Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constant

Murphy, Michael T.; Tzanavaris, P.; Webb, John R.; Lovis, C.

doi:10.1111/j.1365-2966.2007.11768.x

Cited by 92 publications

(111 citation statements)

References 21 publications

(43 reference statements)

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“…HIRES_REDUX performs an optimal extraction of the flux and produces a robust, formal statistical error spectrum. Due to the sensitivity of ∆α/α on the wavelength calibration, we also paid particularly close attention to identifying ThAr lines properly from a list made using the same algorithm as Murphy et al (2007). We extracted the corresponding ThAr exposure using the same profile weights and parameters as the quasar and then improved the polynomial fit to the ThAr dispersion relation until we had wavelength calibration residuals smaller than 90 m s −1 .…”

Section: Keckmentioning

confidence: 99%

“…This uses flat fields and biases to correct the science exposures and identifies the centers of the orders using a quartz lamp exposure taken with shortened, narrow slit. The pipeline then creates a 2D wavelength solution for the CCDs by comparing the ThAr calibration exposures to a carefully selected ThAr line list developed by Murphy et al (2007). These exposures were then extracted and put onto a common, vacuum-corrected, heliocentric wavelength grid.…”

Section: Vltmentioning

confidence: 99%

“…For the former, a bright standard star exposure was used to etablish an initial trace and that trace was modified iteratively to optimally match the quasar flux distribution. For the latter, the ThAr flux was extracted along same trace as established for the corresponding object exposure and the Murphy et al (2007) ThAr line-list was used to determine the wavelength solution. The final spectrum had a SNR∼76 at 6000 Å after the 4 extracted quasar exposures were averaged.…”

Section: Subarumentioning

confidence: 99%

See 2 more Smart Citations

The UVES Large Program for testing fundamental physics – III. Constraints on the fine-structure constant from three telescopes

Evans¹,

Murphy²,

Whitmore³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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102

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Large statistical samples of quasar spectra have previously indicated possible cosmological variations in the fine-structure constant, α. A smaller sample of higher signal-to-noise ratio spectra, with dedicated calibration, would allow a detailed test of this evidence. Towards that end, we observed equatorial quasar HS 1549+1919 with three telescopes: the Very Large Telescope, Keck and, for the first time in such analyses, Subaru. By directly comparing these spectra to each other, and by 'supercalibrating' them using asteroid and iodine-cell tests, we detected and removed long-range distortions of the quasar spectra's wavelength scales which would have caused significant systematic errors in our α measurements. For each telescope we measure the relative deviation in α from the current laboratory value, ∆α/α, in 3 absorption systems at redshifts z abs = 1.143, 1.342, and 1.802. The nine measurements of ∆α/α are all consistent with zero at the 2-σ level, with 1-σ statistical (systematic) uncertainties 5.6-24 (1.8-7.0) parts per million (ppm). They are also consistent with each other at the 1-σ level, allowing us to form a combined value for each telescope and, finally, a single value for this line of sight: ∆α/α = −5.4 ± 3.3 stat ± 1.5 sys ppm, consistent with both zero and previous, large samples. We also average all Large Programme results measuring ∆α/α = −0.6±1.9 stat ±0.9 sys ppm. Our results demonstrate the robustness and reliability at the 3 ppm level afforded by supercalibration techniques and direct comparison of spectra from different telescopes.

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Section: Keckmentioning

confidence: 99%

Section: Vltmentioning

confidence: 99%

Section: Subarumentioning

confidence: 99%

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The UVES Large Program for testing fundamental physics – III. Constraints on the fine-structure constant from three telescopes

Evans¹,

Murphy²,

Whitmore³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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102

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show abstract

“…From the very slight variation of parameter α for cosmological distances King et al, 2011;Molaro et al, 2008;Murphy et al, 2008;2007; Science Publications PI Tzanavaris et al, 2005;Chand et al, 2004;Murphy et al, 2003;Webb et al, 2001;Dzuba et al, 1999;Webb et al, 1999), we conclude that the selfvariation of the electric charge evolves at an extremely slow rate. .…”

