Fibre optics at the 4.2 m telescope (WHT)

We summarize some of the work on optical fibres carried out at the 4.2 m (WHT) telescope. We will briefly describe the Fibre Linked Experimental spectrograph.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Two-dimensional optical spectroscopy of ULIRG's: comparison with HST imaging

We present preliminary results of our programme aimed at the study of asample of ULIRGs on the basis of two-dimensional (integral field)optical spectroscopy and multi-frequency high spatial resolution HSTimaging. In particular, we show here results on Mrk 273 and IRAS 12112+0305recently obtained with the INTEGRAL system at the 4.2 m WHT. Abrief comparison with the HST images is also made.     

Properties of optical fibres at cryogenic temperatures

A perhaps surprising property of optical fibres is that they remain flexible at cryogenic temperatures. This implies that they may be used for multiple-object and integral field spectroscopy in the thermal infrared in cryogenic instrumentation. In this paper the results of performance tests of optical fibres (silica and zirconium fluoride) at cryogenic temperatures are presented. By mounting the fibres in glass tubes with the appropriate adhesive, it was found that only negligible focal ratio degradation occurs when the fibre is cooled to 77 K.     

TIGRE: A new robotic spectroscopy telescope at Guanajuato,Mexico

TIGRE is a new robotic spectroscopy telescope located in central Mexico at the La Luz Observatory of the University of Guanajuato. The 1.2 m telescope is fiber‐coupled to an ´echelle spectrograph with a spectral resolving power exceeding 20000 over most of the covered spectral range between 3800 Å and 8800 Å, with a small gap of 130 Å around 5800 Å. TIGRE operates robotically, i.e. it (normally) carries out all observations without any human intervention, including, in particular, the target selection in any given observing night. In this paper we describe the properties of the TIGRE instrumentation and its technical realization, as well as our first operational experience with the performance and efficiency of the overall system. Finally, we present some examples of recent TIGRE observations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Two-dimensional spectroscopy of double-barred galaxies

We describe the results of our spectroscopy for a sample of barred galaxies whose inner regions exhibit an isophotal twist commonly interpreted as a secondary bar. The line-of-sight velocity fields of the ionized gas and stars and the light-of-sight velocity dispersion fields of the stars were constructed from two-dimensional spectroscopy with the 6-m Special Astrophysical Observatory telescope. We detected various types of noncircular motions of ionized gas: radial flows within large-scale bars, counterrotation of the gas and stars at the center of NGC 3945, a polar gaseous disk in NGC 5850, etc. Our analysis of the optical and near-infrared galaxy images (both ground-based and those from the Hubble Space Telescope) revealed circumnuclear minispirals in five objects. The presence of an inner (secondary) bar in the galaxy images is shown to have no effect on the circumnuclear kinematics of the gas and stars. Thus, contrary to popular belief, the secondary bar is not a dynamically decoupled galactic structure. We conclude that the so-called double-barred galaxies are not a separate type of galaxy but are a combination of objects with distinctly different morphologies of their circumnuclear regions.     

HERMES at Mercator,competitive high‐resolution spectroscopy with a small telescope

HERMES, a fibre‐fed high‐resolution (R = 85000) échelle spectrograph with good stability and excellent throughput, is the work‐horse instrument of the 1.2‐m Mercator telescope on La Palma. HERMES targets building up time series of high‐quality data of variable stellar phenomena, mainly for asteroseismology and binary‐evolution research. In this paper we present the HERMES project and discuss the instrument design, performance, and a future upgrade. We also present some results of the first four years of HERMES observations. We illustrate the value of small telescopes, equipped with efficient instrumentation, for high‐resolution spectroscopy. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Search for fast optical activity of SGR 1806-20 at the SAO RAS 6-m telescope

The region of SGR 1806-20 localization was observed during its gamma-ray activity in 2001. The observations have been performed on the 6-meter telescope of the Special Astrophysical Observatory, using the Panoramic Photometer-Polarimeter (PPP). The search for variability was performed on the 10⁻⁶–10 s time scale, and its results were compared to the properties of corresponding X-ray flares. This work has been supported by the Russian Foundation for Basic Research (grant No 04-02-17555), Russian Academy of Sciences (program “Evolution of Stars and Galaxies”), and by the Russian Science Support Foundation. The authors would also like to thank the anonymous referee for his/her valuable comments.     

A discussion on the maximum aperture of a ground-based optical telescope

Because of the limitations both from the slit width and the slit length of the spectrograph used in high resolution work, the efficiency of a telescope, with an aperture between D₀ = 9m and D′₀ = 55m, will be no better than that of a telescope with aperture D₀. D₀ can be identified as the maximum aperture of a ground-based telescope.     

Exact optics: a unification of optical telescope design

A strong emission line at 2.8935 μm discovered by Rubin et al. in an ISO SWS02 spectrum of the Orion Nebula is identified as the     multiplet of O  i . Line formation is due to de-excitation cascades following UV-pumping of high ³S^o and ³D^o terms and occurs in the O  i zone immediately behind the hydrogen ionization front. This cascade mechanism also accounts for permitted O  i triplet lines in the optical spectrum of the Nebula, as shown by Grandi. An escape probability treatment of the O  i cascades accounts for the strength of the λ 2.89-μm line and suggests interesting diagnostic possibilities for the optical lines.     

