It is now evident that the exceptional seeing at Dome C will allow, in the next years, to pursue astronomical programs with conditions better than at any other observatory in the world, and very close to space experiments. Considering a new type of wide-field telescope, particular astronomical programs could be well optimized for observations at Dome C such as surveys for the discovery and follow up of near-Earth asteroids, search for extra-solar planets using transit or micro-lensing events, and stellar luminosity variations. We propose to build a 1.5-2 m class three-reflect ions telescope, with 1-1.5 degree FOV, four times shorter than an equivalent Schmidt telescope, and providing a flat field without requiring a triplet- or quadruplet-lens corrector since its design is anastigmatic. We present the preliminary optical tests of such designs: MINITRUST 1 and 2 are two 45 cm identical prototypes based in France and Italy, and manufactured using active optics techniques.

We present a project for a wide–field, compact telescope that has been deisgned for observation in difficult sites, such as in the Antacrtic Plateau. The basic optics is an F/3 two-mirror system (2MTRT), in which the primary acts as 1st and 3rd reflecting surface. The Amoretti design provides a corrected and unvignetted 2◦ FOV and planarity of the focal plane. Three 2MTRT prototypes are described. We propose to put a robotic ∼60 cm 2MTRT au Dome C with the following main aims: discovery and tracking potentially hazarduous NEOs, asteroseimsological researchs of rich stellar fields, identification of GRBs.

The first prototype of a Three Reflection Telescope (TRT), designed at the Istituto di Astrofisica Spaziale (IAS-CNR), 30 cm diameter primary mirror, F/3, 2x2 degrees FOV, has been realized. The two mirrors, that were obtained with traditional artisan methods, have been evaluated with simple optical devices and with other physical measurement instruments. They have been mounted in an especially designed housing and roughly lined-up. Using an old German mount, refurbished for this purpose. we have taken, on 35 mm colour film, some astronomical fields and digitized them in 3072X2048-24 bits RGB pixels, and converted to 8 bits B&W images. Later, a thermo-electric cooled 2x2 k pixels CCD camera, especially developed for astronomical purposes, much more sophisticated than former units build at OAR, was adapted on the TRT prototype focal plane, leading to 2X2 k-16 bits images. Here we show some results of their analysis.

MART-LIME is a coded mask imaging hard X-Ray telescope to be flown onboard the international SPECTRUM RG observatory in early 1996. This instrument, the heart of which is a high-pressure proportional counter sensitive to the 5—150 keV energy range, will be characterised by a limiting sensitivity of about 1 milliCrab for a 105 s observation period. The imaging capability of MART-LIME is provided by a coded-mask aperture system, used in conjunction with the position sensitive detector. The basic pattern of the square coded aperture is a 71 x 73 URA mask (twin prime). This is surrounded by an outer frame comprising 17 and 16 pixels, respectively, on adjacent sides, giving a mask of 105 x 105 pixels in total. With this configuration, a fully coded field-of-view of 5.2° x 5.2° is obtained, whilst a partially coded field-of-view is achieved up to 6°, the acceptance angle of the ferrite collimator. The basic concept of the MART-LIME telescope is presented.

Results of a timing analysis of the Crab Pulsar and Cygnus X-l are presented. These two strong Galactic sources were observed on 1985 August 5 with the POKER experiment in the energy range 15-130 keV. The spectral behavior, showing a canonical spectrum for the Crab and a low emission state for Cyg X-l, has already been reported in Ubertini et al. (1991a).The phase-averaged Crab pulsar emission is well represented by a power law of photon index Gamma = 2.06 and a 30 keV intensity of 1.04 x 10(-3) ph cm(-2) s(-1) keV(-1). The pulsar light curve shows a wide first peak (2.4 ms FWHM) if compared with similar high statistics observations in the same energy range.For Cyg X-1 we find no indication of flaring activity nor any other strong time variability in our observation. Nevertheless, the 15-100 keV data are inconsistent with steady state emission at a statistical confidence level greater than 99%.Our data also confirm the presence of the recently reported quasi-periodic oscillations (QPO), showing different frequencies at different times and centered in our observation at 0.013 Hz and 0.040 Hz and modulating a few percent of the total flux.An upper limit of 24% on chaotic variability at 0.24-14 Hz is also set.

IAS, a CNR institute for space research in Astrophysics, in collaboration with IKI on their invitation, has developed, and is now under building, an X-Ray Imaging and Spectroscopic telescope as the high energy instrument on board the Observatory Spectrum X-Gamma. The scientific aim of this instrument, named MART-LIME, will be the detailed study of X-Ray sources emitting in the energy range 5 - 150 keV. The MART-LIME telescope is a follow up in a series of X-Ray detectors that have been developed, built at IAS and flown on board stratospheric balloons. It consists of a high pressure gas operated multiwire proportional counter with bidimensional spectral resolution coupled with a coded mask placed at 2.3 meter.

