scholarly journals Consistent and accurate estimation of stellar parameters from HARPS-N Spectroscopy using Deep Learning

2021 ◽  
Vol 2 ◽  
Author(s):  
Frederik Boe Hüttel ◽  
Line Katrine Harder Clemmensen
Keyword(s):  
Signal To Noise Ratio ◽  
Rotational Velocity ◽  
High Accuracy ◽  
Data Driven ◽  
Accurate Estimation ◽  
The Sun ◽  
Signal To Noise ◽  
Wide Range ◽  
Processing Steps ◽  
Astrophysical Research

Consistent and accurate estimation of stellar parameters is of great importance for information retrieval in astrophysical research. The parameters span a wide range from effective temperature to rotational velocity. We propose to estimate the stellar parameters directly from spectral signals coming from the HARPS-N spectrograph pipeline before any spectrum-processing steps are applied to extract the 1D spectrum. We propose an attention-based model to estimate the stellar parameters, which estimate both mean and uncertainty of the stellar parameters through estimation of the parameters of a Gaussian distribution. The estimated distributions create a basis to generate data-driven Gaussian confidence intervals for the estimated stellar parameters. We show that residual networks and attention-based models can estimate the stellar parameters with high accuracy for low Signal-to-noise ratio (SNR) compared to previous methods. With an observation of the Sun from the HARPS-N spectrograph, we show that the models can estimate stellar parameters from real observational data.

scholarly journals A photometric search for ‘5-min’ oscillations in the components of Alpha Centauri and two other double stars

1988 ◽  
Vol 123 ◽  
pp. 253-254
Author(s):  
L. A. Balona ◽  
F. Marang
Keyword(s):  
Small Amplitude ◽  
Signal To Noise Ratio ◽  
Broad Band ◽  
Double Star ◽  
The Other ◽  
The Sun ◽  
Star System ◽  
Signal To Noise ◽  
Double Stars ◽  
Wide Range

The discovery of global solar 5-min oscillations has prompted the search for such oscillations in other stars. The main problem in detecting these variations is their expected small amplitude (in the sun it is less than 1 m/s in velocity and 10−6 in integrated light). Two recent studies by Fossat et al. (1984) and Noyes et al. (1984) have suggested that the 5-min oscillations in α Cen and ε Eri may have been detected.We attempted to detect these oscillations by means of conventional broad-band photometry in the components of three double star systems (α Cen, HR4677 and HR5568). We selected these stars because they cover a wide range of spectral types (F2V to M2V). It was hoped that there may be a region where the pulsation amplitudes are particularly large. By using one component of a double star system to correct for transparency variations in the other, we also expected to obtain a larger signal-to-noise ratio.

scholarly journals Improvement of SAXS Lab Equipment by Using Scatterless Apertures

2014 ◽  
Vol 70 (a1) ◽  
pp. C1330-C1330
Author(s):  
Joerg Wiesmann ◽  
Andreas Kleine ◽  
Christopher Umland ◽  
André Beerlink ◽  
Juergen Graf ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Experimental Setup ◽  
High Flux ◽  
Signal To Noise ◽  
Minimum Diameter ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
Beam Stop ◽  
Synchrotron Beamlines

Parasitic scattering caused by apertures is a well-known problem in X-ray analytics, which forces users and manufacturers to adapt their experimental setup to this unwanted phenomenon. Increased measurement times due to lower photon fluxes, a lower resolution caused by an enlarged beam stop, a larger beam defining pinhole-to-sample distance due to the integration of an antiscatter guard and generally a lower signal-to-noise ratio leads to a loss in data quality. In this presentation we will explain how the lately developed scatterless pinholes called SCATEX overcome the aforementioned problems. SCATEX pinholes are either made of Germanium or of Tantalum and momentarily have a minimum diameter of 30µm. Thus, these novel apertures are applicable to a wide range of different applications and X-ray energies. We will show measurements which were performed either at home-lab small angle X-ray scattering (SAXS) systems such as the NANOSTAR of Bruker AXS or at synchrotron beamlines. At the PTB four-crystal monochromator beamline at BESSY II data was collected for a comparison of conventional pinholes, scatterless Germanium slit systems and SCATEX pinholes. At the Nanofocus Endstation P03 beamline at PETRA III we compared the performance of our SCATEX apertures with conventional Tungsten slit systems under high flux density conditions.

