pith. machine review for the scientific record. sign in

arxiv: 2603.18233 · v1 · submitted 2026-03-18 · 🌌 astro-ph.EP

Recognition: no theorem link

TOI-4552 b: A new ultra-short period rocky world revealed by NIRPS and TESS

Avidaan Srivastava , Ren\'e Doyon , Fran\c{c}ois Bouchy , \'Etienne Artigau , Charles Cadieux , Nicole Gromek , Elisa Delgado-Mena , Yuri S. Messias
show 52 more authors
Xavier Bonfils Roseane de Lima Gomes Susana C. C. Barros Bj\"orn Benneke Marta Bryan Ryan Cloutier Nicolas B. Cowan Eduardo Cristo Xavier Delfosse Xavier Dumusque David Ehrenreich Jonay I. Gonz\'alez Hern\'andez David Lafreni\`ere Izan de Castro Le\~ao Christophe Lovis Alejandro Su\'arez Mascare\~no Bruno L. Canto Martins Jose Renan De Medeiros Lucile Mignon Christoph Mordasini Francesco Pepe Rafael Rebolo Jason Rowe Nuno C. Santos Damien S\'egransan St\'ephane Udry Diana Valencia Gregg Wade Jose Manuel Almenara Karen A. Collins Dennis M. Conti George Dransfield Elsa Ducrot Zahra Essack Dasaev O. Fontinele Thierry Forveille Marziye Jafariyazani Pierrot Lamontagne Alexandrine L'Heureux Khaled Al Moulla Ares Osborn L\'ena Parc David R. Rodriguez Richard P. Schwartz Madison G. Scott Avi Shporer Atanas K. Stefanov Mathilde Timmermans Amaury H.M.J. Triaud Joost P. Wardenier Drew Weisserman Sebasti\'an Z\'u\~niga-Fern\'andez
Authors on Pith no claims yet

Pith reviewed 2026-05-15 08:29 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords ultra-short period planetsrocky exoplanetsM dwarf starsradial velocitytransit photometryinterior compositionTOI-4552bexoplanet characterization
0
0 comments X

The pith

TOI-4552b is a newly validated ultra-short-period rocky planet whose measured density suggests a possible iron-rich interior compared to Earth.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reports the discovery and characterization of TOI-4552b, an Earth-sized planet orbiting an M4.5V star every 0.3 days. Using TESS photometry, ground-based transits from multiple facilities, and radial velocities from NIRPS and HARPS, the authors measure its radius as 1.11 Earth radii and mass as 1.83 Earth masses. This places the planet between Earth-like and iron-rich composition lines on the mass-radius diagram, with an interior model giving a core mass fraction of 0.54 and density of 7.74 g/cm³. The large mass uncertainty means the exact composition remains unclear, but the planet's short period, quiet host star, and high emission metric make it promising for atmospheric observations with JWST. Sympathetic readers would care because ultra-short period rocky planets around M dwarfs remain rare, and this one adds to the sample with constrained mass and radius.

Core claim

TOI-4552b is an ultra-short period planet with a 0.3-day orbital period around a nearby M4.5V dwarf. Its measured mass and radius of 1.83 ± 0.47 Earth masses and 1.11 ± 0.04 Earth radii result in a bulk density of 7.74 g/cm³ and a core mass fraction of 0.54 according to the EXOPIE model, positioning it between Earth-like and iron-rich tracks. The star shows no significant activity, and the planet has a high emission spectroscopic metric of 19.5, positioning it as a target for future atmospheric studies.

What carries the argument

Placement on the mass-radius diagram combined with the EXOPIE interior structure model without refractory abundance constraints to derive core mass fraction and bulk density.

Load-bearing premise

The planetary mass measurement from radial velocity observations carries a large uncertainty of 0.47 Earth masses, which allows the core mass fraction to span a wide range and prevents a definitive compositional determination.

What would settle it

A future radial velocity campaign that reduces the mass uncertainty below 0.2 Earth masses and yields a mass below 1.5 Earth masses would place the planet firmly on the Earth-like track and falsify the iron-enrichment suggestion.

