scholarly journals The Penn State - Toruń Centre for Astronomy Planet Search stars

2018 ◽  
Vol 615 ◽  
pp. A31 ◽  
Author(s):  
B. Deka-Szymankiewicz ◽  
A. Niedzielski ◽  
M. Adamczyk ◽  
M. Adamów ◽  
G. Nowak ◽  
...  
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Equilibrium Analysis ◽  
High Signal ◽  
Physical Parameters ◽  
Solar Mass ◽  
Dwarf Stars ◽  
Penn State ◽  
Definition Of ◽  
Stellar Masses

Context. Our knowledge of the intrinsic parameters of exoplanets is as precise as our determinations of their stellar hosts parameters. In the case of radial velocity searches for planets, stellar masses appear to be crucial. But before estimating stellar masses properly, detailed spectroscopic analysis is essential. With this paper we conclude a general spectroscopic description of the Pennsylvania-Toruń Planet Search (PTPS) sample of stars. Aims. We aim at a detailed description of basic parameters of stars representing the complete PTPS sample. We present atmospheric and physical parameters for dwarf stars observed within the PTPS along with updated physical parameters for the remaining stars from this sample after the first Gaia data release. Methods. We used high resolution (R = 60 000) and high signal-to-noise-ratio (S/N = 150–250) spectra from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar atmospheric parameters were determined through a strictly spectroscopic local thermodynamic equilibrium analysis (LTE) of the equivalent widths of Fe I and Fe II lines. Stellar masses, ages, and luminosities were estimated through a Bayesian analysis of theoretical isochrones. Results. We present Teff, log g, [Fe/H], microturbulence velocities, absolute radial velocities, and rotational velocities for 156 stars from the dwarf sample of PTPS. For most of these stars these are the first determinations. We refine the definition of PTPS subsamples of stars (giants, subgiants, and dwarfs) and update the luminosity classes for all PTPS stars. Using available Gaia and HIPPARCOS parallaxes, we redetermine the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS stars. Conclusions. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238 subgiants, and 515 giants, of which the vast majority are of roughly solar mass; however, 114 have masses higher than 1.5 M⊙ and 30 of over 2 M⊙. The PTPS extends toward much less metal abundant and much more distant stars than other planet search projects aimed at detecting planets around evolved stars; 29% of our targets belong to the Galactic thick disc and 2% belong to the halo.

scholarly journals The 12C/13C Ratio in Unevolved Cool Stars

1988 ◽  
Vol 132 ◽  
pp. 589-592
Author(s):  
Y. Chmielewski ◽  
D. L. Lambert
Keyword(s):  
High Resolution ◽  
Preliminary Analysis ◽  
Isotope Ratio ◽  
Signal To Noise Ratio ◽  
Carbon Isotope Ratio ◽  
High Signal ◽  
Reasonable Accuracy ◽  
Signal To Noise ◽  
Dwarf Stars ◽  
Cool Stars

We show that the carbon isotope ratio 12C/13C in the atmosphere of dwarf stars can be determined with reasonable accuracy from high resolution, high signal-to-noise ratio observations of the CH G-band in their spectra. Lines suitable for this purpose are selected from consideration of the solar case, for which 12C/13C = 89 is derived. A preliminary analysis of these features in the spectra of μ Her, δ Eri and τ Cet yields 12C/13C values of 84, 80 and 150 respectively.

scholarly journals High-speed high-resolution laser diode-based photoacoustic microscopy for in vivo microvasculature imaging

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiufeng Li ◽  
Victor T C Tsang ◽  
Lei Kang ◽  
Yan Zhang ◽  
Terence T W Wong
Keyword(s):  
High Resolution ◽  
High Speed ◽  
High Performance ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Cost Effective ◽  
High Signal ◽  
Photoacoustic Microscopy ◽  
Mouse Ear

AbstractLaser diodes (LDs) have been considered as cost-effective and compact excitation sources to overcome the requirement of costly and bulky pulsed laser sources that are commonly used in photoacoustic microscopy (PAM). However, the spatial resolution and/or imaging speed of previously reported LD-based PAM systems have not been optimized simultaneously. In this paper, we developed a high-speed and high-resolution LD-based PAM system using a continuous wave LD, operating at a pulsed mode, with a repetition rate of 30 kHz, as an excitation source. A hybrid scanning mechanism that synchronizes a one-dimensional galvanometer mirror and a two-dimensional motorized stage is applied to achieve a fast imaging capability without signal averaging due to the high signal-to-noise ratio. By optimizing the optical system, a high lateral resolution of 4.8 μm has been achieved. In vivo microvasculature imaging of a mouse ear has been demonstrated to show the high performance of our LD-based PAM system.

scholarly journals A new and homogeneous metallicity scale for Galactic classical Cepheids

2018 ◽  
Vol 616 ◽  
pp. A82 ◽  
Author(s):  
B. Proxauf ◽  
R. da Silva ◽  
V. V. Kovtyukh ◽  
G. Bono ◽  
L. Inno ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Physical Parameters ◽  
Classical Cepheids ◽  
Microturbulent Velocity ◽  
Metal Abundances ◽  
Pulsation Cycle ◽  
Intrinsic Error ◽  
Better Than

