내용
사진
사진 업로드
DSS Images Other Images
관련 글
A high-resolution spectroscopy survey of β Cephei pulsations in bright stars
We present a study of absorption line-profile variations in early-B typenear-main-sequence stars without emission lines. We have surveyed atotal of 171 bright stars using the Nordic Optical Telescope (NOTSA),William Herschel Telescope (ING) and Coudé Auxiliary Telescope(ESO). Our sample contains 75% of all O9.5-B2.5 III-V non-emission-linestars brighter than 5.5 mag. We obtained high signal-to-noise,high-resolution spectra of the SiIII λ4560 triplet - for 125stars of our sample we obtained more than one spectrum - and examinedthese for pulsational-like line-profile variations and/or structure. Weconclude that about half of our sample stars show evidence forline-profile variations (LPV). We find evidence for LPV in about 65% ofour sample stars brighter than V=5.5. For stars with rotationalbroadening V sin i 100 km s-1, we find evidence for LPVin about 75% of the cases. We argue that it is likely that these LPV areof pulsational origin, and that hence more than half of thesolar-neighbourhood O9.5-B2.5 III-V stars is pulsating in modes that canbe detected with high-resolution spectroscopy. We detected LPV in 64stars previously unknown to be pulsators, and label these stars as newβ Cep candidates. We conclude that there is no obvious differencein incidence of (pulsational) LPV for early-B type near-main-sequencestars in binaries or in OB associations, with respect to single fieldstars.
| Radial velocity measurements of B stars in the Scorpius-Centaurus association
We derive single-epoch radial velocities for a sample of 56 B-type starsmembers of the subgroups Upper Scorpius, Upper Centaurus Lupus and LowerCentaurus Crux of the nearby Sco-Cen OB association. The radial velocitymeasurements were obtained by means of high-resolution echelle spectravia analysis of individual lines. The internal accuracy obtained in themeasurements is estimated to be typically 2-3 km s-1, butdepends on the projected rotational velocity of the target. Radialvelocity measurements taken for 2-3 epochs for the targets HD 120307, HD142990 and HD 139365 are variable and confirm that they arespectroscopic binaries, as previously identified in the literature.Spectral lines from two stellar components are resolved in the observedspectra of target stars HD 133242, HD 133955 and HD 143018, identifyingthem as spectroscopic binaries.
| Catalog of Galactic β Cephei Stars
We present an extensive and up-to-date catalog of Galactic β Cepheistars. This catalog is intended to give a comprehensive overview ofobservational characteristics of all known β Cephei stars, coveringinformation until 2004 June. Ninety-three stars could be confirmed to beβ Cephei stars. We use data from more than 250 papers publishedover the last nearly 100 years, and we provide over 45 notes onindividual stars. For some stars we reanalyzed published data orconducted our own analyses. Sixty-one stars were rejected from the finalβ Cephei list, and 77 stars are suspected to be β Cepheistars. A list of critically selected pulsation frequencies for confirmedβ Cephei stars is also presented.We analyze the β Cephei stars as a group, such as the distributionsof their spectral types, projected rotational velocities, radialvelocities, pulsation periods, and Galactic coordinates. We confirm thatthe majority of the β Cephei stars are multiperiodic pulsators. Weshow that, besides two exceptions, the β Cephei stars with highpulsation amplitudes are slow rotators. Those higher amplitude starshave angular rotational velocities in the same range as thehigh-amplitude δ Scuti stars (Prot>~3 days).We construct a theoretical HR diagram that suggests that almost all 93β Cephei stars are main-sequence objects. We discuss theobservational boundaries of β Cephei pulsation and the physicalparameters of the stars. We corroborate that the excited pulsation modesare near to the radial fundamental mode in frequency and we show thatthe mass distribution of the stars peaks at 12 Msolar. Wepoint out that the theoretical instability strip of the β Cepheistars is filled neither at the cool nor at the hot end and attempt toexplain this observation.
| B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?
