High-resolution transmission spectroscopy of MASCARA-2 b with EXPRES

We report detections of atomic species in the atmosphere of MASCARA-2 b, using the first transit observations obtained with the newly commissioned EXPRES spectrograph. EXPRES is a highly stabilized optical echelle spectrograph, designed to detect stellar reflex motions with amplitudes down to 30 cm s−1, and has recently been deployed at the Lowell Discovery Telescope. By analyzing the transmission spectrum of the ultra-hot Jupiter MASCARA-2 b using the cross-correlation method, we confirm previous detections of Fe I, Fe II, and Na I, which likely originate in the upper regions of the inflated atmosphere. In addition, we report significant detections of Mg I and Cr II. The absorption strengths change slightly with time, possibly indicating different temperatures and chemistry in the day- and nightside terminators. Using the effective stellar line-shape variation induced by the transiting planet, we constrain the projected spin-orbit misalignment of the system to 1.6 ± 3.1 degrees, consistent with an aligned orbit. We demonstrate that EXPRES joins a suite of instruments capable of phase-resolved spectroscopy of exoplanet atmospheres.

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Precise Radial Velocity Measurements with a Cassegrain Spectrograph, I: Wavelength calibration

International Astronomical Union Colloquium ◽

10.1017/s0252921100048363 ◽

1999 ◽

Vol 170 ◽

pp. 63-67

Author(s):

I. V. Ilyin ◽

R. Duemmler

Keyword(s):

High Resolution ◽

Radial Velocity ◽

Cross Correlation ◽

Time Dependent ◽

Instrumental Effects ◽

Velocity Measurements ◽

Echelle Spectrograph ◽

Optical Telescope ◽

La Palma ◽

Observational Strategy

AbstractWe briefly describe the instrumental effects which affect the accuracy of the radial velocity measurements. We have implemented several methods to correct for the instability effects and improve the accuracy of the measurements. These include modifications of the observational strategy and a time-dependent wavelength solution as well as a discussion of the error of the offset from cross-correlation. These methods are applied to observations obtained with the high resolution échelle spectrograph SOFIN mounted at the Cassegrain focus of the alt-azimuth 2.56-m Nordic Optical Telescope, La Palma, Canary Islands.

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Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa748 ◽

2020 ◽

Vol 494 (1) ◽

pp. 363-377 ◽

Cited By ~ 10

Author(s):

Samuel H C Cabot ◽

Nikku Madhusudhan ◽

Luis Welbanks ◽

Anjali Piette ◽

Siddharth Gandhi

Keyword(s):

High Resolution ◽

Transmission Spectrum ◽

Cross Correlation ◽

Hydrogen Atmosphere ◽

Chemical Processes ◽

Thermal Inversion ◽

Hot Jupiters ◽

Roche Limit ◽

Careful Treatment ◽

Host Stars

ABSTRACT The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense irradiation from their host stars. They have proved to be a particularly interesting population for their orbital and atmospheric properties. One such planet, WASP-121b, is in a highly misaligned orbit close to its Roche limit, and its atmosphere exhibits a thermal inversion. These properties make WASP-121b an interesting target for additional atmospheric characterization. In this paper, we present analyses of archival high-resolution optical spectra obtained during transits of WASP-121b. We model the Rossiter-McLaughlin effect and the Centre-to-Limb Variation and find that they do not significantly affect the transmission spectrum in this case. However, we discuss scenarios where these effects warrant more careful treatment by modelling the WASP-121 system and varying its properties. We report a new detection of atmospheric absorption from H α in the planet with a transit depth of $1.87\pm 0.11{{\ \rm per\ cent}}$. We further confirm a previous detection of the Na i doublet, and report a new detection of Fe i via cross-correlation with a model template. We attribute the H α absorption to an extended Hydrogen atmosphere, potentially undergoing escape, and the Fe i to equilibrium chemistry at the planetary photosphere. These detections help to constrain the composition and chemical processes in the atmosphere of WASP-121b.

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A High-Resolution Ultrasonic Ranging System Using Laser Sensing and a Cross-Correlation Method

Applied Sciences ◽

10.3390/app9071483 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1483 ◽

Cited By ~ 1

Author(s):

Lecheng Jia ◽

Bin Xue ◽

Shili Chen ◽

Hanzhong Wu ◽

Xiaoxia Yang ◽

...

