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1.
We present the first ever study of the bright star HD 1. The star was chosen arbitrarily just because of its outstanding Henry Draper number. Surprisingly, almost nothing is known about this bright 7.m4 star. Our observations were performed as part of the commissioning of the robotic telescope facility STELLA and its fiber‐fed high‐resolution optical echelle spectrograph SES in the years 2007–2010. We found long‐term radial velocity variations with a full amplitude of 9 km s–1 with an average velocity of –29.8 km s–1 and suggest the star to be a hitherto unknown single‐lined spectroscopic binary. A preliminary orbit with a period of 6.2 years (2279±69 days) and an eccentricity of 0.50±0.01 is given. Its rms uncertainty is just 73 m s–1. HD 1 appears to be a G9‐K0 giant of luminosity class IIIa with Teff = 4850±100 K, logg = 2.0±0.2, L ≈ 155 L⊙, a mass of 3.0±0.3 M⊙, a radius of 17.7 R⊙, and an age of ≈350 Myr. A relative abundance analysis led to a metallicity of [Fe/H] = –0.12 ± 0.09. The α ‐element silicon may indicate an overabundance of +0.13 though. The low strengths of some s‐process lines and a lower limit for the 12C/13C isotope ratio of ≥16 indicate that HD 1 is on the first ascend of the RGB. The absorption spectral lines appear rotationally broadened with a v sin i of 5.5±1.2 km s–1 but no chromospheric activity is evident. We also present photometric monitoring BV (RI)C data taken in parallel with STELLA. The star is likely a small‐amplitude (<10 mmag) photometric variable although no periodicity was found (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

2.
We present differential Hα and Hβ photometry of the very bright RS CVn‐binary α Aurigae (Capella)obtained with theVienna automatic photoelectric telescope in the years 1996 through 2000. Low‐level photometric variations of up to 0m.04 are detected in Hα. A multifrequency analysis suggests two real periods of 106 ± 3 days and 8.64 ± 0.09 days, that we interpret to be the rotation periods of the cool and the hot component of the Capella binary, respectively. These periods confirm that the hotter component of Capella rotates asynchronously, while the cooler component appears to be synchronized with the binary motion. The combined Hα data possibly contains an additional period of 80.4 days that we, however, believe is either spurious and was introduced due to seasonal amplitude variations or stems from a time‐variable circumbinary mass flow. The rotational periods result in stellar radii of 14.3 ± 4.6 R⊙ and 8.5 ± 0.5 R⊙ for the cool and hot component, respectively, and are in good agreement with previously published radii based on radiometric and interferometric techniques. The long‐period eclipsing binary Aurigae served as our check star, and we detected complex light variations outside of eclipse of up to 0m.15 in H α and 0m.20 in Hβ. Our frequency analysis suggests the existence of at least three significant periods of 132, 89, and 73 days. One of our comparison stars (HD 33167, F5V) was discovered to be a very‐low amplitude variable with a period of 2.6360 ± 0.0055 days.  相似文献   

3.
