Toward a Self-calibrating, Empirical, Light-weight Model for Tellurics in High-resolution Spectra

Leet, Christopher; Fischer, Debra A.; Valenti, Jeff A.

doi:10.3847/1538-3881/ab0d86

Cited by 28 publications

(22 citation statements)

References 24 publications

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“…In particular, the data-driven method presented by Bedell et al (2019) proves to work sufficiently well in removing the telluric contamination without requiring any prior knowledge on the telluric spectra. There are also data-driven methods for iodine-calibrated RV spectra as well, such as the work by Díaz et al (2019) and Leet et al (2019).…”

Section: Discussionmentioning

confidence: 99%

The Effects of Telluric Contamination in Iodine-calibrated Precise Radial Velocities

Wang

Wright

Bender

et al. 2019

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We characterized the effects of telluric absorption lines on the radial velocity (RV) precision of stellar spectra taken through an iodine cell. To isolate the effects induced by telluric contamination from other stellar, instrumental, or numerical systematic RV noise, we extracted RVs from simulated iodine-calibrated spectra of three RV standard stars regularly observed by Keck/HIRES. We add in water absorption lines according to measured precipitable water vapor (PWV) contents over a one-year period. We conclude that telluric contamination introduces additional RV noise and spurious periodic signals at the level of 10-20cm s −1 , consistent with similar previous studies. Our findings show that forward modeling the telluric lines effectively recovers the RV precision and accuracy, with no prior knowledge of the PWV needed. Such a recovery is less effective when the water absorption lines are relatively deep in the stellar template used in the forward modeling. Overall, telluric contamination plays an insignificant role in typical iodine-calibrated RV programs aiming at ∼1-2m s −1 , but we recommend adding modeling of telluric lines and taking stellar template observations on nights with low humidity for programs aiming to achieve a precision of better than 1 m s -1 .

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Section: Discussionmentioning

confidence: 99%

The Effects of Telluric Contamination in Iodine-calibrated Precise Radial Velocities

Wang

Wright

Bender

et al. 2019

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“…Since its equivalent width (EW) can be interpreted as a proxy for water column density, this later is at first order proportional to the flux correction to apply. We note that a similar flux corrections is applied in Leet et al (2019) with the SELENITE code, where the modelled correction is using as prior information both precipitable water vapour content and airmass.…”

Section: Telluric Line Correctionmentioning

confidence: 99%

YARARA: Significant improvement in RV precision through post-processing of spectral time series

Cretignier

Dumusque

Hara

et al. 2021

A&A

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Aims. Even the most precise radial-velocity instruments gather high-resolution spectra that present systematic errors that a data reduction pipeline cannot identify and correct for efficiently by simply analysing a set of calibrations and a single science frame. In this paper we aim at improving the radial-velocity precision of HARPS measurements by 'cleaning' individual extracted spectra using the wealth of information contained in spectral time series. Methods. We developed YARARA, a post-processing pipeline designed to clean high-resolution spectra of instrumental systematics and atmospheric contamination. Spectra are corrected for: tellurics, interference patterns, detector stitching, ghosts, and fibre B contaminations, as well as more advanced spectral line-by-line corrections. YARARA uses principal component analysis on spectral time series with prior information to disentangle contaminations from real Doppler shifts. We applied YARARA to three systems, HD10700, HD215152, and HD10180, and compared our results to the standard HARPS data reduction software and the SERVAL post-processing pipeline.Results. We ran YARARA on the radial-velocity dataset of three stars intensively observed with HARPS: HD10700, HD215152, and HD10180. For HD10700, we show that YARARA enables us to obtain radial-velocity measurements that present an rms smaller than 1 m s −1 over the 13 years of the HARPS observations, which is 20% and 10% better than the HARPS data reduction software and the SERVAL post-processing pipeline, respectively. We also injected simulated planets into the data of HD10700 and demonstrated that YARARA does not alter pure Doppler-shifted signals. For HD215152, we demonstrated that the 1-year signal visible in the periodogram becomes marginal after processing with YARARA and that the signals of the known planets become more significant. Finally, for HD10180, the six known exoplanets are well recovered, although different orbital parameters and planetary masses are provided by the new reduced spectra. Conclusions. The post-processing correction of spectra using spectral time series allows the radial-velocity precision of HARPS data to be significantly improved and demonstrates that for the extremely quiet star HD10700 a radial-velocity rms better than 1 m/s can be reached over the 13 years of HARPS observations. Since the processing proposed in this paper does not absorb planetary signals, its application to intensively followed systems is promising and will certainly result in advances in the detections of the lightest exoplanets.

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“…Two sets of wavelengths are provided: one set with a classic polynomial wavelength solution, and one set generated using excalibur, a hierarchical, nonparametric wavelength solution (Zhao et al 2021). The provided spectra also include a model of telluric lines generated using SELENITE (Leet et al 2019), a continuum model, and the associated combined flat image that can be used to recover photon counts 3 .…”

Section: Spectroscopic Data From Expresmentioning

confidence: 99%

The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Zhao,

Fischer,

Ford

et al. 2022

Preprint

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Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme precision radial velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The EXPRES Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed RV correction, or separated out shape-and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV RMS than classic linear decorrelation, but no method is yet consistently reducing the RV RMS to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets-such as solar data or data with known injected planetary and/or stellar signals-to better understand method performance and whether planetary signals are preserved.

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Toward a Self-calibrating, Empirical, Light-weight Model for Tellurics in High-resolution Spectra

Cited by 28 publications

References 24 publications

The Effects of Telluric Contamination in Iodine-calibrated Precise Radial Velocities

The Effects of Telluric Contamination in Iodine-calibrated Precise Radial Velocities

YARARA: Significant improvement in RV precision through post-processing of spectral time series

The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

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