read the original abstract

A particularly intriguing subclass of rocky exoplanets are the ultra-short period (USP) worlds that orbit their host stars in less than a day. These planets are particularly rare around M dwarf stars, with so far only ten that have a constrained mass and radius. We present the validation and characterization of the ultra-short period (0.3-days), Earth-sized planet TOI-4552b orbiting a nearby (27.26-pc away) M4.5V dwarf. Complementing the TESS photometry, ground-based transit observations from LCO, ExTrA and SPECULOOS validated the planetary radius and cleared the field of any contaminants. Speckle imaging with Zorro (Gemini-S) rules out false positive scenarios caused by eclipsing binary sources. Spectroscopic observations with NIRPS and HARPS were used to obtain stellar abundances, constrain the planetary mass, and, in conjunction with the transit observations, estimate the orbital parameters. TOI-4552 is a quiet star exhibiting no short-term stellar variations seen in photometric or radial velocity data that can be associated to stellar rotation. TOI-4552b ($M_p=1.83\pm0.47\,M_e$, $R_p=1.11\pm0.04\,R_e$) lies between the Earth-like and iron-rich composition tracks on the Mass-Radius diagram. The EXOPIE interior structure model, without constraints from refractory abundance ratio, yields a core mass fraction (CMF) of 0.54 and a bulk density of 7.74g/cm$^3$. Since the CMF spans a wide range due to the large uncertainty on the mass, the definitive interior composition cannot be determined with the current dataset. TOI-4552b hints as being marginally more iron-rich compared to the Earth but confirmation of its status requires additional, precise radial velocity measurements. Combined with its high emission spectroscopic metric (ESM=19.5), negligible stellar activity and short orbital period, TOI-4552b emerges as a compelling target for atmospheric and surface composition studies with JWST.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript reports the validation and characterization of TOI-4552b, an ultra-short-period (0.3 d) Earth-sized rocky planet orbiting a nearby (27.26 pc) M4.5V dwarf. TESS photometry is supplemented by ground-based transit observations from LCO, ExTrA and SPECULOOS to refine the radius (Rp = 1.11 ± 0.04 R⊕); Zorro speckle imaging rules out false-positive scenarios; and NIRPS/HARPS radial velocities yield the mass (Mp = 1.83 ± 0.47 M⊕) and orbital parameters. The planet lies between Earth-like and iron-rich tracks on the mass-radius diagram; the EXOPIE interior model gives a core mass fraction of 0.54 and bulk density 7.74 g cm⁻³, although the large mass uncertainty precludes a definitive compositional determination. The high ESM (= 19.5) and low stellar activity are highlighted as making the target suitable for JWST atmospheric studies.

Significance. If the reported parameters hold, the work adds a well-validated data point to the small sample of USP planets around M dwarfs that possess both mass and radius constraints. The multi-technique validation chain (photometry + speckle + RVs) is robust, and the planet’s short period, high ESM, and quiet host star make it a compelling target for emission spectroscopy and surface-composition studies with JWST.

minor comments (3)
  1. [Abstract] Abstract: the statement that TOI-4552b 'hints as being marginally more iron-rich compared to the Earth' would benefit from an explicit comparison value (Earth CMF ≈ 0.32–0.35) so readers can immediately gauge the offset.
  2. [§3] §3 (RV analysis): the joint NIRPS + HARPS modeling is described at a high level; adding a brief table of the adopted jitter terms, number of epochs per instrument, and the resulting K amplitude with its formal uncertainty would improve reproducibility.
  3. [Figure 7] Figure 7 (mass-radius diagram): the plotted EXOPIE tracks should include a legend entry for the exact refractory abundance ratio assumed (or note that none was imposed) to match the text statement that the model was run 'without constraints from refractory abundance ratio'.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive review and recommendation to accept the manuscript. We appreciate the recognition of the robust validation chain and the potential of TOI-4552b for future JWST studies.

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper's central results (Mp=1.83±0.47 Me, Rp=1.11±0.04 Re, CMF=0.54 from EXOPIE) are obtained by direct application of standard observational pipelines to TESS photometry, ground-based transit data, speckle imaging, and NIRPS/HARPS radial velocities. The EXOPIE interior model is invoked as an external tool without self-citation or ansatz that reduces the output to the input by construction. The text explicitly qualifies the wide CMF range due to mass uncertainty, confirming the derivation does not force the claimed placement on the mass-radius diagram. No self-definitional steps, fitted inputs renamed as predictions, or load-bearing self-citations appear in the validation or modeling chain.

Axiom & Free-Parameter Ledger

2 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard exoplanet detection and interior modeling techniques with fitted orbital and structural parameters from data.

free parameters (2)
  • planetary mass = 1.83 Earth masses
    Fitted from radial velocity semi-amplitude using NIRPS and HARPS data
  • core mass fraction = 0.54
    Output from EXOPIE interior structure model without refractory abundance constraints
axioms (2)
  • standard math Keplerian orbital model for transit and radial velocity fitting
    Standard assumption used to derive period, mass, and radius from photometric and spectroscopic time series
  • domain assumption M4.5V stellar classification and parameters from spectroscopy
    Used to convert observed signals into planetary mass and radius

pith-pipeline@v0.9.0 · 6032 in / 1425 out tokens · 47816 ms · 2026-05-15T08:29:13.816996+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.