J/A+A/706/A98 Spectroscopy study of nearby LOFAR M dwarfs (Koo+, 2026)
Spectroscopic characterization of LOFAR radio-emitting M dwarfs.
Koo E., Stefansson G., Kavanagh R.D., Delamer M., Mahadevan S.,
Callingham J.R., Vedantham H., Robertson P., Bruijne D., Bender C.F.,
Canas C.I., Diddams S., Espinoza-Retamal J.I., Fernandes R.B.,
Halverson S., Kanodia S., Krolikowski D., Lin A.S.J., Pope B.J.S.,
Roy A., Schwab C., Terrien R., Wright J.T.
<Astron. Astrophys. 706, A98 (2026)>
=2026A&A...706A..98K 2026A&A...706A..98K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Stars, dwarfs ; Spectroscopy ; Optical ;
Radio sources ; Infrared ; Spectral types ; Abundances, [Fe/H] ;
Effective temperatures ; Rotational velocities ;
Radial velocities ; Stars, diameters
Keywords: techniques: radial velocities - techniques: spectroscopic -
planets and satellites: fundamental parameters -
planet-star interactions - binaries: spectroscopic - stars: low-mass
Abstract:
Recent observations with the LOw Frequency ARray (LOFAR) have revealed
19 nearby M dwarfs showing bright circularly polarised radio
emission. One of the possible sources of such emission is through
magnetic star-planet interactions (MSPI) with unseen close-in planets.
We present initial results from a spectroscopic survey with the
Habitable-zone Planet Finder (HPF) and NEID spectrographs designed to
characterize this sample and further investigate the origin of the
radio emission. We provide four new insights into the sample. I) We
uniformly characterize the stellar properties, constraining their
effective temperatures (Teff), surface gravities (logg),
metallicities ([Fe/H]), projected rotational velocities (vsini*),
rotation periods (Prot), stellar radii (R*), and stellar inclinations
(i*) where possible. Further, from a homogenous analysis of the HPF
spectra, we infer their chromospheric activity and spectroscopic
multiplicity states. From this, we identify GJ 625, GJ 1151, and LHS
2395 as single, quiescent stars amenable to precise RV follow-up,
making them strong MSPI candidates. II) We show that the distribution
of stellar inclinations are compatible with an isotropic distribution,
providing no evidence for a preference to pole-on configurations. III)
We refine the radial velocity solution for GJ 625 b, the only
currently known close-in planet in the sample, reducing the
uncertainty in its orbital period by a factor of three, to facilitate
future phase-dependent radio analysis. IV) Finally, we identify GJ
3861 as a spectroscopic binary with an orbital period of
P=14.841181-0.00010+0.00011d and with a mass ratio of
q=0.7663-0.0018+0.0020, making it the only confirmed binary with
a relatively short orbit in the sample, where we surmise the radio
emission is likely related to magnetospheric interactions between the
two stars. These results advance our understanding of radio-emitting
M dwarfs and establish an observational foundation for identifying
MSPI.
Description:
The stellar properties of 19 LOFAR radio-emitting M dwarfs and the
available radial velocities of GJ 625 and GJ 3861 are included in
respectively gj625.dat and gj3861.dat. GJ 381 RVs are taken with HPF.
