An Atlas of Spectrophotometric Landolt Standard Stars
We present CCD observations of 102 Landolt standard stars obtained withthe Ritchey-Chrétien spectrograph on the Cerro TololoInter-American Observatory 1.5 m telescope. Using stellar atmospheremodels, we have extended the flux points to our six spectrophotometricsecondary standards, in both the blue and the red, allowing us toproduce flux-calibrated spectra that span a wavelength range from 3050Å to 1.1 μm. Mean differences between UBVRI spectrophotometrycomputed using Bessell's standard passbands and Landolt's publishedphotometry were determined to be 1% or less. Observers in bothhemispheres will find these spectra useful for flux-calibrating spectra,and through the use of accurately constructed instrumental passbands,will be able to compute accurate corrections to bring instrumentalmagnitudes to any desired standard photometric system (S-corrections).In addition, by combining empirical and modeled spectra of the Sun,Sirius, and Vega, we calculate and compare synthetic photometry toobserved photometry taken from the literature for these three stars.
|
Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars
This paper presents the catalogue and the method of determination ofaveraged quadratic effective magnetic fields < B_e > for 596 mainsequence and giant stars. The catalogue is based on measurements of thestellar effective (or mean longitudinal) magnetic field strengths B_e,which were compiled from the existing literature.We analysed the properties of 352 chemically peculiar A and B stars inthe catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, andall ApSr type stars. We have found that the number distribution of allchemically peculiar (CP) stars vs. averaged magnetic field strength isdescribed by a decreasing exponential function. Relations of this typehold also for stars of all the analysed subclasses of chemicalpeculiarity. The exponential form of the above distribution function canbreak down below about 100 G, the latter value representingapproximately the resolution of our analysis for A type stars.Table A.1 and its references are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9are only available in electronic form at http://www.edpsciences.org
|
Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
|
A search for magnetic stars in late stages of stellar evolution
No abstract submitted
|
CP2 stars as viewed by the UVBY H_beta system
The aim of this work is to study the capacity of the uvby H_βsystem for detecting the chemically peculiar (CP) stars based on theeffect that peculiar features in the flux distribution have on all theStromgren-Crawford indices. Our study focuses on the classical magneticpeculiar stars (CP2), though Am stars (CP1) are also included forcomparison with cool CP2 stars. Satisfactory results were obtained forhot CP2 stars: the definition of a new index p, which is a linearcombination of uvby H_β colours, allowed us to separate a highpercentage of hot CP2 stars from normal stars. According to this newindex, 60 new CP2 candidates are proposed. The working sample wasextracted from The General Catalogue of Ap and Am stars by \cite[Rensonet al. (1991)]{ren91}. Photometric observations to enlarge the sample ofCP2 stars with complete uvby H_β photometry were carried out. Theseobservations are also reported in the present paper. The new index p isalso used to correct the reddening of early CP2 stars computed as ifthey were normal stars. Tables 2, 3 and 7 are also available inelectronic form from CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
|
The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu.Most Bp - Ap stars lie on the main sequence occupying the whole width ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|
New pulsational properties of eight `anomalous' RR Lyrae variables
CCD photometry in the V band is presented for seven field RR Lyrae starsselected from a sample of eight variables; these, according to datacollected in the literature, are expected to be ab-type pulsators, tohave short periods (and hence high metallicity), and to be located at ahigh z from the Galactic plane. New periods and epochs are derived forthem. The new periods are only slightly shorter than the valuespublished in the fourth edition of the General Catalogue of VariableStars (GCVS4). In six cases our amplitude of the light variation issignificantly smaller than that published in the GCVS4, and in at leastthree cases the actual pulsation appears to be in the first harmonicrather than in the fundamental mode. All the suggested c-type pulsatorsshow variations in the amplitude and/or quite scattered light curves.Some possible explanations are given. From a spectrophotometric analysisof the sample, only DL Com is confirmed to pulsate in the fundamentalmode, to have a short period, and to be located at a relatively high z.However, a single object cannot be taken as evidence for a significantmetal-rich population at a large distance from the Galactic plane.
|
A search for stars with strong magnetic fields among horizontal-branch stars and hot subdwarfs
Observations obtained with the 6-m BTA telescope for a few A, Bhorizontal-branch stars and hot subdwarfs have been used to measuretheir effective magnetic fields. No magnetic fields similar to those ofAp, Bp main-sequence stars were found.
|
A search for stars with strong magnetic fields among horizontal-branch stars and hot subdwarfs
Not Available
|
Photoelectric UBV photometry of northern stars from the HK objective-prism survey. II
Photoelectric UBV photometry is presented for a sample of 165 starsdrawn from the extension of the HK objective-prism/interference-filtersurvey of Beers, Preston, and Shectman to the northern galactichemisphere. These results are part of continuing follow-up observationsof candidate metal-deficient and horizontal-branch field stars and otherinteresting stars identified in the survey. A complete set ofphotometric observations is now available for three of the25-square-degree survey fields. The complete photometric sample of 299northern HK candidates obtained to date contains on order 90main-sequence turnoff, subgiant, and giant stars with (Fe/H) of lessthan or equal to -1.0, 50 field blue horizontal-branch stars, and 30stars with the photometric properties of field-blue stragglers.
|
UBV(RI)c photometry of equatorial standard stars - A direct comparison between the northern and southern systems
UBV(RI)c photometry of 212 stars from Landolt's list of equatorialstandards is presented. The observations are tied to the system definedby Cousin's E-region standards. A comparison of the present results withLandolt's reveals reasonably good agreement for (V-R)c and (V-I)c, butmarked systematic differences for (B-V) and (U-B). The UBV systems ofCousins and Landolt are evidently not the same and both probably differfrom Johnson's original system.
