J/AJ/163/19 EXPRES. III. Photometry & RVel of eps Eridani (Roettenbacher+, 2022)
EXPRES.
III. Revealing the Stellar Activity Radial Velocity Signature of
εEridani with photometry and interferometry.
Roettenbacher R.M., Cabot S.H.C., Fischer D.A., Monnier J.D.,Henry G.W.,
Harmon R.O., Korhonen H., Brewer J.M., Llama J., Petersburg R.R., Zhao L.L.,
Kraus S., Le Bouquin J.-B., Anugu N., Davies C.L., Gardner T.,
Lanthermann C., Schaefer G., Setterholm B., Clark C.A., Jorstad S.G.,
Kuehn K., Levine S.
<Astron. J., 163, 19 (2022)>
=2022AJ....163...19R 2022AJ....163...19R
ADC_Keywords: Stars, K-type; Exoplanets; Spectra, optical; Photometry;
Radial velocities
Keywords: Planet hosting stars ; Radial velocity ; Starspots
Abstract:
The distortions of absorption line profiles caused by photospheric
brightness variations on the surfaces of cool, main-sequence stars can
mimic or overwhelm radial velocity (RV) shifts due to the presence of
exoplanets. The latest generation of precision RV spectrographs aims
to detect velocity amplitudes ≲10cm/s, but requires mitigation of
stellar signals. Statistical techniques are being developed to
differentiate between Keplerian and activity-related velocity
perturbations. Two important challenges, however, are the
interpretability of the stellar activity component as RV models become
more sophisticated, and ensuring the lowest-amplitude Keplerian
signatures are not inadvertently accounted for in flexible models of
stellar activity. For the K2V exoplanet host εEridani, we
separately used ground-based photometry to constrain Gaussian
processes for modeling RVs and TESS photometry with a light-curve
inversion algorithm to reconstruct the stellar surface. From the
reconstructions of TESS photometry, we produced an activity model that
reduced the rms scatter in RVs obtained with EXPRES from 4.72 to
1.98m/s. We present a pilot study using the CHARA Array and MIRC-X
beam combiner to directly image the starspots seen in the TESS
photometry. With the limited phase coverage, our spot detections are
marginal with current data but a future dedicated observing campaign
should allow for imaging, as well as allow the stellar inclination and
orientation with respect to the debris disk to be definitively
determined. This work shows that stellar surface maps obtained with
high-cadence, time-series photometric and interferometric data can
provide the constraints needed to accurately reduce RV scatter.
Description:
High-resolution spectra of εEri were acquired with the EXtreme
PREcision Spectrograph (EXPRES) commissioned at the 4.3m Lowell
Discovery Telescope (LDT). EXPRES is an optical spectrograph optimized
for wavelengths 380-780nm, reaching a typical resolving power of
R∼137500.
εEri was observed with two Automatic Photoelectric Telescopes
(APTs) at Fairborn Observatory. 600 observations were obtained with
the T8 (0.8m) telescope from 2013 October 11 through 2020 February 20
and 64 observations on the T4 (0.75m) telescope from 2020 October 30
through 2020 November 30. Differential photometric observations were
obtained in the Stromgren b and y bandpasses, but are presented as a
combined (b+y)/2 bandpass.
Object:
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RA (2000) DE Designation(s) (Period)
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03 32 55.84 -09 27 29.7 epsilon Eridani = * eps Eri (P=11.4d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 26 164 EXPRES radial velocities
table2.dat 27 600 Stroemgren (b+y)/2 differential photometric data of
epsilon Eri with the APT T8
table3.dat 27 64 Stroemgren (b+y)/2 differential photometric data of
epsilon Eri with the APT T4
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See also:
J/A+AS/114/247 : Limb-darkening coefficients for R I J H K (Claret+, 1995)
J/A+A/527/A140 : Mass limits on substellar companions (Reffert+, 2011)
J/ApJ/744/138 : Calibrated visibilities of ε Eri (Baines+, 2012)
J/ApJ/763/L26 : SMARTS observations of eps Eridani (Metcalfe+, 2013)
J/A+A/552/A78 : Solar like stars radial velocities (Zechmeister+, 2013)
J/A+A/564/A125 : AGN Torus model comparison of AGN in the CDFS (Buchner+, 2014)
J/ApJS/210/5 : The twenty-five year Lick planet search (Fischer+, 2014)
J/ApJ/807/23 : Companions RS CVn primaries. I. sig Gem (Roettenbacher+, 2015)
J/A+A/618/A20 : Limb-darkening for TESS, Kepler, Corot, MOST (Claret, 2018)
J/A+A/628/A9 : MASCARA-2b transmission spectra (Casasayas-Barris+, 2019)
J/AJ/157/33 : Radial velocity exploration of εEridani (Mawet+, 2019)
J/ApJ/874/107 : HARPS-N solar radial velocities & activity (Milbourne+, 2019)
J/A+A/635/A13 : HD41248 Radial velocities & activity indicators (Faria+, 2020)
J/AJ/159/187 : 1st RVs with EXPRES spectrograph: 51Peg (Petersburg+, 2020)
J/AJ/161/26 : EXPRES. II. HD101501 photo. & radial velocity (Cabot+, 2021)
J/A+A/648/A103 : Thorium line list (Dumusque+, 2021)
J/A+A/646/A6 : sigma Gem BV photometry (Korhonen+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d RJD [58710/59167] Reduced Julian Date; RJD-2400000
14- 20 F7.3 m/s RVel [-14.5/10.9] Radial velocity of eps Eridani
22- 26 F5.3 m/s e_RVel [0.2/0.7] Radial velocity uncertainty
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 d HJD [56576/58900] Heliocentric Julian Date; HJD-2400000
11- 18 F8.5 mag Omag [-2/-1.95] Observed Stroemgren differential mag
(b+y)/2
20- 27 F8.5 mag Cmag [-1.99/-1.95] Long-term trend-removed mag (b+y)/2
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 d HJD [59152/59184] Heliocentric Julian Date; HJD-2400000
11- 18 F8.5 mag Omag [-1.98/-1.95] Observed Stroemgren differential mag
(b+y)/2
20- 27 F8.5 mag Cmag [-1.97/-1.96] Long-term trend-removed mag (b+y)/2
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History:
From electronic version of the journal
References:
Brewer et al. Paper I : 2020AJ....160...67B 2020AJ....160...67B
Cabot et al. Paper II : 2021AJ....161...26C 2021AJ....161...26C Cat. J/AJ/161/26
(End) Prepared by [AAS], Coralie Fix [CDS], 30-Mar-2022