GJ625 RVs include observations from HARPS-N, HIRES, CARMENES, and
NEID. For the 19 M dwarfs, we combined physical stellar parameters in
targets.dat
Objects:
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RA (2000) DE Designation(s)
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16 25 24.62 +54 18 14.7 GJ 625 = 1RXS J162523.4+541811
14 36 52.98 +58 20 54.9 GJ 3861 = 1RXS J143652.6+582104
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File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 115 19 Stellar parameters derived for the
V-LoTSS Mdwarf sample
tablea1.dat 72 291 Radial velocities of GJ 625
tablea2.dat 42 11 Radial velocities of GJ 3861
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See also:
I/352 : Distances to 1.47 billion stars in Gaia EDR3
(Bailer-Jones+, 2021)
I/356 : Gaia DR3 Part 2. Extra-galactic
(Gaia Collaboration, 2022)
J/A+A/682/A170 : AU Mic dynamic spectra of 42 radio observations
(Bloot+, 2024)
J/A+A/671/A50 : GJ 1151 CARMENES and HARPS-N data (Blanco-Pozo+, 2023)
J/A+A/670/A124 : Circularly polarised LoTSS sources (Callingham+, 2023)
J/A+A/670/A139 : CARMENES search for exoplanets around M dwarfs
(Ribas+, 2023)
J/A+A/662/A41 : Magnetic fields in 292 M dwarfs. (Reiners+, 2022)
J/A+A/649/A6 : Gaia Catalogue of Nearby Stars - GCNS
(Gaia collaboration, 2021)
J/A+A/649/L12 : GJ 1151 radial velocity curve (Perger+, 2021)
J/A+A/648/A2 : LOFAR Two-metre Sky Survey Deep Fields DR1
(Sabater+, 2021)
J/A+A/638/A5 : HD 285507 and AD Leo light and velocity curves
(Carleo+, 2020)
J/A+A/626/A31 : Radial velocities of nearby stars (Sperauskas+, 2019)
J/A+A/623/A44 : CARMENES M-dwarfs activity indicators (Schoefer+, 2019)
J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source catalog
(Shimwell+, 2019)
J/A+A/577/A128 : CARMENES input catalogue of M dwarfs. I
(Alonso-Floriano+, 2015)
J/A+A/552/A119 : Planet-star and moon-planet interaction (Saur+, 2013)
J/MNRAS/441/2361 : Stellar magnetism, age and rotation (Vidotto+, 2014)
J/MNRAS/390/567 : Magnetic field and velocity of mid M dwarfs
(Morin+, 2008)
J/ApJ/931/L15 : Obs. of two transits of GJ 3470b with NEID
(Stefansson+, 2022)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs
(Mann+, 2015)
J/A+A/331/581 : Rotation and activity in field M dwarfs (Delfosse+ 1998)
J/AJ/168/93 : Phot. follow-up of TOI-2015 & discovery of TOI-2015b
(Jones+, 2024)
J/AJ/160/192 : Photometry and RVs of K2-25b with HPF
(Stefansson+, 2020)
J/AJ/159/100 : Flux & RVs of the dwarf G9-40 with K2 & HPF
(Stefansson+, 2020)
J/AJ/159/139 : Multiple M dwarf stars with Robo-AO and Gaia DR2
(Lamman+, 2020)
J/AJ/157/231 : MLSDSS-GaiaDR2 sample of M and L dwarfs (Kiman+, 2019)
J/AJ/156/102 : The TESS Input Catalog and Candidate Target List
(Stassun+, 2018)
J/AJ/156/45 : M-dwarf multiples in the SDSS-III/APOGEE (Skinner+,2018)
J/AJ/155/192 : Radial velocities & photometry of AD Leonis & GJ 674
(Tuomi+, 2018)
J/ApJS/150/455 : New HIP-based parallaxes for 424 faint stars
(Gould+, 2004)
J/other/Sci/382.1031 : LHS 3154 RV and activity indicators (Stefansson+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Target Target Mdwarf name
12- 14 A3 --- n_Target Note on targets (1)
16- 19 A4 --- SpType Spectral types (SpType)
21- 23 F3.1 --- e_SpType ? Uncertainty of spectral type (errSpType)
25 A1 --- r_SpType Spectral reference for Mdwarf G 240-45 as
Callingham et al. (2021NatAs...5.1233C 2021NatAs...5.1233C)
(refSpType)
27- 30 I4 K Teff ? Effective temperature (Teff)
32- 34 I3 K e_Teff ? Uncertainty of Teff (errTeff)
36- 40 F5.3 [cm/s2] logg ? Logarithm of the surface gravity (logg)
