J/AJ/161/26 EXPRES. II. HD 101501 photometry and radial velocity (Cabot+, 2021)
EXPRES.
II. Searching for planets around active stars: a case study of HD101501.
Cabot S.H.C., Roettenbacher R.M., Henry G.W., Zhao L., Harmon R.O.,
Fischer D.A., Brewer J.M., Llama J., Petersburg R.R., Szymkowiak A.E.
<Astron. J., 161, 26 (2021)>
=2021AJ....161...26C 2021AJ....161...26C
ADC_Keywords: Exoplanets; Stars, G-type; Radial velocities; Spectra, optical;
Photometry
Keywords: Exoplanet detection methods ; Radial velocity ;
Gaussian Processes regression
Abstract:
By controlling instrumental errors to below 10cm/s, the EXtreme
PREcision Spectrograph (EXPRES) allows for a more insightful study of
photospheric velocities that can mask weak Keplerian signals. Gaussian
processes (GP) have become a standard tool for modeling correlated
noise in radial velocity data sets. While GPs are constrained and
motivated by physical properties of the star, in some cases they are
still flexible enough to absorb unresolved Keplerian signals. We apply
GP regression to EXPRES radial velocity measurements of the 3.5Gyr old
chromospherically active Sun-like star, HD101501. We obtain tight
constraints on the stellar rotation period and the evolution of spot
distributions using 28 seasons of ground-based photometry, as well as
recent Transiting Exoplanet Survey Satellite data. Light-curve
inversion was carried out on both photometry data sets to reveal the
spot distribution and spot evolution timescales on the star. We find
that the >5m/s rms radial velocity variations in HD101501 are well
modeled with a GP stellar activity model without planets, yielding a
residual rms scatter of 45cm/s. We carry out simulations, injecting
and recovering signals with the GP framework, to demonstrate that
high-cadence observations are required to use GPs most efficiently to
detect low-mass planets around active stars like HD101501. Sparse
sampling prevents GPs from learning the correlated noise structure and
can allow it to absorb prospective Keplerian signals. We quantify the
moderate to high-cadence monitoring that provides the necessary
information to disentangle photospheric features using GPs and to
detect planets around active stars.
Description:
We analyze 76 RVs (over 33 distinct nights) of HD101501 obtained
between 2018 and 2020. Data were collected with the EXtreme PREcision
Spectrograph (EXPRES) commissioned at the 4.3m Lowell Discovery
Telescope. EXPRES achieves ∼30cm/s measurement precision for a pixel
signal-to-noise ratio of 250 at 5500Å. EXPRES has typical resolving
power of R∼137500 and spans a wavelength range of 380-780nm.
Fairborn Observatory's Automatic Photoelectric Telescopes (APTs)
observed HD101501 for 28 seasons (spanning 1993 April 18 to 2020 June
21).
Transiting Exoplanets Survey Satellite (TESS) observed HD101501 during
Sector 22 (2020 February 18 to 2020 March 18).
Objects:
---------------------------------------------------------
RA (2000) DE Designation(s) (Period)
---------------------------------------------------------
11 41 03.02 +34 12 05.9 HD101501 = * 61 UMa (P=16d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 44 76 RV measurements and activity indicators
table6.dat 52 28 Summary of APT photometric observations for HD101501
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/622/1102 : The planet-metallicity correlation. (Fischer+, 2005)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/A+A/469/309 : Chromospheric activity in late-type stars (Cincunegui+,2007)
J/A+A/506/303 : CoRoT-7 radial velocities (Queloz+, 2009)
J/ApJ/746/101 : Diameters and temperatures of AFG stars (Boyajian+, 2012)
J/A+A/552/A16 : Limb-darkening for CoRoT, Kepler, Spitzer II. (Claret+,2013)
J/A+A/551/A79 : Radial velocity periodic variations τCeti (Tuomi+, 2013)
J/A+A/564/A125 : AGN Torus model comparison of AGN in CDFS (Buchner+, 2014)
J/ApJS/210/5 : The twenty-five year Lick planet search (Fischer+, 2014)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/A+A/608/A35 : K2-18 HARPS time-series (Cloutier+, 2017)
J/MNRAS/474/2094 : Inferring probabilistic stellar rotation per (Angus+, 2018)
J/A+A/618/A20 : Limb-darkening for TESS, Kepler, Corot, MOST (Claret, 2018)
J/A+A/639/A50 : HD 164922 d HARPS-N time series (Benatti+, 2020)
J/A+A/635/A13 : HD41248 Radial velocities & activity indicator (Faria+,2020)
J/AJ/159/187 : First RVs with EXPRES spectrograph: 51Peg (Petersburg+,2020)
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d HJD [18237/19034] Heliocentric Julian Date; JD-2440000
12- 18 F7.3 m/s RVel [-10.9/14.1] Radial velocity
20- 24 F5.3 m/s e_RVel [0.004/1] Error on RVel
26- 31 F6.4 0.1nm EWHa [0.91/2.03]? Hα equivalent width
33- 37 F5.1 m/s BIS [-78/83]? Bisector span
39- 44 F6.1 m/s FWMH [572/7646]? FWMH of th CCF
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Seas-b [1992/2019] Year of the season beginning
6- 9 I4 yr Seas-e [1993/2020] Year of the season ending
11- 13 I3 --- Nobs [37/146] Number of observations during season
15- 19 I5 d HJD-b [49095/58802] Heliocentric julian date of the
beginning of observation; JD-2400000
21- 25 I5 d HJD-e [49161/59022] Heliocentric julian date of the end
of observation; JD-2400000
27- 33 F7.5 mag Sigma [0.002/0.008] APT magnitude observed
35- 46 A12 mag Mean Seasonal mean
48- 52 F5.2 d Per [12.2/16.8] Period
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History:
From electronic version of the journal
References:
Brewer et al. Paper I : 2020AJ....160...67B 2020AJ....160...67B
(End) Prepared by Coralie Fix [CDS], 12-Mar-2021