The source GRS 1758-258, lying 40' away from GX 5-1 was first detected by the two instruments ART-P and SIGMA on board the GRANAT satellite. The source then was thought to be responsible for the hard X-ray flux previously ascribed to the bright quasi periodic source GX 5-1. These two sources were within the 1.9-degrees field of view of the POKER instrument during an extended observation of the Galactic Center region on May 17, 1989. The POKER instrument, consisting of 3 Multiwire Proportional Counters of geometric area 8000 cm2, collected data from the sources for 1300 s. Spectral behaviour of the high energy source is discussed and comparison is made with previous data reported by TTM, Spacelab 2 and GRANAT.

We present a simple X-ray experiment, named SIXE (Spanish Italian X-ray Experiment). This experiment was born as a subsystem of the experiment MAEX (Mision Astronomica en el Extremo ultravioleta y en rayos X) in order to fly onboard the first platform of the Spanish space program MINISAT, managed by INTA (Instituto Nacional de Tecnica Aeroespacial), within 1995, with an expected operational life-time of two years. Since the experiment MAEX has been withdrawn by INTA on February 1992, SIXE could become the unique payload of the first platform of the Spanish MINISAT program. For this reason, its geometrical area can be as large as almost-equal-to 3200 cm2. SIXE is formed by four identical gas filled MWPC in the energy range almost-equal-to 3 - 50 keV. The continuum sensitivity of SIXE, for a 3sigma detection in 10(5) s, is almost-equal-to 3 x 10(-6) photons/cm2.s.keV. The main scientific goals of SIXE are the study of the short and long term spectral and intensity variabilities of few selected X-ray sources - which are representative of homogeneous classes of cosmic sources - and the behaviour of the eventual Fe lines. The perspectives of SIXE are unique for this generation of X-ray experiments, since no one is dedicated to a continuous long term monitoring of X-ray sources.

MART-LIME is a coded mask imaging telescope to be flown onboard the international observatory SPECTRUM X-(Gamma) in 1995. This high-energy instrument, the center of which is a high-pressure proportional counter sensitive to the 5 - 150 keV energy range, will be characterized by a limiting sensitivity of about 1 milliCrab for a 105 s observation period. The imaging capability of the instrument is provided by a coded-mask aperture system, used in conjunction with a position sensitive detector. The basic pattern of the coded aperture is a 71 X 73 URA mask (twin prime). With the addition of an outer frame comprising 18 pixels on each side, a fully coded field-of-view of 2.6 degree(s) X 2.6 degree(s) is obtained, while a partially coded field-of-view is achieved up to 6 degree(s). Test procedures used to determine the performance of the MART-LIME detector are discussed. Results showing the spectroscopic capabilities of a Laboratory-Prototype detector are presented.

We report the first evidence of strong flux variability in the hard X-ray range from IE 1740.7-2942 obtained during an observation of the region on 1989 May 17. The measurement was performed with a high-sensitivity array of multiwire proportional counter operative in the energy range 15-180 keV, and with a field of view of 1.9-degrees FWHM. The balloon-borne observation, lasting for 8100 s including background data, was pointed on 1E 1740.7-2942 as the reference source, following the suggestion by Skinner et al. and Cook et al. that this object was the point source responsible for the high-energy emission from the Galactic center. Our data, when compared with previous data in the same energy range obtained either by narrow field of view or imaging instruments, imply a flux variability of a factor of 3 at 40 keV and 2.5 at 100 keV. The spectrum on 1989 May 17 can be described by a single power law with spectral index of 1.95 and intensity of 2.85 x 10(-4) cm-2 s-1 keV-1 at 30 keV. Because of the 1.9-degrees field of view, we cannot rule out a low-energy contribution due to the presence of the well-known source A1742-2942 and the new GRANAT sources identified in the 4.3-degrees x 3.7-degrees ART-P images of the Galactic center in the energy range 3-17 keV. Since the newly discovered very hard sources GRS 1758-258 and GX 1 + 4 were not within the instrument's field of view during our observation, we can assume the low detected value of hard X-ray emission as evidence of flux variability of 1E 1740.7-2942. The detection of 1E 1740.7-2942 in a condition very close to the low state of Cyg X1 confirms the similarity between these two sources, thus supporting the black hole nature of the Galactic center high-energy emitter.

