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ABSTRACT: We present a spectroscopic and photometric analysis of the multiple system
and early-type eclipsing binary SZ Cam (O9IV + B0.5V), which consists of an
eclipsing SB2 pair of orbital period P=2.7 days in a long orbit (about 55 yrs)
around a non-eclipsing SB1 pair of orbital period P=2.8 days. We have
reconstructed the spectra of the individual components of SZ Cam from the
observed composite spectra using the technique of spectral disentangling. We
used them together with extensive and accurate BVI CCD photometry to obtain an
orbital solution. Our photometry revealed the presence of a beta Cep variable
in the SZ Cam hierarchical system, probably located within the non-eclipsing
SB1 pair. The pulsation period is 0.33265+/-0.00005 days and the observed total
amplitude in the B band is 0.0105 +/- 0.0005 mag. NLTE analysis of the
disentangled spectra provided atmospheric parameters for all three components,
consistent with those derived from orbital solution.
02/2012;
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[show abstract]
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ABSTRACT: We present an Echelle+CCD, high S/N, high resolution (R = 20\,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectro-photometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve the planning for and training of automated classification algorithms designed for RAVE, Gaia, HERMES and other large scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas. Comment: AJ in press (issue 140:6 December 2010)
09/2010;
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U. Munari, L. Tomasella,
M. Fiorucci,
O. Bienayme,
J. Binney,
J. Bland-Hawthorn,
C. Boeche R. Campbell,
K. C. Freeman,
B. Gibson,
G. Gilmore, [......],
J. F. Navarro,
Q. A. Parker,
G. M. Seabroke,
A. Siebert,
A. Siviero,
M. Steinmetz,
F. G. Watson,
M Williams,
R. F. G. Wyse,
T. Zwitter
[show abstract]
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ABSTRACT: We have used spectra of hot stars from the RAVE Survey in order to investigate the visibility and properties of five diffuse interstellar bands previously reported in the literature. The RAVE spectroscopic survey for Galactic structure and kinematics records CCD spectra covering the 8400-8800 Ang wavelength region at 7500 resolving power. The spectra are obtained with the UK Schmidt at the AAO, equipped with the 6dF multi-fiber positioner. The DIB at 8620.4 Ang is by far the strongest and cleanest of all DIBs occurring within the RAVE wavelength range, with no interference by underlying absorption stellar lines in hot stars. It correlates so tightly with reddening that it turns out to be a reliable tool to measure it, following the relation E(B-V) = 2.72 (+/- 0.03) x E.W.(Ang), valid throughout the general interstellar medium of our Galaxy. The presence of a DIB at 8648 Ang is confirmed. Its intensity appears unrelated to reddening, in agreement with scanty and preliminary reports available in the literature, and its measurability is strongly compromised by severe blending with underlying stellar HeI doublet at 8649 Ang. The two weak DIBS at 8531 and 8572 Ang do not appear real and should actually be blends of underlying stellar lines. The very weak DIB at 8439 Ang cannot be resolved within the profile of the much stronger underlying hydrogen Paschen 18 stellar line. Comment: Accepted in press by A&A
08/2008;
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T. Zwitter,
A. Siebert,
U. Munari,
K. C. Freeman,
A. Siviero,
F. G. Watson,
J. P. Fulbright,
R. F. G. Wyse,
R Campbell,
G. M. Seabroke, [......],
W. Reid,
S. Roeser,
G. Ruchti,
R. -D. Scholz,
M. C. Smith,
R. Sordo,
E. Tolstoi, L. Tomasella,
S. Vidrih,
E. Wylie de Boer
[show abstract]
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ABSTRACT: We present the second data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities (RVs) and stellar atmosphere parameters of up to one million stars using the 6dF multi-object spectrograph on the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO). It is obtaining medium resolution spectra (median R=7,500) in the Ca-triplet region (8,410--8,795 \AA) for southern hemisphere stars in the magnitude range 9<I<12. Following the first data release (Steinmetz et al. 2006) the current release doubles the sample of published RVs, now containing 51,829 RVs for 49,327 individual stars observed on 141 nights between April 11 2003 and March 31 2005. Comparison with external data sets shows that the new data collected since April 3 2004 show a standard deviation