| 1. |
- Davies, Melvyn B, et al.
(author)
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The MODEST questions: Challenges and future directions in stellar cluster research
- 2006
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In: New Astronomy. - : Elsevier BV. - 1384-1092 .- 1384-1076. ; 12:3, s. 201-214
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Research review (peer-reviewed)abstract
- We present a review of some of the current major challenges in stellar cluster research, including young clusters, globular clusters, and galactic nuclei. Topics considered include: primordial mass segregation and runaway mergers, expulsion of gas from clusters, the production of stellar exotica seen in some clusters (e.g., blue stragglers and extreme horizontal-branch stars), binary populations within clusters, the black-hole population within stellar clusters, the final parsec problem, stellar dynamics around a massive black hole, and stellar collisions. The Modest Questions posed here are the outcome of discussions which took place at the Modest-6A workshop held in Lund, Sweden, in December, 2005. Modest-6A was organised as part of the activities of the Modest Collaboration (see www.manybody.org for further details).
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| 2. |
- Johansson, Sveneric, et al.
(author)
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Possibility of measuring the width of narrow FeII astrophysical laser lines in the vicinity of eta Carinae by means of Brown-Twiss-Townes heterodyne correlation interferometry
- 2005
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In: New Astronomy. - : Elsevier BV. - 1384-1092 .- 1384-1076. ; 10:5, s. 361-369
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Journal article (peer-reviewed)abstract
- We consider the possibility of measuring the true width of the narrow Fe II optical lines observed in spectra of the Weigelt blobs in the vicinity of eta Carinae. The lines originate as a result of stimulated amplification of spontaneous emission of radiation in quantum transitions between energy levels showing inverted population [Johansson, S., Letokhov, V., 2002. JETP Lett. 75 (10) 495; Johansson, S., Letokhov, V., 2003. Phys. Rev. Lett. 90 (1) 01110-1; Johansson, S., Letokhov, V., 2004. A&A 428, 497]. The lines should have a subDoppler spectral width of 30-100 MHz, depending on the geometry of the lasing volume. To make measurements with a spectral resolution of R > 10(7) and an angular resolution better than 0.1 '', we suggest the use of the Brown-Twiss-Townes optical heterodyne intensity correlation interferometry. The estimates made of the SIN ratio for the optical heterodyne astrophysical laser experiment imply that it is feasible.
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| 3. |
- Thompson, Rodger I., et al.
(author)
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Alternative data reduction procedures for UVES: Wavelength calibration and spectrum addition
- 2009
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In: New Astronomy. - : Elsevier BV. - 1384-1076 .- 1384-1092. ; 14:4, s. 379-390
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Journal article (peer-reviewed)abstract
- This paper addresses alternative procedures to the ESO supplied pipeline procedures for the reduction of UVES spectra of two quasar spectra to determine the value of the fundamental constant μ=Mp/Me at early times in the universe. The procedures utilize intermediate product images and spectra produced by the pipeline with alternative wavelength calibration and spectrum addition methods. Spectroscopic studies that require extreme wavelength precision need customized wavelength calibration procedures beyond that usually supplied by the standard data reduction pipelines. An example of such studies is the measurement of the values of the fundamental constants at early times in the universe. This article describes a wavelength calibration procedure for the UV–visual Echelle spectrometer on the very large telescope, however, it can be extended to other spectrometers as well. The procedure described here provides relative wavelength precision of better than 3×10-7 for the long-slit Thorium–Argon calibration lamp exposures. The gain in precision over the pipeline wavelength calibration is almost entirely due to a more exclusive selection of Th/Ar calibration lines.
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