The region containing the galactic source Scorpius X-1 was studied on 1989 May 17 in the energy range 15-160 keV with the balloon-borne experiment "POKER" comprising a large area array of three high-pressure multiwire proportional counters (MWPC).During the observation Sco X-1 was detected in the quiescent state at an average intensity level of 2.15 x 10(-3) photons cm-2 s-1 keV-1 at 30 keV, and an upper limit of 10(-5) photons cm-2 s-1 keV-1 was set above 60 keV. The data are compatible either with Comptonized emission from an accretion disk with a temperature of 5.3 keV and optical depth tau = 5.36, or with emission from a hot thin plasma with a temperature of 7.54 keV and a Gaunt factor correction corresponding to alpha = 0.46.Search for high-energy quasi-periodic oscillations and low-frequency noise, even though affected by the limited statistics due to the weakness of the source in the hard X-ray range, was negative at a level less-than-or-equal-to 18.8% on a bin of 1 Hz in the range 3-10 Hz for QPOs, and at a level less-than-or-equal-to 11.7% for LFN in the bin 0-1 Hz. Our data set the first upper limit above 20 keV on the fraction of photons showing QPOs and LFN at high energy.This observation also establishes an upper limit 10 times lower than the previously reported hard tail for energies greater than 60 keV.Finally, search for fast pulsations gave a negative result setting an upper limit to the pulsed fraction between 4.4% and 12.3% depending on the assumed duty cycle (from 12.5% to 50%). This confirms the non-magnetized nature of the compact object in the binary system.Our spectroscopic and timing data support the oscillating thick disk obscuration model proposed to explain the EXOSAT data on QPOs by van der Klis et al. in 1987.

The Galactic Center region, including the high energy emitter 1E1740.7–2942, has been observed on May 17, 1989 in the energy range 15–150 keV. The measurement was performed with the balloon borne experiment ‘‘POKER’’ based on an array of three high pressure Multiwire Proportional counters (MWPC) with energy resolution of 10% at 120 keV. The total geometric area was 8,000 cm2 and the experiment was passively collimated with copper hexagonal collimator with 1.9 degree FWHM field of view. Data analysis is still in progress and preliminary results are presented.

The region containing the galactic source Sco X‐1 has been observed on May 17, 1989 in the energy range 15–160 keV. The measurement was performed with the balloon borne experiment ‘‘POKER’’ based on an array of three high pressure Multiwire Proportional Counters (MWPC) with energy resolution of 10% at 120 keV. The total sensitive area was 8,000 cm2 and the experiment was passively collimated with a copper hexagonal collimator with 1.9 degree FWHM field of view. The preliminary data analysis confirmed the detection of the source at energies up to 60 keV.

The black hole candidate Cygnus X-1 was observed at a low flux level on 1985 August 5 with the "POKER" experiment in the hard X-Ray range (15-120 keV). During the same flight the Crab Nebula was also observed as an in-flight calibration source, and the spectral results are reported. The measurement shows a low flux from Cygnus X-1, at a level between the ones reported as gamma-1 and gamma-2 during the 1979 observations by the Gamma-Ray Spectrometer on board HEAO 3, and similar to the more recent observations by the MIFRASO balloon experiment (1987) and by the HEXE detector on board the MIR-KVANT module during 1987 July-1988 April. The photon spectrum is well described by a single power law, with a photon index of alpha = 1.87 and an intensity of 2.57 x 10(-3) photons cm-2 s-1 keV-1 at 50 keV, corresponding to 1.11 Crab. The low hard X-ray flux of the POKER observation is well matched at lower energies with the EXOSAT data, collected on 1985 August 12 even though the two observations are not contemporary and a source transition cannot be ruled out.Compared with other available high-statistics measurements our observation shows a source behavior characterized by a quite hard spectral shape and low intensity, just above the one considered typical of the gamma-1 state.Applying the Sunyaev and Titarchuk model to an accretion disk surrounding a black hole, the emission from a few keV up to the MeV region is consistent with a single temperature Comptonized spectrum.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation A. Bazzano, C. La Padula, R. K. Manchanda, V. F. Polcaro, P. Ubertini, R. Staubert, E. Kendziorra; Low state hard x‐ray observation of Cyg X‐1. AIP Conf. Proc. 1 August 1991; 232 (1): 370–372. https://doi.org/10.1063/1.40909 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The nearby active-nucleus galaxy Centaurus A was observed on May 17, 1989 with the POKER experiment in the energy range 15-150 keV). During the observation the source was in a low emission state at an average intensity of 2.25 X 10(-4) ph cm-2 s-1 keV at 30 keV and showed a quite hard spectrum compatible with a power law fit with a spectral slope of alpha = 1.60. Our data confirm the scenario suggesting Cen A to be one of the strongly variable high energy emitters with intensity variability of one order of magnitude or more. Nevertheless, our spectral measurement, collected during a quiescent state, confirms the presence of a quite constant spectral slope, with a ''canonical'' value of congruent-to 1.6 in photon index, in good agreement with the radio emission. Finally our data set supports the hypothesis that the same emission mechanism is responsible for the power law emission in the radio and hard X-rays wavelengths, confirming SSC models.

Les observations RX, UV, optiques et IR de deux etoiles particulieres, BD+37°1146 er DB+37°1160, incluses dans le rectangle d'erreur de la source RX 1H 0521+373 sont presentees. Les spectres sont analyses.