Projected rotational velocities (vsini) have been measured for 216 B0-B9stars in the rich, dense h and χ Persei double cluster and comparedwith the distribution of rotational velocities for a sample of fieldstars having comparable ages (t~12-15 Myr) and masses (M~4-15Msolar). For stars that are relatively little evolved fromtheir initial locations on the zero-age main sequence (ZAMS) (those withmasses M~4-5 Msolar), the mean vsini measured for the h andχ Per sample is slightly more than 2 times larger than the meandetermined for field stars of comparable mass, and the cluster and fieldvsini distributions differ with a high degree of significance. Forsomewhat more evolved stars with masses in the range 5-9Msolar, the mean vsini in h and χ Per is 1.5 times thatof the field; the vsini distributions differ as well, but with a lowerdegree of statistical significance. For stars that have evolvedsignificantly from the ZAMS and are approaching the hydrogen exhaustionphase (those with masses in the range 9-15 Msolar), thecluster and field star means and distributions are only slightlydifferent. We argue that both the higher rotation rates and the patternof rotation speeds as a function of mass that differentiatemain-sequence B stars in h and χ Per from their field analogs werelikely imprinted during the star formation process rather than a resultof angular momentum evolution over the 12-15 Myr cluster lifetime. Wespeculate that these differences may reflect the effects of the higheraccretion rates that theory suggests are characteristic of regions thatgive birth to dense clusters, namely, (1) higher initial rotationspeeds; (2) higher initial radii along the stellar birth line, resultingin greater spin-up between the birth line and the ZAMS; and (3) a morepronounced maximum in the birth line radius-mass relationship thatresults in differentially greater spin-up for stars that become mid- tolate-B stars on the ZAMS.
| β Cep stars from a spectroscopic point of view
In this review we present the current status of line-profile-variationstudies of β Cep stars. Such studies have been performed for 26bright members of this class of pulsating stars in the past 25 years. Wedescribe all these currently available data and summarize theinterpretations based on them in terms of the excited pulsation modes.We emphasize that line-profile variations offer a much more detailedpicture of the pulsational behaviour of pulsating stars compared toground-based photometric data. The latter, however, remain necessary tounravel the often complex frequency pattern and to achieve unambiguousmode identification for multiperiodic β Cep stars and also toderive the pulsational properties of the faint members of the class. Wehighlight the statistical properties of the sample of 26 stars for whichaccurate spectroscopic studies are available and point out some futureprospects.
| The 10 October 1999 HIP 9369 occultation by the northern polar region of Jupiter: ingress and egress lightcurves analysis
The occultation of bright star HIP9369 by the northern polar region ofJupiter was observed from four locations in North and South America,providing four data sets for ingress and egress. The inversion of theeight occultation lightcurves provides temperature profiles at differentlatitudes ranging from 55°N to 73.2°N. We estimate the errors onthe profiles due to the uncertainties of the inversion method andcompare the value of the temperature at the deepest level probed (~ 50μbar) with previous observations. The shape of the temperaturegradient profile is found similar to previous investigations ofplanetary atmospheres with propagating and breaking gravity waves. Weanalyze the small scale structures in both lightcurves and temperatureprofiles using the continuous wavelet transform. The calculated powerspectra of localized fluctuations in the temperature profiles showslopes close to -3 for all eight profiles. We also isolate andreconstruct the three-dimensional geometry of a single wave mode withvertical and horizontal wavelengths of respectively 3 and 70 km. Theidentified wave is consistent with the gravity wave regime, with ahorizontal phase speed nearly parallel to the planetary meridian.Nevertheless, the dissipation of the corresponding wave in Jupiter'sstratosphere should preclude its detection at the observed levels and anacoustic wave cannot be ruled out.
