Impact of micro-telluric lines on precise radial velocities and its correction

Cunha, Diana; Santos, N. C.; Figueira, P.; Santerne, A.; Bertaux, Jean-Loup; Lovis, C.

doi:10.1051/0004-6361/201423723

Cited by 54 publications

(75 citation statements)

References 22 publications

(31 reference statements)

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“…The impact at optical wavelengths is of order ∼ 0.2 − −1 m s −1 where (Figure 22) micro-telluric lines have depths of 0.2 -2% (Cunha et al 2014;Artigau et al 2014b). …”

Section: Telluric Contaminationmentioning

confidence: 97%

State of the Field: Extreme Precision Radial Velocities

Fischer

Anglada‐Escudé

Arriagada³

et al. 2016

PASP

308

254

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The Second Workshop on Extreme Precision Radial Velocities defined circa 2015 the state of the art Doppler precision and identified the critical path challenges for reaching 10 cm s −1 measurement precision. The presentations and discussion of key issues for instrumentation and data analysis and the workshop recommendations for achieving this bold precision are summarized here.Beginning with the HARPS spectrograph, technological advances for precision radial velocity measurements have focused on building extremely stable instruments. To reach still higher precision, future spectrometers will need to improve upon the state of the art, producing even higher fidelity spectra. This should be possible with improved environmental control, greater stability in the illumination of the spectrometer optics, better detectors, more precise wavelength calibration, and broader bandwidth spectra. Key data analysis challenges for the precision radial velocity community include distinguishing center of mass Keplerian motion from photospheric velocities (time correlated noise) and the proper treatment of telluric contamination. Success here is coupled to the instrument design, but also requires the implementation of robust statistical and modeling techniques. Center of mass velocities produce Doppler shifts that affect every line identically, while photospheric velocities produce line profile asymmetries with wavelength and temporal dependencies that are different from Keplerian signals.Exoplanets are an important subfield of astronomy and there has been an impressive rate of discovery over the past two decades. However, higher precision radial velocity measurements are required to serve as a discovery technique for potentially habitable worlds, to confirm and characterize detections from transit missions, and to provide mass measurements for other space-based missions. The future of exoplanet science has very different trajectories depending on the precision that can ultimately be achieved with Doppler measurements.

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“…The impact at optical wavelengths is of order ∼ 0.2 − −1 m s −1 where (Figure 22) micro-telluric lines have depths of 0.2 -2% (Cunha et al 2014;Artigau et al 2014b). …”

Section: Telluric Contaminationmentioning

confidence: 97%

State of the Field: Extreme Precision Radial Velocities

Fischer

Anglada‐Escudé

Arriagada³

et al. 2016

PASP

308

254

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“…Even for stars with constant radial velocity, the barycentric velocity of the Earth causes the telluric lines to raster across stellar absorption lines with annual amplitudes up to 30 km s −1 , producing small, but systematic, time-variable line profile variations. Optical RV programs aiming for 10 -20 cm s −1 precision will need to account for microtelluric lines because they introduce errors that exceed the target RV precision Cunha et al (2014). Figure 1.…”

Section: Telluric Spectramentioning

confidence: 99%

“…The atmospheric temperature and pressure model for the geographic region near La Silla is updated every six hours, and the model with the closest match in time to observations is adopted with small empirical adjustments to water vapor column density. Based on simulations with synthetic spectra, Cunha et al (2014) expected that the improvement in RV precision for most stars would be in the range of 10 -20 cm s −1 . Achieving RV accuracies of 10 cm s −1 necessitates accurate modelling of microtellurics.…”

