J/AJ/169/47 Radial velocities of HD 101581 & exoplanets search (Kunimoto+, 2025)
Two Earth-size planets and an Earth-size candidate transiting the nearby star
HD 101581.
Kunimoto M., Lin Z., Millholland S., Venner A., Hinkel N.R., Shporer A.,
Vanderburg A., Bailey J., Brahm R., Burt J.A., Butler R.P., Carter B.,
Ciardi D.R., Collins K.A., Collins K.I., Colon K.D., Crane J.D.,
Daylan T., Diaz M.R., Doty J.P., Feng F., Guenther E.W., Horner J.,
Howell S.B., Janik J., Jones H.R.A., Kabath P., Kanodia S.,
Littlefield C., Osborn H.P., O'Toole S., Paegert M., Pintr P.,
Schwarz R.P., Shectman S., Srdoc G., Stassun K.G., Teske J.K.,
Twicken J.D., Vanzi L., Wang S.X., Wittenmyer R.A., Jenkins J.M.,
Ricker G.R., Seager S., Winn J.
<Astron. J., 169, 47 (2025)>
=2025AJ....169...47K 2025AJ....169...47K
ADC_Keywords: Exoplanets; Radial velocities; Spectroscopy; Optical;
Stars, dwarfs; Stars, K-type
Keywords: Exoplanet systems ; Exoplanet dynamics ; Exoplanets ;
Transit photometry
Abstract:
We report the validation of multiple planets transiting the nearby
(d=12.8pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481). This
system consists of at least two Earth-size planets whose orbits are
near a mutual 4:3 mean-motion resonance,
HD 101581 b (Rp=0.956-0.061+0.063R⊕, P=4.47d) and
HD 101581c (Rp=0.990-0.070+0.070R⊕, P=6.21d). Both
planets were discovered in Sectors 63 and 64 TESS observations and
statistically validated with supporting ground-based follow-up. We
also identify a signal that probably originates from a third
transiting planet, TOI-6276.03 (Rp=0.982-0.098+0.114R⊕,
P=7.87d). These planets are remarkably uniform in size and their
orbits are evenly spaced, representing a prime example of the
"peas-in-a-pod" architecture seen in other compact multiplanet
systems. At V=7.77, HD 101581 is the brightest star known to host
multiple transiting planets smaller than 1.5R⊕. HD 101581 is a
promising system for atmospheric characterization and comparative
planetology of small planets.
Description:
We obtained high-resolution spectra and RV measurements through the
TESS Follow-up Observing Program (TFOP) Subgroup 2 to search for
evidence of the target star being a spectroscopic binary or having a
stellar-mass companion based on large RV variations.
We obtained 14 spectra from the upgraded version of the Pontificia
Universidad Catolica High Echelle Resolution Optical Spectrograph
(PUCHEROS+), which is currently installed at the 1.52m telescope at
La Silla observatory, Chile. PUCHEROS+ is an R∼18,000 spectrograph
with a spectral coverage of 400-700nm. Observations were taken between
2023 May and 2024 March.
HD 101581 was observed between 2011 April and 2023 June as part of the
Magellan Exoplanet Long Term Survey (LTS), which is carried out on the
6.5m Magellan II Telescope at Las Campanas Observatory in Chile using
the Carnegie Planet Finder Spectrograph (PFS). PFS is a
high-resolution optical echelle spectrograph with a total wavelength
coverage of 391-734nm. The use of an iodine cell to measure RVs
results in a wavelength range used for RV derivation of 500-620nm. We
obtained 50 RVs.
HD 101581 was observed between 2002 April and 2015 January as part of
the Anglo-Australian Planet Search (Tinney+, 2001ApJ...551..507T 2001ApJ...551..507T),
which was carried out on the 3.9m Anglo-Australian Telescope (AAT) at
the Siding Spring Observatory in Australia using the University
College of London Echelle Spectrograph (UCLES). UCLES is a
high-resolution echelle spectrograph covering 482-855nm, limited to
500-620nm for RV derivation using an iodine cell. We obtained 79 RVs.