Section: Fundamental Equations Of the Cosmological Model Of The Selfvmentioning

confidence: 99%

On the Absence of Antimatter From the Universe, Dark Matter, the Fine Structure Parameter, the Fluctuations of the Cosmic Microwave Background Radiation and the Temperature Difference Between the Northern and Southern Hemisphere of the Universe

Manousos¹

2014

Physics International

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The theory of selfvariations correlates five cosmological observations considered to be unrelated by the physical theories of the previous century. The absence of antimatter from the Universe, the Dark Matter, the slight variation of the fine structure parameter, the temperature fluctuations of the cosmic microwave background radiation and the temperature difference between the northern and southern hemisphere of the Universe can be justified by a common cause. This cause is the selfvariation of the electric charge of material particles. The antimatter particles of the very early Universe lose their electric charge with the passage of time and end up as electrically neutral. These electrically neutral particles constitute a significant part of Dark Matter. The cosmological Model of the Selfvariations predicts another possible mechanism for the creation of Dark Matter particles. Thus, we can justify the fact that the amount of Dark Matter is greater than the amount of the ordinary, luminous, matter. A fluctuation of the electric charge at cosmological distances is predicted in the region of the Universe that we observe. This fluctuation is recorded in the cosmological data in the value of the fine structure parameter measured at cosmological distances, in the temperature of the cosmic microwave background radiation and is responsible for the temperature difference between the two hemispheres of the Universe. The study we present proves in detail that the law of selfvariations contains enough information to justify the totality of cosmological data that cannot be justified by the standard cosmological model. These data have been observed by the ultrasensitive modern observation instruments. The high sensitivity of the instruments is necessary to record the effects from the extremely small variation of the electric charge. We regard as necessary a re-evaluation of the cosmological data based on the law of selfvariations.

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“…Moreover, their positions depend on the accuracy of the wavelength calibration of conventional cross-dispersed spectrographs. The laboratory wavelengths of the hollow cathode thorium lamps and iodine absorption cells used for spectrometer calibration are known with a precision that varies from about 15 m s −1 to more than 100 m s −1 , depending on the line strength (Murphy et al 2007;Lovis & Pepe 2007). Wilken et al (2010) found that CCD manufacturing defects might be responsible for an A&A 544, A125 (2012) Notes.…”

Section: Introductionmentioning

confidence: 99%

Solar atlas revised

Molaro¹,

Monai²

2012

A&A

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Context. Present knowledge of the solar spectrum is limited because it is very difficult to observe the integrated solar spectrum at high resolution. The reflected solar light from asteroids has been shown to provide a relatively straightforward integrated and unmodified solar spectrum. Aims. We exploit this methodology to improve our knowledge of solar photospheric line positions both in terms of line number and precision with respect to the available solar line atlas. Methods. We used the DAOSPEC program to measure solar line positions automatically in high signal-to-noise spectra of Ceres obtained with HARPS at the 3.6 m ESO telescope. The line positions were then verified with the solar HARPS spectra of Ganymede and daylight as well as with a new FTS solar spectra. Results. A new atlas with 2334 lines in the range 4000−6859 Å is provided. The new atlas is consistent with that based on FTS solar spectra but the new line list improves the precision of individual lines by at least a factor 3−5. Conclusions. The new atlas provides a benchmark for 3D models of the solar photosphere and can be used to trace possible line drifts related to solar activity or to calibrate space and ground spectrographs.

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Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constant

Cited by 92 publications

References 21 publications

The UVES Large Program for testing fundamental physics – III. Constraints on the fine-structure constant from three telescopes

The UVES Large Program for testing fundamental physics – III. Constraints on the fine-structure constant from three telescopes

On the Absence of Antimatter From the Universe, Dark Matter, the Fine Structure Parameter, the Fluctuations of the Cosmic Microwave Background Radiation and the Temperature Difference Between the Northern and Southern Hemisphere of the Universe

Solar atlas revised

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