The Use of Absorption Cells as a Wavelength Reference for Precision Radial Velocity Measurements in the Near-Infrared

Mahadevan, Suvrath; Ge, Jian

doi:10.1088/0004-637x/692/2/1590

Cited by 59 publications

(37 citation statements)

References 49 publications

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“…As already discussed by Mahadevan & Ge (2009), using the gas cell as a simultaneous reference superimposed on the stellar spectrum is limited by the definition of the stellar continuum. In the case of M stars, one of the main drivers for RV in the IR, the continuum is shaped by a dense forest of unresolved spectral lines.…”

Section: Discussionmentioning

confidence: 99%

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Radial velocities with CRIRES

Figueira¹,

Pepe²,

Melo

et al. 2010

A&A

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With the advent of high-resolution infrared spectrographs, radial relocity (RV) searches enter into a new domain. As of today, the most important technical question to address is which wavelength reference is the most suitable for high-precision RV measurements. In this work we use atmospheric absorption features as wavelength reference on CRIRES data obtained on two programs and three different targets. We analyzed the data from the TW Hya campaign again, reaching a dispersion of about 6 m/s on the RV standard on a time scale of roughly 1 week. We confirm that there is a low-amplitude RV signal on TW Hya itself, with an amplitude roughly 3 times smaller than the one reported at visible wavelengths. We present RV measurements of Gl 86 as well, showing that our approach is capable of detecting the signal induced by a planet and correctly quantifying it. Our data show that CRIRES is capable of reaching an RV precision of less than 10 m/s on a time scale of one week. The limitations of this particular approach are discussed, along with the limiting factors on RV precision in the IR in a general way. The implications of this work on the design of future dedicated IR spectrographs are addressed as well.

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Section: Discussionmentioning

confidence: 99%

“…Several hybrid alternatives were put forward to attempt to solve this problem, such as gas cell plus emission lamp or coupling of different gas cells. For a detailed description of the problem and proposed solutions the reader is referred to the work of Mahadevan & Ge (2009).…”

Section: Wavelength References In the Irmentioning

confidence: 99%

Radial velocities with CRIRES

Figueira¹,

Pepe²,

Melo

et al. 2010

A&A

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“…Valdivielso et al (2010) found different mixtures for gas cells providing a dense forest of lines in the NIR in the H and K band. In addition, Mahadevan & Ge (2009) reported on a mixture that produces a dense absorption spectrum in the H band. Bean et al (2010) reported that for their CRIRES survey consisting of a search for planets around M-dwarfs, they reach a RV precision of 5 m s −1 using a NH 3 gas cell in the K band.…”

Section: Instrumental Limitationsmentioning

confidence: 99%

Detecting planets around very cool dwarfs at near infrared wavelengths with the radial velocity technique

Rodler

Burgo

Witte

et al. 2011

A&A

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Context. Radial velocity monitoring of very cool dwarfs such as late M-and hot L-dwarfs has become a promising tool in the search for rocky planets as well as follow-up planetary candidates around dwarfs detected by transit surveys. These stars are faint at optical wavelengths, as their spectral flux distribution peaks at near-infrared (NIR) wavelengths. For this reason, it is desirable to measure the radial velocities in this wavelength regime. However, in the NIR very few medium-and high-resolution spectrographs are available at large telescopes. In the near future, high-resolution spectrographs for the NIR will be built, which will allow us to search for rocky planets around cool M-dwarfs and L-dwarfs from radial velocities monitoring. Aims. We investigate the precision that can be attained in radial velocity measurements of very cool dwarfs in the NIR. The goal is to determine in which atmospheric window of the Earth's atmosphere the highest radial velocity precision can be achieved to help in designing the next generation of NIR high-resolution spectrographs. Methods. We use stellar atmosphere synthetic models for an M-and an L-dwarf with temperatures of 2200 K and 1800 K, respectively, and a theoretical spectrum of the Earth's transmission in the spectral range from 0.9 to 2.5 μm. We simulate a series of Doppler-shifted spectra observed with different resolving powers and signal-to-noise ratios, and for different rotational broadenings of the dwarf. For different combinations of the input parameters, we recover the radial velocity by means of cross-correlation with a high signal-to-noise ratio template and determine the associate uncertainties. Results. The highest precision in radial velocity measurements for the cool M-dwarf is found in the Y band around 1.0 μm, while for the L-dwarf it is determined in the J band around 1.25 μm. We note that synthetic models may lack some faint absorption features or underestimate their abundances. In addition, some instrumental/calibration aspects that are not taken into account in our estimations would increase the uncertainties.

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“…Seifahrt & Kaeufl 2008;Mahadevan & Ge 2009;Reiners et al 2010;Valdivielso et al 2010). Besides "plain" spectroscopy, new techniques based on a combination of interferometry and spectroscopy have emerged (e.g.…”

Section: Historical Backgroundmentioning

confidence: 99%

A multi-method approach to radial-velocity measurement for single-object spectra

David

Blomme

Frémat

et al. 2014

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Context. The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. Aims. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. Methods. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral information in a different way, leading to different values for the measurement. A comparison or a combination of the various results either leads to a "best estimate" or indicates to the user that the observed spectrum is problematic and should be analysed manually. Results. We selected three methods and analysed the relationships and differences between them from a unified point of view; with each method an appropriate estimator for the individual random error is chosen. We also develop a procedure for tackling the problem of template mismatch in a systematic way. Furthermore, we propose several tests for studying and comparing the performance of the various methods as a function of the atmospheric parameters of the observed objects. Finally, we describe a procedure for obtaining a knowledge-based combination of the various Doppler-shift measurements.

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The Use of Absorption Cells as a Wavelength Reference for Precision Radial Velocity Measurements in the Near-Infrared

Cited by 59 publications

References 49 publications

Radial velocities with CRIRES

Radial velocities with CRIRES

Detecting planets around very cool dwarfs at near infrared wavelengths with the radial velocity technique

A multi-method approach to radial-velocity measurement for single-object spectra

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