Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
HD 143418: an unusual light variable and a double-lined spectroscopic binary with a CP primary
Aims.After a serendipitious discovery that HD 143418 is a lightvariable, we analyzed numerous UB{}V observations and HipparcosHp magnitudes transformed to Johnson V to find out whetherthe object is a very unusual spectroscopic binary. Methods:.Initial reductions of new photometry were carried out with the HEC22program, while the new spectra were reduced in the IRAF and SPEFOprograms. Orbital elements were derived with the FOTEL program, theKOREL disentangling was applied, and period searches were carried outusing phase dispersion minimalization technique and the programPERIOD04. Final modeling of radial-velocity and light variations wascarried out in PHOEBE. Results: .The brightness of HD 143418varies with a period of 2.282520d ± 0.000010d and with littlecolor changes. The light curve has a non-sinusoidal shape, whichmoreover changes from season to season. In each season, it can bedescribed by the basic frequency and its first harmonic. Its long-termvariations are characterized by cyclic variations of the amplitudes ofthe two frequencies and also the phase of the first frequency, the phaseof the first harmonic remaining secularly constant. The amplitude of theprincipal frequency varies over a larger range and in antiphase to thatof the first harmonic. Radial-velocity variations with the same periodidentify the object as a double-lined spectroscopic binary. Thesecondary spectrum is very faint, however. The rotation of the CPprimary is strongly subsynchronous (its probable rotation period is 6.8d± 0.2d). We show that the observed light variations can beunderstood as a combination of the ellipsoidal variability in the binarysystem and either a secularly varying pattern of spots on the secondaryor an inhomogeneous corotating cloud ejected from the primary.Conclusions: .Obviously, HD 143418 is an astrophysically interesting anddynamically unusual system that deserves future systematic spectral andphotometric monitoring and theoretical modeling.Based on spectral and photometric observations from the followingobservatories: Hvar, Ondřejov, San Pedro Mártir, Tubitak,and Phoenix. Table 3 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/263
| 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
| Properties and nature of Be stars. XVIII. Spectral, light and colour variations of 4 Herculis
An analysis of a rich series of spectroscopic and photometricobservations of the Be star 4 Her led to the following conclusions:4 Her is another example of a long-term Be variable with a type ofcorrelation between the brightness and emission strength, similar to 88Her (V744 Her) and BU Tau (Pleione). It is argued that the formation ofa new Be envelope of 4 Her starts with the creation of a slightly coolerpseudophotosphere at the equatorial regions of the star (seen under someintermediate inclination angle) which only gradually grows into anoptically thin extended envelope. Radial-velocity measurements of thecentre of the Hα emission and of the photospheric lines confirmthe binary nature of the star. The first reliable orbital elements arepresented. The 46-d orbit is nearly circular and has a semiamplitude of5-8 . () kms() -1. An LTE model atmosphere analysis of the photosphericspectrum of the primary leads to Teff=12500K, log g = 4.0,and v\sin i=300kms^-1. No direct evidence of the low-mass secondary wasfound and the possibility that the secondary fills its Roche lobe can besafely excluded. The central quasi-emission bumps (CQEB) visible as"doubling" of some shell lines appear during the phase of the formationof a new shell. They are strongest during the light minimum and becomefainter as the Hα emission strengthens. An unusual blue-shiftedabsorption component of the Hα line, never reported before,re-appears strictly periodically in the V peak of the Hα emissionat a limited range of velocities and orbital phases. It is argued thatthe observational facts about 4 Her are probably best reconciled by amodel which assumes that the secondary is a hot and rotationallyunstable object which looses mass towards the primary via a gas stream.However, some important findings remain unexplained. This research isbased on spectra from the \Ond\ and Haute Provence Observatories and onphotometry from Hvar, \Ond, Mt. Kobau, Toronto, APT Phoenix-10, andAAVSO observers.
| Reliable photometric reductions to the standard UBV (or uvby) system and accurate UBV magnitudes of bright standard stars from the northern part of the international Be program
A modified method of computer reduction of UBV (or uvby) photoelectricobservations to standard systems, which combines advantages of what hasso far been achieved in this area, is described in detail. A completereduction of over 46000 UBV observations obtained at Hvar Observatorybetween 1972 and 1991, and of nearly 5000 UBV observations secured atSkalnate Pleso Observatory between 1980 and 1987, was carried out usingthe new technique. It is argued that replacing the original Johnson'sUBV values for the non-variable stars that were observed by the meanvalues based on repeated observations over several years and applyingthe new reduction technique can ensure a stable reproduction of UBVmagnitudes, obviously quite close to the standard Johnson's ones, overmany years and from observatories situated at very different altitudesabove sea level within about 0.01mag in all three UBV magnitudes. A listof new accurate mean UBV values of 191 stars which were regularlyobserved at Hvar - and a part of them also at Skalnate Pleso - ascomparison, check and standard stars in the Be- and Ap-star observingprograms, is included for future use by photometric observers in theNorthern Hemisphere. For a number of these stars, we can guaranteesecular constancy within 0.mag01 during the past 5 to 15 years.
| Photoelectric monitoring of bright Be stars. II - 1989, 1990, 1991
UBV photometry obtained with the 0.25-m Automatic Photometric Telescopeof 12 bright, active Be stars: Theta Coronae Borealis, 4 Herculis, 88Herculis, 66 Ophiuchi, MWC 601, CX Draconis, 12 Vulpeculae, 28 Cygni, QRVulpeculae, Omicron Andromedae, EW Lacertae, and KX Andromedae isreported and discussed. The nature and cause of the photometricvariations and their relationship to variations at other wavelengths areexplored.
| UVBY beta photometry of peculiar B and A stars, discovered at Abastumani
Stromgren uvby photometry for 70 peculiar Bp, Ap, or Am type stars ispresented. The model grid of Relyea and Kurucz (1978) is used to obtaineffective temperatures and log g values, confirming the dwarf-nature ofAm stars. Good agreement is found between effective temperatures andequivalent spectral classes derived from the (b-y)0 values, although theA4-A5 stars in this sample may be cooler than normal stars ofluminosity-class III-V in this spectral range.
| Research Note - Absolute UBV Photometry at the Zacatecas Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985RMxAA..11...55S&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Herkul |
| Sað Açýklýk: | 15h58m25.68s |
| Yükselim: | +43°12'49.4" |
| Görünürdeki Parlaklýk: | 7.406 |
| Uzaklýk: | 177.936 parsek |
| özdevim Sað Açýklýk: | -17.1 |
| özdevim Yükselim: | -8.2 |
| B-T magnitude: | 7.627 |
| V-T magnitude: | 7.425 |
Kataloglar ve belirtme:
|
