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TOI-1080 b: a temperate, rocky planet orbiting a quiet M4V host

Y. Gómez Maqueo Chew, G. Dransfield, K. Barkaoui, C. Cadieux, E. Ducrot, B. V. Rackham, M. Timmermans, A. J. Burgasser, A. Segura, K. G. Stassun, C. Ziegler, A. Soubkiou, J. M. Almenara, B. O. Demory, M. Gillon, J. M. Jenkins, E. Jofré, A. Khandelwal, S. Páez, R. Petrucci, L. Parc, M. Pichardo Marcano, I. Plauchu-Frayn, U. Schroffenegger, R. Schwarz, T. G. Tan, A. H. M. J. Triaud, Z. Benkhaldoun, X. Bonfils, F. Bouchy, K. A. Collins, F. Davoudi, R. Doyon, M. Gachaoui, M. J. Hooton, E. Jehin, F. J. Pozuelos, M. G. Scott, S. Yalçınkaya, F. Zong Lang, S. Zúñiga-Fernández, J. R. De Medeiros, J. I. González-Hernández, N. C. Santos

Abstract

We present the detection and validation of a small, temperate transiting exoplanet orbiting TOI-1080 every 3.9652482$^{+0.0000014}_{-0.0000015}$ days. The host is a quiet M4V star at 25.6 pc. The planet signal was first detected by TESS and validated using TESS and ground-based observations. By fitting the available light curves, the planet radius is measured to be 1.200+- 0.058 Rearth and its equilibrium temperature of 368$^{+12}_{-10}$ K. With NIRPS radial velocities, we are able to place a 3-sigma upper limit on the mass of TOI-1080 b of 10.7 Mearth. Our injection-recovery tests enable us to discard additional transiting planets in the TOI-1080 system with radii down to 0.9 Rearth and periods between 0.5 and 7.7 days, and planets with radii larger than 1.4 Rearth for periods up to 19 days. We demonstrate that it is highly amenable to characterisation of its mass and putative atmosphere. In particular, we find that TOI-1080 b is an exceptional target for the ongoing JWST+HST Rocky Worlds DDT programme, having a priority score that is higher than four out of nine targets currently being investigated by the programme. TOI-1080 b can be added to the sample of nearby benchmark planets accessible for detailed study with JWST.

TOI-1080 b: a temperate, rocky planet orbiting a quiet M4V host

Abstract

We present the detection and validation of a small, temperate transiting exoplanet orbiting TOI-1080 every 3.9652482 days. The host is a quiet M4V star at 25.6 pc. The planet signal was first detected by TESS and validated using TESS and ground-based observations. By fitting the available light curves, the planet radius is measured to be 1.200+- 0.058 Rearth and its equilibrium temperature of 368 K. With NIRPS radial velocities, we are able to place a 3-sigma upper limit on the mass of TOI-1080 b of 10.7 Mearth. Our injection-recovery tests enable us to discard additional transiting planets in the TOI-1080 system with radii down to 0.9 Rearth and periods between 0.5 and 7.7 days, and planets with radii larger than 1.4 Rearth for periods up to 19 days. We demonstrate that it is highly amenable to characterisation of its mass and putative atmosphere. In particular, we find that TOI-1080 b is an exceptional target for the ongoing JWST+HST Rocky Worlds DDT programme, having a priority score that is higher than four out of nine targets currently being investigated by the programme. TOI-1080 b can be added to the sample of nearby benchmark planets accessible for detailed study with JWST.
Paper Structure (25 sections, 14 figures, 3 tables)

This paper contains 25 sections, 14 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Stellar characterization of TOI-1080
  3. Spectral type from near-infrared FIRE spectrum
  4. Spectral type from optical MagE Spectrum
  5. Spectral Energy Distribution for TOI-1080
  6. Search for blends
  7. SOAR speckle imaging
  8. Archival images of TOI-1080
  9. Stellar Activity
  10. Transit photometry: observations and data reduction
  11. TESS light curve and planet candidate status
  12. Follow-up, ground-based light curves
  13. SPECULOOS photometry
  14. LCO-SAAO and LCO-SSO photometry
  15. TRAPPIST-South photometry
  16. ...and 10 more sections

Figures (14)

  • Figure 1: FIRE spectrum of TOI-1080. The target spectrum (red) is shown alongside that of the SpeX SXD spectrum of the M3.5 V standard Luyten’s Star (GJ 273; grey). The higher spectral resolution of the FIRE spectrum gives it a more jagged appearance. Strong M-dwarf spectral features and spectral regions with strong tellurics are indicated.
  • Figure 2: MagE optical spectrum of TOI-1080 (black line) normalized at 7500 Å compared to a combined M4+M5 optical spectral template from 2007AJ....133..531B. Standard M dwarf atomic and molecular features are labelled, as well as regions of uncorrected telluric absorption ($\oplus$). The inset box shows the 6555--6580 Å region highlight absorption from H$\alpha$ and Ca I.
  • Figure 3: Spectral energy distribution of TOI-1080. Red symbols represent the observed photometric measurements, where the horizontal bars represent the effective width of the passband. Blue symbols are the model fluxes from the best-fit PHOENIX atmosphere model (black).
  • Figure 4: Detection sensitivity and auto-correlation (inset) functions for the TOI-1080 SOAR speckle imaging. We do not identify any nearby stars within 3$\arcsec$ of TOI-1080.
  • Figure 5: Archival images for TOI-1080 from the Digital Sky Survey (DSS) and 2MASS compared to the SSO Io observations taken in 2021. The position of TOI-1080 in the 2021 SSO Io stack image is marked in all panels by the circle and the coordinates are given in J2000. All images are the same size of 0.03$^{\circ} \times$0.03$^{\circ}$, and are centered on TOI-1080's position in the 2021 SSO Io observations. The color scale for each frame has been optimized to better show the stars.
  • ...and 9 more figures