of 1.3 km/s, about twice better than for the first data release. For the first time this data release contains values of stellar parameters from 22,407 spectra of 21,121 individual stars. They were derived by a penalized \chi^2 method using an extensive grid of synthetic spectra calculated from the latest version of Kurucz models. From comparison with external data sets, our conservative estimates of errors of the stellar parameters (for a spectrum with S/N=40) are 400 K in temperature, 0.5 dex in gravity, and 0.2 dex in metallicity. We note however that the internal errors estimated from repeat RAVE observations of 822 stars are at least a factor 2 smaller. We demonstrate that the results show no systematic offsets if compared to values derived from photometry or complementary spectroscopic analyses. The data release includes proper motion and photometric measurements. It can be accessed via the RAVE webpage: http://www.rave-survey.org and through CDS. Comment: 85 pages, 23 figures, 14 tables, accepted for publication in the Astronomical Journal
06/2008;
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ABSTRACT: The orbit and physical parameters of the previously unsolved SB2 EB V570 Per are derived using high resolution Asiago Echelle spectroscopy and B, V photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02 +/- 0.03, and reddening from interstellar NaI and KI absorption lines is E(B-V) =0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350 +/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2} =40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos distance of 123 +/- 11 pc. The observed properties of V570 Per components are compared to BaSTI models computed on purpose for exactly the observed masses and varied chemical compositions. This system is interesting since both components have their masses in the range where the efficiency of convective core overshooting has to decrease with the total mass as a consequence of the decreasing size of the convective core during the central H-burning stage. Our numerical simulations show that, a small but not null overshooting is required, with efficiencies lambda_{OV} =0.14 and 0.11 for the 1.449 and 1.350 Msun components, respectively. This confirms the finding of Paper II on the similar system V505 Per. At the approx 0.8 Gyr age of the system, the element diffusion has reduced the surface metallicity of the models from the initial [M/H]=+0.17 to [M/H]=+0.02, in perfect agreement with the spectroscopically derived [M/H]=+0.02 +/- 0.03 value. Comment: accepted by A&A. This revised upload to astro-ph correct a formatting error generated by uncorrect A&A style file
03/2008;
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[show abstract]
[hide abstract]
ABSTRACT: The orbit and fundamental physical parameters of the double-lined eclipsing binary V505 Per are derived by means of Echelle high resolution, high S/N spectroscopy and B, V photometry. Effective temperatures, gravities, rotational velocities and metallicities are obtained from atmospheric chi^2 analysis. An E(B-V)<=0.01 mag reddening is derived from interstellar NaI and KI lines. The distance to the system computed from orbital parameters (60.6 +/- 1 pc) is identical to the newly re-reduced Hipparcos parallax (61.5 +/- 1.9 pc). The masses of the two components (M(1) = 1.2693 +/- 0.0011 and M(2) = 1.2514 +/- 0.0012 Msun) place them in the transition region between convective and radiative stellar cores of the HR diagram, with the more massive of the two showing already the effect of evolution within the Main Sequence band (T(1) = 6512 +/- 21 K, T(2) = 6462 +/- 12 K, R(1) = 1.287 +/- 0.014, R(2) = 1.266 +/- 0.013 Rsun). This makes this system of particular relevance to theoretical stellar models, as a test on the overshooting. We compare the firm observational results for V505 Per component stars with the predictions of various libraries of theoretical stellar models (BaSTI, Padova, Granada, Yonsei-Yale, Victoria-Regina) as well as BaSTI models computed specifically for the masses and chemical abundances of V505 Per. We found that the overshooting at the masses of V505 Per component stars is already pretty low, but not null, and described by efficiencies lambda(OV)=0.093 and 0.087 for the 1.27 and 1.25 Msun components, respectively. According to the computed BaSTI models, the age of the system is about 0.9 Gyr and the element diffusion during this time has reduced the surface metallicity from the initial [M/H]=-0.03 to the current [M/H]=-0.13, in excellent agreement with observed [M/H]=-0.12 +/- 0.03.
