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Optical Telescope (optical + telescope)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

GLITP optical monitoring of QSO 0957+561: VR light curves and variability

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003
A. Ullán
ABSTRACT The Gravitational Lenses International Time Project (GLITP) collaboration observed the first gravitational lens system (QSO 0957+561) from 2000 February 3 to March 31. The daily VR observations were made with the 2.56-m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma, Spain. We have derived detailed and robust VR light curves of the two components Q0957+561A and Q0957+561B. In spite of the excellent sampling rate, we have not found evidence in favour of true daily variability. With respect to variability on time-scales of several weeks, we measure VR gradients of about ,0.8 mmag d,1 in Q0957+561A and +0.3 mmag d,1 in Q0957+561B. The gradients are very probably originated in the far source. Thus, adopting this reasonable hypothesis (intrinsic variability), we compare them to the expected gradients during the evolution of a compact supernova remnant at the redshift of the source quasar. The starburst scenario is roughly consistent with some former events, but the new gradients do not seem to be caused by supernova remnant activity. [source]

New pulsating white dwarfs in cataclysmic variables,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006
R. Nilsson
ABSTRACT The number of discovered non-radially pulsating white dwarfs (WDs) in cataclysmic variables (CVs) is increasing rapidly by the aid of the Sloan Digital Sky Survey (SDSS). We performed photometric observations of two additional objects, SDSS J133941.11+484727.5 (SDSS 1339), independently discovered as a pulsator by Gänsicke et al., and SDSS J151413.72+454911.9, which we identified as a CV/ZZ Ceti hybrid. In this Letter we present the results of the remote observations of these targets performed with the Nordic Optical Telescope (NOT) during the Nordic,Baltic Research School at Mol,tai Observatory, and follow-up observations executed by NOT in service mode. We also present three candidates we found to be non-pulsating. The results of our observations show that the main pulsation frequencies agree with those found in previous CV/ZZ Ceti hybrids, but specifically for SDSS 1339 the principal period differs slightly between individual observations and also from the recent independent observation by Gänsicke et al. Analysis of SDSS colour data for the small sample of pulsating and non-pulsating CV/ZZ Ceti hybrids found so far seems to indicate that the r,i colour could be a good marker for the instability strip of this class of pulsating WDs. [source]

Measurements of mean longitudinal magnetic fields in the Of?p stars HD 108 and HD 191612,

ASTRONOMISCHE NACHRICHTEN, Issue 8 2010
S. Hubrig
Abstract Using polarimetric spectra obtained with the SOFIN spectrograph installed at the Nordic Optical Telescope, we detect a longitudinal magnetic field ,Bz, = ,168±35 G in the Of?p star HD 108. This result is in agreement with the longitudinal magnetic field measurement of the order of ,150 G recently reported by the MiMeS team. The measurement of the longitudinal magnetic field in the Of?p star HD 191612 results in ,Bz, = +450±153 G. The only previously published magnetic field measurement for this star showed a negative longitudinal magnetic field ,Bz, = ,220±38 G, indicating a change of polarity over ,100 days. Further, we report the detection of distinct Zeeman features in the narrow Ca II and Na I doublet lines for both Of?p stars, hinting at the possible presence of material around these stars. The origin of these features is not yet clear and more work is needed to investigate how magnetic fields interact with stellar wind dynamics (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Review of Hinode results

ASTRONOMISCHE NACHRICHTEN, Issue 6 2010
Y. Suematsu
Abstract Hinode is an observatory-style satellite, carrying three advanced instruments being designed and built to work together to explore the physical coupling between the photosphere and the upper layers for understanding the mechanism of dynam- ics and heating. The three instruments aboard are the Solar Optical Telescope (SOT), which can provide high-precision photometric and polarimetric data of the lower atmosphere in the visible light (388,668 nm) with a spatial resolution of 0.2,0.3 arcseconds, the X-Ray Telescope (XRT) which takes a wide field of full sun coverage X-ray images being capable of diagnosing the physical condition of coronal plasmas, and the EUV Imaging Spectrometer (EIS) which observes the upper transition region and coronal emission lines in the wavelength ranges of 17,21 nm and 25,29 nm. Since first-light observations in the end of October 2006, Hinode has been continuously providing unprecedented high-quality solar data. We will present some new findings of the sun with Hinode, focusing on those from SOT (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]