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Orbital parameters of the bright binary alpha Draconis based on amateur spectra from the STAROS database

G. Bertrand, C. Buil, M. Le Lain, V. Desnoux, O. Garde, E. Bertrand, A. Blais, JJ. Broussat, E. Bryssinck, L. Dalbin, X. Dupont, A. Garrigós, M. DiLazzaro, R. Leadbeater, V. Lecocq, J. Lecomte, A. Leduc, P. Louis, A. Maetz, L. Ribé de Pont, A. Stiewing, S. de Visscher, F. Weil

TL;DR

This study demonstrates that coordinated amateur spectroscopy via the STAROS platform can yield high-precision radial velocities for a bright eclipsing binary, Alpha Draconis. By aggregating 227 spectra from 25 observers across 9 countries, the authors produced a homogeneous RV curve and refined the orbital elements, achieving RV precision better than ~1 km s^-1. Spectral disentangling enabled the detection and characterization of the secondary component, including its rotation, while atmospheric parameters for both stars were derived from ATLAS9 models, aligning with recent professional analyses. Overall, the work showcases the potential of large-scale amateur data networks to contribute meaningfully to high-precision stellar spectroscopy and binary-star studies.

Abstract

We present the results of a STAROS monitoring campaign on the bright eclipsing binary star alpha Draconis. Over 200 high-resolution spectra were obtained by an international group of amateur astronomers. We were able to calculate an homogeneously covered radial velocity curve and redetermine the orbital elements of the alpha Draconis system. From the data set, we estimated the quality of our observations and accuracy of our radial velocity measurements. Finally, we have also implemented a spectral disentangling method to search for the signature of a companion star and used atmosphere models to constrain the atmospheric parameters of the system.

Orbital parameters of the bright binary alpha Draconis based on amateur spectra from the STAROS database

TL;DR

This study demonstrates that coordinated amateur spectroscopy via the STAROS platform can yield high-precision radial velocities for a bright eclipsing binary, Alpha Draconis. By aggregating 227 spectra from 25 observers across 9 countries, the authors produced a homogeneous RV curve and refined the orbital elements, achieving RV precision better than ~1 km s^-1. Spectral disentangling enabled the detection and characterization of the secondary component, including its rotation, while atmospheric parameters for both stars were derived from ATLAS9 models, aligning with recent professional analyses. Overall, the work showcases the potential of large-scale amateur data networks to contribute meaningfully to high-precision stellar spectroscopy and binary-star studies.

Abstract

We present the results of a STAROS monitoring campaign on the bright eclipsing binary star alpha Draconis. Over 200 high-resolution spectra were obtained by an international group of amateur astronomers. We were able to calculate an homogeneously covered radial velocity curve and redetermine the orbital elements of the alpha Draconis system. From the data set, we estimated the quality of our observations and accuracy of our radial velocity measurements. Finally, we have also implemented a spectral disentangling method to search for the signature of a companion star and used atmosphere models to constrain the atmospheric parameters of the system.

Paper Structure

This paper contains 10 sections, 14 equations, 7 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Spectroscopic Observations and data quality
  3. Observations
  4. Quality of spectra, measurement precision
  5. RADIAL VELOCITY MEASUREMENTS
  6. ORBIT DETERMINATION
  7. Secondary component extraction
  8. Atmospheric parameters
  9. Conclusions
  10. Individual radial velocity measurements

Figures (7)

  • Figure 1: $\delta\nu$ error in km s$^{-1}$ from Monte Carlo simulation as a function of spectral sampling ($n$), FWHM and the contrast of the line($C$). Each point represents the standard deviation of the Gaussian fit over 1000 synthetic spectra.
  • Figure 2: Result of the automatic removal algorithm of telluric lines. In red, the original spectrum; in black, the spectrum after telluric line removal.
  • Figure 3: Area of least-squares adjustment of the line position, with the calculated profile in red and the observed profile in black. Portion of spectrum from 2023-04-24, C. Buil
  • Figure 4: Dynamical spectra of the H$\alpha$ line in Doppler space.
  • Figure 5: Radial velocity curve calculated from 227 observations in the database STAROS database. The uncertainties include the $\delta\nu$ error described in paragraph 2.2, and the calibration error calculated from carefully selected telluric lines around the H$\alpha$ line.
  • ...and 2 more figures