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V V Flambaum - One of the best experts on this subject based on the ideXlab platform.
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spatial variation in the fine structure constant new results from vlt uves
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:Quasar absorption lines provide a precise test of whether the fine-structure constant, α, is the same in different places and through cosmological time. We present a new analysis of a large sample of quasar absorption-line spectra obtained using the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) in Chile. We apply the many-multiplet method to derive Values of Δα/α≡ (αz−α0)/α0 from 154 absorbers, and combine these Values with 141 Values from previous observations at the Keck Observatory in Hawaii. In the VLT sample, we find evidence that α increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample provided evidence for a smaller α in the distant absorption clouds. Upon combining the samples, an apparent variation of α across the sky emerges which is well represented by an angular dipole model pointing in the direction RA = 17.3 ± 1.0 h and Dec. =−61°± 10°, with amplitude . The dipole model is required at the 4.1σ statistical significance level over a simple monopole model where α is the same across the sky (but possibly different from the current Laboratory Value). The data sets reveal remarkable consistencies: (i) the directions of dipoles fitted to the VLT and Keck samples separately agree; (ii) the directions of dipoles fitted to z 1.6 cuts of the combined VLT+Keck samples agree; and (iii) in the equatorial region of the dipole, where both the Keck and VLT samples contribute a significant number of absorbers, there is no evidence for inconsistency between Keck and VLT. The amplitude of the dipole is clearly larger at higher redshift. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with ‘lookback-time distance’ (r=ct, where t is the lookback time), the amplitude is (1.1 ± 0.2) × 10−6 GLyr−1 and the model is significant at the 4.2σ confidence level over the null model (Δα/α≡ 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in α. To the best of our knowledge, this result is not in conflict with any other observational or experimental result.
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spatial variation in the fine structure constant new results from vlt uves
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current Laboratory Value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model [Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.
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keck constraints on a varying fine structure constant wavelength calibration errors
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Michael T Murphy, J K Webb, V V FlambaumAbstract:The Keck telescope's HIRES spectrograph has previously provided evidence for a smaller fine-structure constant, alpha, compared to the current Laboratory Value, in a sample of 143 quasar absorption systems: da/a=(-0.57+/-0.11)x10^{-5}. This was based on a variety of metal-ion transitions which, if alpha varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial to do so. It is also important to consider new possible instrumental systematic effects which may explain the Keck/HIRES results. Griest et al. (2009, arXiv:0904.4725v1) recently identified distortions in the echelle order wavelength scales of HIRES with typical amplitudes +/-250m/s. Here we investigate the effect such distortions may have had on the Keck/HIRES varying alpha results. We demonstrate that they cause a random effect on da/a from absorber to absorber because the systems are at different redshifts, placing the relevant absorption lines at different positions in different echelle orders. The typical magnitude of the effect on da/a is ~0.4x10^{-5} per absorber which, compared to the median error on da/a in the sample, ~1.9x10^{-5}, is relatively small. Consequently, the weighted mean Value changes by less than 0.05x10^{-5} if the corrections we calculate are applied. Nevertheless, we urge caution, particularly for analyses aiming to achieve high precision da/a measurements on individual systems or small samples, that a much more detailed understanding of such intra-order distortions and their dependence on observational parameters is important if they are to be avoided or modelled reliably. [Abridged]
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keck constraints on a varying fine structure constant wavelength calibration errors
Memorie della Societa Astronomica Italiana (Journal of the Italian Astronomical Society): incorporating proceedings Joint Discussion 9 the 27th IAU Ge, 2009Co-Authors: Michael T Murphy, J K Webb, V V FlambaumAbstract:The Keck telescope's High Resolution Spectrograph (HIRES) has previously provided evidence for a smaller fine-structure constant, α, compared to the current Laboratory Value, in a sample of 143 quasar absorption systems: Δα/α=(-0.57±0.11)×10 −5 . The analysis was based on a variety of metal-ion transitions which, if α varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial to do so. It is also important to consider new possible instrumental systematic effects which may explain the Keck/HIRES results. Griest et al. (2009) recently identified distortions in the echelle order wavelength scales of HIRES with typical amplitudes ±250 m s −1 . Here we investigate the effect such distortions may have had on the Keck/HIRES varying α results. Using a simple model of these intra-order distortions, we demonstrate that they cause a random effect on Δα/α from absorber to absorber because the systems are at different redshifts, placing the relevant absorption lines at different positions in different echelle orders. The typical magnitude of the effect on Δα/α is ~0.4×10 −5 for individual absorbers which, compared to the median error on Δα/α in the sample, ~1.9×10 −5 , is relatively small. Consequently, the weighted mean Value changes by less than 0.05×10 −5 if the corrections we calculate are applied. Unsurprisingly, with corrections this small, we do not find direct evidence that applying them is actually warranted. Nevertheless, we urge caution, particularly for analyses aiming to achieve high precision Δα/α measurements on individual systems or small samples, that a much more detailed understanding of such intra-order distortions and their dependence on observational parameters is important if they are to be avoided or modelled reliably.
