JASMINE is a Japanese planned space mission that aims to reveal the formation history of our Galaxy and discover habitable exoEarths. For these objectives, the JASMINE satellite performs high-precision astrometric observations of the Galactic bulge and high-precision transit monitoring of M-dwarfs in the near-infrared (1.0—1.6 µm in wavelength). For feasibility studies, we develop an image simulation software named JASMINE-imagesim, which produces realistic observation images. This software takes into account various factors such as the optical point spread function (PSF), telescope jitter caused by the satellite’s attitude control error (ACE), detector flat patterns, exposure timing differences between detector pixels, and various noise factors. As an example, we report a simulation for the feasibility study of astrometric observations using JASMINE-imagesim. The simulation confirms that the required position measurement accuracy of 4 milliarcseconds for a single exposure of 12.5-mag objects is achievable if the telescope pointing jitter uniformly dilutes the PSF across all stars in the field of view. On the other hand, the simulation also demonstrates that the combination of realistic pointing jitter and exposure timing differences in the detector can significantly degrade accuracy and prevent achieving the requirement. This means that certain countermeasures against this issue must be developed. This result implies that this kind of simulation is important for mission planning and advanced developments to realize more realistic simulations help us to identify critical issues and also devise effective solutions.
The InfraRed Doppler (IRD) instrument is the Subaru telescope’s high-resolution (R > 70,000) spectrograph covering wavelengths from 1000 to 1700 nm. A laser frequency comb (LFC) spectrum simultaneously obtained with an object spectrum calibrates wavelength shifts caused by instrumental instability. We originally developed IRD to carry out precision radial velocity (RV) measurements at near-infrared wavelengths. The wide wavelength coverage of IRD, and the large mirror (8.2 m) of the Subaru Telescope enables IRD to provide the best sensitivities to detect a planet orbiting a cool M-type star. The first science operation of IRD was conducted in 2018 and the large strategic blind survey for planets orbiting cool M-type stars started in 2019. Since then, there have been many observations not only for exoplanet category but also for stellar physics, Galaxy, and high-energy astrophysics. IRD spectroscopy allowed for characterizing exoplanet atmospheres by measuring OH emissions, He absorptions, and spin-orbit obliquities. The IRD survey discovered a super-Earth in orbit near a habitable zone of Ross 508. The IRD RV measurements for many systems that host transiting planets, including TOI-2285 b and Gliese 12 b, helped confirm those and determine or constrain their masses. Using REACH, IRD can be combined with the extreme adaptive optics SCExAO, enabling the use of a single-mode fiber and characterizations of faint sub-stellar companions orbiting bright stars. In this proceeding paper, we review and highlight the scientific results achieved by the IRD observations.
We assessed the impact of Earth’s atmospheric absorption lines, known as telluric contamination, on near-infrared radial velocity (RV) measurements using IRD/Subaru. We focused on the telluric removal process implemented in the RV pipeline for IRD data, which works in two phases: the creation of a stellar template spectrum and the measurement of RVs through a forward modeling approach. Our analysis revealed that discrepancies of approximately 1% exist between the observed telluric standard star’s spectra and theoretical telluric spectra, both used within the RV pipeline. These discrepancies are particularly significant in regions with strong water vapor absorption. Additionally, we investigated the impacts of residual tellurics on RV measurements through mock spectrum analysis. By comparing RV values derived from mock spectra made with either theoretical or observed tellurics, we found that residual tellurics can introduce an additional scatter of at least 1 m/s in RV measurements. Our findings highlight the necessity for improved telluric removal methods in the near-infrared spectrum to achieve precise RV measurements critical for detecting small-mass planets.
The South Africa Near-infrared Doppler instrument (SAND) is a time-stable high-dispersion spectrograph, covering the z- and Y-bands simultaneously (849 - 1085 nm) with the maximum spectral resolution of ∼60,000. We aim to monitor the radial velocity of M-dwarfs with the precision of a few m/s level, which enables us to search for habitable exoplanets. Our another scientific motivation is the statistical investigation of young planets and stellar atmosphere to comprehensively understand the formation senario of stellar systems. We are planning to install the SAND to telescopes at the South African Astronomical Observatory (SAAO) in Sutherland, since the Southern sky covers plentiful stellar associations with young stars. The SAND is a fiber-fed spectrograph, and we can change telescope used to collect the star light by switching the fiber connection. It will be operated mainly with two telescopes: the Prime-focus Infrared Microlensing Experience telescope (PRIME) and the InfraRed Survey Facility (IRSF), which both are managed by universities in Japan. This strategy of using multiple telescopes gives us opportunities of frequent and long-term observations, which provides well phase coverage in radial velocity monitoring and results in non-bias search for exoplanets. Most of the components used in the spectrograph and the fiber injection module have been fabricated. We will present the detailed status and recent progress: designing the fiber injection module and the thermal control system, examination of fiber characteristics, and estimating our target candidates.
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