| A study of the behaviour of the NaI/KI column density ratio in the interstellar medium using the Na ultraviolet doublet
Here we make a new study of the behaviour of the NaI/KI column densityratio in the interstellar medium, using a sample of new observations of28 stars obtained at the Nordic Optical Telescope (NOT) in 1996 and1997, and previously published observations (obtained by some of theauthors) of 21 stars. The sightlines cover a range of distances anddirections, including into the Galactic halo. We make use of newobservations of the NaI ultraviolet (UV) doublet for some 18 stars. Thisdoublet is much weaker than the NaI D doublet and so is less susceptibleto saturation effects, and it is well known that it can be used toobtain more accurate NaI column densities with a smaller error range. Wefind an average N(NaI)/N(KI) ratio from the NaI UV data of about 90,which is rather higher than that found previously by Hobbs and Lequeux.The Na UV-KI ratio shows a small increase in value with increasingcolumn density, while we also find a sample of low N(NaI)/N(KI) ratioclouds generally seen towards distant objects on high-latitudesightlines that reach into the halo, so that the ratio decreases moresharply at lower column densities. As the values of the ratio for thesehalo clouds (10-20) bracket the cosmic Na/K abundance ratio, we suggestthat these ratios result from a harder radiation field in the lowerhalo, such that the ionized fractions of NaI and KI become similar.Clearly caution needs to be applied in using any kind of `standardvalue' for the NaI/KI column density ratio.
| delta Scorpii: Visual Photometric Variability in 2000-2002
Not Available
| Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations
A list of 62 detached binaries having reliable data on the rotation ofthe line of apsides is considered. Theoretical estimates of the rate ofapsidal motion are obtained. These estimates are compared withobservational data. It is shown that cases in which the theoreticalestimate exceeds the observed value are several times more frequent thancases in which the theoretical value is lower than the observed one.This discrepancy increases when systems with more reliable observationaldata are considered.
| Binary Star Orbits. II. Preliminary First Orbits for 117 Systems
Orbital elements are presented for 117 binary systems with no previousorbit calculation. For nearly all of these systems, these elements mustbe regarded as preliminary, but the ephemerides presented here should berelatively accurate over the next several decades. Further, the analysisof these systems should highlight the need for their continuedobservation by dedicated programs to improve the veracity of theseelements.
| An upper limit to the interstellar C5 abundance in translucent clouds
We have analyzed high resolution spectra of several slightly tomoderately reddened stars collected at two observatories: ESO (La Silla)and Terskol (Northern Caucasia), to estimate the abundance of theC5 molecule in the interstellar medium. We confirm thepresence of a feature near 4975 Å which appears to be a weak DIBrather than the predicted C5 band since the origin band near5109 Å remains invisible even in spectra of high signal-to-noiseratio ( ~ 2500) and spectral resolution (R ~ 220 000). This confirmsthat the C5 abundance in translucent interstellar clouds isvery low. We estimate its limit as low as 1011cm-2 in the scale E(B-V)=0.35 for ``zeta" type objects thatis two times lower than that of Maier et al. (2002). Based on datacollected at the ESO 3.6 m telescope operated on La Silla Observatory,Chile and 2-m telescope of the Terskol Observatory, Russia.
