TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

Rena A. Lee; Fei Dai; Andrew W. Howard; Samuel Halverson; Jonathan Gomez Barrientos; Michael Greklek-McKeon; Heather A. Knutson; Benjamin J. Fulton; Guđmundur Stefánsson; Jack Lubin; Howard Isaacson; Casey L. Brinkman; Nicholas Saunders; Daniel Hey; Daniel Huber; Lauren M. Weiss; Leslie A. Rogers; Diana Valencia; Mykhaylo Plotnykov; Kimberly Paragas; Renyu Hu; Te Han; Erik A. Petigura; Ryan Rubenzahl; David R. Ciardi; Aaron Householder; Gregory J. Gilbert; J. M.Joel Ong; Jingwen Zhang; Jacob Luhn; Luke Handley; Corey Beard; Steven Giacalone; Rae Holcomb; Judah Van Zandt; Ashley D. Baker; Max Brodheim; Matt Brown; David Charbonneau; Karen A. Collins; Ian J.M. Crossfield; William Deich; Xavier Dumusque; Steven R. Gibson; Emily Gilbert; Grant M. Hill; Bradford Holden; Jon M. Jenkins; Stephen Kaye; Russ R. Laher; Kyle Lanclos; W. Garett Levine; Joel Payne; Alex S. Polanski; John O’Meara; George R. Ricker; Kodi Rider; Paul Robertson; Arpita Roy; Joshua E. Schlieder; Christian Schwab; Sara Seager; Abby P. Shaum; Martin M. Sirk; Stephanie Striegel; Johanna Teske; John Valliant; Roland Vanderspek; Gautam Vasisht; Josh Walawender; Sharon Xuesong Wang; Joshua N. Winn; Edward Wishnow; Sherry Yeh

doi:10.3847/2041-8213/adadd7

TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

Rena A. Lee, Fei Dai, Andrew W. Howard, Samuel Halverson, Jonathan Gomez Barrientos, Michael Greklek-McKeon, Heather A. Knutson, Benjamin J. Fulton, Guđmundur Stefánsson, Jack Lubin, Howard Isaacson, Casey L. Brinkman, Nicholas Saunders, Daniel Hey, Daniel Huber, Lauren M. Weiss, Leslie A. Rogers, Diana Valencia, Mykhaylo Plotnykov, Kimberly ParagasRenyu Hu, Te Han, Erik A. Petigura, Ryan Rubenzahl, David R. Ciardi, Aaron Householder, Gregory J. Gilbert, J. M.Joel Ong, Jingwen Zhang, Jacob Luhn, Luke Handley, Corey Beard, Steven Giacalone, Rae Holcomb, Judah Van Zandt, Ashley D. Baker, Max Brodheim, Matt Brown, David Charbonneau, Karen A. Collins, Ian J.M. Crossfield, William Deich, Xavier Dumusque, Steven R. Gibson, Emily Gilbert, Grant M. Hill, Bradford Holden, Jon M. Jenkins, Stephen Kaye, Russ R. Laher, Kyle Lanclos, W. Garett Levine, Joel Payne, Alex S. Polanski, John O’Meara, George R. Ricker, Kodi Rider, Paul Robertson, Arpita Roy, Joshua E. Schlieder, Christian Schwab, Sara Seager, Abby P. Shaum, Martin M. Sirk, Stephanie Striegel, Johanna Teske, John Valliant, Roland Vanderspek, Gautam Vasisht, Josh Walawender, Sharon Xuesong Wang, Joshua N. Winn, Edward Wishnow, Sherry Yeh

Astrophysical Sciences

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Abstract

We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R_⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M_⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.