Detached eclipsing binaries constitute potential accurate distance tracers. They are also useful as the test bench of stellar evolution. In BD–00° 3357 eclipses are partial and its orbital period is 1.d4. Our combined spectroscopic and photometric solution yields secure parameters of this system. The model of the star was obtained using the Wilson‐Devinney method. As result we obtained a semi major axis of 7.65 R⊙ and a mass ratio of 0.78. The derived masses and radii are M 1 = 1.73 M⊙,M 2 = 1.34 M⊙R 1 = 1.78 R⊙, R 2 = 1.32 R⊙, respectively. These values correspond to the slightly evolved F0 and F6.5 components, both slightly less than 1Gyr old. The distance of the star was estimated to be 310 ± 60 pc, and the corresponding photometric parallax is 3.24 ± 0.74 mas. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
The Hipparcos Space Astrometry Mission photometric observations of V398 Lac, led to the discovery of its variability, allowing to classify it as an eclipsing binary with an orbital period of about 5.4 days. This prompted us to acquire highresolution échelle spectra with the aim of performing accurate radial velocity measurements and to determine the main physical parameters of the system's components. We present, for the first time, a double‐lined radial velocity curve and determine the orbital and physical parameters of the two components, that can be classified both as late B‐type stars. In particular, we obtained an orbital inclination i ∼ 85°. With this value of the inclination, we deduced masses M1 = 3.83±0.35 M⊙ andM2 = 3.29±0.32 M⊙, and radii R1 = 4.89±0.18 R⊙ and R2 = 2.45±0.11 R⊙ for the more massive and less massive components, respectively. Both components are well inside their own Roche lobes. The mass ratio is M2/M1 ∼ 0.86. We derived also the projected rotational velocities as v1 sin i = 79±2 km s–1 and v2 sin i = 19±2 km s–1. Our measurements indicate that the rotation of the primary star is essentially pseudo‐synchronized with the orbital velocity at the periastron, while the secondary appears to rotate very slowly and has not yet attained synchronization. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
We present the first long‐term Johnson UBVR observations and comprehensive photometric analysis of the W UMa‐type eclipsing binary V2612 Oph. Observations in the time interval between 2003 and 2009 enabled us to reveal the seasonal and long‐term variations of the light curve. Hence, we found that the mean brightness level of the light curve shows a variation with a period of 6.7 years. Maximum and minimum brightness levels of the light curve exhibit a variation from year to year which we attribute to a solar‐like activity. The O – C variation of eclipse timings of the system shows a decreasing parabolic trend and reveals a period decrease at a rate of P = 6.27×10‐7 day yr‐1 with an additional low‐amplitude sinusoidal variation that has a similar period as the long‐term brightness variations. Our light curve analysis shows that the system is a W‐subtype W UMa eclipsing binary. We calculated masses and radii of the primary and secondary components as M1 = 1.28 M⊙, M2 = 0.37 M⊙ and R1 = 1.31 R⊙, R2 = 0.75 R⊙, respectively. The derived absolute photometric parameters allow us to calculate a distance of 140 pc, which confirms that the system is a foreground star in the sky field of the Galactic open cluster NGC 6633. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
We report on our follow‐up spectroscopy of HD 1071478 B, a recently detected faint co‐moving companion of the exoplanet host star HD 107148 A. The companion is separated from its primary star by about 35″ (or 1790 AU of projected separation) and its optical and near infrared photometry is consistent with a white dwarf, located at the distance of HD 107148 A. In order to confirm the white dwarf nature of the co‐moving companion, we obtained follow‐up spectroscopic observations of HD 107148 B with CAFOS at the CAHA 2.2 m telescope. According to our CAFOS spectroscopy HD 107148 B is a DA white dwarf with an effective temperature in the range between 5900 and 6400K. The properties of HD 107148 B can further be constrained with the derived effective temperature and the known visual and infrared photometry of the companion, using evolutionary models of DA white dwarfs. We obtain for HD 107148 B a mass of 0.56 ± 0.05 M⊙, a luminosity of (2.0 ± 0.2) × 10–4 L⊙, log g [cm s–2]) = 7.95 ± 0.09, and a cooling age of 2100 ± 270 Myr. With its white dwarf companion the exoplanet host star HD 107148 A forms an evolved stellar system, which hosts at least one exoplanet. So far, only few of these evolved systems are known, which represent only about 5 % of all known exoplanet host multiple stellar systems. HD 107148 B is the second confirmed white dwarf companion of an exoplanet host star with a projected separation to its primary star of more than 1000 AU. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
From accurate radial‐velocity measurements covering 11 circuits of the orbit of the composite‐spectrum binary 45 Cnc, together with high‐resolution spectroscopy spanning nearly 3 circuits, we have (i) isolated cleanly the spectrum of the early‐type secondary, (ii) classified the component spectra as G8 III and A3 III, (iii) derived the first double‐lined orbit for the system and a mass ratio (M1/M2) of 1.035 ± 0.01, and (iv) extracted physical parameters for the component stars, deriving the masses and (log) luminosities of the G star and A star as 3.11 and 3.00 M⊙, and 2.34 and 2.28 L⊙, respectively, with corresponding uncertainties of ±0.10 M⊙ and ±0.09 L⊙. Since the mass ratio is close to unity, we argue that the more evolved component is unlikely to have been a red giant long enough to have made multiple ascents of the RGB, an argument that is supported somewhat by the rather high eccentricity of the orbit (e = 0.46) and the evolutionary time‐scales of the two components, but chiefly by the presence of significant Li I in the spectrum of the cool giant. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
Photometric BV light curves of BO CVn obtained in 1992 and new times of minima are presented. The primary minimum shows a transit, whereas the secondary minimum, shows an occultation. The system may be classified as an A‐type W UMa system. A complete study of minima allows one to detect a possibly increasing period by about 0.037 s/yr. This indicates that the conservative mass transfer rate from the less massive component to the more massive one is 1.57 10—10M⊙ /yr. Because of the variable period, the new ephemeris is determined for future observations. Using the Wilson‐Devinney code a simultaneous solution of the B and V light curves is also performed. The analysis shows that the system is in a contact configuration with q = 0.205 ± 0.001 and fillout factor (f) = 0.18, T1 = 7240 K (fixed), T2 = 7150± 10 K. The high orbital inclination i = 87°.54 ± 0.26 was con firmed by photometric observations of the secondary minimum.  相似文献   

9.