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strong limit on a variable proton to electron mass ratio from molecules in the distant universe
Science, 2008Co-Authors: Michael T Murphy, V V Flambaum, Sebastien Muller, C HenkelAbstract:The Standard Model of particle physics assumes that the so-called fundamental constants are universal and unchanging. Absorption lines arising in molecular clouds along quasar sightlines offer a precise test for variations in the proton-to-electron mass ratio, μ, over cosmological time and distance scales. The inversion transitions of ammonia are particularly sensitive to μ as compared to molecular rotational transitions. Comparing the available ammonia spectra observed toward the quasar B0218+357 with new, high-quality rotational spectra, we present the first detailed measurement of μ with this technique, limiting relative deviations from the Laboratory Value to |Δμ/μ|
Jorge J Castillo - One of the best experts on this subject based on the ideXlab platform.
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high red cell distribution width is an adverse predictive and prognostic factor in patients with diffuse large b cell lymphoma treated with chemoimmunotherapy
Clinical Lymphoma Myeloma & Leukemia, 2019Co-Authors: Brady E Beltran, Sally Paredes, Denisse A Castro, Esther Cotrina, Eduardo M Sotomayor, Jorge J CastilloAbstract:Abstract Introduction The red blood cell distribution width (RDW) is an easy-to-obtain Laboratory Value that has emerged as a potential prognostic factor in solid and hematologic malignancies. Patients and Methods We evaluated 121 patients with de novo diffuse large B-cell lymphoma (DLBCL) treated with standard chemoimmunotherapy at our institution between 2010 and 2012. We categorized patients with high RDW (> 14.6%) and normal RDW (11.6%-14.6%). We fitted multivariate regression models for complete response (CR) and overall survival (OS). Results Patients with high RDW were less likely to achieve CR to chemoimmunotherapy than patients with normal RDW (48% vs. 83%; P Conclusion High RDW appears to be an adverse predictive and prognostic factor in patients with de novo DLBCL treated with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone).
V F Suleimanov - One of the best experts on this subject based on the ideXlab platform.
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evidence for the photoionization absorption edge in a photospheric radius expansion x ray burst from grs 1747 312 in terzan 6
arXiv: High Energy Astrophysical Phenomena, 2018Co-Authors: V F Suleimanov, Juri Poutanen, Tuomo Salmi, M Falanga, Joonas NattilaAbstract:Thermonuclear X-ray bursts on the surface of neutron stars (NSs) can enrich photosphere with metals, which may imprint the photoionization edges on the burst spectra. We report here the discovery of absorption edges in the spectra of the type I X-ray burst from the NS low-mass X-ray binary GRS 1747$-$312 in Terzan 6 during observations by the Rossi X-ray Timing Explorer. We find that the edge energy evolves from $9.45\pm0.51$ keV to $\sim6$ keV and then back to $9.44\pm0.40$ keV during the photospheric radius expansion phase and remains at $8.06\pm0.66$ keV in the cooling tail. The photoionization absorption edges of hydrogen-like Ni, Fe or Fe/Ni mixture and the bound-bound transitions of metals may be responsible for the observed spectral features. The ratio of the measured absorption edge energy in the cooling tail to the Laboratory Value of hydrogen-like Ni(Fe) edge energy allows us to estimate the gravitational redshift factor $1+z=1.34\pm0.11$($1+z=1.15\pm0.09$). The evolution of the spectral parameters during the cooling tail are well-described by the metal-rich atmosphere models. The combined constraints on the NS mass and radius from the direct cooling method and the tidal deformability strongly suggest very high atmospheric abundance of the iron group elements and limit the distance to the source to $11\pm1$ kpc.
M T Murphy - One of the best experts on this subject based on the ideXlab platform.
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spatial variation in the fine structure constant new results from vlt uves
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:Quasar absorption lines provide a precise test of whether the fine-structure constant, α, is the same in different places and through cosmological time. We present a new analysis of a large sample of quasar absorption-line spectra obtained using the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) in Chile. We apply the many-multiplet method to derive Values of Δα/α≡ (αz−α0)/α0 from 154 absorbers, and combine these Values with 141 Values from previous observations at the Keck Observatory in Hawaii. In the VLT sample, we find evidence that α increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample provided evidence for a smaller α in the distant absorption clouds. Upon combining the samples, an apparent variation of α across the sky emerges which is well represented by an angular dipole model pointing in the direction RA = 17.3 ± 1.0 h and Dec. =−61°± 10°, with amplitude . The dipole model is required at the 4.1σ statistical significance level over a simple monopole model where α is the same across the sky (but possibly different from the current Laboratory Value). The data sets reveal remarkable consistencies: (i) the directions of dipoles fitted to the VLT and Keck samples separately agree; (ii) the directions of dipoles fitted to z 1.6 cuts of the combined VLT+Keck samples agree; and (iii) in the equatorial region of the dipole, where both the Keck and VLT samples contribute a significant number of absorbers, there is no evidence for inconsistency between Keck and VLT. The amplitude of the dipole is clearly larger at higher redshift. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with ‘lookback-time distance’ (r=ct, where t is the lookback time), the amplitude is (1.1 ± 0.2) × 10−6 GLyr−1 and the model is significant at the 4.2σ confidence level over the null model (Δα/α≡ 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in α. To the best of our knowledge, this result is not in conflict with any other observational or experimental result.