Original language	English (US)
Article number	L36
Journal	Astrophysical Journal Letters
Volume	983
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/adadd7
State	Published - Apr 20 2025

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/2041-8213/adadd7

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Lee, R. A., Dai, F., Howard, A. W., Halverson, S., Gomez Barrientos, J., Greklek-McKeon, M., Knutson, H. A., Fulton, B. J., Stefánsson, G., Lubin, J., Isaacson, H., Brinkman, C. L., Saunders, N., Hey, D., Huber, D., Weiss, L. M., Rogers, L. A., Valencia, D., Plotnykov, M., ... Yeh, S. (2025). TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf. Astrophysical Journal Letters, 983(2), Article L36. https://doi.org/10.3847/2041-8213/adadd7

@article{cc7e139e66ac4eb895988c758d42b170,

title = "TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf",

abstract = "We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27\% ± 37\%) consistent with that of Earth (∼33\%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.",

author = "Lee, \{Rena A.\} and Fei Dai and Howard, \{Andrew W.\} and Samuel Halverson and \{Gomez Barrientos\}, Jonathan and Michael Greklek-McKeon and Knutson, \{Heather A.\} and Fulton, \{Benjamin J.\} and Gu{\d}mundur Stef{\'a}nsson and Jack Lubin and Howard Isaacson and Brinkman, \{Casey L.\} and Nicholas Saunders and Daniel Hey and Daniel Huber and Weiss, \{Lauren M.\} and Rogers, \{Leslie A.\} and Diana Valencia and Mykhaylo Plotnykov and Kimberly Paragas and Renyu Hu and Te Han and Petigura, \{Erik A.\} and Ryan Rubenzahl and Ciardi, \{David R.\} and Aaron Householder and Gilbert, \{Gregory J.\} and Ong, \{J. M.Joel\} and Jingwen Zhang and Jacob Luhn and Luke Handley and Corey Beard and Steven Giacalone and Rae Holcomb and \{Van Zandt\}, Judah and Baker, \{Ashley D.\} and Max Brodheim and Matt Brown and David Charbonneau and Collins, \{Karen A.\} and Crossfield, \{Ian J.M.\} and William Deich and Xavier Dumusque and Gibson, \{Steven R.\} and Emily Gilbert and Hill, \{Grant M.\} and Bradford Holden and Jenkins, \{Jon M.\} and Stephen Kaye and Laher, \{Russ R.\} and Kyle Lanclos and Levine, \{W. Garett\} and Joel Payne and Polanski, \{Alex S.\} and John O{\textquoteright}Meara and Ricker, \{George R.\} and Kodi Rider and Paul Robertson and Arpita Roy and Schlieder, \{Joshua E.\} and Christian Schwab and Sara Seager and Shaum, \{Abby P.\} and Sirk, \{Martin M.\} and Stephanie Striegel and Johanna Teske and John Valliant and Roland Vanderspek and Gautam Vasisht and Josh Walawender and Wang, \{Sharon Xuesong\} and Winn, \{Joshua N.\} and Edward Wishnow and Sherry Yeh",

note = "Publisher Copyright: {\textcopyright} 2025. The Author(s). Published by the American Astronomical Society.",

year = "2025",

month = apr,

day = "20",

doi = "10.3847/2041-8213/adadd7",

language = "English (US)",

volume = "983",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "American Astronomical Society",

number = "2",

}

Lee, RA, Dai, F, Howard, AW, Halverson, S, Gomez Barrientos, J, Greklek-McKeon, M, Knutson, HA, Fulton, BJ, Stefánsson, G, Lubin, J, Isaacson, H, Brinkman, CL, Saunders, N, Hey, D, Huber, D, Weiss, LM, Rogers, LA, Valencia, D, Plotnykov, M, Paragas, K, Hu, R, Han, T, Petigura, EA, Rubenzahl, R, Ciardi, DR, Householder, A, Gilbert, GJ, Ong, JMJ, Zhang, J, Luhn, J, Handley, L, Beard, C, Giacalone, S, Holcomb, R, Van Zandt, J, Baker, AD, Brodheim, M, Brown, M, Charbonneau, D, Collins, KA, Crossfield, IJM, Deich, W, Dumusque, X, Gibson, SR, Gilbert, E, Hill, GM, Holden, B, Jenkins, JM, Kaye, S, Laher, RR, Lanclos, K, Levine, WG, Payne, J, Polanski, AS, O’Meara, J, Ricker, GR, Rider, K, Robertson, P, Roy, A, Schlieder, JE, Schwab, C, Seager, S, Shaum, AP, Sirk, MM, Striegel, S, Teske, J, Valliant, J, Vanderspek, R, Vasisht, G, Walawender, J, Wang, SX, Winn, JN, Wishnow, E & Yeh, S 2025, 'TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf', Astrophysical Journal Letters, vol. 983, no. 2, L36. https://doi.org/10.3847/2041-8213/adadd7

TY - JOUR

T1 - TOI-6324 b

T2 - An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

AU - Lee, Rena A.