Stokes polarimetry at the Kodaikanal tower tunnel telescope

A Stokes Polarimeter has been developed using a masked CCD arrangement for the measurement of the vector magnetic field of sunspots. Charge shifting within the CCD is used to record near simultaneous orthogonal polarisation. The testing of the Stokes Polarimeter and the behavior of the integrated system combined with the Kodaikanal tower tunnel telescope will be discussed.     

The optical reflector system for the CANGAROO-II imaging atmospheric Cherenkov telescope

A new imaging atmospheric Cherenkov telescope with a light-weight reflector has been constructed. Light, robust, and durable mirror facets of containing carbon fiber reinforced plastic laminates were developed for the telescope. The reflector has a parabolic shape (f/1.1) with a 30 m² surface area, which consists of 60 spherical mirror facets. The image size of each mirror facet is 0°.08 (FWHM) on average. The attitude of each facet can be adjusted by stepping motors. After the first in situ adjustment, a point image of about 0°.14 (FWHM) over 3° field of view was obtained. The effect of gravitational load on the optical system was confirmed to be negligible at the focal plane. The telescope has been in operation with an energy threshold for γ-rays of 300 GeV since May 1999.     

Two-dimensional high-resolution spectroscopy of quiet regions on the sun

In this communication we briefly review the content of Cephei pulsating stars in young open clusters. The actual metallicity differences between clusters are suggested to be detectable as variations of the location of these stars in the photometric diagrams. We make a quantitative estimate of these differences and comment on the connections with the existence and possible determination of a metallicity gradient in the galactic plane.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Observations of the optical afterglow from GRB 060526 with the RTT-150 telescope

Multicolor photometric observations of the optical afterglow from GRB 060526 with the Russian-Turkish 1.5-m RTT-150 telescope (Mount Bakyrlytepe, Turkey) are presented. The afterglow light curve was measured in detail starting from about 5 h after the GRB and over five ensuing nights. In addition, upper limits were obtained on the rapid variability of the afterglow on the first night of observations and the history of afterglow color variations was measured in detail. In the time interval from 6 to 16 h after the burst, the flux gradually decreased approximately as a power law with a slope of ?1.14 ± 0.02. Subsequently, variability was observed on a time scale δt < t and the afterglow began to decay much faster. The afterglow color was approximately constant (V?R ≈ 0.5) throughout the observations, despite the flux variability. Variability time scales up to δt/t ≈ 0.0055 were observed at ΔF _ν/F _ν ≈ 0.3, which violates many constraints on the variability of the observed emission from an ultrarelativistic jet obtained by Ioka et al. (2005). We suggest explaining this variability by the fact that the shell motion is no longer ultrarelativistic at this time.     

Calibration of X-ray telescope prototypes at PANTER

We report on a ground X-ray calibration of two X-ray telescope prototypes at the PANTER X-ray Test Facility, operated by the Max-Planck-Institute for Extraterrestrial Physics, in Neuried, Germany.The X-ray telescope prototypes were developed by the Institute of Precision Optical Engineering(IPOE)of Tongji University, in a conical Wolter-I configuration, using thermal glass slumping technology.Prototype #1 with three layers and Prototype #2 with 21 layers were tested to assess the prototypes' onaxis imaging performance. The measurement of Prototype #1 indicates a Half Power Diameter(HPD) of 82′′ at 1.49 keV. As for Prototype #2, we performed more comprehensive measurements of on-axis angular resolution and effective area at several energies ranging from 0.5–10 keV. The HPD and effective area are111′′ and 39 cm~2 at 1.49 keV, respectively, at which energy the on-axis performance of the prototypes is our greatest concern.     

An X-ray telescope sensitive at high energies

A telescope is described which is capable of producing images of point sources of X-rays without recourse to reflection optics. A mathematical approach to the operation and to the signalto-noise properties of the telescope is presented. This is followed by several examples of its response and a discussion of detectors that could be used with the device.     

Interference-mitigation measures at RATAN-600 radio telescope

We report an analysis of the electromagnetic situation at RATAN-600 radio telescope over the 30-year period of operation of the complex of continuum radiometers. We analyze practical methods for mitigating radio interference ranging from the use of anti-interference adapters to incorporating fast digital signal processors into the standard data acquisition system.     

Affordable échelle spectroscopy with a 60 cm telescope

A new fiber‐fed spectrograph was installed at the 60 cm telescope of the Stará Lesná Observatory. The article presents tests of its performance (spectral resolution, signal‐to‐noise ratio, radial‐velocity stability) and reports observations of selected variable stars and exoplanet host stars. First test observations show that the spectrograph is an ideal tool to observe bright eclipsing and spectroscopic binaries but also symbiotic and nova‐like stars. The radial‐velocity stability (60–80 m s^–1) is sufficient to study spectroscopic binaries and to detect easily the orbital motion of hot‐Jupiter extrasolar planets around bright stars. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)