Context. High resolution observations of the asteroids Iris and Juno have been performed by means of the UV-Visual Echelle Spectrograph (UVES) at the European Southern Observatory (ESO) Very Large ...Telescope (VLT) to obtain the effective accuracy of the spectrograph's radial velocity. The knowledge of this quantity has important bearings on studies searching for a variability in the fine structure constant carried out with this instrument. Aims. Asteroids provide a precise radial velocity reference at the level of 1 m s super(-1), which allows for instrumental calibration and the recognition of small instrumental drifts and calibration systematics. In particular, radial velocity drifts due to nonuniform slit illumination and slit optical misalignment in the two UVES spectrograph arms can be investigated. Methods. We compare the position of the solar spectrum reflected by the asteroids with the solar wavelength positions and with that of asteroid and twilight observations at other epochs to asses the UVES instrumental accuracy. Results. We observe radial velocities offsets in the range of \approx10-50 m s super(-1), likely due to a nonuniform slit illumination. However, no radial velocity patterns with wavelengths are detected and the two UVES arms provide consistent radial velocities. These results suggest that the detected \Delta\alpha/\alpha\,variability by Levshakov et al. (2007) deduced from a drift of-180 \pm 85 m s super(-1) at z_{\rm abs}\, = 1.84, between two sets of Fe II lines falling in the two UVES arms, may be real or induced by other kinds of systematics than those investigated here. The proposed technique allows us to make a real time quality check of the spectrograph and should be followed for very accurate measurements.
Ceres' sunlight atlas super() Molaro, P; Centurion, M
Astronomy and astrophysics (Berlin),
12/2010, Letnik:
525
Journal Article
Recenzirano
Context. Astronomical research dealing with accurate radial velocity measurements need reliable astronomical standards to calibrate the spectrographs and to assess possible systematics. Stellar ...radial velocity standards offer a reference at the level of a few hundred m s super(-1) and are not adequate for most present needs. Aims. We aim to show that sunlight reflected by asteroids is a fairly accessible way to record a high-resolution solar spectrum from the whole disk, which can therefore be used as a radial velocity standard and can improve the uncertainties of solar line positions. Methods. We used solar light reflected by the asteroid Ceres observed with HARPS to measure solar lines' wavelengths. Results. We provide a new solar atlas with 491 line wavelengths in the range 540– 690 nm and 222 lines in the range 400– 410 nm obtained from reflected solar spectrum of Ceres. These measurements are consistent with those of Allende Prieto & Garcia Lopez (1998b) based on FTS solar atlases but with a factor 3 higher precision. Conclusions. This atlas provides a benchmark for wavelength calibration to check radial velocity accuracy down to 44 m s super(-1) locall y and a few m s super(-1) globally. The asteroid-based technique could provide a new way to track radial velocity shifts with solar activity cycle, as well as to derive convective shifts suitable for comparison with theoretical atmospheric models. It could also be used to study radial velocity deviations in spectrographs such as those recently detected in HIRES and UVES. Dedicated HARPS observations of other asteroids could improve present results substantially and these investigations have been solicited.
► A flow-batch system with a hydrolysis and detection chambers was developed. ► The sample treatment takes place in 15min. ► A low cost halogen lamp in sample treatment was used. ► Vienna sausages ...were analysed. ► The obtained results were in good agreement with the reference method.
In this study an automatic method for sample treatment and spectrophotometric determination of hydroxyproline in commercial sausages was developed. A flow-batch system that includes the steps of sample hydrolysis and determination of the analyte was designed. The method presents a linear range between 0.60 and 3.60μgmL−1 of hydroxyproline. A relative standard deviation of 1.68% was obtained from hydroxyproline standard solution (n=6, 1.20μgmL−1) and the detection limit was 0.12μgmL−1. The sample throughput was 1sampleh−1 while the reference method (AOAC) was carried out in about 17h. This method employs 16h of hydrolysis while in the proposed method the hydrolysis time was 15min. For this purpose a pressure hydrolysis chamber with a low cost halogen lamp was used. The flow-batch system is simple and allows the use of both chambers (hydrolysis and detection) simultaneously. The obtained results with the flow-batch method are in good agreement with that obtained with the reference method. Moreover, it is good alternative to the quality control of meat products.
We propose a new methodology for probing the cosmological variability of α from pairs of $\ion{Fe}{ii}$ lines (SIDAM, single ion differential α measurement) observed in individual exposures from a ...high resolution spectrograph. By this we avoid the influence of the spectral shifts due to $(i)$ ionization inhomogeneities in the absorbers; and $(ii)$ non-zero offsets between different exposures. Applied to the $\ion{Fe}{ii}$ lines of the metal absorption line system at zabs = 1.839 in the spectrum of Q 1101–264 obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT), SIDAM provides $\Delta\alpha/\alpha$ = $(2.4\pm3.8_{\rm stat})\times10^{-6}$. The zabs = 1.15 $\ion{Fe}{ii}$ system toward HE 0515–4414 has been re-analyzed by this method thus obtaining for the combined sample $\Delta\alpha/\alpha$ = $(0.4\pm1.5_{\rm stat})\times10^{-6}$. These values are shifted with respect to the Keck/HIRES mean $\Delta\alpha/\alpha$ = $(-5.7\,\pm\,1.1_{\rm stat})\times10^{-6}$ (Murphy et al. 2004) at very high confidence level (95%). The fundamental photon noise limitation in the $\Delta\alpha/\alpha$ measurement with the VLT/UVES is discussed to figure the prospects for future observations. It is suggested that with a spectrograph of ~10 times the UVES dispersion coupled to a 100 m class telescope the present Oklo level ($\Delta\alpha/\alpha$ ≥ 4.5 $\times$ 10-8) can be achieved along cosmological distances with differential measurements of $\Delta\alpha/\alpha$.
