Spectroscopic characterization of LOFAR radio-emitting M dwarfs

E. Koo; G. Stefansson; R. D. Kavanagh; M. Delamer; S. Mahadevan; J. R. Callingham; H. Vedantham; P. Robertson; D. Bruijne; C. F. Bender; C. I. Cañas; S. Diddams; J. I. Espinoza-Retamal; R. B. Fernandes; S. Halverson; S. Kanodia; D. Krolikowski; A. S.J. Lin; B. J.S. Pope; A. Roy; C. Schwab; R. Terrien; J. T. Wright

doi:10.1051/0004-6361/202556483

Spectroscopic characterization of LOFAR radio-emitting M dwarfs

E. Koo
, G. Stefansson
, R. D. Kavanagh
, M. Delamer
, S. Mahadevan
, J. R. Callingham
, H. Vedantham
, P. Robertson
, D. Bruijne
, C. F. Bender
, C. I. Cañas
, S. Diddams
, J. I. Espinoza-Retamal
, R. B. Fernandes
, S. Halverson
, S. Kanodia
, D. Krolikowski
, A. S.J. Lin
, B. J.S. Pope
, A. Roy

C. Schwab, R. Terrien, J. T. Wright

Research output: Contribution to journal › Article › peer-review

Abstract

Recent observations with the LOw Frequency ARray (LOFAR) have revealed 19 nearby M dwarfs showing bright circularly polarized radio emission. One of the possible sources of such emission is through magnetic star-planet interactions (MSPIs) with unseen close-in planets. We present the 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 characterized the stellar properties, constraining their effective temperatures (T_eff), surface gravities (log g), metallicities ([Fe/H]), projected rotational velocities (v sin i_⋆), rotation periods (P_rot), stellar radii (R_⋆), and stellar inclinations (i_⋆) where possible. Further, from a homogeneous analysis of the HPF spectra, we inferred their chromospheric activity and spectroscopic multiplicity states. From this, we identified GJ 625, GJ 1151, and LHS 2395 as single, quiescent stars amenable to precise radial velocity 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 refined 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 identified GJ 3861 as a spectroscopic binary with an orbital period of P = 14.841181^+0.00011_−0.00010 d and with a mass ratio of q = 0.7663^+0.0020_−0.0018, 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 MSPIs.

Original language	English (US)
Article number	A98
Journal	Astronomy and Astrophysics
Volume	706
DOIs	https://doi.org/10.1051/0004-6361/202556483
State	Published - Feb 1 2026

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

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10.1051/0004-6361/202556483

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Koo, E., Stefansson, G., Kavanagh, R. D., Delamer, M., Mahadevan, S., Callingham, J. R., Vedantham, H., Robertson, P., Bruijne, D., Bender, C. F., Cañas, 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., ... Wright, J. T. (2026). Spectroscopic characterization of LOFAR radio-emitting M dwarfs. Astronomy and Astrophysics, 706, Article A98. https://doi.org/10.1051/0004-6361/202556483

@article{322ff234032b4ed68dddd79b6a64fb41,

title = "Spectroscopic characterization of LOFAR radio-emitting M dwarfs",

abstract = "Recent observations with the LOw Frequency ARray (LOFAR) have revealed 19 nearby M dwarfs showing bright circularly polarized radio emission. One of the possible sources of such emission is through magnetic star-planet interactions (MSPIs) with unseen close-in planets. We present the 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 characterized the stellar properties, constraining their effective temperatures (Teff), surface gravities (log g), metallicities ([Fe/H]), projected rotational velocities (v sin i⋆), rotation periods (Prot), stellar radii (R⋆), and stellar inclinations (i⋆) where possible. Further, from a homogeneous analysis of the HPF spectra, we inferred their chromospheric activity and spectroscopic multiplicity states. From this, we identified GJ 625, GJ 1151, and LHS 2395 as single, quiescent stars amenable to precise radial velocity 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 refined 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 identified GJ 3861 as a spectroscopic binary with an orbital period of P = 14.841181+0.00011−0.00010 d and with a mass ratio of q = 0.7663+0.0020−0.0018, 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 MSPIs.",

author = "E. Koo and G. Stefansson and Kavanagh, \{R. D.\} and M. Delamer and S. Mahadevan and Callingham, \{J. R.\} and H. Vedantham and P. Robertson and D. Bruijne and Bender, \{C. F.\} and Ca{\~n}as, \{C. I.\} and S. Diddams and Espinoza-Retamal, \{J. I.\} and Fernandes, \{R. B.\} and S. Halverson and S. Kanodia and D. Krolikowski and Lin, \{A. S.J.\} and Pope, \{B. J.S.\} and A. Roy and C. Schwab and R. Terrien and Wright, \{J. T.\}",