| The mass ratio distribution of B-type visual binaries in the Sco OB2 association
A sample of 115 B-type stars in the Sco OB2 association is examined forexistence of visual companions in the J and K_s bands, using the ADONISnear-infrared adaptive optics system and coronograph. Practically allthe components in the separation range 0farcs3 -6farcs4 (45-900 AU) andmagnitudes down to K = 16 were detected. The K and J - K photometry ofthe primaries and differential photometry and astrometry of the 96secondaries are presented. Ten secondaries are new physical components,as inferred from the photometric and statistical criteria, while therest of the newly detected objects are faint background stars. After asmall correction for detection incompleteness and a conversion of thefluxes into masses, an unbiased distribution of the components massratio q was derived. The power law f(q)~ q-0.5 fits theobservations well, whereas a q-1.8 distribution, whichcorresponds to a random pairing of stars, is rejected. The companionstar fraction is 0.20+/-0.04 per decade of separation which iscomparable to the highest measured binary fraction among low-mass PMSstars and ~ 1.6 times higher than the binary fraction of low-mass dwarfsin the solar neighborhood and in open clusters in the same separationrange. Based on observations collected at the European SouthernObservatory, La Silla, Chile (ESO programme 65.H-0179). Tables 1, 3 andthe full version of Table 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/382/92
| BCD spectrophotometry of stars with the B[e] phenomenon. I. Fundamental parameters
Low resolution spectra in the lambda lambda3500 -4600 Å wavelengthrange of 23 stars with the B[e] phenomenon are presented. Spectralclassification of 15 program stars was performed using the BCDspectrophotometric system, based on the study of the Balmerdiscontinuity, which is independent of interstellar and circumstellardust extinctions and of circumstellar gas emissions and/or absorptions.From calibrations of the (lambda1 ,D) BCD parameters wedetermined the (Teff,log g, Mbol) of the studiedstars. For stars where this method could not be applied, we tried toestimate the temperature of the central star by using the Balmer and Hei emission lines and/or their visible energy distribution. The colourtemperature and the temperatures obtained from the study of Balmer andHe i lines are consistent with each other. The new results are comparedwith those obtained previously by other authors and discussed for eachstar individually. For some stars, differences between the effectivetemperatures derived using the BCD classification system and thoseobtained elsewhere, based on photometric or spectroscopic analysis,imply spectral-type classification disagreements ranging from 2-3 up to6 B sub-spectral types. The fundamental parameters of AS 119,CD-24°5721, Hen2-91, HD 316375 and BD-11°4747 were determinedfor the first time. A simple method was introduced to calculate total(interstellar+circumstellar) dust extinction towards the studied stars.For HD 53179, which is a double stellar system, and for HD 45677 and HD50138, which are suspected to be binaries, we predicted thecharacteristics of the components that are consistent with the observed(lambda1 ,D) parameters. However, the possible binarity of HD45677 and HD 50138 still needs to be confirmed spectroscopically. Dataobtained in CASLEO operated under agreement between the CONICET and theUniversities of La Plata, Córdoba and San Juan, Argentina.Partially based on observations done at ESO La Silla, Chili.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| He, CNO abundances and v sin i values in He-rich stars
We present projected rotational velocities distribution in He-rich starsagainst normal B type stars as well as the abundance analysis of lightelements and their comparison with results of earlier series. Theanalysis is based on high-resolution observations (R=40000) collected atESO, La Silla, Chile in the optical region and includes 11 stars,amongst them 5 new stars in comparison with an earlier sample. Thedistribution of projected rotational velocities shows a significantexcess of slow rotators, no He-rich stars having v sin i > 130 km/sat the significance level of 99.5%. Based on fully consistent LTEmodels, the helium abundance ranges from 0.1 (solar) to 0.4. Theanalysis on the new sample confirms the results of earlier paper: thelight element abundances display a diverse pattern from under-solar upto above-solar values. Carbon has the same abundance in He-rich and instandard stars for cool He-rich stars, following the predictions ofradiative diffusion in the presence of wind. The star HD149363 appearsrather as He-weak as based on the equivalent widths from R=40 000spectra.
| ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
| Observations of Small-Scale Interstellar Structure in Dense Atomic Gas
We present high-resolution (R~170,000) Kitt Peak National Observatorycoudé feed telescope observations of the interstellar K Ilambda7698 line toward five multiple star systems with saturated Na Icomponents. We compare the K I absorption-line profiles in each of thetwo (or three) lines of sight in these systems and find significantdifferences between the sight lines in three out of the five cases. Weinfer that the small-scale structure traced by previous Na Iobservations is also present in at least some of the components withsaturated Na I absorption lines, and thus the small-scale structurestraced by the neutral species are occurring at some level in clouds ofall column densities. We discuss the implications of that conclusion anda potential explanation by density inhomogeneities.
