scholarly journals Isochrone fitting in the Gaia era

2018 ◽  
Vol 618 ◽  
pp. A54 ◽  
Author(s):  
Alexey Mints ◽  
Saskia Hekker
Keyword(s):  
The Sun ◽  
Atmospheric Parameters ◽  
Extinction Data ◽  
Fitting Method ◽  
Spectrophotometric Data ◽  
Fitting In ◽  
Age Estimates

Context. Currently, galactic exploration is being revolutionized by a flow of new data: Gaia provides measurements of stellar distances and kinematics; growing numbers of spectroscopic surveys provide values of stellar atmospheric parameters and abundances of elements; and Kepler and K2 missions provide asteroseismic information for an increasing number of stars. Aims. In this work, we aim to determine stellar distances and ages using Gaia and spectrophotometric data in a consistent way. We estimate precisions of age and distance determinations with Gaia end-of-mission (EoM) and Tycho-Gaia astrometric solution (TGAS) parallax precisions. Methods. To this end, we incorporated parallax and extinction data into the isochrone fitting method used in the Unified tool to estimate Distances, Ages, and Masses (UniDAM). We prepared datasets that allowed us to study the improvement of distance and age estimates with the inclusion of TGAS and Gaia EoM parallax precisions in isochrone fitting. Results. Using TGAS parallaxes in isochrone fitting, we are able to reduce distance and age estimate uncertainties for TGAS stars for distances up to 1 kpc by more than one third compared to results based only on spectrophotometric data. With Gaia EoM parallaxes in isochrone fitting, we will be able to further decrease our distance uncertainties by about a factor of 20 and age uncertainties by a factor of 2 for stars up to 10 kpc away from the Sun. Conclusions. We demonstrate that we will be able to improve our distance estimates for about one third of stars in spectroscopic surveys and to decrease log(age) uncertainties by about a factor of two for over 80% of stars as compared to the uncertainties obtained without parallax priors using Gaia EoM parallaxes consistently with spectrophotometry in isochrone fitting.

scholarly journals High-Order Polynomial Fitting Assistance for Fast Double-Peak Finding in Brillouin-Distributed Sensing

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 187
Author(s):  
Marcelo A. Soto ◽  
Alin Jderu ◽  
Dorel Dorobantu ◽  
Marius Enachescu ◽  
Dominik Ziegler
Keyword(s):  
Optical Fibers ◽  
High Order ◽  
Polynomial Fitting ◽  
Gaussian Fitting ◽  
Peak Finding ◽  
Fitting Method ◽  
Fold Reduction ◽  
Order Polynomial ◽  
Fitting In ◽  
Distributed Brillouin Sensor

A high-order polynomial fitting method is proposed to accelerate the computation of double-Gaussian fitting in the retrieval of the Brillouin frequency shifts (BFS) in optical fibers showing two local Brillouin peaks. The method is experimentally validated in a distributed Brillouin sensor under different signal-to noise ratios and realistic spectral scenarios. Results verify that a sixth-order polynomial fitting can provide a reliable initial estimation of the dual local BFS values, which can be subsequently used as initial parameters of a nonlinear double-Gaussian fitting. The method demonstrates a 4.9-fold reduction in the number of iterations required by double-Gaussian fitting and a 3.4-fold improvement in processing time.

An Improved Iterative Polynomial Fitting Algorithm for Baseline Correction in X-Ray Spectrum

2021 ◽  
Vol 105 ◽  
pp. 90-98
Author(s):  
Xiao Yu Jiang ◽  
Qing Ya Wang ◽  
Mu Qiang Xu ◽  
Jun Hao
Keyword(s):  
Fluorescence Spectrum ◽  
Soil Analysis ◽  
Simulated Data ◽  
Real Data ◽  
Polynomial Fitting ◽  
X Ray ◽  
Iterative Processes ◽  
Fitting Method ◽  
Fitting Algorithm ◽  
Fitting In

An iterative polynomial fitting method is proposed for the estimate of the baseline of the X-ray fluorescence spectrum signal. The new method generates automatic thresholds by comparing the X-ray fluorescence spectrum signal with the calculated signal from polynomial fitting in the iterative processes. The signal peaks are cut out consecutively in the iterative processes so the polynomial fitting will finally give a good estimation of the baseline. Simulated data and real data from the soil analysis spectrum are used to demonstrate the feasibility of the proposed method.

scholarly journals Detailed Analyses of Four Solar Analogs Analysed On High S/N CFH and ESO Spectra