01/2008;
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M. I. Wilkinson,
A. Vallenari,
C. Turon,
U. Munari,
D. Katz,
G. Bono,
M. Cropper,
A. Helmi,
N. Robichon,
F. Thévenin, [......],
M. Perryman,
A. Prša,
A. Recio-Blanco,
F. Royer,
A. Sellier,
A. Siviero,
R. Sordo,
C. Soubiran, L. Tomasella,
Y. Viala
[show abstract]
[hide abstract]
ABSTRACT: The Gaia mission is designed as a Galaxy explorer, and will measure simultaneously, in a survey mode, the five or six phase-space parameters of all stars brighter than 20th magnitude, as well as providing a description of their astrophysical characteristics. These measurements are obtained by combining an astrometric instrument with micro-arcsecond capabilities, a photometric system giving the magnitudes and colours in 15 bands and a medium-resolution spectrograph named the Radial Velocity Spectrometer (RVS). The latter instrument will produce spectra in the 848- to 874-nm wavelength range, with a resolving power R= 11 500, from which radial velocities, rotational velocities, atmospheric parameters and abundances can be derived. A companion paper has presented the characteristics of the RVS and its performance. The present paper details the outstanding scientific impact of this important part of the Gaia satellite on some key open questions in present-day astrophysics. The unbiased and simultaneous acquisition of multi-epoch radial velocities and individual abundances of key elements in parallel with the astrometric parameters is essential for the determination of the dynamical state and formation history of our Galaxy. Moreover, for stars brighter than V≃ 15, the resolving power of the RVS will give information about most of the effects that influence the position of a star in the Hertzsprung–Russell diagram, placing unprecedented constraints on the age, internal structure and evolution of stars of all types. Finally, the RVS multi-epoch observations are ideally suited to the identification, classification and characterization of the many types of double, multiple and variable stars.
Monthly Notices of the Royal Astronomical Society 05/2005; 359(4):1306 - 1335. · 4.90 Impact Factor
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D. Katz,
U. Munari,
M. Cropper,
T. Zwitter,
F. Thévenin,
M. David,
Y. Viala,
F. Crifo,
A. Gomboc,
F. Royer, [......],
A. Holland,
D. Horville,
J.-M. Huet,
P. Laporte,
T. Melse,
F. Sayède,
T.-J. Stevenson,
P. Vola,
D. Walton,
B. Winter
[show abstract]
[hide abstract]
ABSTRACT: The definition and optimization studies for the Gaia satellite spectrograph, the ‘radial velocity spectrometer’ (RVS), converged in late 2002 with the adoption of the instrument baseline. This paper reviews the characteristics of the selected configuration and presents its expected performance. The RVS is a 2.0 × 1.6 degree integral field spectrograph, dispersing the light of all sources entering its field of view with a resolving power R=λ/Δλ= 11 500 over the wavelength range [848, 874] nm. The RVS will continuously and repeatedly scan the sky during the 5-yr Gaia mission. On average, each source will be observed 102 times over this period. The RVS will collect the spectra of about 100–150 million stars up to magnitude V≃ 17–18. At the end of the mission, the RVS will provide radial velocities with precisions of ∼2 km s−1 at V= 15 and ∼15–20 km s−1 at V= 17, for a solar-metallicity G5 dwarf. The RVS will also provide rotational velocities, with precisions (at the end of the mission) for late-type stars of σvsin i≃ 5 km s−1 at V≃ 15 as well as atmospheric parameters up to V≃ 14–15. The individual abundances of elements such as silicon and magnesium, vital for the understanding of Galactic evolution, will be obtained up to V≃ 12–13. Finally, the presence of the 862.0-nm diffuse interstellar band (DIB) in the RVS wavelength range will make it possible to derive the three-dimensional structure of the interstellar reddening.
