Precision radial velocity measurements by the forward-modeling technique in the near-infrared

Abstract

Precision radial velocity (RV) measurements in the near-infrared are a powerful tool to detect and characterize exoplanets around low-mass stars or young stars with higher magnetic activity. However, the presence of strong telluric absorption lines and emission lines in the near infrared that significantly vary in time can prevent extraction of RV information from these spectra by classical techniques, which ignore or mask the telluric lines. We present a methodology and pipeline to derive precision RVs from near-infrared spectra using a forward-modeling technique. We applied this to spectra with a wide wavelength coverage (Y, J, and H bands, simultaneously), taken by the InfraRed Doppler (IRD) spectrograph on the Subaru 8.2-m telescope. Our pipeline extracts the instantaneous instrumental profile of the spectrograph for each spectral segment, based on a reference spectrum of the laser-frequency comb that is injected into the spectrograph simultaneously with the stellar light. These profiles are used to derive the intrinsic stellar template spectrum, which is free from instrumental broadening and telluric features, as well as model and fit individual observed spectra in the RV analysis. Implementing a series of numerical simulations using theoretical spectra that mimic IRD data, we test the pipeline and show that IRD can achieve $<2$ m s${}^{-1}$ precision for slowly rotating mid-to-late M dwarfs with a signal-to-noise ratio $>100$ per pixel at 1000 nm. Dependences of RV precision on various stellar parameters (e.g., $T_{\mathrm{eff}}$, $v\sin i$, [Fe/H]) and the impact of telluric-line blendings on the RV accuracy are discussed through the mock spectra analyses. We also apply the RV-analysis pipeline to the observed spectra of GJ 699 and TRAPPIST-1, demonstrating that the spectrograph and the pipeline are capable of an RV accuracy of $<3$ m s${}^{-1}$ at least on a time scale of a few months.

21 pages, 20 figures; accepted for publication in PASJ; typos corrected

References in corpus (7)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Tempo2, a new pulsar timing package. II: The timing model and precision estimates
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Accurate M Dwarf Metallicities from Spectral Synthesis: A Critical Test of Model Atmospheres
• Evidence for Spin-orbit Alignment in the TRAPPIST-1 System
• Global Analysis of KOI-977: Spectroscopy, Asteroseismology, and Phase-curve Analysis

Cited by in corpus (27)

• First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b using Subaru/IRD
• Two temperate super-Earths transiting a nearby late-type M dwarf
• TOI-1452 b: SPIRou and TESS reveal a super-Earth in a temperate orbit transiting an M4 dwarf
• Statistical methods for exoplanet detection with radial velocities
• Ultraviolet astronomical spectrograph calibration with laser frequency combs from nanophotonic lithium niobate waveguides
• An M dwarf accompanied by a close-in giant orbiter with SPECULOOS
• High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
• The mass determination of TOI-519 b: a close-in giant planet transiting a metal-rich mid-M dwarf
• Characterization of the ESPRESSO Line-Spread Function and Improvement of the Wavelength Calibration Accuracy
• Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
• Gliese 12 b: A temperate Earth-sized planet at 12 pc ideal for atmospheric transmission spectroscopy
• TOI-1696: a nearby M4 dwarf with a $3R_{\oplus }$ planet in the Neptunian desert
• A Super-Earth Orbiting Near the Inner Edge of the Habitable Zone around the M4.5-dwarf Ross 508
• Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b
• Planetary companions orbiting the M dwarfs GJ 724 and GJ 3988. A CARMENES and IRD collaboration
• An Earth-sized Planet around an M5 Dwarf Star at 22 pc
• Zodiacal Exoplanets in Time (ZEIT) XII: A Directly-Imaged Planetary-Mass Companion to a Young Taurus M Dwarf Star
• viper: High-precision radial velocities from the optical to the infrared (Reaching 3 m/s in the K band of CRIRES+ with telluric modelling)
• Direct Imaging Explorations for Companions around Mid-Late M Stars from the Subaru/IRD Strategic Program
• Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B
• The SPIRou Legacy Survey: near-infrared and optical radial velocity analysis of Gl 480 and Gl 382 using SPIRou, HARPS and CARMENES spectrographs
• The SPIRou Legacy Survey: Detection of a nearby world orbiting in the habitable zone of Gl725B achieved by correcting strong telluric contamination in near-infrared radial velocities with WAPITI
• Non-detection of Helium in the upper atmospheres of TRAPPIST-1b, e and f
• Characterizing the Instrumental Profile of LAMOST
• Silicon and Strontium abundances of very metal-poor stars determined from near-infrared spectra
• Sibling Sub-Neptunes Around Sibling M Dwarfs: TOI-521 and TOI-912
• A Search for helium in the atmospheres of three sub-Neptunes and a super-Earth around M-dwarfs