Multiwavelength observations of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330

We report on the X-ray and optical observation of the two unidentified EGRET sources 3EG J0616-3310 and 3EG J1249-8330. The X-ray coverage performed by the ESA space telescope XMM–Newton provided ∼150 X-ray sources within each of the two γ-ray error-circles. The optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2 m telescope have found no candidate counterpart for 125 of these X-ray sources. Among these, we have selected 9 sources with f _X/f _opt≥100, which we consider promising INS candidates.     

New-generation data acquisition and control system for continuum radio-astronomic observations with RATAN-600 radio telescope: Development,observations, and measurements

A new Data Acquisition and Control System for performing continuum radio-astronomical observations with the RATAN-600 radio telescope is presented. One of the “building blocks” of the system is the Embedded Radiometric Data Acquisition System (ER-DAS) developed at the RATAN-600. It is a measurement facility meant for digitizing and reducing radiometer signals and for transmitting the result of these operations via Ethernet networks. ER-DAS system is shown to have a low self-noise level and to lack 1/f-type noise. The measurement facility is shown to operate efficiently in radio-astronomical observations. Radiometric measurements of the parameters of high-sensitivity radiometers are illustrated in the case of the measurements of radiometer gain fluctuations.     

Spatial variations of the sodium/potassium ratio in Mercury’s exosphere uncovered by high-resolution spectroscopy

High-resolution spectroscopy of Mercury has been obtained with two different instruments in 2006: the EMMI instrument at the 3.6-m NTT telescope of ESO La Silla Chile and the ESPADON spectrograph at the 3.6-m CFHT telescope on top of Mauna Kea (Hawaii). The disk of the planet has been scanned for spatial variation of the exospheric species. The large spectral range and high resolution allow simultaneous measurements of the integrated column density of Na and K.We measure Na/K ratio between 80 and 400 with values between 60 and 90 when the telescope was pointed towards the subsolar region of Mercury’s disk and much larger value when we looked to other part of the exosphere. Moreover, we observed that the Na and K exospheres display very different spatial distributions. Even if these two species are probably ejected with very similar mechanisms from the surface, their differences in mass and sensitivity to solar pressure acceleration imply very different behavior in Mercury’s exosphere.     

Spectroscopy of Giants of the Sagittarius Dwarf Galaxy

In this paper we present the first results of the analysis of intermediate resolution (Δλ ～ 3.5 Å) spectra of giants of the Sagittarius dwarf galaxy acquired using the ESO NTT telescope. From the deep CCD photometry of Marconi et al. (1998a) we have selected a sample of giants representative of the metallicity spread suggested by the comparison of the colour-magnitude diagram of Sagittarius with those of galactic globular clusters. The spectra have been used to measure radial velocities, to confirm the membership to Sagittarius, and to provide a metallicity estimate by using spectral synthesis techniques. The analyzed stars show a spread in metallicities in the range ?1.0≤ [Fe/H]≤ +0.7, some 0.5 dex more metal-rich than the photometric estimates.     

Photographic and spectrographic observations with a reducing camera on the 61 cm NCU telescope

A Reducing Camera designed by Meinel has been constructed and tested on the 61 cm NCU Cassegrain telescope. The basic principle of RC is to reduce the reflector'sf/13.5 to the equivalentf/2.7 such that the Cassegrain focus image can be reduced on a 35 mm film with almost no loss in sky coverage and in resolution but the exposure time is reduced by a factor of 25. The camera is able to obtain stellar spectra. With a grism and a standard lens the dispersion is 450 Å mm^–1, which is comparable to that required for the MK classification. RC constructure and testing results are reported. The method of a wide field spectrograph and that of narrow band differential photography of RC are also discussed.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

