scholarly journals Is there Na I in the atmosphere of HD 209458b?

2020 ◽  
Vol 635 ◽  
pp. A206 ◽  
Author(s):  
N. Casasayas-Barris ◽  
E. Pallé ◽  
F. Yan ◽  
G. Chen ◽  
R. Luque ◽  
...  
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Planetary Atmospheres ◽  
Light Curves ◽  
High Resolution Spectroscopy ◽  
Transmission Spectra ◽  
Spin Orbit ◽  
Velocity Data ◽  
Signal To Noise ◽  
Radial Velocity Data

HD 209458b was the first transiting planet discovered, and the first for which an atmosphere, in particular Na I, was detected. With time, it has become one of the most frequently studied planets, with a large diversity of atmospheric studies using low- and high-resolution spectroscopy. Here, we present transit spectroscopy observations of HD 209458b using the HARPS-N and CARMENES spectrographs. We fit the Rossiter-McLaughlin effect by combining radial velocity data from both instruments (nine transits in total), measuring a projected spin-orbit angle of − 1.6 ± 0.3 deg. We also present the analysis of high-resolution transmission spectroscopy around the Na I region at 590 nm, using a total of five transit observations. In contrast to previous studies where atmospheric Na I absorption is detected, we find that for all of the nights, whether individually or combined, the transmission spectra can be explained by the combination of the centre-to-limb variation and the Rossiter-McLaughlin effect. 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 Hα, 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. Thus, the transmission spectrum reveals no detectable Na I absorption in HD 209458b. We discuss how previous pioneering studies of this benchmark object may have overlooked these effects. While for some star–planet systems these effects are small, for other planetary atmospheres the results reported in the literature may require revision.

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

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

<p>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 Hα, 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.</p>

scholarly journals The inhomogeneous wind of the LBV candidate Cyg OB2 No.12

2010 ◽  
Vol 6 (S272) ◽  
pp. 400-401
Author(s):  
Valentina G. Klochkova ◽  
Eugene L. Chentsov ◽  
Anatoly S. Miroshnichenko
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Stellar Atmosphere ◽  
Time Variable ◽  
High Resolution Spectroscopy ◽  
Spectral Features ◽  
Velocity Data ◽  
Absorption Component ◽  
Hα Emission ◽  
Radial Velocity Data

AbstractWe present the results of high-resolution spectroscopy of the extremely luminous star Cyg OB2 No. 12. We identified about 200 spectral features in the range 4552–7939 Å, including the interstellar Na I, K I lines and numerous very strong DIBs, along with the He I, C II, and Si II lines. An MK spectral type we derived for the object is B4.5±0.5 Ia+. Our analysis of the radial velocity data shows the presence of a gradient in the stellar atmosphere, caused by both atmospheric expansion and matter infall onto the star. The Hα emission displays broad Thompson wings, a slightly blue-shifted P Cyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.

scholarly journals Chemical abundances of three new Ba stars from the Keck/HIRES spectra

2021 ◽  
Vol 21 (11) ◽  
pp. 278
Author(s):  
Shuai Liu ◽  
Liang Wang ◽  
Jian-Rong Shi ◽  
Zhen-Yu Wu ◽  
Hong-Liang Yan ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Parameter Space ◽  
Thin Disk ◽  
High Signal ◽  
Velocity Data ◽  
Signal To Noise ◽  
Chemical Abundances ◽  
Radial Velocity Data

Abstract Based on high resolution, high signal-to-noise (S/N) ratio spectra from Keck/HIRES, we have determined abundances of 20 elements for 18 Ba candidates. The parameter space of these stars is in the range of 4880 ≤ T eff ≤ 6050 K, 2.56 ≤ log g ≤ 4.53 dex and − 0.27 ≤ [Fe/H] ≤ 0.09 dex. It is found that four of them can be identified as Ba stars with [s/Fe] > 0.25 dex (s: Sr, Y, Zr, Ba, La, Ce and Nd), and three of them are newly discovered, which include two Ba giants (HD 16178 and HD 22233) and one Ba subgiant (HD 2946). Our results show that the abundances of α, odd and iron-peak elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, Mn, Ni and Cu) for our program stars are similar to those of the thin disk, while the distribution of [hs/ls] (hs: Ba, La, Ce and Nd, ls: Sr, Y and Zr) ratios of our Ba stars is similar to those of the known Ba objects. None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395. It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.