An investigation of the stability of the transfer function of the European Southern Observatory's Very Large Telescope Interferometer has been carried out through observations of Fomalhaut, which was observed over a range in hour angle from 21:50–05:24 on 20 October 2002. No significant variation in the transfer function was found for the zenith angle range 5°–70°. The projected baseline varied between 139.7 m and 49.8 m during the observations and, as an integral part of the determination of the transfer function, a new accurate limb‐darkened angular diameter for Fomalhaut of 2.109 ± 0.013 mas has been established. This has led to improved values for the emergent flux = (3.43 ± 0.10)×108 Wm−2, effective temperature = 8819 ± 67 K and radius = (1.213 ± 0.011)×109 m (R/R⊙ = 1.744 ± 0.016). The luminosity has been found to be (6.34 ± 0.20)×1027 W (L/L⊙ = 16.5 ± 0.5). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
We re‐discuss the evolutionary state of upper main sequence magnetic stars using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. We confirm our previous results obtained from the study of Ap and Bp stars with accurate measurements of the mean magnetic field modulus and mean quadratic magnetic fields that magnetic stars of mass M < 3 M⊙ are concentrated towards the centre of the main‐sequence band. In contrast, stars with masses M > 3 M⊙ seem to be concentrated closer to the ZAMS. The study of a few known members of nearby open clusters with accurate Hipparcos parallaxes confirms these conclusions. Stronger magnetic fields tend to be found in hotter, younger and more massive stars, as well as in stars with shorter rotation periods. The longest rotation periods are found only in stars which spent already more than 40% of their main sequence life, in the mass domain between 1.8 and 3 M⊙ and with log g values ranging from 3.80 to 4.13. No evidence is found for any loss of angular momentum during the main‐sequence life. The magnetic flux remains constant over the stellar life time on the main sequence. An excess of stars with large obliquities β is detected in both higher and lower mass stars. It is quite possible that the angle β becomes close to 0. in slower rotating stars of mass M > 3 M⊙ too, analog to the behaviour of angles β in slowly rotating stars of M < 3 M⊙. The obliquity angle distribution as inferred from the distribution of r ‐values appears random at the time magnetic stars become observable on the H‐R diagram. After quite a short time spent on the main sequence, the obliquity angle β tends to reach values close to either 90. or 0. for M < 3 M⊙. The evolution of the obliquity angle β seems to be somewhat different for low and high mass stars. While we find a strong hint for an increase of β with the elapsed time on the main sequence for stars with M > 3 M⊙, no similar trend is found for stars with M < 3 M⊙. However, the predominance of high values of β at advanced ages in these stars is notable. As the physics governing the processes taking place in magnetised atmospheres remains poorly understood, magnetic field properties have to be considered in the framework of dynamo or fossil field theories. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
Photoelectric light curve (LC) solutions of the close binary system TW And were obtained using the PHOEBE program (version 0.31a). Absolute parameters of the stellar components were then determined, enabling us to discuss the structure and evolutionary status of TW And. The configuration of the system based on the LCs solutions indicates that the secondary component is slightly detached from its critical Roche surface. In addition, times of minima data (“O –C curve”) were analyzed. Apart from an almost parabolic variation of the general trend of the O –C data, indicative of a secular increase in the orbital period with a rate 0.032 s yr–1, which was attributed to a mass transfer with a rate of Δm2 = –1.10 × 10–10 M⊙ yr–1. Additionally, a sinusoidal variation with a period of 52.75 ± 1.80 yr, modulating the orbital period, was found, which we attribute to a third body orbiting the system. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
