Contents
Images
Upload your image
DSS Images Other Images
Related articles
Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Photometry of symbiotic stars. XI. EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, RW Hya, AR Pav, AG Peg, AX Per, QW Sge, IV Vir and the LMXB V934 Her
We present new photometric observations of EG And, Z And, BF Cyg, CHCyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, RW Hya, AG Peg, AX Per, IV Virand the peculiar M giant V934 Her, which were made in the standardJohnson UBV(R) system. QW Sge was measured in the Kron-Cousin B, V,RC, IC system and for AR Pav we present its newvisual estimates. The current issue gathers observations of theseobjects to December 2003. The main results can be summarized as follows:EG And: The primary minimum in the U light curve (LC) occurred at theend of 2002. A 0.2 -- 0.3 mag brightening in U was detected in theautumn of 2003. Z And: At around August 2002 we detected for the firsttime a minimum, which is due to eclipse of the active object by the redgiant. Measurements from 2003.3 are close to those of a quiescent phase.BF Cyg: In February 2003 a short-term flare developed in the LC. Adifference in the depth of recent minima was detected. CH Cyg: This starwas in a quiescent phase at a rather bright state. A shallow minimumoccurred at JD 2 452 730, close to the position of the inferiorconjunction of the giant in the inner binary of the triple-star model ofCH Cyg. CI Cyg: Our observations cover the descending branch of a broadminimum. TX CVn: At/around the beginning of 2003 the star entered abright stage containing a minimum at JD 2 452 660. AG Dra: Newobservations revealed two eruptions, which peaked in October 2002 and2003 at 9.3 in U. AR Pav: Our new visual estimates showed atransient disappearance of a wave-like modulation in the star'sbrightness between the minima at epochs E = 66 and E = 68 and itsreappearance. AG Peg: Our measurements from the end of 2001 showedrather complex profile of the LC. RW Hya: Observations follow behaviourof the wave-like variability of quiet symbiotics. AX Per: In May 2003 a0.5 mag flare was detected following a rapid decrease of the light to aminimum. QW Sge: CCD observations in B, V, RC, ICbands cover a period from 1994.5 to 2003.5. An increase in the star'sbrightness by about 1 mag was observed in all passbands in 1997. Lesspronounced brightening was detected in 1999/2000. V934 Her: Ourobservations did not show any larger variation in the optical as areaction to its X-ray activity.
| The symbiotic star CH Cygni - II. The ejecta from the 1998-2000 active phase
We present Hubble Space Telescope (HST) imaging, a Very Large Array(VLA) radio map (4.74 GHz), optical high-resolution (echelle)spectroscopy and UBV photoelectric photometry of the symbiotic star CHCyg obtained during its 1998-2000 active phase. The HST imaging, takenduring eclipse, shows the central stars are embedded in a nebulaextending to 620 +/- 150 au for a distance of 270 +/- 66 pc. The innernebula is strongly influenced by the onset of activity and associatedoutflow in 1998. The surface brightness contours of the contemporaneousradio VLA observation agree well with HST images. Photometricobservations of the broad 1999 U-minimum suggest that it is due to theeclipse of the active hot component by the giant on the long-period(14.5 yr) outer orbit. We also find that the onset of the 1998 and the1992 active periods occur at the same orbital phase of the inner binary.Spectroscopic observations reveal two types of outflow from the activestar: a high-velocity (>1200 km s-1) hot star windsporadically alternating with a more massive outflow indicated byP-Cygni-like profiles. We present evidence connecting the extendednebulosity with the high-velocity shocked outflow, and hence theactivity in the central binary.
| Photometry of symbiotic stars. X. EG And, Z And, BF Cyg, CH Cyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir
We present new photometric observations of EG And, Z And, BF Cyg, CHCyg, V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir made in the standardJohnson UBVR system. The current issue summarizes observations of theseobjects to 2001 December. The main results can be summarized as follows:EG And: A periodic double-wave variation in all bands as a function ofthe orbital phase was confirmed. A maximum of the light changes wasobserved in U (Delta U ~ 0.5 mag). Z And: Our observations cover anactive phase, which peaked around 8.4 in U at the beginning of 2000December. Consequently, a gradual decrease in the star's brightness hasbeen observed. BF Cyg: A periodic wave-like variation in the opticalcontinuum reflects a quiescent phase of this star. A complex light curve(LC) profile was observed. CH Cyg: The recent episode of activity endedin Spring 2000. We determined the position of an eclipse in the outerbinary at JD 2451426 +/- 3. Recent observations indicate a slow increasein the star's brightness. V1329 Cyg: Observations were made around amaximum at 2001.2. AG Dra: Our measurements from the Autumn of 2001revealed a new eruption, which peaked at ~JD 2452217. RW Hya: The lightminimum in our mean visual LC precedes the time of the spectroscopicconjunction of the giant in the binary. AX Per: A periodic wave-likevariation was observed. Our recent observations revealed a secondaryminimum at the orbital phase 0.5, seen best in the V and B bands. IVVir: The LC displays a double-wave throughout the orbital cycle.
