High Signal-to-Noise Ratio Observations of Weak Interstellar Absorption Lines Towards XI Ophiuchi With the Goddard High-Resolution Spectrograph Aboard the Hubble Space Telescope

1996 ◽  
Vol 112 ◽  
pp. 1128 ◽  
Author(s):  
J. C. Brandt ◽  
S. R. Heap ◽  
E. A. Beaver ◽  
A. Boggess ◽  
K. G. Carpenter ◽  
...  
Keyword(s):  
High Resolution ◽  
Hubble Space Telescope ◽  
Signal To Noise Ratio ◽  
Absorption Lines ◽  
High Signal ◽  
Signal To Noise ◽  
Interstellar Absorption ◽  
Space Telescope ◽  
Noise Ratio

scholarly journals Photometric Characteristics of Data from the Hubble Space Telescope Goddard-High Resolution Spectrograph

1988 ◽  
Vol 132 ◽  
pp. 35-38
Author(s):  
Dennis C. Ebbets ◽  
Sara R. Heap ◽  
Don J. Lindler
Keyword(s):  
Exposure Time ◽  
Hubble Space Telescope ◽  
Signal To Noise Ratio ◽  
Scattered Light ◽  
Signal To Noise ◽  
Space Telescope ◽  
Additional Noise ◽  
Reduction Strategies ◽  
Noise Ratio

The G-HRS is one of four axial scientific instruments which will fly aboard the Hubble Space Telescope (ref 1,2). It will produce spectroscopic observations in the 1050 A ≤ λ ≤ 3300 A region with greater spectral, spatial and temporal resolution than has been possible with previous space-based instruments. Five first order diffraction gratings and one Echelle provide three modes of spectroscopic operation with resolving powers of R = λ/ΔΔ = 2000, 20000 and 90000. Two magnetically focused, pulse-counting digicon detectors, which differ only in the nature of their photocathodes, produce data whose photometric quality is usually determined by statistical noise in the signal (ref 3). Under ideal circumstances the signal to noise ratio increases as the square root of the exposure time. For some observations detector dark count, instrumental scattered light or granularity in the pixel to pixel sensitivity will cause additional noise. The signal to noise ratio of the net spectrum will then depend on several parameters, and will increase more slowly with exposure time. We have analyzed data from the ground based calibration programs, and have developed a theoretical model of the HRS performance (ref 4). Our results allow observing and data reduction strategies to be optimized when factors other than photon statistics influence the photometric quality of the data.

scholarly journals Seismology of southern Be stars

1994 ◽  
Vol 162 ◽  
pp. 104-105
Author(s):  
Eduardo Janot-Pacheco ◽  
Nelson Vani Leister
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Ccd Camera ◽  
High Signal ◽  
Be Stars ◽  
Signal To Noise ◽  
Photometric Variability ◽  
Spectroscopic Observations ◽  
Photometric Observations ◽  
Noise Ratio

We have started in 1990 a search for moving bumps in the HeI λ 667.8 nm of mainly southern, bright Be stars. The objects of our sample have been selected on the basis of photometric variability (Cuypers et al., 1989). High resolution (R≥ 30,000), high signal-to-noise ratio (S/R≥ 300) spectroscopic observations have been performed at the brazilian Laboratório Nacional de Astrofísica with a CCD camera attached to the coudé spectrograph of the 1.60 m telescope (e.g. Table I). Several hundred spectra have been taken during the last three years. Photometric observations simultaneous with spectroscopy were made on the same site in July 1992 with a two-channel photometer (Stromgren b filter) and a CCD camera (Johnson B filter) installed at two 0.60 m telescopes. The idea is try to disentangle the controversy between NRP and RM models with the help of simultaneous spectroscopy and photometry.

scholarly journals Space Observations of Chemically Peculiar and Related Normal Stars

1986 ◽  
Vol 90 ◽  
pp. 109-119
Author(s):  
David S. Leckrone
Keyword(s):  
High Resolution ◽  
Spectroscopic Study ◽  
Spectral Resolution ◽  
Hubble Space Telescope ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Space Telescope ◽  
Ultraviolet Spectra ◽  
Chemically Peculiar ◽  
Quantitative Analyses

AbstractProgress in the spectroscopic study of CP stars and related sharp-lined normal stars from the IUE is briefly reviewed as a preamble to a discussion of the potential for research with the Hubble Space Telescope. The substantial gains in spectral resolution, signal-to-noise ratio and photometric accuracy that will be realized with the High Resolution Spectrograph on the HST will dramatically increase our ability to disentangle the complex ultraviolet spectra of these stars and to carry out accurate quantitative analyses.

scholarly journals 12C/13C Ratios and Li Abundances in Low-Mass C Stars

2000 ◽  
Vol 177 ◽  
pp. 89-95
Author(s):  
Carlos Abia ◽  
Jordi Isern
Keyword(s):  
High Resolution ◽  
Carbon Isotope ◽  
Signal To Noise Ratio ◽  
Isotope Ratios ◽  
High Signal ◽  
Isotopic Ratios ◽  
Signal To Noise ◽  
Carbon Isotope Ratios ◽  
Low Mass ◽  
Noise Ratio

High-resolution and high signal-to-noise-ratio spectroscopy is used to derive 12C/13C ratios from the Red System of the CN molecule at 8000 Å in several galactic low-mass C stars previously analyzed for lithium. It is found that Li-rich C stars usually have low isotopic ratios (< 15). This suggests that the Li and 13C enrichments in C stars might be produced by a similar mechanism. However, due to the large uncertainties in the abundance derivations for both Li and carbon isotope ratios, this result must be confirmed with further studies.

Narrow-frequency sharp-angular filters using all-dielectric cascaded meta-gratings

Nanophotonics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 3443-3450 ◽  
Author(s):  
Wei-Nan Liu ◽  
Rui Chen ◽  
Wei-Yi Shi ◽  
Ke-Bo Zeng ◽  
Fu-Li Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Signal To Noise Ratio ◽  
Incident Angle ◽  
Design Strategy ◽  
Transmission Peak ◽  
High Signal ◽  
Waveguide Array ◽  
Signal To Noise ◽  
Center Wavelength ◽  
Noise Ratio

AbstractSelective transmission or filtering always responds to either frequency or incident angle, so as hardly to maximize signal-to-noise ratio in communication, detection and sensing. Here, we propose compact meta-filters of narrow-frequency sharp-angular transmission peak along with broad omnidirectional reflection sidebands, in all-dielectric cascaded subwavelength meta-gratings. The inherent collective resonance of waveguide-array modes and thin film approximation of meta-grating are employed as the design strategy. A unity transmission peak, locating at the incident angle of 44.4° and the center wavelength of 1550 nm, is demonstrated in a silicon meta-filter consisting of two-layer silicon rectangular meta-grating. These findings provide possibilities in cascaded meta-gratings spectroscopic design and alternative utilities for high signal-to-noise ratio applications in focus-free spatial filtering and anti-noise systems in telecommunications.

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