New BV light curves and times of minimum light for the short period W UMa system LO And were analyzed to derive the preliminary physical parameters of the system. The light curves were obtained at Ankara University Observatory during 5 nights in 2003. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson‐Devinney 2003 code. The present solution reveals that LO And has a photometric mass ratio q = 0.371 and is an A‐type contact binary. The period of the system is still increasing, which can be attributed to light‐time effect and mass transfer between the components. With the assumption of coplanar orbit of the third body the revealed mass is M3 = 0.21M⊙. If the period change dP/dt = 0.0212 sec/yr is caused only by the mass transfer between components (from the lighter component to the heavier) the calculated mass transfer rate is dm/dt = 1.682×10−7M⊙/yr. The absolute radii and masses estimated for the components, based on our photometric solution and the absolute parameters of the systems which have nearly same period are R1 = 1.30R⊙, R2 = 0.85R⊙, M1 = 1.31M⊙, M2 = 0.49M⊙ respectively for the primary and secondary components. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
The semi‐regular variable star RU Vulpeculae (RU Vul) is being observed visually since 1935. Its pulsation period and amplitude are declining since ∼1954. A leading hypothesis to explain the period decrease in asymptotic giant branch (AGB) stars such as RU Vul is an ongoing flash of the He‐burning shell, also called a thermal pulse (TP), inside the star. In this paper, we present a CCD photometric light curve of RU Vul, derive its fundamental parameters, and test if the TP hypothesis can describe the observed period decline. We use CCD photometry to determine the present‐day pulsation period and amplitude in three photometric bands, and high‐resolution optical spectroscopy to derive the fundamental parameters. The period evolution of RU Vul is compared to predictions by evolutionary models of the AGB phase. We find that RU Vul is a metal‐poor star with a metallicity [M/H] = –1.59 ± 0.05 and an effective surface temperature of Teff = 3634 ± 20 K. The low metallicity of RU Vul and its kinematics indicate that it is an old, low‐mass member of the thick disc or the halo population. The present day pulsation period determined from our photometry is ∼108 d, the semiamplitude in the V ‐band is 0.39 ± 0.03 mag. The observed period decline is found to be well matched by an evolutionary AGB model with stellar parameters comparable to those of RU Vul. We conclude that the TP hypothesis is in good agreement with the observed period evolution of RU Vul. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

14.
Data from 11 years of continuous spectroscopic observations of the active RS CVn‐type binary star EI Eridani – gained at NSO/McMath‐Pierce, KPNO/Coudé Feed and during the MUSICOS 98 campaign – were used to obtain 34 Doppler maps in three spectroscopic lines for 32 epochs, 28 of which are independent of each other. Various parameters are extracted from our Doppler maps: average temperature, fractional spottedness, and longitudinal and latitudinal spot‐occurrence functions. We find that none of these parameters show a distinct variation nor a correlation with the proposed activity cycle as seen from photometric long‐term observations. This suggests that the photometric brightness cycle may not necessarily be due to just a cool spot cycle. The general morphology of the spot pattern remains persistent over the whole period of 11 years. A large cap‐like polar spot was recovered from all our images. A high degree of variable activity was noticed near latitudes of ≈60–70° where the appendages of the polar spot emerged and dissolved (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
We search for stellar and substellar companions of young nearby stars to investigate stellar multiplicity and formation of stellar and substellar companions. We detect common proper‐motion companions of stars via multi‐epoch imaging. Their companionship is finally confirmed with photometry and spectroscopy. Here we report the discovery of a new co‐moving (13 σ) stellar companion ∼17.8 arcsec (350AU in projected separation) north of the nearby star HD141272 (21 pc).With EMMI/NTT optical spectroscopy we determined the spectral type of the companion to be M3±0.5V. The derived spectral type as well as the near infrared photometry of the companion are both fully consistent with a M⊙ dwarf located at the distance of HD141272 (21 pc). Furthermore the photometry data rules out the pre‐main sequence status, since the system is consistent with the ZAMS of the Pleiades. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