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spatial variation in the fine structure constant new results from vlt uves
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current Laboratory Value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model [Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.
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further evidence for a variable fine structure constant from keck hires qso absorption spectra
Monthly Notices of the Royal Astronomical Society, 2003Co-Authors: M T Murphy, J K Webb, V V FlambaumAbstract:We have previously presented evidence for a varying fine-str ucture constant, α, in two independent samples of Keck/HIRES QSO absorption spectra. Here we present a detailed manymultiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2 < zabs < 3.7. The results, with raw statistical errors, indicate a small er weighted mean α in the absorption clouds: �α/α = ( 0.574 ± 0.102) × 10 5 . All three samples separately yield consistent and significant Values of �α/α. The analyses of low-z (i.e. zabs < 1.8) and high-z systems rely on different ions and transitions with very different dependencies on α, yet they also give consistent results. We identify an addit ional source of random error in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical erro rs on �α/α for these systems gives our fiducial result, a weighted mean �α/α = ( 0.543 ± 0.116) × 10 5 , representing 4.7 σ evidence for a varying α. Assuming that �α/α = 0 at zabs = 0, the data marginally prefer a linear increase in α with time rather than a constant offset from the Laboratory Value: u α/α = (6.40 ± 1.35) × 10 16 yr 1 . The two-point correlation function for α is consistent with zero over 0.2‐13 Gpc comoving scales and the angular distribution of �α/α shows no significant dipolar anisotropy. We therefore have no eviden ce for spatial variations in �α/α. We extend our previous searches for possible systematic errors, giving detailed analyses of potential kinematic effects, line blending, wavelength miscalibration, spectrograph temperature variations, atmospheric dispersion and isotopic /hyperfine structure effects. The latter two are potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of indep endent QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.
J K Webb - One of the best experts on this subject based on the ideXlab platform.
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spatial variation in the fine structure constant new results from vlt uves
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:Quasar absorption lines provide a precise test of whether the fine-structure constant, α, is the same in different places and through cosmological time. We present a new analysis of a large sample of quasar absorption-line spectra obtained using the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) in Chile. We apply the many-multiplet method to derive Values of Δα/α≡ (αz−α0)/α0 from 154 absorbers, and combine these Values with 141 Values from previous observations at the Keck Observatory in Hawaii. In the VLT sample, we find evidence that α increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample provided evidence for a smaller α in the distant absorption clouds. Upon combining the samples, an apparent variation of α across the sky emerges which is well represented by an angular dipole model pointing in the direction RA = 17.3 ± 1.0 h and Dec. =−61°± 10°, with amplitude . The dipole model is required at the 4.1σ statistical significance level over a simple monopole model where α is the same across the sky (but possibly different from the current Laboratory Value). The data sets reveal remarkable consistencies: (i) the directions of dipoles fitted to the VLT and Keck samples separately agree; (ii) the directions of dipoles fitted to z 1.6 cuts of the combined VLT+Keck samples agree; and (iii) in the equatorial region of the dipole, where both the Keck and VLT samples contribute a significant number of absorbers, there is no evidence for inconsistency between Keck and VLT. The amplitude of the dipole is clearly larger at higher redshift. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with ‘lookback-time distance’ (r=ct, where t is the lookback time), the amplitude is (1.1 ± 0.2) × 10−6 GLyr−1 and the model is significant at the 4.2σ confidence level over the null model (Δα/α≡ 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in α. To the best of our knowledge, this result is not in conflict with any other observational or experimental result.
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spatial variation in the fine structure constant new results from vlt uves
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Julian A King, V V Flambaum, R F Carswell, J K Webb, M T Murphy, Matthew B Bainbridge, Michael R Wilczynska, Elliot F KochAbstract:(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current Laboratory Value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model [Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.
