J/ApJ/885/9 Triple system HD 28363; RVel and visual observations (Torres+, 2019) ================================================================================ Dynamical masses for the Triple system HD28363 in the Hyades Cluster. Torres G., Stefanik R.P., Latham D.W. =2019ApJ...885....9T ================================================================================ ADC_Keywords: Stars, double and multiple; Spectra, optical; Radial velocities; Keywords: Visual binary stars ; Open star clusters ; Spectroscopy ; Space astrometry ; Stellar masses ; Fundamental parameters of stars ; Main sequence stars ; Multiple stars ; Radial velocity Abstract: The star HD28363 in the Hyades cluster has been known for over a century as a visual binary with a period of 40yr. The secondary is, in turn, a single-lined spectroscopic binary with a 21day period. Here we report extensive spectroscopic monitoring of this hierarchical triple system that reveals the spectral lines of the third star for the first time. Combined with astrometric information, this makes it possible to determine the dynamical masses of all three stars. Only six other binaries in the Hyades have had their individual component masses determined dynamically. We infer the properties of the system by combining our radial-velocity measurements with visual observations, lunar occultation measurements, and with proper motions from the Hipparcos and Gaia missions that provide a constraint on the astrometric acceleration. We derive a mass of 1.341_-0.024_^+0.026^M{odot} for the visual primary, and 1.210{+/-}0.021 and 0.781{+/-}0.014 M{sun} for the other two stars. These measurements along with those for the other six systems establish an empirical mass-luminosity relation in the Hyades that is in broad agreement with current models of stellar evolution for the known age and chemical composition of the cluster. Description: Our spectroscopic monitoring of HD28363 at the Center for Astrophysics (CfA), carried out as part of a large survey of the Hyades cluster, began in 1980 November and continued until 2013 September. Observations were gathered with four different instruments. Spectra through 2007 November were made with the CfA Digital Speedometers (DS) on the 1.5m Tillinghast reflector at the Fred L. Whipple Observatory (Mount Hopkins, AZ), the 1.5m Wyeth reflector at the Oak Ridge Observatory (in the town of Harvard, MA), now closed, and the 4.5m equivalent Multiple Mirror Telescope (also on Mount Hopkins) before its conversion to a monolithic 6.5m mirror. These echelle instruments with a resolving power of R~35000 were equipped with intensified photon-counting Reticon detectors and recorded a single order 45{AA} wide centered at 5187{AA}, featuring the MgIb triplet. An additional 28 spectra of higher quality were obtained using the Tillinghast Reflector Echelle Spectrograph (TRES), a bench-mounted fiber-fed echelle instrument attached to the 1.5m Tillinghast reflector, with a resolving power of R~44000. These spectra cover the wavelength range 3800-9100{AA} in 51 orders. Since its discovery in 1904 the relative positions of HD28363 (angular separations, and position angles) have been measured by visual observers about 130 times, not counting another dozen occasions in which the pair was not resolved. The most recent observation was obtained at the end of 2016. Measurements until about 1970 were made with filar micrometers, and most observations since were made using the speckle interferometry technique. A listing of all measurements was kindly provided to us by Brian Mason (U.S. Naval Observatory), extracted from the Washington Double Star Catalog (WDS), with the dates of observation having been uniformly converted from the traditional Besselian years to Julian years. Objects: ---------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------- 04 28 59.75 +16 09 32.7 HD 28363 = HD 28363 ---------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 61 169 CfA radial velocities for HD 28363 table2.dat 65 131 Visual observations of HD 28363 ------------------------------------------------------------------------------- See also: B/wds : The Washington Visual Double Star Catalog (Mason+, 2001-2020) I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/345 : Gaia DR2 (Gaia Collaboration, 2018) J/A+A/341/121 : Visual binary orbits and masses (Soederhjelm 1999 J/AJ/124/1144 : Orbits of 171 single-lined spectroscopic binaries (Latham,2002) J/AJ/132/111 : BV(RI)_C_photometry of 77 Hyades stars (Joner+, 2006) J/A+A/498/949 : Velocities 1253 F-K dwarfs in open clusters (Mermilliod+, 2009) J/ApJ/883/105 : PA & angular separation measurements of 80 Tau (Torres, 2019) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.4 d HJD [44560/56559] Heliocentric Julian Date, JD-2400000 12- 16 F5.2 km/s RVelA [28.71/46.98] Radial velocity, component A 18- 21 F4.2 km/s e_RVelA [0.1/2.6] Uncertainty in RVel-A 23- 27 F5.2 km/s RVelBa [7.1/91.81] Radial velocity, component Ba 29- 32 F4.2 km/s e_RVelBa [0.09/1.9] Uncertainty in RVel-Ba 34- 39 F6.2 km/s RVelBb [-40.08/94.8]? Radial velocity, component Bb 41- 45 F5.2 km/s e_RVelBb [1.1/16.5]? Uncertainty in RVel-Bb 47- 53 F7.5 --- Phase-I [0.05/0.87] Inner Orbital phase 55- 61 F7.5 --- Phase-O [0.0007/1] Outer Orbital phase -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 F9.4 yr Date [1904/2017] Julian year 11- 16 F6.2 deg PA [68.8/275]? Position angle 18- 25 F8.6 arcsec e_PA [0.001/0.03]? Uncertainty in PA (1) 27- 31 F5.2 deg (OC)PA [-9.63/23.42]? Residual, Positional Angle 33- 37 F5.2 --- (OC)PA-n [-2.09/2.94]? Normalized Residual, (O-C)PA/(e_PA/Sep) 39- 44 F6.4 arcsec Sep [0.07/0.49]? Separation 46- 51 F6.4 arcsec e_Sep [0.0002/0.06]? Uncertainty in Sep (1) 53- 59 F7.4 arcsec (OC)Sep [-0.11/0.1]? Residual, separation 61- 65 F5.2 --- (OC)Sep-n [-2.06/2.69]? Normalized Residual, (O-C)Sep/(e_Sep) -------------------------------------------------------------------------------- Note (1): The uncertainties listed in the table correspond to the e_Sep and e_PA values given in the text multiplied by the error inflation factors, fSep and fPA, reported in Section 4, and represent the final errors used in the solution described there. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Coralie Fix, 31-May-2021