scholarly journals Three years of HARPS-N high-resolution spectroscopy and precise radial velocity data for the Sun

2021 ◽  
Author(s):  
X. Dumusque ◽  
M. Cretignier ◽  
D. Sosnowska ◽  
N. Buchschacher ◽  
C. Lovis ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
High Resolution Spectroscopy ◽  
The Sun ◽  
Velocity Data ◽  
Radial Velocity Data

An Efficient Dual-Resolution Approach for Ensemble Data Assimilation and Tests with Simulated Doppler Radar Data

2008 ◽  
Vol 136 (3) ◽  
pp. 945-963 ◽  
Author(s):  
Jidong Gao ◽  
Ming Xue
Keyword(s):  
High Resolution ◽  
Data Assimilation ◽  
Radial Velocity ◽  
Computational Cost ◽  
Radar Data ◽  
Horizontal Resolution ◽  
Velocity Data ◽  
Background Error ◽  
Cross Covariance ◽  
Radial Velocity Data

Abstract A new efficient dual-resolution (DR) data assimilation algorithm is developed based on the ensemble Kalman filter (EnKF) method and tested using simulated radar radial velocity data for a supercell storm. Radar observations are assimilated on both high-resolution and lower-resolution grids using the EnKF algorithm with flow-dependent background error covariances estimated from the lower-resolution ensemble. It is shown that the flow-dependent and dynamically evolved background error covariances thus estimated are effective in producing quality analyses on the high-resolution grid. The DR method has the advantage of being able to significantly reduce the computational cost of the EnKF analysis. In the system, the lower-resolution ensemble provides the flow-dependent background error covariance, while the single-high-resolution forecast and analysis provides the benefit of higher resolution, which is important for resolving the internal structures of thunderstorms. The relative smoothness of the covariance obtained from the lower 4-km-resolution ensemble does not appear to significantly degrade the quality of analysis. This is because the cross covariance among different variables is of first-order importance for “retrieving” unobserved variables from the radar radial velocity data. For the DR analysis, an ensemble size of 40 appears to be a reasonable choice with the use of a 4-km horizontal resolution in the ensemble and a 1-km resolution in the high-resolution analysis. Several sensitivity tests show that the DR EnKF system is quite robust to different observation errors. A 4-km thinned data resolution is a compromise that is acceptable under the constraint of real-time applications. A data density of 8 km leads to a significant degradation in the analysis.

scholarly journals TOI-150b and TOI-163b: two transiting hot Jupiters, one eccentric and one inflated, revealed by TESS near and at the edge of the JWST CVZ

2019 ◽  
Vol 490 (1) ◽  
pp. 1094-1110 ◽  
Author(s):  
Diana Kossakowski ◽  
Néstor Espinoza ◽  
Rafael Brahm ◽  
Andrés Jordán ◽  
Thomas Henning ◽  
...  
Keyword(s):  
High Resolution ◽  
Time Scale ◽  
High Resolution Spectroscopy ◽  
Spin Orbit ◽  
Eccentric Orbit ◽  
Hot Jupiters ◽  
Eclipse Observations ◽  
James Webb Space Telescope ◽  
Hot Jupiter

Abstract We present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-min cadence Transiting Exoplanet Survey Satellite (TESS) photometry from Sector 1 and thoroughly characterized through follow-up photometry (CHAT, Hazelwood, LCO/CTIO, El Sauce, TRAPPIST-S), high-resolution spectroscopy (FEROS, CORALIE), and speckle imaging (Gemini/DSSI), confirming the planetary nature of the two signals. A simultaneous joint fit of photometry and radial velocity using a new fitting package juliet reveals that TOI-150b is a $1.254\pm 0.016\ \rm {R}_ \rm{J}$, massive ($2.61^{+0.19}_{-0.12}\ \rm {M}_ \rm{J}$) hot Jupiter in a 5.857-d orbit, while TOI-163b is an inflated ($R_ \rm{P}$ = $1.478^{+0.022}_{-0.029} \,\mathrm{ R}_ \rm{J}$, $M_ \rm{P}$ = $1.219\pm 0.11 \, \rm{M}_ \rm{J}$) hot Jupiter on a P = 4.231-d orbit; both planets orbit F-type stars. A particularly interesting result is that TOI-150b shows an eccentric orbit ($e=0.262^{+0.045}_{-0.037}$), which is quite uncommon among hot Jupiters. We estimate that this is consistent, however, with the circularization time-scale, which is slightly larger than the age of the system. These two hot Jupiters are both prime candidates for further characterization – in particular, both are excellent candidates for determining spin-orbit alignments via the Rossiter–McLaughlin (RM) effect and for characterizing atmospheric thermal structures using secondary eclipse observations considering they are both located closely to the James Webb Space Telescope (JWST) Continuous Viewing Zone (CVZ).

