Astrometric-Spectroscopic Determination of the Absolute Masses of the HgMn Binary Star φ Herculis

Torres, Guillermo

doi:10.1086/516756

Cited by 7 publications

(5 citation statements)

References 20 publications

(76 reference statements)

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“…φ Her: This star is a spectroscopic binary which has recently been resolved (Zavala et al 2007) and for which the mass of the CP star has been refined (Torres 2007). No field is detected, with an longitudinal field uncertainty of about 2 G.…”

Section: Hgmn Starsmentioning

confidence: 99%

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

Aurière

Wade

Lignières

et al. 2010

A&A

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Aims. We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am and HgMn stars. Methods. Using the NARVAL spectropolarimeter at the Télescope Bernard Lyot (Observatoire du Pic du Midi, France), we obtained high-resolution circular polarisation spectroscopy of 12 Am stars and 3 HgMn stars. Results. Using least squares deconvolution (LSD), no magnetic field is detected in any of the 15 observed stars. Uncertaintiies as low as 0.3 G (respectively 1 G) have been reached for surface-averaged longitudinal magnetic field measurements for Am (respectively HgMn) stars. Conclusions. Associated with the results obtained previously for Ap/Bp stars, our study confirms the existence of a magnetic dichotomy among A-type stars. Our data demonstrate that there is at least one order of magnitude difference in field strength between Zeeman detected stars (Ap/Bp stars) and non Zeeman detected stars (Am and HgMn stars). This result confirms that the spectroscopically-defined Ap/Bp stars are the only A-type stars harbouring detectable large-scale surface magnetic fields.

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Section: Hgmn Starsmentioning

confidence: 99%

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

Aurière

Wade

Lignières

et al. 2010

A&A

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“…16.2 (1998) and Pourbaix & Jorissen (2000), and another example of a similar application may be seen in the work of Torres (2007). Initial errors for the CfA velocities were taken as reported by the XCSAO correlation task.…”

Section: Combined Orbital Solutionmentioning

confidence: 99%

Observations and Orbital Analysis of the Giant White Dwarf Binary System Hr 5692

Stefanik¹,

Torres²,

Latham³

et al. 2011

The Astronomical Journal

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We report spectroscopic observations of the red giant star HR 5692, previously known to be a binary system both from other spectroscopic work and from deviations in the astrometric motion detected by the Hipparcos satellite. Earlier International Ultraviolet Explorer (IUE) observations had shown the presence of a hot white dwarf companion to the giant primary. We have combined our radial velocity observations with other existing measurements and with the Hipparcos intermediate astrometric data to determine a complete astrometric-spectroscopic orbital solution, providing the inclination angle for the first time. We also determine an improved parallax for the system of 10.12 ± 0.67 mas. We derive the physical properties of the primary, and with an estimate of its mass from stellar evolution models (1.84±0.40 M), we infer the mass of the white dwarf companion to be M WD = 0.59 ± 0.12 M. An analysis of an IUE white dwarf spectrum, using our parallax, yields T eff = 30,400 ± 780 K, log g = 8.25 ± 0.15, and a mass M WD = 0.79 ± 0.09 M , in marginal agreement with the dynamical mass.

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“…The mathematical formalism for modeling the Hipparcos abscissa residuals follows closely that described by van Leeuwen & Evans (1998), Pourbaix (2000), and Jancart et al (2005), including the correlations between measurements from the two independent data reduction consortia that processed the original Hipparcos observations (see Perryman et al 1997). Full details along with another example of the application of this technique may be found in Torres (2007).…”

Section: Orbital Solutionmentioning

confidence: 99%

Binary Orbit, Physical Properties, and Evolutionary State of Capella (Α Aurigae)

Torres

Claret

Young

2009

ApJ

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We report extensive radial-velocity measurements of the two giant components of the detached, 104day period binary system of Capella. Our highly accurate three-dimensional orbital solution based on all existing spectroscopic and astrometric observations including our own yields much improved masses for the primary and secondary of 2.466 ± 0.018 M ⊙ and 2.443 ± 0.013 M ⊙ , with relative errors of only 0.7% and 0.5%, respectively. The mass ratio is considerably closer to unity than previously believed, which has an impact on assessing the evolutionary state of the system. Improved values are presented also for the radii (11.87 ± 0.56 R ⊙ and 8.75 ± 0.32 R ⊙ ), effective temperatures (4920 ± 70 K and 5680 ± 70 K), and luminosities (79.5 ± 4.8 L ⊙ and 72.1 ± 3.6 L ⊙ ). The distance is determined to be 13.042 ± 0.028 pc, based on the accurate orbital parallax. The projected rotational velocities and individual rotation periods are also known. Capella is unique among evolved stars in that, in addition to all of the above, the chemical composition is known as well. This includes the overall metallicity [m/H], the carbon isotope ratio 12 C/ 13 C for the primary, and the lithium abundance and C/N ratios for both components. We present new or revised values for some of these. The latter three quantities are sensitive diagnostics of evolution, and change drastically for giants as a result of the deepening of the convective envelope during the first dredge-up. The secondary is crossing the Hertzprung gap, while the primary is believed to be in the longer-lived core-helium burning phase. Previous studies using only the masses, temperatures, and luminosities have found good agreement with stellar evolution models placing the primary in the clump. Here we compare all of the constraints simultaneously against three sets of current models. We find that they are unable to match all of the observations for both components at the same time, and at a single age, for any evolutionary state of the primary. This shows the great importance of chemical information for assessing the evolutionary state of giant stars. A comparison with models of tidal evolution yields similarly disappointing results, when tested against the fact that the orbit is circular, the primary is rotating synchronously, the secondary ∼12 times faster than synchronous, and the spin axes are apparently aligned with the axis of the orbit. When confronted in detail, our understanding of the advanced stages of stellar evolution is thus still very incomplete.

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Astrometric-Spectroscopic Determination of the Absolute Masses of the HgMn Binary Star φ Herculis

Cited by 7 publications

References 20 publications

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

Observations and Orbital Analysis of the Giant White Dwarf Binary System Hr 5692

Binary Orbit, Physical Properties, and Evolutionary State of Capella (Α Aurigae)

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