scholarly journals A Preliminary System to Predict Snow Instability using Acoustic Emissions

1980 ◽  
Vol 26 (94) ◽  
pp. 520
Author(s):  
R. A. Sommerfeld
Keyword(s):  
Narrow Band ◽  
Signal To Noise Ratio ◽  
Acoustic Emissions ◽  
Digital Data ◽  
Signal To Noise ◽  
Data Manipulation ◽  
Wide Range ◽  
Stressed Region ◽  
Power Line Noise ◽  
Weak Interference

Abstract Results From the last four winters’ studies on acoustic emissions from snow slopes have shown that periods of higher noise in the frequency band 5 to 125 Hz are associated with periods of instability, but that the phenomenon of acoustic emissions from unstable snow is very weak. Interference with the acoustic emissions from extraneous sources such as chairlifts, trucks, and airplanes causes ambiguities in the data which interfere with the straightforward prediction of instability. Spectra of the noises were examined, with the idea that filters might improve the signal-to-noise ratio. It was found that the noise generated by unstable snow can occur over a fairly wide range of frequencies and that there is no band of frequencies which is unique to unstable snow. It was found that the noise from the chairlift had a very stable spectrum and that it had a band from 50 to 65 Hz which was pronounced and in which the snow noise was fairly low. The r.m.s. voltage in the band 5 to 125 Hz can therefore be reduced by subtracting a proportion of the r.m.s. output of a narrow-band 55 Hz filter. By adjusting the constant of proportionality, it was possible to eliminate interference from the chairlift almost entirely, and this will be used. Spectral analyses have also shown that ambiguities are generated by variations in the 60 Hz power-line noise. It is possible to suppress this with the use of filters, but without complex digital data manipulation, it is not possible to eliminate it. The fact that the snow noise does not transmit over large distances means that events of interest should not occur simultaneously on two, widely spaced geophones. The system will include a geophone in an unstressed region whose r.m.s. voltage will be subtracted from that of the geophone in the stressed region to eliminate signals which are common to both. It is hoped that this technique will eliminate ambiguities caused by extraneous sources such as trucks and airplanes.

scholarly journals System Requirements for Polarization Capability

1984 ◽  
Vol 79 ◽  
pp. 569-573
Author(s):  
J. Tinbergen
Keyword(s):  
Signal To Noise Ratio ◽  
Point Sources ◽  
High Signal ◽  
The Sun ◽  
Proper Treatment ◽  
Signal To Noise ◽  
Observational Technique ◽  
Imaging Polarimetry ◽  
System Requirements ◽  
Optical Telescopes

The purpose of this paper is to point out that1) proper treatment of polarization by a telescope is not only important for polarimetry, but also for other observations requiring high signal-to-noise ratio, and2) this does put a constraint on telescope design, which, however, is not unduly restrictive.Polarimetry is the observational technique which can detect anisotropics in point sources, their environment, or the medium between them and us. Modern optical polarimetry can be linear or circular, and is making progress towards spectropolarimetry and imaging polarimetry using panoramic detectors (e.g. McLean, 1984). Given sufficient photons, the precision obtained is as high as 1 part in 50 000 (see Odell, 1981 for a project requiring this precision), but more often a precision between 1 part in 1 000 to 10 000 is sufficient. (Spectro)polarimetry has been applied to planets, the Sun and other stars, stellar systems and galaxy nuclei; for a few modern investigations, see Baur, 1981; Jones et al, 1981; Schmidt and Miller, 1980. Experience in radio-astronomy has shown that when facilities for polarimetry are offered, many applications emerge from the astronomical community, yielding data that cannot be obtained by other techniques. It is essential that at least some of the large optical telescopes are capable of ob-serving polarization cleanly.

scholarly journals What Drives Symbiotic Calcium Signalling in Legumes? Insights and Challenges of Imaging

