J/AJ/158/136 Keck & APF radial velocities for HD 200964 (Rosenthal+, 2019)
Measuring the orbital parameters of radial velocity systems in mean-motion
resonance: a case study of HD 200964.
Rosenthal M.M., Jacobson-Galan W., Nelson B., Murray-Clay R.A., Burt J.A.,
Holden B., Chang E., Kaaz N., Yant J., Butler R.P., Vogt S.S.
<Astron. J., 158, 136-136 (2019)>
=2019AJ....158..136R 2019AJ....158..136R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Radial velocities
Keywords: planets and satellites: detection -
planets and satellites: dynamical evolution and stability -
planets and satellites: fundamental parameters -
planets and satellites: individual HD 200964 b, HD 200964 c -
techniques: radial velocities
Abstract:
The presence of mean-motion resonances (MMRs) complicates analysis and
fitting of planetary systems that are observed through the radial velocity
(RV) technique. MMR can allow planets to remain stable in regions of phase
space where strong planet-planet interactions would otherwise destabilize
the system. These stable orbits can occupy small phase space volumes,
allowing MMRs to strongly constrain system parameters, but making searches
for stable orbital parameters challenging. Furthermore, libration of the
resonant angle and dynamical interaction between the planets introduces
another long-period variation into the observed RV signal, complicating
analysis of the periods of the planets in the system. We discuss this
phenomenon using the example of HD 200964. By searching through parameter
space and numerically integrating each proposed set of planetary
parameters to test for long-term stability, we find stable solutions in
the 7:5 and 3:2 MMRs in addition to the originally identified 4:3 MMR.
The 7:5 configuration provides the best match to the data, while the 3:2
configuration provides the most easily understood formation scenario.
In reanalysis of the originally published shorter-baseline data, we find
fits in both the 4:3 and 3:2 resonances, but not in the 7:5. Because the
time baseline of the data is shorter than the resonant libration period,
the current best fit to the data may not reflect the actual resonant
configuration. In the absence of a full sample of the longer libration
period, we find that it is of paramount importance to incorporate long-term
stability when the orbital configuration of the system is fit.
Description:
The RV measurements of HD 200964 used in this analysis come from three
different facilities: the Hamilton spectrometer (Vogt 1987PASP...99.1214V 1987PASP...99.1214V)
paired with the Shane 3 m or the 0.6 m Coude Auxiliary Telescope, the
HIRES spectrometer (Vogt et al. 1994SPIE.2198..362V 1994SPIE.2198..362V) on Keck I, and the
Levy spectrometer on the APF telescope (Vogt et al. 2014PASP..126..359V 2014PASP..126..359V).
In all cases, the star's Doppler shifts were measured by placing a cell of
gaseous iodine in the converging beam of the telescope, imprinting the
stellar spectrum with a dense forest of iodine lines from 5000 to 6200 Å
(Butler et al. 1996PASP..108..500B 1996PASP..108..500B). These iodine lines were used to
generate a wavelength calibration that reflects any changes in temperature
or pressure that the spectrometer undergoes, and enables the measurement
of each spectrometer's point-spread function. Although each spectrometer
covers a much broader wavelength range, 3400-9000 Å for the Hamilton and
3700-8000 Å for HIRES and the Levy, only the iodine-rich 5000-6200 Å
region was used for determining the observation's RV shift. For each stellar
spectrum, the iodine region was divided into ∼700 individual 2 Å chunks.
Each chunk produces an independent measure of the wavelength, point-spread
function, and Doppler shift. The final measured velocity is the weighted
mean of the velocities of all the individual chunks. It is important
to note that all RVs reported here have been corrected to the solar system
barycenter, but are not tied to any absolute RV system. As such, they are
relative velocities, with a zero-point that is usually set simply to the
mean of each data set. New to this paper are 50 velocities taken with Keck
HIRES and 36 velocities taken with the APF, all obtained as part of
the long-running LCES Doppler survey (Butler et al. 2017, J/AJ/153/208).
Objects:
----------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------
21 06 39.84 +03 48 11.2 HD 200964 = HIP 104202
----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 25 50 Keck radial velocities for HD 200964
table3.dat 25 42 APF radial velocities for HD 200964
--------------------------------------------------------------------------------
See also:
J/AJ/153/208 : LCES HIRES/Keck radial velocity Exoplanet Survey (Butler+, 2017)
J/AJ/157/149 : Transit parameters for planets around subgiants (Luhn+, 2019)
Byte-by-byte Description of file: table2.dat table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 F13.5 --- JD Julian Date
15- 20 F6.2 m/s RV [-59.08/47.35] Radial velocity
22- 25 F4.2 m/s e_RV [0.57/4.34] Uncertainty in RV
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 25-Oct-2019