The performance of the Apache Point Observatory 3.5 m telescope

The Astrophysical Research Consortium 3.5 m telescope facility on Apache Point (2800 m above sea level) near the National Solar Observatory in southern New Mexico is nearing completion. The telescope mount has been installed and testing and fabrication of remaining subassemblies are underway. Thef/1.75 lightweight honeycomb primary mirror was cast April 1988 by the Steward Observatory Mirror Laboratory and is currently being figured.The 3.5 m optical telescope is an altitude over azimuth mechanical structure with Ritchey-Chrétien optics. The lightweight (1800 kg) mirror leads to a mount weighting only 41000 kg; readily available rolling element bearings are used to achieve the necessary performance at low cost and without the heat dissipation of externally pressurized types. Drive torques are applied by DC servo-driven capstans. These are coupled by friction to large diameter drive disks on each axis. No gears are used. Position feedback comes from low cost incremental encoders, also capstan coupled.We have recently completed a series of measurements of the telescope mount. These measurements show that the telescope is very stiff; the lowest natural frequencies are about 7.2 Hz. Initial tracking performance is good and the mount shows high resistance to wind-induced vibration. Our experience during acceptance testing suggests that routine power spectral analysis of drive motor torque and other parameters could be an important tool in the early detection of failures.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Taiwan Oscillation Network

The Taiwan Oscillation Network (TON) is a ground-based network to measure solar intensity oscillations to study the internal structure of the Sun. K-line full-disk images of 1000 pixels diameter are taken at a rate of one image per minute. Such data would provide information onp-modes withl as high as 1000. The TON will consist of six identical telescope systems at proper longitudes around the world. Three telescope systems have been installed at Teide Observatory (Tenerife), Huairou Solar Observing Station (near Beijing), and Big Bear Solar Observatory (California). The telescopes at these three sites have been taking data simultaneously since October of 1994. Anl – v diagram derived from 512 images is included to show the quality of the data.     

Counts, Sizes and Colours of Faint Infrared-Selected Galaxies

Deep J- and K _s-band images covering a 5 × 5 arcmin area centred on the NTT Deep Field have been obtained during the Science Verification of SOFI at the NTT. These images were made available via the Web in early June, 1998. The preliminary results we have obtained by the analysis of these data are the following: (i) the counts continue to rise with no evidence of a turnover or of a flattening down to the limits of the survey (K _s = 22.5 and J = 24 mag); (ii) we find a slope d log(N)/dm≈ 0.37, in agreement with most of the faintest surveys but much steeper than the Hawaii survey; (iii) fainter than K _s ≈ 19and J ≈ 20 mag, the median J-K colour of galaxies shows a break in its reddening trend turning toward bluer colours; (iv) faint bluer galaxies also display a larger compactness index, and a smaller apparent size. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Enigmatic Behaviour of the Old Nova RR Pic

We report preliminary results of an observing run at the 1--m telescope at CTIO during which we followed RR Pic over several nights in February 2005. The resulting light curves show no sign of an eclipse. Apart from the 3.48 h period, which is usually interpreted as the orbital one, we find an additional period at P=3.78 h, which we interpret as the superhump period of the system.We furthermore present high–resolution Doppler maps in Hα, Hβ and He II, which we derived from observations at the NTT, La Silla in February 2004. They show strong variations in the emission distribution from one day to the next. While Hα and Hβ emission clearly show the accretion disc with some additional isolated sources, the He II emission is confined to an elongated region at low velocities.     

Optical layout of the T-170M space telescope

The optical layout of the T-170M telescope for observation of astronomical objects in the ultraviolet spectral range 0.115–0.35 μm from the spacecraft SPECTRUM-UV is described. The telescope represents a Ritchey-Chretien aplanat with an aperture 1.7 m in diameter, a relative hole of f/10, and a field of view of 0.5°. The spectrographs are designated for obtaining spectra of stars and spread objects with a resolution of 2000–50 000. It is planned to record direct images using two field cameras: a wide-angle (f/10) and a telefocus (f/75–f/100) camera. The tolerances for basic parameters and the characteristics of the optimal system of baffles and the optics control unit are given.     

Recent observations of high-degree solar p-mode oscillations at the Kitt Peak National Observatory

A brief summary is given of a program which is currently being carried out with the McMath telescope of the Kitt Peak National Observatory in order to study high-degree (l ≳ 150) solar p-mode oscillations. This program uses a 244 × 248 pixel CID camera and the main spectrograph of the McMath telescope to obtain velocity-time maps of the oscillations which can be converted into two-dimensional (k _h - ω) power spectra of the oscillations. Several different regions of the solar spectrum have been used in order to study the oscillations at different elevations in the solar atmosphere. The program concentrates on eastward- and westward-propagating sectoral harmonic waves so that measurements can be made of the absolute rotational velocities of the solar photospheric and shallow sub-photospheric layers. Some preliminary results from this program are now available. First, we have been unable to confirm the existence of a radial gradient in the equatorial rotational velocity as was previously suggested. Second, we have indeed been able to confirm the presence of p-mode waves in the solar chromosphere as was first suggested by Rhodes et al. (1977). Third, we have been able to demonstrate differences in photospheric and chromospheric power spectra.