Monthly Notices of the Royal Astronomical Society 10/2004; 354(4):1223 - 1238. · 4.90 Impact Factor
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D Katz,
U. Munari,
M. Cropper,
T. Zwitter,
F. Thevenin,
M David,
Y. Viala,
F. Crifo,
A. Gomboc,
F. Royer, [......],
C. Turon,
A. Helmi,
G. Bono,
M. Perryman,
A. Gomez, L. Tomasella,
F. Boschi,
D. Morin,
M. Haywood,
C. Soubiran
[show abstract]
[hide abstract]
ABSTRACT: The definition and optimisation studies for the Gaia satellite spectrograph, the Radial Velocity Spectrometer (RVS), converged in late 2002 with the adoption of the instrument baseline. This paper reviews the characteristics of the selected configuration and presents its expected performance. The RVS is a 2.0 by 1.6 degree integral field spectrograph, dispersing the light of all sources entering its field of view with a resolving power R=11 500 over the wavelength range [848, 874] nm. The RVS will continuously and repeatedly scan the sky during the 5 years of the Gaia mission. On average, each source will be observed 102 times over this period. The RVS will collect the spectra of about 100-150 million stars up to magnitude V~17-18. At the end of the mission, the RVS will provide radial velocities with precisions of ~2 km/s at V=15 and \~15-20 km/s at V=17, for a solar metallicity G5 dwarf. The RVS will also provide rotational velocities, with precisions (at the end of the mission) for late type stars of sigma_vsini ~5 km/s at V~15 as well as atmospheric parameters up to V~14-15. The individual abundances of elements such as Silicon and Magnesium, vital for the understanding of Galactic evolution, will be obtained up to V~12-13. Finally, the presence of the 862.0 nm Diffuse Interstellar Band (DIB) in the RVS wavelength range will make it possible to derive the three dimensional structure of the interstellar reddening. Comment: 17 pages, 9 figures, accepted for publication in MNRAS. Fig. 1,2,4,5, 6 in degraded resolution; available in full resolution at http://blackwell-synergy.com/links/doi/10.1111/j.1365-2966.2004.08282.x/pdf
09/2004;
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ABSTRACT: Between 1996 and 2003 we have obtained 226 high resolution spectra of 16 stars in the field of the young open cluster NGC 6913, to the aim of constraining its main properties and study its internal kinematics. Twelve of the program stars turned out to be members, one of them probably unbound. Nine are binaries (one eclipsing and another double lined) and for seven of them the observations allowed to derive the orbital elements. All but two of the nine discovered binaries are cluster members. In spite of the young age (a few Myr), the cluster already shows signs that could be interpreted as evidence of dynamical relaxation and mass segregation. However, they may be also the result of an unconventional formation scenario. The dynamical (virial) mass as estimated from the radial velocity dispersion is larger than the cluster luminous mass, which may be explained by a combination of the optically thick interstellar cloud that occults part of the cluster, the unbound state or undetected very wide binary orbit of some of the members that inflate the velocity dispersion and a high inclination for the axis of a possible cluster angular momentum. All discovered binaries are hard enough to survive average close encounters within the cluster and do not yet show sign of relaxation of the orbital elements to values typical of field binaries. Comment: Astron.Astrophys. submitted, 8 figures, 7 tables, 12 pages. Figures 1 and 6 degraded in quality with respect to originals to save file dimensions
10/2003;
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[show abstract]
