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Post Info TOPIC: Double Stars of Taurus


Posts: 131433
Theta^2 Tauri

Title: Spectra disentangling applied to the Hyades binary Theta^2 Tau AB: new orbit, orbital parallax and component properties
Authors: K. B. V. Torres, P. Lampens, Y. Frémat, H. Hensberge, Y. Lebreton, Y., P. Skoda

Theta^2 Tauri is a detached and single-lined interferometric-spectroscopic binary as well as the most massive binary system of the Hyades cluster. The system revolves in an eccentric orbit with a periodicity of 140.7 days. The secondary has a similar temperature but is less evolved and fainter than the primary. It is also rotating more rapidly. Since the composite spectra are heavily blended, the direct extraction of radial velocities over the orbit of component B was hitherto unsuccessful. Using high-resolution spectroscopic data recently obtained with the Elodie (OHP, France) and Hermes (ORM, La Palma, Spain) spectrographs, and applying a spectra disentangling algorithm to three independent data sets including spectra from the Oak Ridge Observatory (USA), we derived an improved spectroscopic orbit and refined the solution by performing a combined astrometric-spectroscopic analysis based on the new spectroscopy and the long-baseline data from the Mark III optical interferometer. As a result, the velocity amplitude of the fainter component is obtained in a direct and objective way. Major progress based on this new determination includes an improved computation of the orbital parallax. Our mass ratio is in good agreement with the older estimates of Peterson et al. (1991, 1993), but the mass of the primary is 15-25% higher than the more recent estimates by Torres et al. (1997) and Armstrong et al. (2006). Due to the strategic position of the components in the turnoff region of the cluster, these new determinations imply stricter constraints for the age and the metallicity of the Hyades cluster. The location of component B can be explained by current evolutionary models, but the location of the more evolved component A is not trivially explained and requires a detailed abundance analysis of its disentangled spectrum.

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Posts: 131433
RE: Double Stars of Taurus

Title: The Detection of Low Mass Companions in Hyades Cluster Spectroscopic Binary Stars
Authors: C. F. Bender (1), M. Simon (2) ((1) Naval Research Laboratory, (2) Stony Brook University)

We have observed a large sample of spectroscopic binary stars in the Hyades Cluster, using high resolution infrared spectroscopy to detect low mass companions. We combine our double-lined infrared measurements with well constrained orbital parameters from visible light single-lined observations to derive dynamical mass ratios. Using these results, along with photometry and theoretical mass-luminosity relationships, we estimate the masses of the individual components in our binaries. In this paper we present double-lined solutions for 25 binaries in our sample, with mass ratios from ~0.1-0.8. This corresponds to secondary masses as small as ~0.15 Msun. We include here our preliminary detection of the companion to vB 142, with a very small mass ratio of q=0.06+-0.04; this indicates that the companion may be a brown dwarf. This paper is an initial step in a program to produce distributions of mass ratio and secondary mass for Hyades cluster binaries with a wide range of periods, in order to better understand binary star formation. As such, our emphasis is on measuring these distributions, not on measuring precise orbital parameters for individual binaries.

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Posts: 131433

theta1 and theta2 Tauri
This pair, theta1 Tau and theta2 Tau, are a wide double in the Hyades cluster. The magnitudes of 77 and 78 Tauri are 3.4 and 3.8.
They are separated by 337 of arc.
Primary : yellow ( 77, Theta-1)
Companion: blue-white (78, Theta-2)
The pair are visible in binoculars.

theta1 and  theta2 Tauri
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Theta2 and theta1.kmz

Position(2000): RA 04 28 43.33, Dec +15 53 27.7

Kappa1 and Kappa2 Tauri
This pair are a close double in Taurus. The magnitudes of this pair are 4.2 and 5.3.
They are separated by 5.3 of arc.
¹ Tauri is a white A-type subgiant with an apparent magnitude of +4.21. ² Tauri is a white A-type main sequence dwarf with an apparent magnitude of +5.27.
Between the two bright stars is a binary star made up of two 9th magnitude stars, Kappa Tauri C and Kappa Tauri D, which are 5.3 arcseconds from each other and 183 arcseconds from ¹ Tau. Two more 12th magnitude companions fill out the star system, Kappa Tauri E, which is 136 arcseconds from ¹ Tau, and Kappa Tauri F, 340 arcseconds away from ² Tau.
Kappa Tauri is approximately 153 light years from Earth.
The pair are visible in binoculars.

Kappa1 and Kappa2 Tauri
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Kappa1 and Kappa2 Tauri.kmz

Position(2000): RA 04 25 23.33, Dec +22 14 07.7

Sigma2 and sigma1 Tauri
This pair are a wide double in Taurus. The magnitudes of this pair are 4.8 and 5.2.
They are separated by 431 of arc.
The pair are visible in binoculars.

Sigma2 and sigma1 Tauri
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Sigma2 and sigma1 Tauri.kmz

Position(2000): RA 04 39 13.33, Dec +15º 51 57.7

Tau Chi Tauri (59 Tau)
magnitude: 5.4
Distance (light years): 270
Spectral type: B9V
Its companion is mag 8.4, at 19.6" separation.

Chi Tauri.kmz

Position(2000): RA 04 22 34.9436 , Dec +25º 37 45.531

Tau Psi Tauri (42 Tau)
magnitude: 5.2
Distance (light years): 92
Yellow-white dwarf
Spectral type: F1V

Psi Tauri
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Psi Tauri.kmz

Position(2000): RA 04 07 00.4547, Dec +29º 00 04.678

62 Taurus

Magnitude: 6.36/ 7.94
Spectral Class: B3V A1V
A pair of white stars. The primary is a spectral class B3V. The secondary is spectral class A1V and is almost pure white. The secondary is located at position angle 290º (WNW), with a separation of over 28.
Visible in small scopes.

62 Taurus
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62 Taurus.kmz

Position(2000): RA: 4h23m59.70s Dec:+24º18'03.0"

7 Taurus
visual triple
Magnitude 5.94/ 9.92 HR1086 HD22091
An attractive double for small scopes. The primary is a creamy white colour with a spectral class of A2V. The secondary is located at 56 degrees (ENE) with a separation of 23.
The primary is also a very close visual double separated by just over 0.7 with a magnitude of 6.6 & 6.86, Spectral class A3V+A3V. Visible in 8 -12 scopes.

7 Taurus.kmz

Position(2000): RA: 3h34m26.60s Dec +24º27'52.0"

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