     

RTS2: Lessons learned from a widely distributed telescope network

RTS2 (Remote Telescope System 2) is a highly modular open source telescope and observatory management software package. It evolved from RTS, which was developed in Python to control a telescope aimed at observing optical transients of γ ray burts. The development of a network system capable of operating robotic telescopes is both difficult and complicated. Along with continued software development one must be concerned with maintaining operations and obtaining results. This is a review of experiences gained building a network of robotic telescopes. It focuses on describing which issues are important during development of the robotic observatory software and requirements for future development of the RTS2 package. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hypersensitization of Kodak infrared plates: Results of some chemical methods and pre-exposure

Tests have been carried out on Kodak Spectroscopic Plates Type I-N, in order to find a treatment which could be easily applied to the infrared plates to be used with the Loiano 152 cm,f/8, Ritchey-Chrétien telescope. Different techniques have been tested, not only with the aim of achieving the higher speed gain, but also to obtain the better uniformity and reproducibility. Our results suggest that the advantages of preexposure techniques are underestimated in this respect. Furthermore, we find that blue and infrared preexposures (at 0.8 s) give different results, suggesting a different degree of dispersity in the latent image produced by pre-exposure in the two cases.Baths including both ammonia and Ag-compounds provide the higher speed gains, but the increment of the fog is often non-uniform and/or very high. The best results have been obtained with baths including AgNO₃ and AgCl. The rejuvenation process found by Sanduleak and the results obtained by Jenkins and Farnell on the reversibility of the gains due to silver-nitrate baths have been confirmed.     

Fourier analysis of the light curves of eclipsing variables,XV

A new general expression for the theoretical momentsA _2m of the light curves of eclipsing systems has been presented in the form of infinite series expansion. In this expansion, the terms have been given as the product of two different polynomials which satisfy certain three-term recursion formulae, and the coefficients diminish rapidly with increasing number of terms. Thus, the numerical values of the theoretical momentsA _2m can be generated recursively up to four significant figures for any given set of eclipse elements. This can be utilized to solve the eclipse elements in two ways: (i) with an indirect method (for the procedures see Paper XIV, Kopal and Demircan, 1978), (ii) with a direct method as minimization to the observational momentsA _2m (area fitting). The procedures given in Paper XIV for obtaining the elements of any eclipsing system consisting of spherical stars have been automated by making use of the new expression for the momentsA _2m of the light curves. The theoretical functionsf ₀,f ₂,f ₄,f ₆,g ₂ andg ₄ which are the functions ofa andc ₀, have been used to solve the eclipse elements from the observed photometric data. The closed-form expressions for the functionsf ₂,f ₄ andf ₆ have also been derived (Section 3) in terms of Kopal'sI-integrals.The automated methods for obtaining the eclipse elements from one minimum alone have been tested on the light curves of YZ (21) Cassiopeiae under the spherical model assumptions. The results of these applications will be given in Section 5 which follows a brief introduction to the procedure we followed.     

The Galileo Italian National Telescope and its Instrumentation

The main features of the 3.5m Telescopio Nazionale GALILEO (TNG) have been derived from those of the ESO NTT, although with modifications in several areas, as described e.g. in Barbieri et al., 1994. The site of the TNG is the Observatorio del Roque de los Muchachos, in the Canary Island of La Palma. Construction activities, started in 1993, are nearing completion. The telescope structure, after testing in the Ansaldo factory near Milano, has been disassembled and is gradually being transported and installed on site, in parallel with the rotating dome. The three main mirrors, figured by ZEISS, will be transported in spring '96 to the WHT plant at the Roque for aluminisation before installation on the telescope.Three major subsystems still undergo intensive activity in Italy, namely testing of the M2 and M3 units, testing of the operational version of the control hardware and software, and construction of the two Rotator Adapters (R/A) for the Nasmyth foci.First light instruments are also being built. Nasmyth Arm A is reserved for the imaging section, composed by a visual camera, a near-IR camera, plus a common adaptive optics module. On arm B, a faint object spectrograph with long slit, atmospheric dispersion corrector, multiobject and imaging capabilities, will be mounted. A fixed high resolution spectrograph with optical derotation is also being designed.Attention has already been given to the archive of the data.It is planned to have first light at the end of 1996, and to start regular scientific operations after an adequate period of debugging and commissioning.     