2019 ◽  
Vol 20 (9) ◽  
pp. 2245
Author(s):  
Teresa Vaz Martins ◽  
Valerie N. Livina
Keyword(s):  
Root Hair ◽  
Cytoplasmic Streaming ◽  
Root Nodule ◽  
Signal To Noise Ratio ◽  
Calcium Signalling ◽  
Signal To Noise ◽  
Image Recording ◽  
Wide Range ◽  
Key Steps ◽  
Disciplinary Area

We review the contribution of bioimaging in building a coherent understanding of Ca 2 + signalling during legume-bacteria symbiosis. Currently, two different calcium signals are believed to control key steps of the symbiosis: a Ca 2 + gradient at the tip of the legume root hair is involved in the development of an infection thread, while nuclear Ca 2 + oscillations, the hallmark signal of this symbiosis, control the formation of the root nodule, where bacteria fix nitrogen. Additionally, different Ca 2 + spiking signatures have been associated with specific infection stages. Bioimaging is intrinsically a cross-disciplinary area that requires integration of image recording, processing and analysis. We used experimental examples to critically evaluate previously-established conclusions and draw attention to challenges caused by the varying nature of the signal-to-noise ratio in live imaging. We hypothesise that nuclear Ca 2 + spiking is a wide-range signal involving the entire root hair and that the Ca 2 + signature may be related to cytoplasmic streaming.

scholarly journals Model atmosphere analysis of two new early–type O4 dwarfs stars

2017 ◽  
Vol 2 (2) ◽  
pp. 559-564 ◽  
Author(s):  
D.A. Fouda ◽  
M. Hamdy ◽  
M. Nouh ◽  
M. Beheary ◽  
Abdelaziz Bakrey ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Rotational Velocity ◽  
Model Atmosphere ◽  
Surface Gravity ◽  
High Signal ◽  
Early Type ◽  
Atmospheric Models ◽  
Signal To Noise ◽  
Dwarf Stars ◽  
Synthetic Spectra

AbstractWe present a synthetic spectra study of two new galactic early-type O4 dwarf stars(ALS 19618 and BD+50886) with high signal-to-noise ratio, typically S/N ∼ 300, medium-rosalution R ∼ 2500 optical spectra of O4 dwarfs stars from Galactic O-Stars Spectroscopic Survey (GOSSS), The main stellar parameters (Teff, surface gravity, rotational velocity) have been established using non-LTE, line-blanketed, atmospheric models calculated by TLUSTY204 and SYNSPEC49.

scholarly journals Optimization of Direct Direction Finding Method with Two-Dimensional Correlative Processing of Spatial Signal

2018 ◽  
Vol 8 ◽  
pp. 46-53
Author(s):  
Vitaliy V. Tsyporenko ◽  
Valentyn G. Tsyporenko
Keyword(s):  
Main Parameter ◽  
Noise Immunity ◽  
Signal To Noise Ratio ◽  
Direction Finding ◽  
High Accuracy ◽  
Signal To Noise ◽  
High Noise ◽  
Spatial Shift ◽  
Simulation Results ◽  
Finding Method

In this article, the main parameter of the correlative-interferometric direction finding method with twodimensional correlative processing of spatial signal in the aperture of a linear antenna array (AA) is determined as the value of spatial shift within the AA aperture. The corresponding objective function is also formed. Analytical optimization of this parameter is presented and a comparative analysis of analytical calculations based on simulation results is conducted. In the simulation, a range of dependencies of the middle square deviation of estimation of direction on the value of the spatial shift for a signal-to-noise ratio of 0 dB, for minimum 3-sample and 4-sample Blackman-Harris windows of the spectral analysis, is received. The value of the middle square deviation of estimation of direction will be minimal and will equal 0.02 degrees using a minimum 3-sample Blackman-Harris window with the −67 dB level of side lobes. It offers high noise immunity and high accuracy of direction finding.