AU - Dai, Fei

AU - Howard, Andrew W.

AU - Halverson, Samuel

AU - Gomez Barrientos, Jonathan

AU - Greklek-McKeon, Michael

AU - Knutson, Heather A.

AU - Fulton, Benjamin J.

AU - Stefánsson, Guđmundur

AU - Lubin, Jack

AU - Isaacson, Howard

AU - Brinkman, Casey L.

AU - Saunders, Nicholas

AU - Hey, Daniel

AU - Huber, Daniel

AU - Weiss, Lauren M.

AU - Rogers, Leslie A.

AU - Valencia, Diana

AU - Plotnykov, Mykhaylo

AU - Paragas, Kimberly

AU - Hu, Renyu

AU - Han, Te

AU - Petigura, Erik A.

AU - Rubenzahl, Ryan

AU - Ciardi, David R.

AU - Householder, Aaron

AU - Gilbert, Gregory J.

AU - Ong, J. M.Joel

AU - Zhang, Jingwen

AU - Luhn, Jacob

AU - Handley, Luke

AU - Beard, Corey

AU - Giacalone, Steven

AU - Holcomb, Rae

AU - Van Zandt, Judah

AU - Baker, Ashley D.

AU - Brodheim, Max

AU - Brown, Matt

AU - Charbonneau, David

AU - Collins, Karen A.

AU - Crossfield, Ian J.M.

AU - Deich, William

AU - Dumusque, Xavier

AU - Gibson, Steven R.

AU - Gilbert, Emily

AU - Hill, Grant M.

AU - Holden, Bradford

AU - Jenkins, Jon M.

AU - Kaye, Stephen

AU - Laher, Russ R.

AU - Lanclos, Kyle

AU - Levine, W. Garett

AU - Payne, Joel

AU - Polanski, Alex S.

AU - O’Meara, John

AU - Ricker, George R.

AU - Rider, Kodi

AU - Robertson, Paul

AU - Roy, Arpita

AU - Schlieder, Joshua E.

AU - Schwab, Christian

AU - Seager, Sara

AU - Shaum, Abby P.

AU - Sirk, Martin M.

AU - Striegel, Stephanie

AU - Teske, Johanna

AU - Valliant, John

AU - Vanderspek, Roland

AU - Vasisht, Gautam

AU - Walawender, Josh

AU - Wang, Sharon Xuesong

AU - Winn, Joshua N.

AU - Wishnow, Edward

AU - Yeh, Sherry

PY - 2025/4/20

Y1 - 2025/4/20

N2 - We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.

AB - We report the confirmation of TOI-6324 b, an Earth-sized (1.059 ± 0.041 R⊕) ultra-short-period (USP) planet orbiting a nearby (∼20 pc) M dwarf. Using the newly commissioned Keck Planet Finder spectrograph, we have measured the mass of TOI-6324 b 1.17 ± 0.22 M⊕. Because of its extremely short orbit of just ∼6.7 hr, TOI-6324 b is intensely irradiated by its M dwarf host and is expected to be stripped of any thick H/He envelope. We were able to constrain its interior composition and found an iron-core mass fraction (CMF = 27% ± 37%) consistent with that of Earth (∼33%) and other confirmed USPs. TOI-6324 b is the closest to an Earth-sized USP confirmed to date. TOI-6324 b is a promising target for JWST phase-curve and secondary eclipse observations (emission spectroscopy metric = 25), which may reveal its surface mineralogy, day-night temperature contrast, and possible tidal deformation. From seven sectors of TESS data, we report a tentative detection of the optical phase-curve variation with an amplitude of 42 ± 28 ppm.

UR - https://www.scopus.com/pages/publications/105003113495

UR - https://www.scopus.com/inward/citedby.url?scp=105003113495&partnerID=8YFLogxK

U2 - 10.3847/2041-8213/adadd7

DO - 10.3847/2041-8213/adadd7

M3 - Article

AN - SCOPUS:105003113495

SN - 2041-8205

VL - 983

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L36

ER -

TOI-6324 b: An Earth-mass Ultra-short-period Planet Transiting a Nearby M Dwarf

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