scholarly journals On cross-correlations, averages and noise in electron microscopy

2019 ◽  
Vol 75 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Michael Radermacher ◽  
Teresa Ruiz
Keyword(s):  
High Resolution ◽  
Cross Correlation ◽  
Signal To Noise Ratio ◽  
3D Structure ◽  
Signal To Noise ◽  
High Resolution Structure ◽  
Multiple Copies ◽  
High Level ◽  
2D Images ◽  
Resolution Structure

Biological samples are radiation-sensitive and require imaging under low-dose conditions to minimize damage. As a result, images contain a high level of noise and exhibit signal-to-noise ratios that are typically significantly smaller than 1. Averaging techniques, either implicit or explicit, are used to overcome the limitations imposed by the high level of noise. Averaging of 2D images showing the same molecule in the same orientation results in highly significant projections. A high-resolution structure can be obtained by combining the information from many single-particle images to determine a 3D structure. Similarly, averaging of multiple copies of macromolecular assembly subvolumes extracted from tomographic reconstructions can lead to a virtually noise-free high-resolution structure. Cross-correlation methods are often used in the alignment and classification steps of averaging processes for both 2D images and 3D volumes. However, the high noise level can bias alignment and certain classification results. While other approaches may be implicitly affected, sensitivity to noise is most apparent in multireference alignments, 3D reference-based projection alignments and projection-based volume alignments. Here, the influence of the image signal-to-noise ratio on the value of the cross-correlation coefficient is analyzed and a method for compensating for this effect is provided.

scholarly journals Properties of sub-Neptune atmospheres: TOI-270 system

2020 ◽  
Vol 495 (1) ◽  
pp. 962-970
Author(s):  
J Chouqar ◽  
Z Benkhaldoun ◽  
A Jabiri ◽  
J Lustig-Yaeger ◽  
A Soubkiou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Signal To Noise Ratio ◽  
Spectral Features ◽  
Transmission Spectra ◽  
Infrared Transmission ◽  
Signal To Noise ◽  
Space Telescope ◽  
Molecular Features ◽  
James Webb Space Telescope ◽  
Mean Molecular Weight

ABSTRACT We investigate the potential for the James Webb Space Telescope (JWST) to detect and characterize the atmospheres of the sub-Neptunian exoplanets in the TOI-270 system. Sub-Neptunes are considered more likely to be water worlds than gas dwarfs. We model their atmospheres using three atmospheric compositions – two examples of hydrogen-dominated atmospheres and a water-dominated atmosphere. We then simulate the infrared transmission spectra of these atmospheres for JWST instrument modes optimized for transit observation of exoplanet atmospheres: NIRISS, NIRSpec, and MIRI. We then predict the observability of each exoplanet’s atmosphere. TOI-270c and d are excellent targets for detecting atmospheres with JWST transmission spectroscopy, requiring only 1 transit observation with NIRISS, NIRSpec, and MIRI; higher signal-to-noise ratio can be obtained for a clear H-rich atmosphere. Fewer than three transits with NIRISS and NIRSpec may be enough to reveal molecular features. Water-dominated atmospheres require more transits. Water spectral features in water-dominated atmospheres may be detectable with NIRISS in two or three transits. We find that the detection of spectral features in a cloudy, H-rich atmosphere does not require integrations as long as those required for the water-dominated atmosphere, which is consistent with the differences in atmospheric mean molecular weight. TOI-270c and d could be prime targets for JWST transit observations of sub-Neptune atmospheres. These results provide useful predictions for observers who may propose to use JWST to detect and characterize the TOI-270 planet atmospheres.

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