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Discovery of a Nearby Habitable Zone Super-Earth Candidate Amenable to Direct Imaging

Corey Beard, Paul Robertson, Jack Lubin, Eric B. Ford, Suvrath Mahadevan, Gudmundur Stefansson, Jason T. Wright, Eric Wolf, Vincent Kofman, Vidya Venkatesan, Ravi Kopparapu, Roan Arendtsz, Rae Holcomb, Raquel A. Martinez, Stephanie Sallum, Jacob K. Luhn, Chad F. Bender, Cullen H. Blake, William D. Cochran, Megan Delamer, Scott A. Diddams, Michael Endl, Samuel Halverson, Shubham Kanodia, Daniel M. Krolikowski, Andrea S. J. Lin, Sarah E. Logsdon, Michael W. McElwain, Andrew Monson, Joe P. Ninan, Jayadev Rajagopal, Arpita Roy, Christian Schwab, Ryan C. Terrien

Abstract

We present the discovery of GJ 251 c, a candidate super-Earth orbiting in the Habitable Zone (HZ) of its M dwarf host star. Using high-precision Habitable-zone Planet Finder (HPF) and NEID RVs, in conjunction with archival RVs from the Keck I High Resolution Echelle Spectrometer (HIRES), the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrograph (CARMENES), and the SPectropolarimètre InfraROUge (SPIRou), we improve the measured parameters of the known planet, GJ 251 b ($P_{b}$ = 14.2370 days; $m \sin(i)$ = 3.85$^{+0.35}_{-0.33}$ M$_{\oplus}$), and we significantly constrain the minimum mass of GJ 251 c, placing it in a plausibly terrestrial regime (P$_{c}$ = 53.647 $\pm$ 0.044 days; $ m \sin i_{c}$ = 3.84 $\pm$ 0.75 M$_{\oplus}$). Using activity mitigation techniques that leverage chromatic information content, we perform a color-dependent analysis of the system and a detailed comparison of more than 50 models that describe the nature of the planets and stellar activity in the system. Due to GJ 251's proximity to Earth (5.5 pc), next generation, thirty meter class telescopes will likely be able to image terrestrial planets in GJ 251's HZ. In fact, GJ 251 c is currently the best candidate for terrestrial, HZ planet imaging in the Northern Sky.

Discovery of a Nearby Habitable Zone Super-Earth Candidate Amenable to Direct Imaging

Abstract

We present the discovery of GJ 251 c, a candidate super-Earth orbiting in the Habitable Zone (HZ) of its M dwarf host star. Using high-precision Habitable-zone Planet Finder (HPF) and NEID RVs, in conjunction with archival RVs from the Keck I High Resolution Echelle Spectrometer (HIRES), the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrograph (CARMENES), and the SPectropolarimètre InfraROUge (SPIRou), we improve the measured parameters of the known planet, GJ 251 b ( = 14.2370 days; = 3.85 M), and we significantly constrain the minimum mass of GJ 251 c, placing it in a plausibly terrestrial regime (P = 53.647 0.044 days; = 3.84 0.75 M). Using activity mitigation techniques that leverage chromatic information content, we perform a color-dependent analysis of the system and a detailed comparison of more than 50 models that describe the nature of the planets and stellar activity in the system. Due to GJ 251's proximity to Earth (5.5 pc), next generation, thirty meter class telescopes will likely be able to image terrestrial planets in GJ 251's HZ. In fact, GJ 251 c is currently the best candidate for terrestrial, HZ planet imaging in the Northern Sky.
Paper Structure (9 sections, 1 figure)

This paper contains 9 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Observations
  3. RVs with Keck/HIRES
  4. RVs with the CARMENES Spectrograph
  5. RVs with SPIRou
  6. RVs with the Habitable-Zone Planet Finder
  7. RVs with the NEID Spectrometer
  8. Extracting Chromatic RVs
  9. Stellar Parameters

Figures (1)

  • Figure 1: Science fiber flux as a function of wavelength for the GJ 251 NEID spectra taken on 2021 October 11. Each order of flux is centered around a different peak wavelength. The NEID spectrograph has 174 orders, though the instrument response is primarily meaningful for orders 52 through 174. Notable is the low S/N for the bluer orders. As an early M dwarf, GJ 251 contains most of its flux at longer wavelengths. The section highlighted in red corresponds to a peak order wavelength greater than 8000 Å. These red orders are used in our creation of "red" NEID RVs for GJ 251.