|
Some Non-Variable Stars
Not Available
|
Radial velocity measurements. I - Ground-based observations of the program stars for the HIPPARCOS satellite
The radial velocities of 272 stars brighter than m(pg) = 8.5 aredetermined by digital microphotometric measurement of plates obtainedwith dispersion 80 A/mm using the Marly slit spectrograph on the 120-cmtelescope of the Observatoire de Haute Provence. The objects wereselected as probable members of the input catalog for the ESA Hipparcosastrometric satellite. The measurement techniques and data-reductionprocedures are described in detail, and the results are presented inextensive tables and graphs and briefly characterized.
|
The galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
|
Four-colour photometry of B stars north of B = + 45 deg and comparison with the south
Four-color photometry of 33 Henry Draper B stars north of b = + 45 degis presented. Most are little-reddened B or intermediate-A stars. A newAm star is discovered. The new measures essentially complete uvbyphotometry of all HD B stars within 45 deg of either galactic pole. Thenorthern and southern cones of HD B stars are compared, and selectioneffects deduced. Far from the galactic plane, it appears that B starsmay be equally distributed north and south of the plane; closer to thesun, an asymmetry associated with Gould's Belt is evident.
|
A catalog of selected compact radio sources for the construction of an extragalactic radio/optical reference frame
A catalog of 234 strong compact extragalactic radio sources that displayoptical counterparts is presented. This catalog identifies proposedsources for establishing an almost inertial reference frame againstwhich the motions of the earth, solar system, galactic objects, andspacecraft may be measured. This catalog also defines those sources forwhich precise optical positions should be determined in order to relatethis reference frame with the optical FK 5 fundamental system. Theaccuracy of the radio source positions of these sources is not greaterthan 0.1 arcsec with the majority not greater than 0.01 arcsec. Furtherrefinement to not greater than 0.005 arcsec by future observations isexpected soon.
|
Chemical separation in horizontal-branch stars
Horizontal branch (HB) and halo Population II star abundance anomaliesare predicted to arise from diffusion processes, and for cases where theouter envelope is stable enough for the gravitational settling of He tobe efficient, it is shown that heavy element overabundances aresimultaneously produced. Selective radiative acceleration and abundancetime evolution calculations are presented for C, N, O, Ca, Fe, and Sr,in a series of models representative of HB stars. The role of turbulentmixing in the reduction of abundance anomalies is discussed, and it isshown that despite sufficient turbulence to keep He from settling, heavyelement abundance anomalies remain possible. While chemical separationis important in the blue HB stars, it may not be in cooler stars wheremass loss may be able to eliminate any chemical separation effect.
|
UBVRI photometric standard stars around the celestial equator
It is pointed out that accurate, internally consistent, and readilyaccessible standard star photometric sequences are necessary for thecalibration of the intensity and color data which astronomers obtain atthe telescope. The photometric results provided in connection with thepresent study represent the first part of an effort which is concernedwith the presentation of UBVRI photoelectric photometric standard starsin the magnitude range from 7 to 17 over as broad a range in color aspossible. All of the photometric observations were made with a 31034type photomultiplier used in a pulse counting mode. Some 15 to 25standard stars chosen from Cousins' lists (1973, 1976) in the E-regionswere observed with an 0.4-m telescope each night along with the programstars. UBVRI standard stars were observed periodically throughout thenight. Observations with a 0.9-m telescope were also conducted. TheUBVRI photoelectric observations take into account 223 stars.
|
List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry
A list is presented of 333 stars, excluded from the GCVS and itssupplements, whose probability of variability ranges from high tocertain. The standard deviations observed in the V magnitude togetherwith the known spectral types, however, only allow speculation as to thetype of variable in question pending supplementary observations whichreveal the individual characteristics of these stars.
|
Geneva photometric boxes. II - The reddening towards the galactic poles
It is noted that photometric boxes allow a very accurate estimation ofindividual reddenings for B- and early A-type stars. A catalog of 129stars with galactic latitudes higher than 30 deg is given. A small butsignificant reddening is seen in the direction of both the northern andsouthern galactic poles: E(B-V) approximately 0.04.
|
Ultraviolet photometry with the Astronomical Netherlands Satellite /ANS/ - Faint blue stars in the halo
Blue stars at high galactic latitudes have been observed with the UVtelescope on board ANS. In this paper a subset of the collected datapertaining to the cooler stars is discussed. Most of them have energydistributions in general agreement with the visual spectral type. Onestar is exceptionally blue, and of seven possible horizontal-branchstars, two have UV energy distributions distinct from main-sequencestars in the sense that they have an excess at 1550 A and a large Balmerjump.
|
Catalogue of photometric data related to surface magnetic fields for B-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..111C&db_key=AST
|
Jupiter and Galilean satellites' positions obtained in April 1978 with the GPO 40 CM /f = 4 m/ of the ESO, La Silla
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...40..375D&db_key=AST
|
Photometry of faint blue stars. IV - Four-colour photometry of some northern stars
Photometry in the uvby system has been obtained for 33 northern faintblue stars. The stars are given photometric classification usingpreviously described criteria. Data are discussed which providesupporting evidence for the existence of gaps in the blue horizontalbranch.
|
A spectroscopic study of the blue halo silicon star HD 97859.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&A....31...89S&db_key=AST
|
Horizontal-Branch Stars and Interstellar Lines at High Latitude
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...152..431G&db_key=AST
|
Mean absolute magnitude of the blue stars at high galactic latitude.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67..740K&db_key=AST
|
A search for blue stars in high galactic latitudes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..484C&db_key=AST
|
INHABITED SKY