Keyword(s):

High Resolution ◽

Sound Velocity ◽

Cross Correlation ◽

Reference Signal ◽

Correlation Method ◽

Repeatability Error ◽

Laser Sensing ◽

Measurement Resolution ◽

Ultrasonic Ranging ◽

Potential Applications

Ultrasound has been proven to be a valid tool for ranging, especially in water. In this paper, we design a high-resolution ultrasonic ranging system that uses a thin laser beam as an ultrasonic sensor. The laser sensing provides a noncontact method for ultrasound detection based on acousto-optic diffraction. Unlike conventional methods, the ultrasound transmitted from the transducer is recorded as the reference signal when it first passes through the laser. It can be used to improve the accuracy and resolution of the time-of-flight (TOF) by a cross-correlation method. Transducers with a central frequency of 1 MHz and diameters of 20 mm and 28 mm are used in the experiment. Five targets and a test piece are used to evaluate the ranging performance. The sound velocity is measured by the sound velocity profiler (SVP). The repeatability error of TOF is less than 4 ns, and the theoretical resolution of TOF is 0.4 ns. The results show a measurement resolution within one-tenth of the wavelength of ultrasound and an accuracy better than 0.3 mm for targets at a distance up to 0.8 m. The proposed system has potential applications in underwater ranging and thickness detection.

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The atmosphere of WASP-76b seen with CARMENES: looking for CaII IRT and HeI

10.5194/epsc2021-622 ◽

2021 ◽

Author(s):

Núria Casasayas-Barris ◽

Jaume Orell-Miquel ◽

Monika Stangret ◽

Lisa Nortmann ◽

Fei Yan ◽

...

Keyword(s):

High Resolution ◽

Transmission Spectrum ◽

Potential Candidate ◽

Hot Jupiters ◽

Transmission Spectroscopy ◽

Follow Up Studies ◽

Ionised Calcium

Currently, one of the most used techniques to study the atmosphere of the exoplanets is transmission spectroscopy by means of high-resolution facilities (R > 105). This methodology has led to the detection of several species in the atmosphere of exoplanets, showing that ultra-hot Jupiters (Teq > 2000 K) are one of the most intriguing exoplanets, possessing the richest atmospheres measured to date. Here, using two transit observations with the high-resolution spectrograph CARMENES, we study the atmosphere of one of the most famous ultra-hot Jupiters: WASP-76b. We take advantage of the redder wavelength coverage of CARMENES, in comparison with the facilities used in previous studies of this same planet, and focus our analysis on the CaII IRT triplet at 850nm and the metastable HeI triplet at 1083nm. In line with recent studies, we detect ionised calcium in the atmosphere of WASP-76b and, additionally, find possible evidence of HeI. We contextualise our findings with previous atmospheric studies of other ultra-hot Jupiters and, in particular, with those showing the presence of CaII and HeI absorption in their transmission spectrum. We show that this planet is a potential candidate for further follow up studies of the HeI lines using high-resolution spectrographs located at larger telescopes, such as CRIRES+.

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Assessing telluric correction methods for Na detections with high-resolution exoplanet transmission spectroscopy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab134 ◽

2021 ◽

Vol 502 (3) ◽

pp. 4392-4404

Author(s):

Adam B Langeveld ◽

Nikku Madhusudhan ◽

Samuel H C Cabot ◽

Simon T Hodgkin

Keyword(s):