Efficient Response Amplification of Electrothermally Driven Resonators Using Magnets

2021 ◽  
Author(s):  
Ghanimah Abuhaimed ◽  
Nizar Jaber ◽  
Nouha Alcheikh ◽  
Mohammad I. Younis
Keyword(s):  
Parametric Excitation ◽  
Energy Demand ◽  
Signal To Noise Ratio ◽  
Ambient Pressure ◽  
Thermal Relaxation ◽  
Primary Resonance ◽  
Signal To Noise ◽  
Electrothermal Actuation ◽  
Wide Range ◽  
Noise Ratio

Abstract Micro/Nano-electromechanical systems, MEMS/NEMS-based resonators are presently an important part of a wide range of applications. However, many of these devices suffer from the low signal-to-noise ratio and the need for a large driving force. Different principles were proposed to enhance the sensitivity and improve their signal-to-noise ratios (SNR), such as bifurcations, jumps and higher-order excitation. However, these methods require special designs and high actuation voltages, which are not always available in the standard function generators and power supplies. Also, it increases the devices’ overall cost and power requirements. Furthermore, parametric excitation is explored as an option to amplify the signal at a lower cost and energy demand. However, this type of excitation requires specific geometrical settings, in addition to very low damping conditions. Electrothermal actuation is investigated to achieve excitation of primary resonance, which can be used for parametric excitation. This type of excitation is desirable due to its simplicity, robustness and ability to create large internal forces at low voltages. However, the time response is limited by the thermal relaxation time. In this work, we demonstrate the use of electromagnetic actuation to significantly amplify the response of electrothermally actuated clamped-clamped resonators at first mode (primary) resonance. At ambient pressure, experimental data show 18 times amplification of the response amplitude compared with electrothermal actuation only. The method is based on introducing a permanent magnetic field to induce an out-of-plane Lorentz-force. The results show the great potential of this technique being used for a variety of sensing and signal processing applications, especially, where a large signal-to-noise ratio is required while using low operational voltages.

scholarly journals Pulsation of α Cir (HD 128898)

1989 ◽  
Vol 111 ◽  
pp. 288-288
Author(s):  
Werner W. Weiss ◽  
Hartmut Schneider
Keyword(s):  
Diagnostic Tool ◽  
Signal To Noise Ratio ◽  
High Accuracy ◽  
Integration Time ◽  
Signal To Noise ◽  
Additional Information ◽  
Stellar Interiors ◽  
Noise Ratio ◽  
Ap Stars

AbstractThe group of pulsating CP2-stars (also called “rapidly oscillating Ap stars” provides asteroseismology with oscillation spectra of high accuracy. The potential as a diagnostic tool for modelling stellar interiors is widely appreciated. The identification of pulsation modes is important for such an analysis. However, this is rarely possible in an unambiguous manner. To improve the situation and to make use of additional information, we observed HD 128898 simultaneously spectroscopically and photometrically at ESO. For each of our individual CAT-CES spectra (1 minute integration time) it was thus possible to determine the pulsation phase at mid-exposure. A total of 887 spectra (R = 50000) were binned according to their pulsation phase and coadded to improve significantly the signal to noise ratio.

scholarly journals Image Simulation for Mingantu Ultrawide Spectral Radioheliograph in the Decimetre Wave Range

2015 ◽  
Vol 32 ◽  
Author(s):  
Jing Du ◽  
Yihua Yan ◽  
Wei Wang ◽  
Donghao Liu
Keyword(s):  
Inner Mongolia ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Frequency Resolution ◽  
The Sun ◽  
Image Simulation ◽  
Time Space ◽  
Wide Range ◽  
Wave Range ◽  
Imaging Performance

AbstractThe MUSER is a solar-dedicated radio interferometric array, which will observe the Sun over a wide range of radio frequencies (0.4–15 GHz), and make high time, space and frequency resolution images of the Sun simultaneously. MUSER is located in Mingantu Station in Inner Mongolia of China, which is about 400 kilometres away from Beijing. MUSER consists of two arrays: MUSER-I and MUSER-II. MUSER-I contains 40 antennas with 4.5-m aperture operating at 400 MHz to 2 GHz. MUSER-II contains 60 antennas with 2-m aperture operating at 2 to 15 GHz. Currently, MUSER has already been established and entered into the stage of test observation. This work is focus on the imaging performance of MUSER-I. This paper introduces MUSER-I briefly, presents the analysis of the array configurations, and evaluates the image quality mainly using the dynamic range, fidelity index, and the peak signal-to-noise ratio, also make some actual solar model simulations with CASA, the results will be shown below.

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