J/AJ/159/83 Transit analysis for the K2-25 system (Kain+, 2020)
The young planetary system K2-25: constraints on companions and starspots.
Kain I.J., Newton E.R., Dittmann J.A., Irwin J.M., Mann A.W., Thao P.C.,
Charbonneau D., Winters J.G.
<Astron. J., 159, 83 (2020)>
=2020AJ....159...83K 2020AJ....159...83K
ADC_Keywords: Stars, M-type; Exoplanets; Photometry, RI
Keywords: Exoplanet astronomy ; Exoplanet systems ; Exoplanet dynamics ;
Exoplanets ; Hot Neptunes
Abstract:
The abundance of planets with orbital periods of a few to tens of days
suggests that exoplanets experience complex dynamical histories.
Planets in young stellar clusters or associations have
well-constrained ages and therefore provide an opportunity to explore
the dynamical evolution of exoplanets. K2-25b is a Neptune-sized
planet in an eccentric, 3.48day orbit around an M4.5 dwarf star in the
Hyades cluster (650Myr). In order to investigate its non-zero
eccentricity and tight orbit, we analyze transit timing variations
(TTVs) which could reveal clues to the migration processes that may
have acted on the planet. We obtain 12 nonconsecutive transits using
the MEarth observatories and long-term photometric monitoring, which
we combine with 10 transits from the Spitzer Space Telescope and 20
transits from K2. Tables of MEarth photometry accompany this work. We
fit each transit lightcurve independently. We first investigate
whether inhomogeneities on the stellar surface (such as spots or
plages) are differentially affecting our transit observations. The
measured transit depth does not vary significantly between transits,
though we see some deviations from the fiducial transit model. We then
looked for TTVs as evidence of a nontransiting perturber in the
system. We find no evidence for >1M⊕ mass companions within a
2:1 period ratio, or for >5M⊕ mass planets within a 7:2 period
ratio.
Description:
We present new transit observations and long-term photometric
monitoring of K2-25b obtained using the MEarth observatories. We
combine our data with transits observed from the Spitzer and K2 space
telescopes.
K2-25 was observed by the Kepler spacecraft in Campaign 4, between
2015 February 8 and 2015 April 20 at a 30min cadence. We downloaded
the lightcurves available on the Mikulski Archive for Space Telescopes
(MAST) on 7 September 2018.
Spitzer observed 10 full transits of K2-25b, five in each of
3.6µm and 4.5µm, both taken with the Infrared Array Camera (IRAC)
over the period of 2016 November 28 to 2017 May 11 (Program ID: 13037,
PI: Mann).
These data are presented in detail in Thao+ (2020AJ....159...32T 2020AJ....159...32T).
We obtained lightcurves of K2-25 with the MEarth Observatories.
MEarth-North comprises eight 40cm telescopes at the Fred Lawrence
Whipple Observatory on Mount Hopkins, Arizona, and MEarth-South is a
near-twin located at the Cerro Tololo Inter-American Observatory in
Chile. The MEarth CCDs are 2048x2048pixels with pixels scales of
0.78"/pixel in the north and 0.84"/pixel in the south. All data
presented here were observed using the Schott RG715 filter.
Integration times of 60s were used throughout, and the recorded
observation time is the midpoint of the exposure. Photometric
monitoring began on 2015 December 9, and this work includes data
obtained through 2018 August 4.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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04 13 05.61 +15 14 52.0 K2-25 = EPIC 210490365 (P=3.4845638)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 40 16089 *MEarth transits photometry
fig2.dat 33 3302 Stellar rotational variability over three years
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Note on fig1.dat: The data are uncorrected for stellar variability.
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See also:
J/A+A/331/81 : Hyades membership (Perryman+ 1998)
J/A+A/367/111 : A Hipparcos study of the Hyades cluster (de+, 2001)
J/ApJ/709/168 : Eccentric orbits in exoplanets (Anglada-Escude+, 2010)
J/ApJ/795/161 : Activity & rotation in Praesepe and the Hyades (Douglas+, 2014)
J/ApJS/216/7 : Planets Around Low-Mass Stars (PALMS). IV. (Bowler+, 2015)
J/ApJ/818/153 : MEarth photometry: nearby M-dwarf magnitudes (Dittmann+, 2016)
J/ApJ/821/93 : Rotation & Galactic kinematics of mid M dwarfs (Newton+, 2016)
J/A+A/592/A13 : HD 219828 radial velocity curve (Santos+, 2016)
J/ApJ/825/19 : Mass-radius relationship for planets with Rp<4 (Wolfgang+,2016)
J/ApJ/836/167 : K2 planetary syst. around low-mass stars. I. (Dressing+, 2017)
J/AJ/154/142 : Corrected photometry for GJ1132 for eclipses (Dittmann+, 2017)
J/AJ/154/224 : Transiting planets in young clusters from K2 (Rizzuto+, 2017)
J/AJ/156/140 : 4 new eclipsing mid M-dwarf systems from MEarth (Irwin+, 2018)
J/AJ/156/217 : Stellar properties for M dwarfs in MEarth-South (Newton+, 2018)
J/A+A/610/A20 : HITEP. II. Transiting exoplanets imaging (Evans+, 2018)
J/A+A/613/A41 : 5 exoplanet light and RV curves (Mancini+, 2018)
J/A+A/616/A10 : 46 open clusters GaiaDR2 HR diagrams (Gaia Collaboration, 2018)
http://www.cfa.harvard.edu/MEarth : MEarth project home page
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- N [87/192] Transit number
5- 18 F14.6 d BJD [2457365/2457732] Barycentric Julian Date
20- 28 F9.6 mag Dmag [-0.28/0.08] Differential magnitude
30- 37 F8.6 mag e_Dmag [0.002/0.09] Uncertainty in Dmag
39- 40 I2 --- Tel [1/18] MEarth telescope identifier
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD [2457366/2458335] Barycentric Julian Date
16- 24 F9.6 mag mag [-0.06/0.05] Relative brightness
26- 33 F8.6 mag e_mag [0.002/0.03] Uncertainty in mag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 16-Apr-2020