High Resolution ◽

Transmission Spectrum ◽

Atmospheric Model ◽

Atmospheric Conditions ◽

Transmission Spectroscopy ◽

Doublet Line ◽

Exoplanetary Atmospheres ◽

Planetary Transmission ◽

Spurious Signals

ABSTRACT Using high-resolution ground-based transmission spectroscopy to probe exoplanetary atmospheres is difficult due to the inherent telluric contamination from absorption in Earth’s atmosphere. A variety of methods have previously been used to remove telluric features in the optical regime and calculate the planetary transmission spectrum. In this paper we present and compare two such methods, specifically focusing on Na detections using high-resolution optical transmission spectra: (1) calculating the telluric absorption empirically based on the airmass and (2) using a model of the Earth’s transmission spectrum. We test these methods on the transmission spectrum of the hot Jupiter HD 189733 b using archival data obtained with the HARPS spectrograph during three transits. Using models for Centre-to-Limb Variation and the Rossiter–McLaughlin effect, spurious signals which are imprinted within the transmission spectrum are reduced. We find that correcting tellurics with an atmospheric model of the Earth is more robust and produces consistent results when applied to data from different nights with changing atmospheric conditions. We confirm the detection of sodium in the atmosphere of HD 189733 b, with doublet line contrasts of $-0.64 \pm 0.07~{{\ \rm per\ cent}}$ (D2) and $-0.53 \pm 0.07~{{\ \rm per\ cent}}$ (D1). The average line contrast corresponds to an effective photosphere in the Na line located around 1.13 Rp. We also confirm an overall blueshift of the line centroids corresponding to net atmospheric eastward winds with a speed of 1.8 ± 1.2 km s−1. Our study highlights the importance of accurate telluric removal for consistent and reliable characterization of exoplanetary atmospheres using high-resolution transmission spectroscopy.

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HORuS transmission spectroscopy of 55 Cnc e

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2583 ◽

2020 ◽

Vol 498 (3) ◽

pp. 4222-4229

Author(s):

H M Tabernero ◽

C Allende Prieto ◽

M R Zapatero Osorio ◽

J I González Hernández ◽

C del Burgo ◽

...

Keyword(s):

Transmission Spectrum ◽

Optical Resolution ◽

Difference Spectrum ◽

Echelle Spectrograph ◽

Earth Planet ◽

Transmission Spectroscopy ◽

Order Of Magnitude ◽

Noise Limit ◽

The Difference ◽

Planetary Transmission

ABSTRACT The High Optical Resolution Spectrograph (HORuS) is a new high-resolution echelle spectrograph available on the 10.4-m Gran Telescopio Canarias (GTC). We report on the first HORuS observations of a transit of the super-Earth planet 55 Cnc e. We investigate the presence of Na i and Hα in its transmission spectrum and explore the capabilities of HORuS for planetary transmission spectroscopy. Our methodology leads to residuals in the difference spectrum between the in-transit and out-of-transit spectra for the Na i doublet lines of (3.4 ± 0.4) × 10−4, which sets an upper limit to the detection of line absorption from the planetary atmosphere that is one order of magnitude more stringent that those reported in the literature. We demonstrate that we are able to reach the photon-noise limit in the residual spectra using HORuS to a degree that we would be able to easily detect giant planets with larger atmospheres. In addition, we modelled the structure, chemistry, and transmission spectrum of 55 Cnc e using state-of-the-art open source tools.

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The atmosphere of WASP-17b: Optical high-resolution transmission spectroscopy

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732029 ◽

2018 ◽

Vol 618 ◽

pp. A98 ◽

Cited By ~ 7

Author(s):

Sara Khalafinejad ◽

Michael Salz ◽

Patricio E. Cubillos ◽

George Zhou ◽

Carolina von Essen ◽

...

Keyword(s):

High Resolution ◽

Light Curve ◽

Physical Properties ◽

Transmission Spectrum ◽

Atmospheric Model ◽

Atmospheric Temperature ◽

Temporal Variations ◽

Light Curves ◽

Sodium Absorption ◽

Transmission Spectroscopy

High-resolution transmission spectroscopy is a method for understanding the chemical and physical properties of upper exoplanetary atmospheres. Due to large absorption cross-sections, resonance lines of atomic sodium D-lines (at 5889.95 and 5895.92 Å) produce large transmission signals. Our aim is to unveil the physical properties of WASP-17b through an accurate measurement of the sodium absorption in the transmission spectrum. We analyze 37 high-resolution spectra observed during a single transit of WASP-17b with the MIKE instrument on the 6.5 m Magellan Telescopes. We exclude stellar flaring activity during the observations by analyzing the temporal variations of Hα and Ca II infrared triplet (IRT) lines. We then obtain the excess absorption light curves in wavelength bands of 0.75, 1, 1.5, and 3 Å around the center of each sodium line (i.e., the light curve approach). We model the effects of differential limb-darkening, and the changing planetary radial velocity on the light curves. We also analyze the sodium absorption directly in the transmission spectrum, which is obtained by dividing in-transit by out-of-transit spectra (i.e., the division approach). We then compare our measurements with a radiative transfer atmospheric model. Our analysis results in a tentative detection of exoplanetary sodium: we measure the width and amplitude of the exoplanetary sodium feature to be σNa = (0.128 ± 0.078) Å and ANa = (1.7 ± 0.9)% in the excess light curve approach and σNa = (0.850 ± 0.034) Å and ANa = (1.3 ± 0.6)% in the division approach. By comparing our measurements with a simple atmospheric model, we retrieve an atmospheric temperature of 15501550 −200+700 K and radius (at 0.1 bar) of 1.81 ± 0.02 RJup for WASP-17b.