note = "Publisher Copyright: {\textcopyright} The Authors 2026.",

year = "2026",

month = feb,

day = "1",

doi = "10.1051/0004-6361/202556483",

language = "English (US)",

volume = "706",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Koo, E, Stefansson, G, Kavanagh, RD, Delamer, M, Mahadevan, S, Callingham, JR, Vedantham, H, Robertson, P, Bruijne, D, Bender, CF, Cañas, CI, Diddams, S, Espinoza-Retamal, JI, Fernandes, RB, Halverson, S, Kanodia, S, Krolikowski, D, Lin, ASJ, Pope, BJS, Roy, A, Schwab, C, Terrien, R & Wright, JT 2026, 'Spectroscopic characterization of LOFAR radio-emitting M dwarfs', Astronomy and Astrophysics, vol. 706, A98. https://doi.org/10.1051/0004-6361/202556483

TY - JOUR

T1 - Spectroscopic characterization of LOFAR radio-emitting M dwarfs

AU - Koo, E.

AU - Stefansson, G.

AU - Kavanagh, R. D.

AU - Delamer, M.

AU - Mahadevan, S.

AU - Callingham, J. R.

AU - Vedantham, H.

AU - Robertson, P.

AU - Bruijne, D.

AU - Bender, C. F.

AU - Cañas, C. I.

AU - Diddams, S.

AU - Espinoza-Retamal, J. I.

AU - Fernandes, R. B.

AU - Halverson, S.

AU - Kanodia, S.

AU - Krolikowski, D.

AU - Lin, A. S.J.

AU - Pope, B. J.S.

AU - Roy, A.

AU - Schwab, C.

AU - Terrien, R.

AU - Wright, J. T.

PY - 2026/2/1

Y1 - 2026/2/1

N2 - Recent observations with the LOw Frequency ARray (LOFAR) have revealed 19 nearby M dwarfs showing bright circularly polarized radio emission. One of the possible sources of such emission is through magnetic star-planet interactions (MSPIs) with unseen close-in planets. We present the 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 characterized the stellar properties, constraining their effective temperatures (Teff), surface gravities (log g), metallicities ([Fe/H]), projected rotational velocities (v sin i⋆), rotation periods (Prot), stellar radii (R⋆), and stellar inclinations (i⋆) where possible. Further, from a homogeneous analysis of the HPF spectra, we inferred their chromospheric activity and spectroscopic multiplicity states. From this, we identified GJ 625, GJ 1151, and LHS 2395 as single, quiescent stars amenable to precise radial velocity 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 refined 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 identified GJ 3861 as a spectroscopic binary with an orbital period of P = 14.841181+0.00011−0.00010 d and with a mass ratio of q = 0.7663+0.0020−0.0018, 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 MSPIs.

AB - Recent observations with the LOw Frequency ARray (LOFAR) have revealed 19 nearby M dwarfs showing bright circularly polarized radio emission. One of the possible sources of such emission is through magnetic star-planet interactions (MSPIs) with unseen close-in planets. We present the 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 characterized the stellar properties, constraining their effective temperatures (Teff), surface gravities (log g), metallicities ([Fe/H]), projected rotational velocities (v sin i⋆), rotation periods (Prot), stellar radii (R⋆), and stellar inclinations (i⋆) where possible. Further, from a homogeneous analysis of the HPF spectra, we inferred their chromospheric activity and spectroscopic multiplicity states. From this, we identified GJ 625, GJ 1151, and LHS 2395 as single, quiescent stars amenable to precise radial velocity 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 refined 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 identified GJ 3861 as a spectroscopic binary with an orbital period of P = 14.841181+0.00011−0.00010 d and with a mass ratio of q = 0.7663+0.0020−0.0018, 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 MSPIs.

UR - https://www.scopus.com/pages/publications/105030544303

UR - https://www.scopus.com/pages/publications/105030544303#tab=citedBy

U2 - 10.1051/0004-6361/202556483

DO - 10.1051/0004-6361/202556483

M3 - Article

AN - SCOPUS:105030544303

SN - 0004-6361

VL - 706

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A98

ER -

Spectroscopic characterization of LOFAR radio-emitting M dwarfs

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