HD 101581 was observed between 2004 January and 2007 March by the High
Accuracy Radial Velocity Planet Searcher (HARPS) on the ESO 3.6m
telescope at La Silla Observatory, Chile, as part of the HARPS GTO
planet search program (Sousa+2008, J/A+A/487/373). HARPS is a
high-resolution echelle spectrograph covering 380-690nm. We obtained 6
RVs.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
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11 41 02.46 -44 24 18.6 HD 101581 = TOI-6276
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 50 149 Radial velocity measurements
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See also:
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
I/322A : UCAC4 Catalogue (Zacharias+, 2012)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
VI/120 : High-resolution synthetic stellar library (Coelho+, 2005)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)
J/AJ/132/161 : NStars project: The southern sample. I. (Gray+, 2006)
J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)
J/A+A/487/373 : Spectroscopic parameters of 451 HARPS-GTO stars (Sousa+, 2008)
J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)
J/AJ/142/19 : Speckle observations of KOI (Howell+, 2011)
J/ApJS/197/8 : Kepler's candidate multiple transiting planets (Lissauer+, 2011)
J/AJ/148/54 : The Hypatia Catalog ((Hinkel+, 2014)
J/AJ/152/180 : Bolometric fluxes of eclip. binaries in Tycho-2 (Stassun+, 2016)
J/ApJ/834/17 : Mass & radius of planets, moons, low mass stars (Chen+, 2017)
J/AJ/153/136 : Planets & their host stars with Gaia parallaxes (Stassun+, 2017)
J/A+A/619/L10 : pi Men radial velocity curves (Gandolfi+, 2018)
J/AJ/155/106 : New Doppler velocity measurements of GJ 876 (Millholland+, 2018)
J/A+A/615/A76 : Spectroscopic parameters of stars (SPECIES). I. (Soto+, 2018)
J/ApJS/235/38 : Kepler planetary cand. VIII. DR25 reliability (Thompson+, 2018)
J/AJ/155/48 : California-Kepler Survey (CKS). V. Masses & radii (Weiss+, 2018)
J/A+A/629/A111 : L 98-59 (TOI 175) HARPS observations (Cloutier+, 2019)
J/A+A/622/L7 : GJ143 and HD23472 radial velocity curves (Trifonov+, 2019)
J/ApJ/888/43 : APOGEE-Kepler Cool Dwarf star ages determinati. (Claytor+, 2020)
J/A+A/636/A74 : HARPS radial velocity database (Trifonov+, 2020)
J/AJ/161/106 : Radial velocities of 12 Psc and HD 159062 (Bowler+, 2021)
J/ApJS/254/42 : Hipparcos-Gaia (EDR3) Catalog of Accelerations (Brandt, 2021)
J/AJ/161/24 : TRICERATOPS predictions for 384 TOIs (Giacalone+, 2021)
J/ApJS/254/39 : Exoplanet candidates from TESS first 2yr obs (Guerrero+, 2021)
J/AJ/161/23 : RV & light curve of low mass star TOI 540 (Ment+, 2021)
J/A+A/665/A154 : HD23472 radial velocity observations (Barros+, 2022)
J/A+A/673/A69 : LTT 1445A ESPRESSO observations (Lavie+, 2023)
J/AJ/167/233 : Best-in-class TOIs for atmosph. characterisation (Hord+, 2024)
J/A+A/683/A125 : HARPS radial velocity database (Perdelwitz+, 2024)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Inst Instrument (1)
11- 26 F16.8 d BJD [2452389/2460385] Barycentric Julian Date
28- 36 F9.3 m/s RVel [-16.7/14464] Radial velocity (2)
38- 43 F6.3 m/s e_RVel [0.58/54] Uncertainty in rv
45- 50 F6.4 --- S [0.25/0.44]? S-index activity indicator
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Note (1): Instruments as follows:
HARPS = the High Accuracy Radial Velocity Planet Searcher (HARPS) on the
ESO 3.6m telescope at La Silla Observatory, Chile; 6 occurrences
PFS = the Carnegie Planet Finder Spectrograph (PFS) on the
6.5m Magellan II Telescope at Las Campanas Observatory in Chile;
50 occurrences
PUCHEROS+ = the Pontificia Universidad Catolica High Echelle Resolution
Optical Spectrograph (PUCHEROS+) on the 1.52m telescope at
La Silla observatory, Chile; 14 occurrences
UCLES = the University College of London Echelle Spectrograph (UCLES) on
the 3.9m Anglo-Australian Telescope (AAT) at the Siding Spring
Observatory in Australia; 79 occurrences
Note (2): The PUCHEROS+ RVs in the interactive plot have had a mean of
14.358km/s subtracted from the values provided in this table.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 17-Nov-2025