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Revisiting the atmosphere of HD 209458b with HARPS-N, CARMENES and ESPRESSO

10.5194/epsc2020-811 ◽

2020 ◽

Author(s):

Núria Casasayas-Barris ◽

Enric Palle ◽

Monika Stangret ◽

Guo Chen ◽

Fei Yan ◽

...

Keyword(s):

High Resolution ◽

Time Evolution ◽

Transmission Spectrum ◽

State Of The Art ◽

Signal To Noise Ratio ◽

Light Curves ◽

High Resolution Spectroscopy ◽

Transmission Spectra ◽

Signal To Noise ◽

Transmission Spectroscopy

HD 209458b was the first transiting planet discovered, and the first for which its atmosphere, in particular Na I, was detected. With time, it has become one of the most studied planets, with a large diversity of atmospheric studies using low- and high-resolution spectroscopy. Here, we present the analysis of high-resolution transmission spectroscopy of HD 209458b using a total of five transit observations with HARPS-N and CARMENES spectrographs. In contrast to previous studies where atmospheric Na I absorption is detected, we find that, for all of the nights, either individually or combined, the transmission spectra can be explained by the combination of the centre-to-limb variation and the Rossiter-McLaughlin effect. Thus, the transmission spectrum reveals no detectable Na I absorption in HD 209458b. This is also observed in the time-evolution maps and transmission light curves, but at lower signal-to-noise ratio. Other strong lines such as H&#945;, Ca II IRT, the Mg I triplet region, and K I D1 are analysed, and are also consistent with the modelled effects, without considering any contribution from the exoplanet atmosphere. New ESPRESSO observations, with state-of-the-art stability and considerably larger signal-to-noise, confirm the results of our study and will also be shown.

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Masked Correlation for Improvement of 2D Glacier Motion Estimation Based on Terrasar-x Imagery

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsannals-ii-7-9-2014 ◽

2014 ◽

Vol II-7 ◽

pp. 9-13

Author(s):

L. Fang ◽

U. Stilla

Keyword(s):

High Resolution ◽

Motion Estimation ◽

Cross Correlation ◽

Correlation Method ◽

Correlation Technique ◽

Binary Mask ◽

Normalized Cross Correlation ◽

The Law ◽

Cross Correlation Technique ◽

Glacier Motion

In this paper, the impacts of the non-glacier information in the template window used in cross-correlation calculation for 2D motion estimation of glaciers are discussed and illustrated by the example of the Taku glacier, which is the biggest glacier in the Juneau Icefield, Alaska. For this, the glacier motion maps are extracted by the traditional normalized cross-correlation technique and the masked cross-correlation method, which uses a manually generated binary mask to threshold the non-glacier pixels, based on geocoded high resolution TerraSAR-X images. Based on the comparison of the different results, it was found that without the disturbing information (e.g., mountain, water) the accuracy of the cross-correlation of sequential patches in masked cross-correlation method is improved and the estimation results are much more reasonable, which respect the law that glacier flows like a river with higher velocity in the middle and than that in the sides.

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Application of cross correlation to HREM images of surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128080 ◽

1987 ◽

Vol 45 ◽

pp. 754-755

Author(s):

D. E. Luzzi ◽

L. D. Marks ◽

M. I. Buckett

Keyword(s):

Cross Correlation ◽

A Priori ◽

Matrix Material ◽

Correlation Method ◽

Accurate Knowledge ◽

Complex Image ◽

Fourier Filtering ◽

The Matrix ◽

Low Pass ◽

Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

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