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ABSTRACT: We have obtained 782 real spectra and used them as inputs for 6700 automatic cross-correlation runs to the aim of investigating the radial velocity accuracy that GAIA could potentially achieve as function of spectral resolution and signal-to-noise ratio. We have explored the dispersions 0.25, 0.5, 1 and 2 Ang/pix (bracketing the 0.75 Ang/pix currently baselined for the 8490--8740 Ang GAIA range centered on the near-infrared CaII triplet) over S/N ranging from 10 to 110. We have carefully maintained the condition FWHM (PSF) = 2 pixels during the acquisition of the 782 input spectra, and therefore the resolutions that we have explored are 0.5, 1, 2 and 4 Ang corresponding to resolving powers R=17200, 8600, 4300 and 2150. We have investigated late-F to early-M stars (constituting the vast majority of GAIA targets), slowly rotating (V_{rot} sin i = 4 km/sec, as for field stars at these spectral types), of solar metallicity (<[Fe/H]> = -0.07) and not binary. The results are accurately described by the simple law: lg sigma = 0.6(lg S/N)^2 - 2.4(lg S/N) + 1.75(lg D) + 3, where sigma is the cross-correlation standard error (in km/sec) and D is the spectral dispersion (in Ang/pix). The spectral dispersion has turned out to be the dominant factor governing the accuracy of radial velocities, with S/N being less important and the spectral mis-match being a weak player. These results are relevant not only within the GAIA context but also to ground-based observers because the absence of telluric absorptions and proximity to the wavelengths of peak emission make the explored 8490--8740 Ang interval an interesting option for studies of cool stars with conventional telescopes.
06/2001;
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[show abstract]
[hide abstract]
ABSTRACT: The orbits and physical parameters of three detached, double-lined A-F eclipsing binaries have been derived combining H_P, V_T, B_T photometry from the Hipparcos/Tycho mission with 8500-8750 Ang ground-based spectroscopy, mimicking the photometric+spectroscopic observations that should be obtained by GAIA, the approved Cornerstone 6 mission by ESA. This study has two main objectives, namely (a) to derive reasonable orbits for a number of new eclipsing binaries and (b) to evaluate the expected performances by GAIA on eclipsing binaries and the accuracy achievable on the determination of fundamental stellar parameters like masses and radii. It is shown that a 1% precision in the basic stellar parameters can be achieved by GAIA on well observed detached eclipsing binaries provided that the spectroscopic observations are performed at high enough resolution. Other types of eclipsing binaries (including semi-detached and contact types) and different spectral types will be investigated in following papers along this series. Comment: A&A, 11 pages, 5 figures, 5 tables
05/2001;
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[show abstract]
[hide abstract]
ABSTRACT: BVI photometry (from South Africa Astron. Obs.), Echelle high resolution spectroscopy and AFOSC integral field spectroscopy (from Asiago, Italy) of the young open cluster NGC 6604 are presented. Age, distance, reddening, membership, radial and rotational velocities are derived and discussed. An age of 5 million years, a distance of 1.7 kpc and a reddening E(B-V)=1.02 are found. The cluster radial velocity is in agreement with the Hron (1987) model for the Galaxy disk rotation. Pre-ZAMS objects are not present down to M_V = +1.5 mag. Comment: accepted in Astron.Astrophys.Suppl. Figure 2 is degraded in resolution
04/2000;
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[show abstract]
[hide abstract]
ABSTRACT: The spectroscopic and photometric evolution of the 1999 outburst of the eclipsing and recurrent nova U Sco is presented. The photometric evolution closely matches that of the previous events. The FWZI=10,000 km/sec for emission lines at maximum has decreased to 4000 km/sec by day +23, with continuous and dramatic changes in the line profiles. No nebular line has become visible and the ionization degree has increased during the brightness decline. A not previously reported and quite puzzling splitting of the emission lines into three components after the first two weeks is outstanding in our spectra. The radiated luminosity is found to be a tiny fraction of that of classical novae for any reasonable distance to U Sco. Comment: Astron.Astrophys.Lett., in press
06/1999;
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[show abstract]
[hide abstract]
ABSTRACT: We present evidence from high resolution optical spectra for the
presence of bipolar jets in the bright super soft X-ray source RX
J0019.8+2156, the second such discovered case after RX J0513.9-6951. The
jets seem to appear and disappear over a time scale of several months.
