A New Gas Cell for High-Precision Doppler Measurements in the Near-Infrared

Valdivielso, L.; Esparza, P.; Martín, E. L.; Maukonen, D.; Peale, Robert E.

doi:10.1088/0004-637x/715/2/1366

Cited by 34 publications

(12 citation statements)

References 15 publications

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“…There are other gases and isotopologues that provide useful absorption features around 1500 nm. Some of the most promising ones have already been discussed by Mahadevan &Ge (2009) andValdivielso et al (2010). From our obtained spectra, a higher-presure cell combining 14 NH 3 and 13 CH 4 would seem to be a good choice to cover a good fraction of the H band.…”

Section: H Bandmentioning

confidence: 82%

Design and Construction of Absorption Cells for Precision Radial Velocities in theKBand Using Methane Isotopologues

Anglada-Escudé¹,

Plavchan²,

Mills³

et al. 2012

Publications of the Astronomical Society of the Pacific

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We present a method to optimize absorption cells for precise wavelength calibration in the near-infrared. We apply it to design and optimize methane isotopologue cells for precision radial velocity measurements in the K band. We also describe the construction and installation of two such cells for the CSHELL spectrograph at NASA's IRTF. We have obtained their high-resolution laboratory spectra, which we can then use in precision radial velocity measurements and which can also have other applications. In terms of obtainable RV precision methane should out-perform other proposed cells, such as the ammonia cell ( 14 NH 3 ) recently demonstrated on CRIRES/VLT. The laboratory spectra of Ammonia and the Methane cells show strong absorption features in the H band that could also be exploited for precision Doppler measurements. We present spectra and preliminary radial velocity measurements obtained during our first-light run. These initial results show that a precision down to 20-30 m s −1 can be obtained using a wavelength interval of only 5 nm in the K band and S/N∼150. This -2supports the prediction that a precision down to a few m s −1 can be achieved on late M dwarfs using the new generation of NIR spectrographs, thus enabling the detection of terrestrial planets in their habitable zones. Doppler measurements in the NIR can also be used to mitigate the radial velocity jitter due to stellar activity enabling more efficient surveys on young active stars.

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Section: H Bandmentioning

confidence: 82%

Design and Construction of Absorption Cells for Precision Radial Velocities in theKBand Using Methane Isotopologues

Anglada-Escudé¹,

Plavchan²,

Mills³

et al. 2012

Publications of the Astronomical Society of the Pacific

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“…We should keep in mind that for very cool dwarfs, even with very efficient NIR spectrographs mounted at 8m class telescopes, the integration times are still long in order to get a high SNR. Valdivielso et al (2010) present different mixtures for a gas cells providing a dense forest of lines in the NIR in the H and K band. In addition to that, Mahadevan & Ge (2009) report on a mixture that provide a dense absorption spectrum in the H 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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“…The cells were filled with different molecular gases using a vacuum pump system in our laboratory located in the chemistry department of the Universidad de La Laguna. The procedure for filling the cells with gas is described in more detail in Valdivielso et al (2010). The gas cells with ammonia (NH3), argon (Ar), and methane (CH4) were completely filled with each of those gases at the atmospheric pressure.…”

Section: Low-resolution Laboratory Spectramentioning

confidence: 99%

Ammonia-methane ratios from H-band near-infrared spectra of late-T and Y dwarfs

Martín

Zhang

Esparza

et al. 2021

A&A

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Aims. Our goals are to investigate the relative absorption strengths of ammonia and methane using low-resolution H-band (1.5−1.7 microns) spectra obtained in the laboratory and compared with observational spectra of late-T and Y dwarfs, and to estimate what can be expected from the wide-angle low-resolution near-infrared spectroscopic survey that will be provided by the upcoming Euclid space mission. Methods. Gas cells containing ammonia and methane at atmospheric pressure were custom-made in our chemical laboratory. Low-resolution near-infrared spectroscopy of these gas cells was collected in our optical laboratory. It is compared with simulated spectra using the high-resolution transmission molecular absorption database (HITRAN) for temperatures of 300 K and 500 K, and with near-infrared spectra of late-T dwarfs, Y dwarfs, Jupiter, and Saturn. We selected for this investigation the spectral region between 1.5 and 1.7 microns (H band) because it is covered by the Euclid red grism, it is particularly sensitive to the relative proportions of ammonia and methane opacity, and it is free from strong contributions of other abundant molecules, such as water vapor. Results. The laboratory spectra showed that the ammonia and methane features present in the simulations that used the HITRAN database are incomplete. Using our laboratory spectra, we propose a modified version of the NH3-H spectral ratio with expanded integration limits that increases the amplitude of variation in the index with respect to spectral type. Combinations of our laboratory spectra were used to find the best fits to the observed spectra with the relative absorption ratio of ammonia to methane as a free parameter. A relationship was found between the Teff and the ratio of ammonia to methane from spectral classes T5 to Y2 (1100 K–350 K), in fairly good qualitative agreement with theoretical predictions for high-gravity objects and temperatures from 1100 K to 500 K. The ammonia-to-methane ratios in late-T and Y dwarfs are similar to that of Jupiter, suggesting a similar chemical composition. Simulations of the spectroscopic performance of Euclid suggest that it will yield Teff values and ratios of ammonia to methane for over 103 late-T dwarfs in the entire wide survey.

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A New Gas Cell for High-Precision Doppler Measurements in the Near-Infrared

Cited by 34 publications

References 15 publications

Design and Construction of Absorption Cells for Precision Radial Velocities in theKBand Using Methane Isotopologues

Design and Construction of Absorption Cells for Precision Radial Velocities in theKBand Using Methane Isotopologues

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

Ammonia-methane ratios from H-band near-infrared spectra of late-T and Y dwarfs

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