| Photometry of symbiotic stars. IX. TX CVn, CH Cyg, AX Per and AR Pav
We present new photometric observations of TX CVn, CH Cyg, AX Per and ARPav. The main results can be summarized as follows: TX CVn: Thehistorical 1893-2000 photographic/B-band light curve (LC) is presentedfor the first time. From 1892 to ~1920, the star was quiet, but thenentered a series of outbursts peaking in 1920, 1945, 1952 and 1962. From~1988 till the present time, TX Cvn has gradually declined. CH Cyg: Ourobservations cover an active phase, which began in May 1998. At thebeginning of June 1999 the star's brightness in the U band rapidlydecreased due to an eclipse of the active inner binary (the symbioticpair) by a cool giant in the outer orbit. AX Per: The historical1887-2000 photographic/B-band LC is summarized here for the first time.It is characterized by long-lasting periods of quiescence with thesuperposition of a few bright stages lasting about 1.5 orbital cycles.Our photoelectric U,B,V observations revealed a drastic change in the LCprofile, which occurred after JD 2 450 000 (1995.8). A small 0.6 magflare at that time and consequently very broad wave-like variation inthe LC developed. This event was caused by the dilution of a shellaround the hot star. AR Pav: Our observations show that the recentactive phase, which began in 1985.7 is over. During the activity, AR Pavdeveloped a complex wave-like variation at the level of ~1.5 mag in thevisual band. The transition to a quiet phase was rapid -- the wave-likevariation disappeared.
| Observations of Two HIPPARCOS Eclipsing Variables
Not Available
| Photometric study of the eclipsing binary EG CEP
New photoelectric B and V observations of EG Cep were taken and 11 newminima times were determined. They confirm the long-term increase of theorbital period. The light-curve analysis shows that the system issemi-detached. Mass transfer from the less to the more massive componentis responsible for the observed orbital period increase. Variations inthe transferred matter projected onto the surface of the components areresponsible for the colour dependent variable shift of the minima. Thiseffect, more pronounced in the secondary minima, explains also thedisagreement of the limb-darkening coefficient of the secondarycomponent with the theoretical value.
| Photometric Peculiarities of CH Cyg during its Recent, 1997-97, Quiescent Phase
Not Available
| Multifrequency observations of the eclipsing symbiotic triple system CH CYG during the 1992-94 active phase.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.282..327S&db_key=AST
| Photometric Observations of Eclipses in the Symbiotic Triple System CH Cygni
Not Available
| Echelle spectroscopy of the symbiotic star CH Cygni through quiescence
High- and low-resolution optical spectroscopy, coupled with opticalphotometry, of Ch Cygni during the period from June 1986 to May 1990 ispresented. The variation in Balmer line fluxes correlates with changesin emission from the hot component, and is consistent with thepreviously published orbital solution. Radial velocities for lines fromvarious parts of the system are determined and compared with previousresults. The origin of the double-peaked profiles of the Balmer lines isexplored. Variations in radial velocity about the orbital RV curve areargued to be greater than those normally observed for isolated redgiants. Observations of the forbidden O III 5007A emission line in June1986 confirm that if this originates in the gas associated with theradio jets, the jets are moving approximately in the plane of the sky. Acollimation mechanism associated with the orbital plane of the binary isinferred from this. Infrared spectroscopy in May 1990 indicates that thecool component is of the spectral type M7 or later.
| Mean positions and proper motions of 224 stars based on PZT observations at Ondrejov in 1973-1986
An improvement of the positions and proper motions for the Ondrejov PZTstar list based on observations of 224 stars in the period 1973-1986 ispresented. The mean epoch of the PZT 86 catalogue is found to be 1981.56with a standard error in right ascension equal to + or - 0.0015 s/ andin delination equal to + or - 0.017 arcsec. The proper motions in rightascension and declination were obtained with an accuracy characterizedby the average standard errors of + or - 0.051 s/cy and + or - 0.57arcsec/cy, respectively. The PZT 86 catalogue is compared with theprevious PZT (1978 and 1983) catalogues, and with the AGK 3 (Dieckvoss,1975) catalogue.
| Mean positions and proper motions of 305 stars obtained from the combination of PZT observations at Ondrejov with AGK positions
Observations of 305 stars carried out at the Ondrejov Observatory in theperiod 1973-1983 were compared to the positions of the same stars in theAGK 2 and AGK 3 catalogs in order to obtain their mean positions andproper motions. The observations were performed in the course of 1140nights using the PZT telescope and comprise more than 32 thousand startransits. The average mean errors in the right ascension and declinationof a star that was observed thoughout the whole period were + or -0.0019 s and + or - 0.019 arcsec in the epoch around 1979. It ispredicted that the errors will increase + or - 0.0055 sec and + or -0.059 arcsec in the year 2000. A table listing the errors in the rightascension and declination is provided.
| The determination of mean positions and proper motions of 304 stars from PZT observations at Ondrejov
Not Available
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Cygne |
| Right ascension: | 19h25m29.72s |
| Declination: | +50°04'14.9" |
| Apparent magnitude: | 8.34 |
| Distance: | 220.264 parsecs |
| Proper motion RA: | -39.2 |
| Proper motion Dec: | -32 |
| B-T magnitude: | 8.909 |
| V-T magnitude: | 8.387 |
Catalogs and designations:
|