No jet precession is observed. From the velocity separation of the
emission lines produced by the jets a lower limit of ~ 79degr is posed
to the orbital inclination. This gives support to the interpretation in
terms of eclipses for the periodic features in the RX J0019.8+2156
lightcurve.
Astronomy and Astrophysics 04/1998; 333:L67-L69. · 4.59 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Low resolution B&C+CCD (range 3600 Angstroms - 1.0 mu m) and high
resolution Echelle+CCD (range 5800-8100 Angstroms) spectrophotometry of
type Ib/c SN 1997X near maximum light is presented and discussed. The
supernova is noteworthy in having presented absorption lines of He I at
early phases (at an expansion velocity of 11000 km sec(-1) ). From the
interstellar NaI D lines a reddening of E _{B-V}=0.18+/-0.02 mag has
been derived, which arises in the host galaxy. From the emission lines
of the underlying H II region, a density of N_e <= 100 and a velocity
of RV_sun=1098+/-3 km sec(-1) are obtained.
Astronomy and Astrophysics 04/1998; 333:159-162. · 4.59 Impact Factor
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298:427.
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[show abstract]
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ABSTRACT: We present an Echelle+CCD high resolution spectroscopic atlas (0.25 Å/pix dispersion, 0.43 Å FWHM resolution and 20 000 resolving power) mapping the MKK classification system over the interval $\lambda\lambda$ $8500-8750$ Å. The wavelength interval is remarkably free from telluric lines and it is centered on the near-IR triplet of Ca II, the head of hydrogen Paschen series and several strong metallic lines. The spectra of 131 stars of types between O4 and M8 and luminosity classes I through V are included in the atlas. Special care was put in maintaining the highest instrumental homogeneity over the whole set of data. The capability to derive accurate MKK spectral types from high resolution observations over the interval $\lambda\lambda$ $8500-8750$ Å is discussed. The observations have been performed as part of an evaluation study of possible spectroscopic performances for the astrometric mission GAIA planned by ESA.
http://dx.doi.org/10.1051/aas:1999490.
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[hide abstract]
ABSTRACT: $BVI_{\rm C}$ photometry and classification spectroscopy is presented for the young open cluster NGC 6604. Additional Echelle spectroscopy of the brightest members is used to check the reddening against the interstellar NaI and KI absorption lines, to measure the cluster radial velocity and to derive the individual rotational velocities. We obtain 1.7 kpc as the cluster distance, an age of $\sim 5~10^{6}$ years and a reddening $E_{B-V}$= 1.02 ($\pm 0.01$ from three independent methods). Pre-ZAMS objects are apparently not detected over the $\bigtriangleup m$ = 8.5 mag explored range. The cluster radial velocity is in agreement with the [CITE] model for the Galaxy disk rotation.
http://dx.doi.org/10.1051/aas:2000193.
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[show abstract]
[hide abstract]
ABSTRACT: The orbits and physical parameters of three detached, double-lined A-F eclipsing binaries have been derived combining $H_{\rm P}, V_{\rm T}, B_{\rm T}$ photometry from the Hipparcos/Tycho mission with 8500-8750 Å ground-based spectroscopy, mimicking the photometric+spectroscopic observations that should be obtained by GAIA, the approved Cornerstone 6 mission by ESA. This study has two main objectives, namely ($a$) to derive reasonable orbits for a number of new eclipsing binaries and ($b$) to evaluate the expected performances by GAIA on eclipsing binaries and the accuracy achievable on the determination of fundamental stellar parameters like masses and radii. It is shown that a 1% precision in the basic stellar parameters can be achieved by GAIA on well observed detached eclipsing binaries provided that the spectroscopic observations are performed at high enough resolution. Other types of eclipsing binaries (including semi-detached and contact types) and different spectral types will be investigated in subseguent papers in this series.
http://dx.doi.org/10.1051/0004-6361:20011230.
