant results with higher chromospheric/coronal activity measures. While the forbidden and permitted lines give fairly consistent results for solar-type disk dwarfs, spuriously high O I triplet abundances are observed in young Hyades and Pleiades stars, as well as in individual components of RS CVn binaries (up to 1.8 dex). The distinct behaviour of the [O I]-based abundances which consistently remain near-solar suggests that this phenomenon mostly results from large departures from LTE affecting the O I triplet at high activity level that are currently unaccounted for, but also possibly from a failure to adequately model the atmospheres of K-type stars. These results suggest that some caution should be exercised when interpreting oxygen abundances in active binaries or young open cluster stars. Based on observations collected at the European Southern Observatory, Chile (Proposals 64.L-0249 and 071.D-0260). Table \ref{tab_data} is only available in electronic form at http://www.edpsciences.org [less ▲]

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See detailThe European Large-Area ISO Survey (ELAIS): the final band-merged catalogue
Rowan-Robinson, M.; Lari, C.; Perez-Fournon, I. et al

in Monthly Notices of the Royal Astronomical Society (2004), 351

We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g', r', i', Z, J, H, K and 20 cm. The origin of the survey ... [more ▼]

We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g', r', i', Z, J, H, K and 20 cm. The origin of the survey, infrared and radio observations, data-reduction and optical identifications are briefly reviewed, and a summary of the area covered and the completeness limit for each infrared band is given. A detailed discussion of the band-merging and optical association strategy is given. The total Catalogue consists of 3762 sources. 23 per cent of the 15-μm sources and 75 per cent of the 6.7-μm sources are stars. For extragalactic sources observed in three or more infrared bands, colour-colour diagrams are presented and discussed in terms of the contributing infrared populations. Spectral energy distributions (SEDs) are shown for selected sources and compared with cirrus, M82 and Arp220 starburst, and active galactic nuclei (AGN) dust torus models. Spectroscopic redshifts are tabulated, where available. For the N1 and N2 areas, the Isaac Newton Telescope ugriz Wide Field Survey permits photometric redshifts to be estimated for galaxies and quasars. These agree well with the spectroscopic redshifts, within the uncertainty of the photometric method [~10 per cent in (1 +z) for galaxies]. The redshift distribution is given for selected ELAIS bands and colour-redshift diagrams are discussed. There is a high proportion of ultraluminous infrared galaxies (log[SUB]10[/SUB] of 1-1000 μm luminosity L[SUB]ir[/SUB] > 12.22) in the ELAIS Catalogue (14 per cent of 15-μm galaxies with known z), many with Arp220-like SEDs. 10 per cent of the 15-μm sources are genuine optically blank fields to r'= 24: these must have very high infrared-to-optical ratios and probably have z > 0.6, so are high-luminosity dusty starbursts or Type 2 AGN. Nine hyperluminous infrared galaxies (L[SUB]ir[/SUB] > 13.22) and nine extremely red objects (EROs) (r-K > 6) are found in the survey. The latter are interpreted as ultraluminous dusty infrared galaxies at z~ 1. The large numbers of ultraluminous galaxies imply very strong evolution in the star formation rate between z= 0 and 1. There is also a surprisingly large population of luminous (L[SUB]ir[/SUB] > 11.5), cool (cirrus-type SEDs) galaxies, with L[SUB]ir[/SUB]-L[SUB]opt[/SUB] > 0, implying A[SUB]V[/SUB] > 1. [less ▲]

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See detailLarge-scale wind structures in OB supergiants: a search for rotationally modulated Halpha variability
Morel, Thierry ULg; Marchenko, S. V.; Pati, A. K. et al

in Monthly Notices of the Royal Astronomical Society (2004), 351

We present the results of a long-term monitoring campaign of the Hα line in a sample of bright OB supergiants (O7.5-B9) which aims at detecting rotationally modulated changes potentially related to the ... [more ▼]

We present the results of a long-term monitoring campaign of the Hα line in a sample of bright OB supergiants (O7.5-B9) which aims at detecting rotationally modulated changes potentially related to the existence of large-scale wind structures. A total of 22 objects were monitored during 36 nights spread over six months in 2001-2002. Coordinated broad-band photometric observations were also obtained for some targets. Conspicuous evidence for variability in Hα is found for the stars displaying a feature contaminated by wind emission. Most changes take place on a daily time-scale, although hourly variations are also occasionally detected. Convincing evidence for a cyclical pattern of variability in Hα has been found in two stars: HD 14134 and HD 42087. Periodic signals are also detected in other stars, but independent confirmation is required. Rotational modulation is suggested from the similarity between the observed recurrence time-scales (in the range 13-25 d) and estimated periods of stellar rotation. We call attention to the atypical case of HD 14134, which exhibits a clear 12.8-d periodicity, both in the photometric and in the spectroscopic data sets. This places this object among a handful of early-type stars where one may observe a clear link between extended wind structures and photospheric disturbances. Further modelling may test the hypothesis that azimuthally-extended wind streams are responsible for the patterns of spectral variability in our target stars. [less ▲]