We present the results of our investigation of the geometrical and physical parameters of the W UMa‐type binary V404 Peg from analysis of CCD (BVRI) light curves and radial velocity data. The photometric data were obtained during 2010 at Ankara University Observatory (AUO). Light and radial velocity observations were analyzed simultaneously by using the well‐known Wilson‐Devinney (2007 revision) code to obtain absolute and geometrical parameters. Our solution indicates that V404 Peg is an A‐type overcontact binary with a mass ratio of q = 0.243 and an overcontact degree of f = 32.1 %. Combining our light curves with the radial velocity curves from Maciejewski & Ligeza (2004), we determined the absolute parameters of this system as follows: a = 2.672 R⊙, M1 = 1.175 M⊙, M2 = 0.286 M⊙, R1 = 1.346 R⊙, and R2 = 0.710 R⊙. Finally, we discuss the evolutionary condition of the system (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
In this study we determined precise orbital and physical parameters of the very short‐period low‐mass contact binary system CC Com. The parameters are obtained by analysis of new CCD data combined with archival spectroscopic data. The physical parameters of the cool and hot components are derived as Mc = 0.717(14) M⊙, Mh = 0.378(8) M⊙, Rc = 0.708(12) R⊙, Rh = 0.530(10) R⊙, Lc = 0.138(12) L⊙, and Lh = 0.085(7) L⊙, respectively, and the distance of the system is estimated as 64(4) pc. The times of minima obtained in this study and with those published before enable us to calculate the mass transfer rate between the components which is 1.6 × 10–8 M⊙ yr–1. Finally, we discuss the possible evolutionary scenario of CC Com (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

18.
We separate and analyse the component spectra of the composite‐spectrum binary HD 208253. We find that the cool primary is an evolving star of spectral type G7 III, while its hot secondary is an early‐A dwarf. The giant is currently near the lowest point of the red‐giant branch and is slightly less luminous than its dwarf companion. We provide a set of precise radial‐velocity measurements for both stars. The double‐lined orbit which we derive from them shows that the component mass ratio is close to unity (q = 1.05 ± 0.01). We deduce the physical properties of both stars, determine their respective masses to be 2.75 ± 0.07 Me (giant) and 2.62 ± 0.07 Me (dwarf), and show that the orbit's inclination is within a degree or two of 68°. The spectrum of the A‐type component has quite component has quite narrow lines (we infer a rotational velocity of 18 km s–1), though since the period of the orbit is well over 1 year that component cannot be in synchronous rotation. An intriguing property of the dwarf is its enhanced Sr and Ba, though it does not exhibit the other spectral peculiarities that would signal a classical Am star. While by no means unique amongst the multitude of oddities exhibited by A and early‐F stars, this dwarf which we have uncovered in a long‐period binary offers valuable constraints and challenges to stellar‐evolution theory. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

19.
We have redetermined the kinematic parameters of the Gould Belt using currently available data on the motion of nearby young (log t < 7.91) open clusters, OB associations, and moving stellar groups. Our modeling shows that the residual velocities reach their maximum values of ?4 km s?1 for rotation (in the direction of Galactic rotation) and +4 km s?1 for expansion at a distance from the kinematic center of ≈300 pc. We have taken the following parameters of the Gould Belt center: R 0 = 150 pc and l 0 = 128°. The whole structure is shown to move relative to the local standard of rest at a velocity of 10.7 ± 0.7 km s?1 in the direction l = 274° ± 4° and b = ?1° ± 3°. Using the derived rotation velocity, we have estimated the virial mass of the Gould Belt to be 1.5 × 106 M ⊙.  相似文献   

20.
A period study of the young binary AR Aur based on the extensive series of published photoelectric/ccd minima times indicates the cyclic (O – C) variation for the system. This continuous oscillatory variation covers almost three cycles, about 6000 orbital periods, by the present observational data. It can be attributed to the light‐time effect due to a third body with a period of 23.68 ± 0.17 years in the system. The analysis yields a light‐time semi‐amplitude of 0.0084 ± 0.0002 day and an orbital eccentricity of 0.20 ± 0.04. Adopting the total mass of AR Aur, the mass of the third body assumed in the co‐planar orbit with the binary is M3 = 0.54 ± 0.03 M⊙ and the semimajor axis of its orbit is a3 = 13.0 + 0.2 AU. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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