1988 ◽  
Vol 132 ◽  
pp. 429-432
Author(s):  
C. Bentolila ◽  
G. Cayrel de Strobel
Keyword(s):  
High Resolution ◽  
Effective Temperature ◽  
The Sun ◽  
Atmospheric Parameters ◽  
Iron Abundance ◽  
Solar Type ◽  
Solar Analogs

Four solar type G stars claimed to be photometrically very similar to the Sun have been analyzed in detail on high resolution, high S/N spectra. Their atmospheric parameters : effective temperature, spectroscopic gravity, microturbulence and iron abundance, [Fe/H], have been determined.

scholarly journals Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

2018 ◽  
Author(s):  
Joshua M. Chadney ◽  
Daniel K. Whiter
Keyword(s):  
Water Vapour ◽  
Atmospheric Parameter ◽  
Atmospheric Parameters ◽  
Atmospheric Water ◽  
Echelle Spectrograph ◽  
Atmospheric Water Vapour ◽  
Spectral Fitting ◽  
Fitting Method ◽  
Airglow Emissions ◽  
High Throughput Imaging

Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725–740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES), located on Svalbard. In this paper, we describe our new method and show the results of Monte-Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method as well as provide an indication of uncertainties on the retrieval of each atmospheric parameter.

scholarly journals Lithium Abundances in Solar-Type Stars

2000 ◽  
Vol 198 ◽  
pp. 495-497 ◽  
Author(s):  
L. da Silva ◽  
G. F. Porto de Mello
Keyword(s):  
Angular Momentum ◽  
Momentum Distribution ◽  
The Sun ◽  
Atmospheric Parameters ◽  
Solar Type ◽  
Subgiant Stars ◽  
High Degree ◽  
Li Content

We report Li abundances from the λ6707 line for 19 nearby dwarf and subgiant solar-type stars. The unevolved stars in this sample present high (> 2.00) Li abundances. We found a few cases of subgiant stars which present high Li content. The Sun seems to be part of a population of nearly unevolved stars which have depleted their Li to a high degree: all other metal-normal, near ZAMS stars in our sample show higher than solar Li content. There seems to be no correlation of the degree of Li depletion with mass, atmospheric parameters or state of evolution: as an example we found a star (HR1532) almost identical to the Sun in its state of evolution and atmospheric parameters, but with over ten times the solar Li abundance. We propose that different histories of angular momentum distribution at star birth, and/or post-birth angular momentum evolution, may account for these differences.

Early treatment of trans-tibial amputees: retrospective analysis of early fitting and elastic bandaging

2005 ◽  
Vol 29 (1) ◽  
pp. 3-12 ◽  
Author(s):  
A. D. van Velzen ◽  
M. J. Nederhand ◽  
C. H. Emmelot ◽  
M. J. Ijzerman
Keyword(s):  
Wound Healing ◽  
Knee Flexion ◽  
Plaster Cast ◽  
Flexion Contracture ◽  
Pressure Sores ◽  
Fitting Method ◽  
Increased Risk ◽  
In Trans ◽  
Fitting In ◽  
Discharge From Hospital

This study investigates the effects of early fitting in trans-tibial amputees. The assumption is that compared to elastic bandaging, the use of a rigid dressing in early fitting will result in quicker wound healing and earlier ambulation. A retrospective file search was carried out in three different hospitals, analysing the time to first prosthesis, the incidence of local and general complications and the functional outcome after discharge from hospital. Each of the hospitals used a different method of postoperative care: elastic bandaging, immediate postoperative application of the plaster cast or delayed application of the plaster cast within one week post amputation. In comparison to the elastic bandaging method (N=52), the use of a rigid dressing in the early fitting method (immediate and delayed, N=97) resulted in a statistically significant shorter period from amputation to the delivery of a first regular prosthesis (110 days vs 50 days) and a decreased risk of knee flexion contracture. Although, differences in local complications were not observed, the risk of pressure sores in other places than the stump was increased in early fitting. Instead of further reducing the time to first prosthesis by immediate fitting, the use of delayed fitting resulted in a statistically significant shorter period from amputation to the delivery of a first regular prosthesis (56 vs 40 days). However, delayed fitting was associated with an increased risk for reamputation. In conclusion, this study indicates that early fitting by use of a rigid dressing after trans-tibial amputation is the treatment of choice. If it is possible to apply a plaster cast in the operating room, the authors would prefer the immediate fitting method.

