Precision Radial Velocity Measurements by the Forward Modeling Technique in the Near Infrared. (arXiv:2007.11013v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hirano_T/0/1/0/all/0/1">Teruyuki Hirano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuzuhara_M/0/1/0/all/0/1">Masayuki Kuzuhara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kotani_T/0/1/0/all/0/1">Takayuki Kotani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Omiya_M/0/1/0/all/0/1">Masashi Omiya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kudo_T/0/1/0/all/0/1">Tomoyuki Kudo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harakawa_H/0/1/0/all/0/1">Hiroki Harakawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vievard_S/0/1/0/all/0/1">Sébastien Vievard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kurokawa_T/0/1/0/all/0/1">Takashi Kurokawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nishikawa_J/0/1/0/all/0/1">Jun Nishikawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tamura_M/0/1/0/all/0/1">Motohide Tamura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hodapp_K/0/1/0/all/0/1">Klaus Hodapp</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ishizuka_M/0/1/0/all/0/1">Masato Ishizuka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jacobson_S/0/1/0/all/0/1">Shane Jacobson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Konishi_M/0/1/0/all/0/1">Mihoko Konishi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serizawa_T/0/1/0/all/0/1">Takuma Serizawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ueda_A/0/1/0/all/0/1">Akitoshi Ueda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaidos_E/0/1/0/all/0/1">Eric Gaidos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sato_B/0/1/0/all/0/1">Bun'ei Sato</a>
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., $T_{rm eff}$, $vsin i$, [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.
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., $T_{rm eff}$, $vsin i$, [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.
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