Photometry of groups of galaxies. II. The NGC 972 group

A nearby group of galaxies, centered at the spiral galaxy NGC 972 and conspicuously rich in faint dwarf spheroidal galaxies, has been investigated photometrically on the B and V plates, obtained with the Tautenburg 2m Schmidt telescope. For ten certain and probable group members the equivalent B and V brightness profiles have been extracted. Integrated magnitudes and mean colours of faint group members have been estimated. Typically, the dwarfs show a “subexponential” (i.e. a convex curvature over the linear radius) surface brightness profile and often a central excess. Their equivalent profiles are reasonably well fitted by modified isothermal (King) models.     

The XMM-Newton Bright Serendipitous Survey: First Extragalactic Results

We present here some initial results from the ongoing XMM-Newton bright serendipitous survey. The survey is aimed at selecting and spectroscopically identifying a large and statistically representative sample of bright (f _x ≳ 7× 10⁻¹⁴ c.g.s) serendipitous X-ray sources in the 0.5–4.5 keV energy band (BSS) and a complementary (smaller) sample in the 4.5–7.5 keV energy band (HBSS). The work is partly based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributors directly founded by ESA member states and the USA(NASA) and on observations collected at TNG. The TNG telescope is operated on the island of La Palma by the Centro Galileo Galilei of the INAF in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias. On behalf of the XMM-Newton Survey Science Center.     

An image drift compensation system for a solar pointed space telescope

An Image Drift Compensation System has been designed for a solar pointed space borne telescope and has performed successfully on two sounding rocket flights, yielding new scientific results. The system employs limb-sensing photodiodes at the telescope focal plane and provides drift compensation to better than 0.1 arc sec. A variation of the system will be used on the Shuttle/Spacelab 2 flight of the High Resolution Telescope and Spectrograph (HRTS) Instrument.Originally submitted to the journalSpace Science Instrumentation.     

More on the narrowing of impact broadened radio recombination lines at high principal quantum number

Recently Alexander and Gulyaev have suggested that the apparent decrease in impact broadening of radio recombination lines seen at high principal quantum number n may be a product of the data reduction process, possibly resulting from the presence of noise on the telescope spectra that is not present on the calculated comparison spectra. This is an interesting proposal. However, there are serious problems with their analysis that need to be pointed out. Perhaps the most important of these is the fact that for principal quantum numbers below n=200, where the widths are not in question, their processed generated profile widths do not fit the widths of the processed lines obtained at the telescope. After processing, the halfwidths of the generated and telescope profiles must agree below n=200 if we are to believe that the processed generated linewidths above n=200 are meaningful. Theirs do not. Furthermore, we find that after applying the linewidth reduction factors found by Alexander and Gulyaev for their noise added profiles to our generated profiles to simulate their noise adding effect, the processed widths we obtain still do not come close to explaining the narrowing seen in the telescope lines for n values in the range 200<n<250. It is concluded that what is needed to solve this mystery is a completely new approach using a different observing technique instead of simply a further manipulation of the frequency-switched data.     

Evening and morning twilight airglow emissions of 5577 Å and 5893 Å lines at Calcutta and Allahabad and their correlation with flare index

Evening and morning twilight enhancements of 5577 Å and 5893 Å lines were observed by Dunn-Manring type photometer at Calcutta during the period 1983–1985 and that of 5577 Å have been collected from Allahabad observatory. The following paper presents the correlation between the enhanced intensity of airglow lines (A _G ) and solar flare index (I _f ) which is calculated considering all the flares which occurred 24 hr before the times of occurrence of enhancements. It is observed that the intensity of airglow lines varies with the flare index in an oscillatory manner upto a certain limiting value ofI _f . Afterwards intensity of both lines increases with the increase ofI _f . The nature of variation is the same for both sunspot maximum and minimum periods. A possible explanation of such type of variation has also been invoked.