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keck constraints on a varying fine structure constant wavelength calibration errors
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Michael T Murphy, J K Webb, V V FlambaumAbstract:The Keck telescope's HIRES spectrograph has previously provided evidence for a smaller fine-structure constant, alpha, compared to the current Laboratory Value, in a sample of 143 quasar absorption systems: da/a=(-0.57+/-0.11)x10^{-5}. This was based on a variety of metal-ion transitions which, if alpha varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial to do so. It is also important to consider new possible instrumental systematic effects which may explain the Keck/HIRES results. Griest et al. (2009, arXiv:0904.4725v1) recently identified distortions in the echelle order wavelength scales of HIRES with typical amplitudes +/-250m/s. Here we investigate the effect such distortions may have had on the Keck/HIRES varying alpha results. We demonstrate that they cause a random effect on da/a from absorber to absorber because the systems are at different redshifts, placing the relevant absorption lines at different positions in different echelle orders. The typical magnitude of the effect on da/a is ~0.4x10^{-5} per absorber which, compared to the median error on da/a in the sample, ~1.9x10^{-5}, is relatively small. Consequently, the weighted mean Value changes by less than 0.05x10^{-5} if the corrections we calculate are applied. Nevertheless, we urge caution, particularly for analyses aiming to achieve high precision da/a measurements on individual systems or small samples, that a much more detailed understanding of such intra-order distortions and their dependence on observational parameters is important if they are to be avoided or modelled reliably. [Abridged]
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keck constraints on a varying fine structure constant wavelength calibration errors
Memorie della Societa Astronomica Italiana (Journal of the Italian Astronomical Society): incorporating proceedings Joint Discussion 9 the 27th IAU Ge, 2009Co-Authors: Michael T Murphy, J K Webb, V V FlambaumAbstract:The Keck telescope's High Resolution Spectrograph (HIRES) has previously provided evidence for a smaller fine-structure constant, α, compared to the current Laboratory Value, in a sample of 143 quasar absorption systems: Δα/α=(-0.57±0.11)×10 −5 . The analysis was based on a variety of metal-ion transitions which, if α varies, experience different relative velocity shifts. This result is yet to be robustly contradicted, or confirmed, by measurements on other telescopes and spectrographs; it remains crucial to do so. It is also important to consider new possible instrumental systematic effects which may explain the Keck/HIRES results. Griest et al. (2009) recently identified distortions in the echelle order wavelength scales of HIRES with typical amplitudes ±250 m s −1 . Here we investigate the effect such distortions may have had on the Keck/HIRES varying α results. Using a simple model of these intra-order distortions, we demonstrate that they cause a random effect on Δα/α from absorber to absorber because the systems are at different redshifts, placing the relevant absorption lines at different positions in different echelle orders. The typical magnitude of the effect on Δα/α is ~0.4×10 −5 for individual absorbers which, compared to the median error on Δα/α in the sample, ~1.9×10 −5 , is relatively small. Consequently, the weighted mean Value changes by less than 0.05×10 −5 if the corrections we calculate are applied. Unsurprisingly, with corrections this small, we do not find direct evidence that applying them is actually warranted. Nevertheless, we urge caution, particularly for analyses aiming to achieve high precision Δα/α measurements on individual systems or small samples, that a much more detailed understanding of such intra-order distortions and their dependence on observational parameters is important if they are to be avoided or modelled reliably.
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further evidence for a variable fine structure constant from keck hires qso absorption spectra
Monthly Notices of the Royal Astronomical Society, 2003Co-Authors: M T Murphy, J K Webb, V V FlambaumAbstract:We have previously presented evidence for a varying fine-str ucture constant, α, in two independent samples of Keck/HIRES QSO absorption spectra. Here we present a detailed manymultiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2 < zabs < 3.7. The results, with raw statistical errors, indicate a small er weighted mean α in the absorption clouds: �α/α = ( 0.574 ± 0.102) × 10 5 . All three samples separately yield consistent and significant Values of �α/α. The analyses of low-z (i.e. zabs < 1.8) and high-z systems rely on different ions and transitions with very different dependencies on α, yet they also give consistent results. We identify an addit ional source of random error in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical erro rs on �α/α for these systems gives our fiducial result, a weighted mean �α/α = ( 0.543 ± 0.116) × 10 5 , representing 4.7 σ evidence for a varying α. Assuming that �α/α = 0 at zabs = 0, the data marginally prefer a linear increase in α with time rather than a constant offset from the Laboratory Value: u α/α = (6.40 ± 1.35) × 10 16 yr 1 . The two-point correlation function for α is consistent with zero over 0.2‐13 Gpc comoving scales and the angular distribution of �α/α shows no significant dipolar anisotropy. We therefore have no eviden ce for spatial variations in �α/α. We extend our previous searches for possible systematic errors, giving detailed analyses of potential kinematic effects, line blending, wavelength miscalibration, spectrograph temperature variations, atmospheric dispersion and isotopic /hyperfine structure effects. The latter two are potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of indep endent QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.