Optical Follow-Up of GRB 970508 Galama, T. J; Groot, P. J; van Paradijs, J ...
The Astrophysical journal,
04/1998, Letnik:
497, Številka:
1
Journal Article
A computational procedure is presented to estimate the spectral shape of the ionizing background between 1 and 10 Ryd by analyzing optically thin absorption systems in the spectra of high redshift ...quasars. The procedure is based on the response surface methodology from the theory of experimental design. The shape of the recovered UV background at $z \sim 3$ shows a significant intensity decrease between 3 and 4 Ryd compared to the metagalactic spectrum of Haardt & Madau (1996, ApJ, 461, 20). This decrease is interpreted as produced by $\ion{He}{ii}$ Gunn-Peterson effect. There are no features indicating a contribution from galaxies to the UV background which is therefore dominated by QSOs at $z \sim 3$.
Four new analogs of 28-homocastasterone have been synthesized and completely characterized for the first time from stigmasterol. (22R,23R,24S)-3β-acetoxy-22,23-dihydroxy-5α-stigmastan-6-one (
17), ...(22R,23R,24S)-3β-bromo-22,23-dihydroxy-5α-stigmastan-6-one (
18), (22R,23R,24S)-3β-acetoxy-5,22,23-trihydroxy-5α-stigmastan-6-one (
20), and (22R,23R,24S)-3β-bromo-5,22,23-trihydroxy-5α-stigmastan-6-one (
21), were obtained through a synthetic route based on regioselective Δ
5 epoxidation. Compounds
17 and
18, bearing a 5αH moiety, were prepared through a reductive opening of the 5β,6β epoxy precursor, and compounds
20 and
21, analogs with a 5αOH moiety were obtained by hydrolytic opening of a mixture of 5α,6α and 5β,6β epoxy precursors. Known compounds
19 and
22 were also obtained following the described synthetic routes, respectively. The new compounds were tested with the traditional auxin-like bioassay for brassinosteroids with
19 and
22 as standards. All compounds were comparatively evaluated for their inhibitory effect on the replication of DNA (HSV-1) virus.
Context. High resolution observations of the asteroids Iris and Juno have been performed by means of the UV-Visual Echelle Spectrograph (UVES) at the European Southern Observatory (ESO) Very Large ...Telescope (VLT) to obtain the effective accuracy of the spectrograph's radial velocity. The knowledge of this quantity has important bearings on studies searching for a variability in the fine structure constant carried out with this instrument. Aims. Asteroids provide a precise radial velocity reference at the level of 1 m s-1, which allows for instrumental calibration and the recognition of small instrumental drifts and calibration systematics. In particular, radial velocity drifts due to nonuniform slit illumination and slit optical misalignment in the two UVES spectrograph arms can be investigated. Methods. We compare the position of the solar spectrum reflected by the asteroids with the solar wavelength positions and with that of asteroid and twilight observations at other epochs to asses the UVES instrumental accuracy. Results. We observe radial velocities offsets in the range of ≈10-50 m s-1, likely due to a nonuniform slit illumination. However, no radial velocity patterns with wavelengths are detected and the two UVES arms provide consistent radial velocities. These results suggest that the detected $\Delta\alpha/\alpha\,$variability by Levshakov et al. (2007) deduced from a drift of -180 ± 85 m s-1 at $z_{\rm abs}\,$ = 1.84, between two sets of Fe II lines falling in the two UVES arms, may be real or induced by other kinds of systematics than those investigated here. The proposed technique allows us to make a real time quality check of the spectrograph and should be followed for very accurate measurements.
Aims. Verification the theoretical prediction of oscillation of the fine-structure constant alpha ( identical with e super(2)/hc) over cosmic time requires high precision Delta alpha / alpha ...measurements at individual redshifts. In earlier studies the mean Delta alpha / alpha values averaged over wide redshift intervals were usually reported. This requirement can be met using the single ion differential alpha measurement (SIDAM) procedure. We apply SIDAM to the Fe II lines associated with the damped Ly alpha system observed at z sub(abs) = 1.15 in the spectrum of HE 0515-4414. Methods. The spectrum was obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT). Results. The weighted mean < Delta alpha / alpha > calculated using carefully selected 34 Fen pairs { lambda 1608, X} (X = 2344,2374, and 2586 AA) is < Delta alpha / alpha > = (-0.07 plus or minus 0.84) x 10 super(-6) (1 sigma C.L.). The precision of this estimate improves by a factor of 2 the previous one reported for the same system. The obtained result represents an absolute improvement with respect to what has been done in the measurements of Delta alpha / alpha .
We used the photometric database of the Sloan Digital Sky Survey (SDSS) to estimate the reddening of 13 SDSS quasars selected on the basis of the presence of zinc absorption lines in an intervening ...Damped Ly alpha (DLA) system. In 5 of these quasars the reddening is detected at 2 sigma confidence level in two independent color indices of the SDSS ugriz photometric system. A detailed analysis of the data supports an origin of the reddening in the intervening absorbers. We used these rare measurements of extinction in DLA systems to probe the relation between extinction and metal column density in the interval of absorption redshift 0.7 z 2.0. We find that the mean extinction in the V band per atom of iron in the dust is remarkably similar to that found in interstellar clouds of the Milky Way. This result lends support to previous estimates of the dust obscuration effect in DLA systems based on a Milky Way extinction/metal column density relation. We propose a simple mechanism, based on dust grain destruction/accretion properties, which may explain the approximate constancy of the extinction per atom of iron in the dust.
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