J/ApJ/883/105 PA & angular separation measurements of 80 Tau (Torres, 2019) ================================================================================ Dynamical masses for the Hyades binary 80 Tauri. Torres G. =2019ApJ...883..105T ================================================================================ ADC_Keywords: Stars, double and multiple Keywords: Visual binary stars Abstract: The empirical mass-luminosity relation in the Hyades cluster rests on dynamical mass determinations for five binary systems, of which one is eclipsing and the other four are visual or interferometric binaries. The last one was identified and first measured more than 20yr ago. Here we present dynamical mass measurements for a new binary system in the cluster, 80 Tau, which is also a visual pair with a much longer orbital period of about 170yr. Although we lack the radial-velocity information that has enabled the individual mass determinations in all of the previous binaries, we show that it is still possible to derive the component masses for 80 Tau using only astrometric observations. This is enabled by the accurate proper motion measurements from the Hipparcos and Gaia missions, which constrain the orbital acceleration in the plane of the sky. Separate proper motion values from Gaia for the primary and secondary provide a direct constraint on the mass ratio. Our mass measurements, M_A_=1.63_-0.13_^+0.30^M_{sun}_ and M_B_=1.11_-0.14_^+0.21^M_{sun}_, are consistent with the mass-luminosity relation defined by the five previously known systems, which in turn is in good agreement with current models of stellar evolution. Description: The discovery of 80 Tau as a visual binary is credited to Struve (1837AN.....14..249S). Some 180 measurements of the position angle and angular separation ({theta}, {rho}) have been recorded in the 180yrs since, the latest one in 2015. They cover a full orbital cycle, with a periastron passage around 1892. A listing of these measurements as contained in the Washington Double Star Catalog (WDS) was kindly provided by Brian Mason (U.S. Naval Observatory, Washington D.C.), with the dates of observation uniformly transformed from Besselian years to Julian years. To these we have added one observation from 1897 that was not included in the WDS listing, which was made by Burnham (1906gcds.book.....B) very close to periastron, and one from the Gaia/DR2 Catalog (I/345) that we constructed by differencing the positions of the two components measured separately by the mission. In all we used 177 measures of the angular separation and 183 of the position angle. See Section 2 and Table 1. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 04 30 08.60 +15 38 16.2 80 Tau = ** STF 554 ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 59 184 Visual observations of 80 Tau -------------------------------------------------------------------------------- See also: B/wds : The Washington Visual Double Star Catalog (Mason+ 2001-2020) I/259 : The Tycho-2 Catalogue (Hog+ 2000) I/345 : Gaia DR2 (Gaia Collaboration, 2018) J/A+AS/101/551 : Optical polarization of 1000 stars (Leroy 1993) J/A+A/331/81 : Hyades membership (Perryman+ 1998) J/A+A/341/121 : Visual binary orbits and masses (Soederhjelm 1999) J/AJ/120/2638 : CCD speckle obs. of binary stars. II. (Horch+, 2000) J/A+A/381/446 : Astrometric Radial Velocities. III. (Madsen+, 2002) J/A+A/393/897 : Rotational velocities of A-type stars II. (Royer+, 2002) J/ApJS/159/100 : Temperatures and Rc photometry in the Hyades (Taylor+, 2005) J/AJ/131/3008 : Double star speckle measures (Horch+, 2006) J/ApJS/176/262 : VRI photometry & theta values in open clusters (Taylor+, 2008) J/A+A/493/1099 : CaII HK emission in rapidly rotating stars (Schroeder+, 2009) J/other/Ser/180.71 : Masses of visual binaries (Cvetkovic+, 2010) J/A+A/531/A92 : Deep all-sky census of the Hyades (Roeser+, 2011) J/A+A/546/A69 : Orbits of visual binaries and dynamical masses (Malkov+, 2012) J/A+A/559/A43 : Pan-STARRS1 (PS1) observations of the Hyades (Goldman+, 2013) J/ApJ/776/67 : Rotational tracks (van Saders+, 2013) J/ApJ/795/161 : Activity & rotation in Praesepe & Hyades (Douglas+, 2014) J/ApJ/804/146 : Atmospheric parameters for nearby B-F stars (David+, 2015) J/ApJ/826/171 : IR data of debris disk vs metallicity of stars (Gaspar+, 2016) J/MNRAS/456/2070 : Eccentricity distribution of wide bin. (Tokovinin+, 2016) J/ApJ/856/23 : BANYAN. XI. The BANYAN {Sigma} algorithm (Gagne+, 2018) J/A+A/623/A72 : Binarity of HIP stars from Gaia pm anomaly (Kervella+, 2019) J/PAZh/45/35 : Orbits of 451 wide visual double stars (Izmailov, 2019) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 F9.4 yr Year [1831.18/2015.846] Year of observation in Julian years 11- 16 F6.3 deg PA [1.7/78.2]? Position angle {theta} (1) 18- 22 F5.3 arcsec e_PA [0.012/0.15]? Position angle uncertainty along tangential direction {sigma}_t_ (2) 24- 28 F5.2 deg (O-C)t [-8.4/22.2]? Position angle (O-C)_{theta}_ value 30- 34 F5.2 --- (O-C)t/sig [-2.7/3.1]? Position angle (O-C)_{theta}_ value divided by uncertainty in theta {sigma}_{theta}_ 36- 40 F5.3 arcsec rho [0.4/1.9]? Angular separation {rho} 42- 46 F5.3 arcsec e_rho [0.012/0.2]? Uncertainty in rho {sigma}_{rho}_ (2) 48- 53 F6.3 arcsec (O-C)rho [-0.4/0.4]? Angular separation (O-C)_{rho}_ value 55- 59 F5.2 --- (O-C)rho/sig [-2.2/2.7]? Angular separation (O-C)_{rho}_ divided by uncertainty in rho {sigma}_{rho}_ -------------------------------------------------------------------------------- Note (1): The position angles listed are the original ones; precession corrections were applied internally during the orbital analysis. Note (2): The uncertainties listed in the table correspond to the e_rho and e_PA values given in the text multiplied by the scaling factors f_{rho}_ and f_{theta}_ reported in Section 3, and represent the final errors used in the solution described there. We also list the residuals in angular separation and position angle normalized to their uncertainties e_rho and {sigma}_{theta}_=e_PA/rho. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Mar-2021