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| Properties of He-rich stars. II. CNO abundances and projected rotational velocities
We present an abundance analysis of light elements in the most massivechemically peculiar (CP) stars, He-rich stars. The analysis is based onboth low and high-resolution observations collected at ESO, La Silla,Chile in the optical region and includes 6 standard and 21 He-richstars. Light element abundances display a diverse pattern fromunder-solar up to above-solar values. Carbon is found underabundant inthe hottest He-rich stars and normal in the coolest ones, according tothe LTE model predictions. The distribution of projected rotationalvelocities shows a significant excess of slow rotators, no He-rich starshaving vsin i > 130 km s(-1) . Based on observations collected at theEuropean Southern Observatory, La Silla, Chile (programmes 7-043 and7-010 of periods 49 and 50 resp.)
| Light element abundances in He-rich stars
We present an abundance analysis of light elements in He-rich stars. Theanalysis is based on both low and high resolution observations collectedat ESO, La Silla, Chile in the optical region and includes 6 standardsand 21 He-rich stars. Light-element abundances display a diversepattern: they range from under-solar up to above-solar values.
| Age variation of helium abundance in He-rich stars.
Not Available
| The Scorpius OB2 Complex
The Sco OB2 complex is a member of the Local Association. Theassociation contains pre-main-sequence stars in addition to objects some3 x 10^7 yr old. If it is assumed that stars in wide binaries arecoeval, then the He-weak variables in the supercluster arepre-main-sequence, elevated above that sequence by an amount similar tothat of the 3 x 10^7 yr old, normal stars but contracting toward thesequence, not evolving from it. The apparent great depth of theassociation is probably a result of some foreground superclustermembers, superposed on Sco OB2, and a rift in the absorption cloudbetween Scorpius and Ophiuchus. The adjoining Chamaeleon complex alsoappears to be a member of the supercluster.
| Weak and post-T Tauri stars around B-type members of the Scorpius-Centaurus OB association
I report medium-resolution spectroscopic observations of six Hemission-line stars proposed by Meyer et al. (1993) to be T Tauri starsformed in the vicinity of the B1 giant Sco, a bright member of theSco-Cen OB association. Using spectroscopic criteria which aredistance-independent, I classify these stars in differentpremain-sequence (PMS) classes. Taking data from the literature, anumber of stars detected by X-ray observations around other B-typemembers of Sco-Cen are also classified. The current census of 'bonafide' low-mass PMS stars identified in about 9 sq deg in Sco-Cenincludes two classical T Tauri stars, 18 weak T Tauri stars (WTTSs), and10 post-T Tauri stars (PTTSs). The presence of a mixture of T Tauri andpost T Tauri stars implies that previous results based on isochronefitting that indicated an extremely young age for the Sco-Cen PMSlow-mass population are incorrect. A distance of about 125 pc forSco-Cen, instead of the 160 pc used in previous works, is consistentwith the Hipparcos parallaxes for many of the B-type stars and wouldlead to older H-R diagram ages. Taking into account that PTTSs aregenerally fainter and harder to identify than WTTSs, I argue that theWTTS-to-PTTS ratio in Sco-Cen may be of order unity. This resultsuggests that the low-mass stars of the OB association span an age rangesimilar to the B-type members the low- and high-mass star populationsare essentially coeval.