Section: The Challenge Of Microtelluricsmentioning

confidence: 99%

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

Leet

Fischer

Valenti

2019

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To discover Earth analogs around other stars, next generation spectrographs must measure radial velocity (RV) with 10 cm/s precision. To achieve 10cm/s precision, however, the effects of telluric contamination must be accounted for. The standard approaches to telluric removal are: (a) observing a standard star and (b) using a radiative transfer code. Observing standard stars, however, takes valuable observing time away from science targets. Radiative transfer codes, meanwhile, rely on imprecise line data in the HITRAN database (typical line position uncertainties range from a few to several hundred m/s) and require difficult-to-obtain measurements of water vapor column density for best performance. To address these issues, we present SELENITE: a SELf-calibrating, Empricial, Light-Weight liNear regressIon TElluric model for high-resolution spectra. The model exploits two simple observations: (a) water tellurics grow proportionally to precipitable water vapor and therefore proportionally to each other and (b) non-water tellurics grow proportionally to airmass. Water tellurics can be identified by looking for pixels whose growth correlates with a known calibration water telluric and modelled by regression against it, and likewise non-water tellurics with airmass. The model doesn't require line data, water vapor measurements and additional observations (beyond one-time calibration observations), achieves fits with a χ 2 red of 1.17 on B stars and 2.95 on K dwarfs, and leaves residuals of 1% (B stars) and 1.1% (K dwarfs) of continuum. Fitting takes seconds on laptop PCs: SELENITE is light-weight enough to guide observing runs.

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“…The developments in this direction in the past few years have been remarkable: from Seifahrt et al (2010) to the recent web interface TAPAS (Bertaux et al 2014), the Telfit (Gullikson et al 2014) and Molecfit codes (Smette et al 2015), to the recent PCA-based approach of Artigau et al (2014a), we have come a long way in the recent years. We are even now starting to analyze the effect of small amplitude or unresolved stellar lines on stellar visible spectra (Cunha et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Radial velocity information content of M dwarf spectra in the near-infrared

Figueira

Adibekyan

Oshagh

et al. 2016

A&A

Self Cite

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Aims. We evaluate the radial velocity (RV) information content and achievable precision on M0-M9 spectra covering the ZYJHK bands. We do so while considering both a perfect atmospheric transmission correction and discarding areas polluted by deep telluric features, as done in previous works. Methods. To simulate the M-dwarf spectra, PHOENIX-ACES model spectra were employed; they were convolved with rotational kernels and instrumental profiles to reproduce stars with a v sin i of 1.0, 5.0, and 10.0 km s −1 when observed at resolutions of 60 000, 80 000, and 100 000. We considered the RV precision as calculated on the whole spectra, after discarding strongly polluted areas, and after applying a perfect telluric correction. In the latter option, we took into account the reduction in the number of recorded photons due to a transmittance lower than unity and considered its effect on the noise of the recorded spectra. In our simulations we paid particular attention to the details of the convolution and sampling of the spectra, and we discuss their impact on the final spectra. Results. Our simulations show that the most important parameter ruling the difference in attainable precision between the considered bands is the spectral type. For M0-M3 stars, the bands that deliver the most precise RV measurements are the Z, Y, and H band, with relative merits depending on the parameters of the simulation. For M6-M9 stars, the bands show a difference in precision that is within a factor of ∼2 and does not clearly depend on the band; this difference is reduced to a factor smaller than ∼1.5 if we consider a non-rotating star seen at high resolution. We also show that an M6-M9 spectrum will deliver a precision about two times better as an M0-M3 spectra with the same signal-to-noise ratio. Finally, we note that the details of modeling the Earth atmosphere and interpreting the results have a significant impact on which wavelength regions are discarded when setting a limit threshold at 2−3%. The resolution element sampling on the observed spectra plays an important role in the atmospheric transmission characterization. As a result of the multiparameter nature of the problem, it is very difficult to precisely quantify the impact of absorption by the telluric lines on the RV precision, but it is an important limiting factor to the achievable RV precision.

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Impact of micro-telluric lines on precise radial velocities and its correction

Cited by 54 publications

References 22 publications

State of the Field: Extreme Precision Radial Velocities

State of the Field: Extreme Precision Radial Velocities

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

Radial velocity information content of M dwarf spectra in the near-infrared

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