42- 46 F5.3 [cm/s2] e_logg ? Uncertainty of logg (errlogg)
48- 52 F5.2 [Sun] [Fe/H] ? Iron to hydrogen abundance ratio ([Fe/H])
54 A1 --- l_Vsini The Upper limit flag of rotational velocity
56- 59 F4.1 km/s Vsini ? The rotational velocity (vsini*)
61- 63 F3.1 km/s e_Vsini ? Uncertainty of Vsini (errvsini*)
65- 69 A5 --- Method Method used to derived Vsini (2)
71- 78 F8.4 d Prot ? Rotation periods (Prot) (3)
80- 86 F7.4 d e_Prot ? Uncertainty of Prot (errProt)
88 A1 --- r_Prot Literature reference of Prot (4)
90- 94 F5.3 Rsun R* ? The stellar radius (R*)
96- 100 F5.3 Rsun e_R* ? Uncertainty of R* (errR*)
102- 105 F4.1 deg i ? Inclination angle (i*)
107- 110 F4.1 deg e_i ? Lower band uncertainty of i
112- 115 F4.1 deg E_i ? Upper band uncertainty of i
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Note (1): Notes on targets are as follows:
1 = Targets shortened for space as 2MASS J09481615+5114518 (2M J094),
2MASS J14333139+3417472 (2M J143), LSPM J1024+3902E (LSPM J102)
and 2MASS J10534129+5253040 (2M J105), 4 sources in our sample
2 = The highly broadened lines of target 2MASS J14333139+3417472
makes it difficult for HPF-SpecMatch to find matching spectra,
and thus produces highly uncertain results. Therefore, we here
show the stellar properties listed in the Tess Input Catalog,
2 sources in our sample
3 = G 240-45 and 2MASS J10534129+5253040 are likely binaries, but do
not show obvious double lines and so we report the HPF-SpecMatch
results here. We suggest caution in interpreting these results,
2 sources in our sample
Note (2): Method are as follows:
alpha = Result from HPF-SpecMatch, 7 sources in our sample
beta = Obtained through the CCF method, 7 sources in our sample
gamma = Obtained from the broadening function, 1 source in our sample
Note (3): Rotation periods are adopted from Pope et al. (2021ApJ...919L..10P 2021ApJ...919L..10P)
unless otherwise noted. All other values are from this work unless
otherwise noted.
Note (4): Literature reference are as follows:
a = Pope et al. 2021ApJ...919L..10P 2021ApJ...919L..10P, 11 sources in our sample
b = This work, 3 sources in our sample
c = Morin et al. 2008MNRAS.390..567M 2008MNRAS.390..567M, Cat. J/MNRAS/390/567,
1 source in our sample
d = Newton et al. 2017ApJ...834...85N 2017ApJ...834...85N, Cat. J/ApJ/834/85,
1 sources in our sample
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Index Index number (Index)
5- 22 F18.10 d BJD Barycentric Julian Date at TDB of measurement
(BJDTDB)
24- 42 F19.16 m/s RV Radial velocity (RV)
44- 61 F18.16 m/s e_RV The 1-sigma uncertainty of RV (σ)
63- 72 A10 --- Inst Instrument for spectroscopy (Instrument) (1)
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Note (1): Instrument names are as follows:
HIRES-pre = HIRES spectrograph before ccd upgrade, 16 sources in
our sample
HIRES-post = HIRES spectrograph after ccd upgrade, 37 sources in
our sample
HARPSN = HARPSN spectrograph, 200 sources in our sample
CARMENES = CARMENES spectrograph, 33 sources in our sample
NEID = NEID spectrograph, 5 sources in our sample
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian Date at TDB of measurement
(time)
16- 22 F7.3 km/s RV1 Radial velocity of the primary star (v1)
24- 28 F5.3 km/s e_RV1 The 1-sigma uncertainty of RV1 (σ1)
30- 36 F7.3 km/s RV2 Radial velocity of the secondary star (v2)
38- 42 F5.3 km/s e_RV2 The 1-sigma uncertainty of RV2 (σ_2)
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Acknowledgements:
Elise Koo, e.j.m.koo(at)uva.nl
(End) Elise Koo [Univ. Amsterdam], Luc Trabelsi [CDS] 21-Nov-2025