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Replication Data for: Towards 10 cm/s radial velocity accuracy using a Fourier transform spectrometer
No full textFTS-Spectra, extracted radial velocities, temperature data as well as code used in evaluation for the aforementioned paper
Towards 10 cm/s radial velocity accuracy on the Sun using a Fourier transform spectrometer
Full text linkThe IAG solar observatory is producing high-fidelity, ultra-high-resolution
spectra (R>500000) of the spatially resolved surface of the Sun using a Fourier
Transform spectrometer (FTS). The radial velocity (RV) calibration of these
spectra is currently performed using absorption lines from Earth's atmosphere,
limiting the precision and accuracy. To improve the frequency calibration
precision and accuracy we plan to use a Fabry-Perot etalon (FP) setup that is
an evolution of the CARMENES FP design and an iodine cell in combination. To
create an accurate wavelength solution, the iodine cell is measured in parallel
with the FP. The FP can then be used to transfer the accurate wavelength
solution provided by the iodine via simultaneous calibration of solar
observations. To verify the stability and precision of the FTS we perform
parallel measurements of the FP and an iodine cell. The measurements show an
intrinsic stability of the FTS of a level of 1 m/s over 90 hours. The
difference between the FP RVs and the iodine cell RVs show no significant
trends during the same time span. The RMS of the RV difference between FP and
iodine cell is 10.7 cm/s, which can be largely attributed to the intrinsic RV
precisions of the iodine cell and the FP (10.2 cm/s and 1.0 cm/s,
respectively). This shows that we can calibrate the FTS to a level of 10 cm/s,
competitive with current state-of-the-art precision RV instruments. Based on
these results we argue that the spectrum of iodine can be used as an absolute
reference to reach an RV accuracy of 10 cm/s.Comment: 13 pages, 9 figures, to be published in Journal of Astronomical
Telescopes, Instruments, and Systems (JATIS
Phase-correction algorithm for Fourier transform spectroscopy of a laser frequency comb
No full textFourier-transform spectrographs (FTS) are among the most important tools for high-resolution spectroscopy over a broad spectral bandwidth. Usually, the frequency axis of an FTS is calibrated with relatively few atomic lines and an absolute wavelength reference, which is often a stabilized He–Ne laser. Normally, the phase-spectrum is measured using a continuous light source to enable phase correction. Laser frequency combs (LFC) provide a much higher stability. Their spectrum consists of closely spaced narrow lines, which are very well suited for the characterization and calibration of an FTS. Due to the pulsed nature of the LFC, however, the phase spectrum cannot be measured in the same way as for continuous light sources. We show how a proper phase spectrum from an FTS measurement of an LFC can be obtained and how the strongly varying phase spectrum noise can be filtered. We analyzed a narrow spectral band 10.200–12.500 cm−1 in which we detected ∼60.000 lines with sufficient intensity. Only with an accurate truncation of the interferogram and a proper shifting, the complex structure of the phase spectrum is revealed. For phase filtering, we adapted Mertz’s algorithm and show how the instrumental line shape is significantly improved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Data analysis methods for laser frequency comb line position measurements with a Fourier transform spectrograph
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