研究目的
To describe an IDL-based radial velocity data reduction pipeline for the TOU spectrograph and achieve sub-m s?1 RV precision for detecting low-mass exoplanets.
研究成果
The TOU data reduction pipeline achieves sub-m s?1 RV precision (～0.9 m s?1 with Tau Ceti), comparable to HARPS, enabling the detection of low-mass exoplanets. Key error sources are quantified, and lessons learned can guide future spectrograph developments. To reach 0.1 m s?1 precision, advancements in calibration, stellar activity mitigation, and observational scheduling are needed.
研究不足
Limitations include errors from wavelength calibration (～0.4 m s?1), micro-telluric lines (0.1–0.2 m s?1), instrument drift correction (～0.36 m s?1), and stellar activity jitter (～0.45 m s?1). The pipeline is optimized for bright stars and may require adjustments for fainter targets or different spectral types. Achieving 0.1 m s?1 precision necessitates improvements in PSF deconvolution, telluric line removal, and better calibration sources.
1：Experimental Design and Method Selection:
The pipeline uses a least-squares fitting algorithm to match observed stellar spectra to a high-SNR template, employing a non-linear Levenberg-Marquardt technique for RV extraction.
2：Sample Selection and Data Sources:
Observations were conducted on 20 nearby bright FGK dwarfs (V < 9) using the TOU spectrograph at the 2 m Automatic Spectroscopic Telescope (AST) at Fairborn Observatory, with Tau Ceti as a stable reference star.
3：List of Experimental Equipment and Materials:
Equipment includes the TOU spectrograph (R=100,000, 380-900 nm), a Fairchild CCD detector (4k x 4k), Thorium-Argon lamps for wavelength calibration, Tungsten lamp for flat-fielding, and a 2 m AST telescope.
4：Experimental Procedures and Operational Workflow:
Steps include spectrum extraction using optimal extraction techniques, wavelength calibration with ThAr lamps, building stellar templates, RV measurement via template matching, barycentric velocity correction, and instrumental drift correction. Daily master calibration frames (bias, flat, wavelength) were taken.
5：Data Analysis Methods:
Data reduction involves bias subtraction, scattered-light subtraction, flat-fielding, cosmic ray rejection, and RV error budget analysis using simulations and theoretical methods like the 'Q' factor for photon noise.
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