A Research of GPS Height Fitting in Mountainous Terrain by CPSO Optimization FLS-SVM

2013 ◽  
Vol 336-338 ◽  
pp. 2339-2343 ◽  
Author(s):  
Yong Gan ◽  
Xin Xin Liu ◽  
Yuan Pan Zheng
Keyword(s):  
Support Vector Machine ◽  
Small Sample ◽  
Least Square ◽  
Support Vector ◽  
Mountainous Area ◽  
Machine Model ◽  
Normal Height ◽  
Fitting Method ◽  
Fitting In ◽  
The Impact

For the problem of data limited in the mountainous area, a method of FLS-SVM (Fuzzy Least Square Vector Machine) that supporting small sample data and having high noise ability was put forward. The CPSO(chaos particle swarm optimization algorithm) is adopted to optimize the parameters of least squares support vector machine algorithm, and to avoid the uncertainty of artificial parameter selection. Meanwhile, considering the impact of terrain, the terrain correction is introduced to the support vector machine model. The experimental results show that the model can get higher precision fitting effect compared with traditional fitting method such as PSO-LSSVM and GA-LSSVM, and suitable for the SRTM application of getting normal height.

Local Maximum Absorption Method for Structure Fitting in CryoEM

2011 ◽  
Vol 460-461 ◽  
pp. 77-82
Author(s):  
Gui Hua Shan ◽  
Jun Liu ◽  
Xue Bin Chi
Keyword(s):  
Domain Knowledge ◽  
Local Maximum ◽  
Atomic Model ◽  
Absorption Method ◽  
Cryo Electron Microscopy ◽  
Novel Structure ◽  
Fitting Method ◽  
Automatic Alignment ◽  
Density Map ◽  
Fitting In

Cryo-electron microscopy (CryoEM) is a very important method for studying the structures of macromolecules. Structure fitting is one of the key problems in CryoEM technique. We propose a novel structure fitting method for automatic alignment of the atomic model and CryoEM density map. Based on the domain knowledge, 3D density map is presented by local maximum points. And the atomic model is presented by atoms with high density value. According to characteristic of CryoEM density map, these atoms must correspond to one of the local maximum, then employ absolute orientation algorithm to calculate the rotation matrix and transfer vector. To show the efficiency of our method, we apply the algorithm on two pairs of test data.

scholarly journals Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

2018 ◽  
Vol 7 (4) ◽  
pp. 317-329 ◽  
Author(s):  
Joshua M. Chadney ◽  
Daniel K. Whiter
Keyword(s):  
Water Vapour ◽  
Atmospheric Parameter ◽  
Atmospheric Parameters ◽  
Atmospheric Water ◽  
Echelle Spectrograph ◽  
Atmospheric Water Vapour ◽  
Spectral Fitting ◽  
Fitting Method ◽  
Airglow Emissions ◽  
High Throughput Imaging

Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725 and 740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. In this paper, we describe our new method and show the results of Monte Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method and provide an indication of uncertainties on the retrieval of each atmospheric parameter. We show that the method allows for the retrieval of OH temperatures with an uncertainty of 6 % when contamination by N2 emission is small. N2 temperatures can be retrieved with uncertainties down to 3 %–5 % when N2 emission intensity is high. We can determine the intensity ratio between the O+ doublets at 732 and 733 nm (which is a function of temperature) with an uncertainty of 5 %.

scholarly journals A Method for Calibrating, in Absolute Flux Units, Ca II H Profiles of Late Type Stars Observed at ESO

1988 ◽  
Vol 132 ◽  
pp. 153-161 ◽  
Author(s):  
F. Castelli ◽  
P. Gouttebroze ◽  
J. Beckman ◽  
L. Crivellari ◽  
B. Foing
Keyword(s):  
Solar Flux ◽  
Calibration Factor ◽  
Synthetic Spectrum ◽  
The Sun ◽  
The Moon ◽  
Late Type ◽  
Equilibrium Models ◽  
Collisional Broadening ◽  
Absolute Flux ◽  
Fitting In

In this paper we have applied to the Sun a method for calibrating, in absolute flux units, Ca II H profiles of late-type stars. After comparing, in the region 3948-3882 A, an LTE synthetic spectrum with the data of the solar flux Atlas by Kurucz et al. (1984), we have defined the wavelength ranges where observations agree with computations, based on specific radiative equilibrium models and collisional broadening parameters. By fitting in these regions the spectrum of the moon observed at ESO with the corresponding synthetic spectrum, we derived a calibration factor that enables us to calibrate, in absolute flux units, the whole observed range.

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