We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with the optical spectrographs UVES at VLT, HARPS at 3.6 m, FEROS at 2.2 m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (5348 ≤ λ ≤ 8427 Å) and in effective temperature (3500 ≤ Teff ≤ 7700 K). This gives us the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100 K. As a consequence of the high signal-to-noise ratio of individual spectra, we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of Fe I (more than one hundred) and Fe II (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1 dex. We focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree very well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.

scholarly journals Studies of the ISM in the LMC using SN1987A

1991 ◽  
Vol 148 ◽  
pp. 431-431
Author(s):  
Max Pettini
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Large Magellanic Cloud ◽  
Absorption Lines ◽  
High Signal ◽  
Hii Region ◽  
Sn 1987A

The exceptional brightness of SN1987A provided a wealth of opportunities for probing not only the interstellar medium in our Galaxy and in the Large Magellanic Cloud (LMC), but also any intergalactic matter between the two. Spectroscopic work has been directed both towards searches for very weak absorption lines, which require data of exceptionally high signal-to-noise ratio, and towards recording spectra of known features at unprecedentedly high resolution. Both approaches have yielded exciting and unexpected results. The first detection of [FeX] absorption has revealed the presence of million-degree gas in the interstellar medium of the LMC, possibly resulting from the explosions of previous supernovae in the 30-Doradus HII region. The ultra-high-resolution observations have been successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds along the line of sight to the supernova. This implies that the clouds are at temperatures of, at most, 170 K and have internal turbulent velocities of not more than 0.2 km s−1; large-scale motions thus appear to be mainly subsonic in these clouds. Radio observations of HI emission at 21-cm with the Parkes telescope have been combined with measurements of a variety of ultraviolet absorption lines, obtained with the International Ultraviolet Explorer satellite, to give the most detailed picture yet of the chemical composition of the gas between the Galaxy and the LMC. Finally, photographic monitoring of the light echo of SN 1987A over the last two years has provided a three-dimensional view of the interstellar environment in which SN 1987A exploded, complementing vividly the information deduced from the spectroscopic results.

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

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 Multi-analyser detector (MAD) for high-resolution and high-energy powder X-ray diffraction

2021 ◽  
Vol 28 (1) ◽  
pp. 146-157
Author(s):  
Alexander Schökel ◽  
Martin Etter ◽  
Andreas Berghäuser ◽  
Alexander Horst ◽  
Dirk Lindackers ◽  
...  
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
High Energy ◽  
High Signal ◽  
X Ray Diffraction ◽  
Stepper Motors ◽  
In Operando ◽  
Characterization Of Materials

For high-resolution powder diffraction in material science, high photon energies are necessary, especially for in situ and in operando experiments. For this purpose, a multi-analyser detector (MAD) was developed for the high-energy beamline P02.1 at PETRA III of the Deutsches Elektronen-Synchrotron (DESY). In order to be able to adjust the detector for the high photon energies of 60 keV, an individually adjustable analyser–crystal setup was designed. The adjustment is performed via piezo stepper motors for each of the ten channels. The detector shows a low and flat background as well as a high signal-to-noise ratio. A range of standard materials were measured for characterizing the performance. Two exemplary experiments were performed to demonstrate the potential for sophisticated structural analysis with the MAD: (i) the structure of a complex material based on strontium niobate titanate and strontium niobate zirconate was determined and (ii) an in situ stroboscopy experiment with an applied electric field on a highly absorbing piezoceramic was performed. These experiments demonstrate the capabilities of the new MAD, which advances the frontiers of the structural characterization of materials.

scholarly journals A New Method for Measuring the Detailed Chemical Composition of Globular Clusters from High-Resolution, Integrated-Light Spectra

2002 ◽  
Vol 207 ◽  
pp. 739-742 ◽  
Author(s):  
Rebecca A. Bernstein ◽  
Andrew McWilliam
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Globular Clusters ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Analysis Method ◽  
Individual Stars ◽  
Light Spectra ◽  
History Of ◽  
Detailed Chemical

We are developing a method for measuring the detailed chemical composition and evolutionary history of extragalactic star clusters from high resolution spectra of their integrated light as one would from spectra of individual stars. In this paper, we show high signal-to-noise ratio echelle spectra of the integrated light of two Galactic globular clusters and equivalent-quality spectra of individual stars in those clusters in order to briefly illustrate some subtleties of the analysis method.

Electron Image Analysis

1971 ◽  
Vol 29 ◽  
pp. 80-81
Author(s):  
D. W. Gibbard ◽  
J. A. Crawley ◽  
M. J. Cowham
Keyword(s):  
Image Analysis ◽  
High Resolution ◽  
High Speed ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Modular Construction ◽  
Wide Range ◽  
Electron Microscopes ◽  
Digital Circuitry ◽  
Accuracy And Repeatability

The history of automatic image analysis is a short one, the techniques being limited until recent years due to the “state of the art” of technology in electronics. A new third generation image analysis machine, the Quantimet 720 was introduced in 1969 designed with a modular construction for application to many fields of interest. It was the first equipment of its type to depart from T.V. standards to scan standards required for optimising the conflicting requirements of high resolution, high speed and high signal to noise ratio. It features high resolution and digital circuitry for accuracy and repeatability and a large and growing range of modules for high computing power. It has also been applied to a wide range of image producing devices including light microscopes, epidiascope (for analysis of photo-micrographs), transmission and scanning electron microscopes.

Sign in / Sign up

Export Citation Format

Share Document