| Kinematical Structure of the Local Interstellar Medium: The Galactic Center Hemisphere
A survey of interstellar Na I D1 and D2 absorption features found in thespectra of 31 early-type stars in the first and fourth Galacticquadrants reveals a new picture of the large-scale kinematics ofinterstellar gas in the vicinity of the Sun. While absorption featuresfound in the spectra of stars in the fourth Galactic quadrant show thegas expanding from stars in the Scorpio-Centaurus OB association, starsin the first Galactic quadrant, in the range of distances covered bythis survey (74--312 pc from the Sun), show interstellar gas fallingtoward the Galactic plane with a bulk motion whose component parallel tothat plane is directed toward the Scorpio-Centaurus association. Thispicture differs completely from generally accepted models in which thenearby interstellar gas flows away from the Scorpio-Centaurusassociation toward the Galactic anticenter. Evidence for the presence ofan expanding shell-like feature that is reaching the solar system ispresented.
| ICCD Speckle Observations of Binary Stars. XVII. Measurements During 1993-1995 From the Mount Wilson 2.5-M Telescope.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1639H&db_key=AST
| Photovisual Magnitude Differences for 169 Double Stars
Photovisual magnitude differences determined from multi-exposurephotographic plates for 169 double stars are presented. The separationsrange from 1.5'' to 113\arcsec, and the photovisual magnitudedifferences vary from 0.03 to 6.14 magnitudes. The internal mean errorof a single magnitude difference estimate is +/-0.064 magnitude.
| Search for forced oscillations in binaries. II. β Scorpii A. New physical parameters and a search for line profile variability.
We present new spectroscopic data and physical parameters for theearly-type binary system β Sco A. Radial velocity measurements ofReticon spectra have been made using both cross-correlation anddisentangling techniques. Spectroscopic orbits, based on the new dataand published radial velocities are presented. The orbital period andapsidal motion rate have been refined using 603 radial velocitiescovering a time interval of 84-years. The anomalistic period is6.828245+/-0.000009-days, and the apsidal motion rate is˙(ω)=0.00131+/-0.00004°/day. The firstvisual-spectroscopic orbit for the system is given here as well, fromwhich we derive a parallax for the system of 0.0070+/-0.0001"corresponding to a distance of 143+/-3pc. This has allowed us to computethe absolute dimensions and mean internal structure constant for thesystem. We find, for the primary and secondary respectively, masses,radii, and effective temperatures of: m_p_/msun_=13.5+/-0.9,m_s_/msun_=9.6+/-0.4, r_p_/rsun_=6.8+/-0.4,r_s_/rsun_=4.2+/-0.3, T_p_=28000+/-2000K, andT_s_=26400+/-2000K. The corresponding spectral types of the componentsare B0.5IV-V and B1.5V. Line photometry produced from the disentanglingsolutions suggests the presence of eclipses in β Sco A, which mustbe verified through systematic photometry. We also present a tentativedetection of possible β Cep -type line profile variability in thesecondary.
| High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2.
We investigate the rotational velocities of early-type stars in the ScoOB2 association. We measure v.sin(i) for 156 established and probablemembers of the association. The measurements are performed with threedifferent techniques, which are in increasing order of expectedv.sin(i): 1) converting the widths of spectral lines directly tov.sin(i), 2) comparing artificially broadened spectra of low v.sin(i)stars to the target spectrum, 3) comparing the HeI λ4026 lineprofile to theoretical models. The sample is extended with literaturedata for 47 established members of Sco OB2. Analysis of the v.sin(i)distributions shows that there are no significant differences betweenthe subgroups of Sco OB2. We find that members of the binary populationof Sco OB2 on the whole rotate more slowly than the single stars. Inaddition, we find that the B7-B9 single star members rotatesignificantly faster than their B0-B6 counterparts. We test varioushypotheses for the distribution of v.sin(i) in the association. Theresults show that we cannot clearly exclude any form of randomdistribution of the direction and/or magnitude of the intrinsicrotational velocity vector. We also investigate the effects of rotationon colours in the Walraven photometric system. We show that positions ofB7-B9 single dwarfs above the main sequence are a consequence ofrotation. This establishes the influence of rotation on the Walravencolours, due primarily to surface gravity effects.
| The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