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See detailA Search for Rotationally Modulated Halpha Variability in OB Supergiants
Morel, Thierry ULg; Marchenko, S. V.; Pati, A. K. et al

in Stellar Rotation (2004, June 01)

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See detailThe near-IR counterpart to the high-mass X-ray binary X1908+075
Morel, Thierry ULg; Grosdidier, Y.

in The Astronomer's Telegram (2004), 291

<html> We report the near-IR identification of the likely counterpart to X1908+075, a highly-absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron star ... [more ▼]

<html> We report the near-IR identification of the likely counterpart to X1908+075, a highly-absorbed Galactic X-ray source recently suspected to belong to the rare class of OB supergiant-neutron star binary systems (Wen et al. 2000, ApJ, 532, 1119; Levine et al. 2004, ApJ, submitted, astro-ph/0404428). The <em>Einstein</em> and <em>HEAO 1</em> satellites have localized this X-ray source with an uncertainty of about 50''. [less ▲]

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See detailThe Photospheric Abundances of Active Binaries: First Results
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Stars as Suns : Activity, Evolution and Planets (2004, January 01)

The coronal abundances of chromospherically active binaries have come under close scrutiny in recent years thanks to several X-ray satellites such as XMM or Chandra. Unfortunately a detailed analysis of ... [more ▼]

The coronal abundances of chromospherically active binaries have come under close scrutiny in recent years thanks to several X-ray satellites such as XMM or Chandra. Unfortunately a detailed analysis of the chemical fractionation processes that are possibly operating between the photosphere and the corona is plagued by the lack of reliable and accurate photospheric abundance determinations. In particular a detailed investigation of the photospheric metal content seems worthwhile in the light of several studies that have questioned the customary use of photometric indices as effective temperature indicators in active binaries. We shall present our ongoing effort to determine in a self-consistent way accurate physical parameters and photospheric abundances for a large number of systems and discuss the implications of our results on their abundance patterns and evolutionary status. Preliminary results suggest that these systems are not as iron-deficient as found in previous studies and indicate an overabundance of several key elements (e.g. Na Mg Al Ca) with respect to the solar pattern. [less ▲]

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See detailThe photospheric abundances of active binaries. II. Atmospheric parameters and abundance patterns for 6 single-lined RS CVn systems
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Astronomy and Astrophysics (2003), 412

Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been ... [more ▼]

Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca. Two methods have been used. The effective temperatures, surface gravities and microturbulent velocities were first derived from a fully self-consistent analysis of the spectra, whereby the temperature is determined from the excitation equilibrium of the Fe I lines. The second approach relies on temperatures derived from the (B-V) colour index. These two methods give broadly consistent results for the stars in our sample, suggesting that the neutral iron lines are formed under conditions close to LTE. We discuss the reliability in the context of chromospherically active stars of various colour indices used as temperature indicators, and conclude that the (V-R) and (V-I) colours are likely to be significantly affected by activity processes. Irrespective of the method used, our results indicate that the X-ray active binaries studied are not as metal poor as previously claimed, but are at most mildly iron-depleted relative to the Sun (-0.41protect <~ [Fe/H]protect la +0.11). A significant overabundance of several chemical species is observed (e.g., the alpha -synthezised elements). These abundance patterns are discussed in relation to stellar activity. Based on observations collected at ESO (La Silla, Chile). Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/495 [less ▲]

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See detailLarge-Scale Structures in OB Supergiants: from an Inhomogeneous Surface to a Structured Wind
Morel, Thierry ULg; Marchenko, S. V.; Pati, A. K. et al

in Bulletin of the American Astronomical Society (2003, May 01)

In 2000-2001 we performed long-term spectroscopic monitoring of a sample of bright OB-supergiants aimed at establishing the incidence of co-rotating, large-scale wind structures. In the optical, this can ... [more ▼]

In 2000-2001 we performed long-term spectroscopic monitoring of a sample of bright OB-supergiants aimed at establishing the incidence of co-rotating, large-scale wind structures. In the optical, this can be achieved by detecting rotationally modulated variability in Hα . Practically all the surveyed stars show dramatic line-profile variations operating on a daily (and in some cases on a hourly) timescale. Here we discuss the case of HD 14134 (B3 Ia) where a periodic modulation seen in the optical continuum (stellar surface, P=12.825d) triggers spectacular variations in the Hα emission line (stellar wind). [less ▲]

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