The Los Alamos Fourier Transform Spectrometer

Palmer, Byron A.; Engleman, Rolf

doi:10.1117/12.970888

Cited by 36 publications

(49 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The pressure variation ∆P between the QSO exposure and the calibration lamp reached 0.6 mbar in one case, in all other cases did not exceed 0.3 mbar, while variations of the ambient temperature were always less than 0.1 K. The pixel sizes are of 25 mÅ, 30 mÅ and 27 mÅ at the positions of λ1608, λ2382 and λ2600, respectively. The wavelength calibration was obtained from a ThAr hollow cathode lamp and the Los Alamos table of ThAr lines (Palmer & Engleman 1983; de Cuyper & Hensberge 1998) and the residuals of the calibrations were as small as about 20 m s −1 . The Fe ii lines selected for the analysis are those located close to the central regions of the corresponding echelle orders to minimize possible distortions of the line profiles caused by the decreasing spectral sensitivity at the edges of echelle orders.…”

Section: ∆α/α At Z Abs = 184 Towards Q 1101-264mentioning

confidence: 99%

Bounds on the fine structure constantvariability from Fe ii absorption lines in QSO spectra

Molaro

Reimers

Agafonova

et al. 2008

Eur. Phys. J. Spec. Top.

View full text Add to dashboard Cite

Abstract. The Single Ion Differential α Measurement (SIDAM) method for measuring ∆α/α and its figures of merit are illustrated together with the results produced by means of Fe ii absorption lines of QSO intervening systems. The method provides ∆α/α = −0.12 ± 1.79 ppm (parts-per-million) at z abs = 1.15 towards HE 0515-4414 and ∆α/α = 5.66 ± 2.67 ppm at z abs = 1.84 towards Q 1101-264, which are so far the most accurate measurements for single systems. SIDAM analysis for 3 systems from the Chand et al. (2004) sample provides inconsistent results which we interpret as due to calibration errors of the Chand et al. data at the level ≈ 10 ppm. In one system evidence for photo-ionization Doppler shift between Mg ii and Fe ii lines is found. This evidence has important bearings on the Many Multiplet method where the signal for ∆α/α variability is carried mainly by systems involving Mg ii absorbers. Some correlations are also found in the Murphy et al. sample which suggest larger errors than previously reported. Thus, we consider unlikely that both the Chand et al. and Murphy et al. datasets could provide an estimate of ∆α/α with an accuracy at the level of 1 ppm. A new spectrograph like the ESPRESSO project will be crucial to make progress in the astronomical determination of ∆α/α .

show abstract

Section: ∆α/α At Z Abs = 184 Towards Q 1101-264mentioning

confidence: 99%

Bounds on the fine structure constantvariability from Fe ii absorption lines in QSO spectra

Molaro

Reimers

Agafonova

et al. 2008

Eur. Phys. J. Spec. Top.

View full text Add to dashboard Cite

show abstract

“…Th-Ar reference wavelengths are taken from the compilations of Palmer et al (1983) . The figure shows that (i) the scatter of ∆λ tab is about a factor 3 smaller than that of δλ fit (ii) no clear correlation is seen between ∆λ tab and δλ fit .…”

Section: Effect Of Using Different Th-ar Line Tables On Wavelength Camentioning

confidence: 99%

Variation of the fine-structure constant: very high resolution spectrum of QSO HE 0515-4414

Chand¹,

Srianand²,

Petitjean

et al. 2006

A&A

View full text Add to dashboard Cite

Aims. We present a detailed analysis of a very high resolution (R ≈ 112 000) spectrum of the quasar HE 0515−4414 obtained using the High Accuracy Radial velocity Planet Searcher (HARPS) mounted on the ESO 3.6 m telescope at the La Silla observatory. The main aim is to use a HARPS spectrum of very high wavelength calibration accuracy (better than 1 mÅ), to constrain the variation of α ≡ e 2 / c and investigate any possible systematic inaccuracies in the wavelength calibration of the UV Echelle Spectrograph (UVES) mounted on the ESO Very Large Telescope (VLT). Methods. A cross-correlation analysis between the Th-Ar lamp spectra obtained with HARPS and UVES is carried out to detect any possible shift between the two spectra. Absolute wavelength calibration accuracies, and how that translates into the uncertainties in ∆α/α are computed using Gaussian fits for both lamp spectra. The value of ∆α/α at z abs = 1.1508 is obtained using the many multiplet method and simultaneous Voigt profile fits of HARPS and UVES spectra. Results. We find the shift between the HARPS and UVES spectra has a mean around zero with a dispersion of σ 1 mÅ. This is shown to be well within the wavelength calibration accuracy of UVES (i.e. σ 4 mÅ). We show that the uncertainties in the wavelength calibration induce an error of about ∆α/α ≤ 10 −6 in determining the variation of the fine-structure constant. Thus, the results of non-evolving ∆α/α reported in the literature based on UVES/VLT data should not be heavily influenced by problems related to wavelength calibration uncertainties. Our higher resolution spectrum of the z abs = 1.1508 Damped Lyman-α system toward HE 0515−4414 reveals more components compared to the UVES spectrum. Using only Fe ii lines of the z abs = 1.1508 system, we obtain ∆α/α = (0.05 ± 0.24) × 10 −5 . This result is consistent with the earlier measurement for this system using the UVES spectrum alone.

show abstract

“…These facts imply that the residual is small and has no significant impact on the BF value of the strongest lines. The wavenumbers and line identifications are taken from the analysis of Palmer et al (1980) and Steinhaus et al (1971).…”

Section: Branching Fractionsmentioning

confidence: 99%

“…Voigt (1975) measured oscillator strengths from an arc, which enabled Corliss (1976) to rescale the line intensities from Meggers et al (1961). In a study by Palmer et al (1980), relative line intensities and accurate wavenumbers were measured from uranium hollow cathode (HC) spectra recorded with the Fourier transform spectrometer (FTS) at Kitt Peak National Observatory. That work also includes a semi-empirical formula for putting the relative intensities on a absolute scale using the values reported by Corliss (1976).…”

Section: Introductionmentioning

confidence: 99%