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Photometrie IR d'un echantillon de 126 variables prises dans un espace de 16 degres carres du nord du GNM. La plupart de ces etoiles etaient auparavant inconnues et la majorite appartient a des variables geantes rouges de longue periode

Five Seyfert 1 galaxies of high absolute luminosity (ranging from 28 to 65 times that of NGC4151 at 3.5 μm) have been monitored since 1984 (or earlier) at JHK & L (1.25, 1.65, 2.2 & 3.5 μm). The results are shown in the accompanying figures. Where the variations were of sufficient amplitude, changes in L are seen to have been delayed ∼ 500 days compared to those at shorter wavelengths. In all cases, even in 3A 0557-383 where the amplitude of variation is small, each galaxy traces out loops with time if magnitudes at two different wavelengths are plotted against each other. The loops are always described in the same sense (clockwise as plotted here), such that variations at the longer wavelengths are seen to be retarded compared to those at the shorter. Plots of this kind appear to be a sensitive way to detect delays even when the data are too sparse to support a credible cross-correlation.

The near- to far-infrared properties of an optically selected sample of ordinary spiral galaxies, H2 (starburst) galaxies and Seyferts types 1 and 2 are summarized. The spectral indices between 1 and 100ym are shown to be almost independent of galaxy type. New JHKL photometry for a sample of Seyferts found from IRAS data by de Grijp et al. (1985) is given. No essential differences are found in the near-infrared behaviour of Seyferts selected by the two different methods. The de Grijp et al. criteria are shown to exclude many Seyfert galaxies known from optical work.

The outstanding feature of the last triennium was most certainly the abrupt generalisation of the use of array detectors, particularly CCDs (charge coupled devices). The latter pervade all subdivisions of instrumental astronomy. The gains achieved by their high quantum efficiency, their stability, their capability of delivering immediately recordable signals which can be processed by appropriate computational means, have been the cause of spectacular progress regarding the photometric precision of weak signal measurements.

We have produced images at 1.2, 1.6, and 2.2µm of a 1° × 2° region of the sky that includes the galactic centre using the drift scan techniques described by Catchpole et al. (1985) and Glass et al. (1987). These images were calibrated by observations of standard stars so that it is possible to make quantitative measurements of 3, H and K magnitudes for individual stars. Colour magnitude diagrams have been constructed, using K against H-K, for the stars within elliptical annuli centred on the galactic centre, with major axes along the galactic plane and an axial ratio of 2.2. The distribution of stars within each colour magnitude diagram is compared with a composite giant branch, based on 47 Tuc as seen at a distance of 8.2 Kpc, but extended to higher luminosity by including photometry of long period variables in the Baade windows. The assumption of a unique giant branch for the galactic centre stars is empirically justified by the small scatter in the colour magnitude diagrams beyond about 1.500B0 from the galactic plane. Fig. la & b give examples of colour magnitude diagrams for 400″ × 400″ areas of sky far from and near to the galactic centre.

We find values of the interstellar absorption from J, H and K scans of a 6.8 × 200 arcmin strip of sky extending from the Sgr I field to the Galactic Centre. The visual absorption, excluding dark clouds, increases from 3 to 30 magnitudes in this region.

THE X-ray burst source MXB1728—34 (ref. 1), which is believed to be associated with the steady source 2S1728—337 (ref. 2), lies in a heavily obscured portion of the Milky Way. The infrared photometer described previously3, attached to the 1.88-m telescope at Sutherland, was therefore used to search for optically invisible sources at K (2.2 µm) in the region of the error circle of 2S1728—337. The results are presented here: five infrared sources were located.

We have produced images at 1.2, 1.6, and 2.2μm of a 1° × 2° region of the sky that includes the galactic centre using the drift scan techniques described by Catchpole et al. (1985) and Glass et al. (1987). These images were calibrated by observations of standard stars so that it is possible to make quantitative measurements of 3, H and K magnitudes for individual stars. Colour magnitude diagrams have been constructed, using K against H–K, for the stars within elliptical annuli centred on the galactic centre, with major axes along the galactic plane and an axial ratio of 2.2. The distribution of stars within each colour magnitude diagram is compared with a composite giant branch, based on 47 Tuc as seen at a distance of 8.2 Kpc, but extended to higher luminosity by including photometry of long period variables in the Baade windows. The assumption of a unique giant branch for the galactic centre stars is empirically justified by the small scatter in the colour magnitude diagrams beyond about 1.5° from the galactic plane. Fig. 1a & b give examples of colour magnitude diagrams for 400″ × 400″ areas of sky far from and near to the galactic centre. The observed distribution of stars relative to the 47 Tuc giant branch allows us to measure both the foreground absorption and the number distribution of stars within a given range of dereddened apparent magnitude. The number of stars counted must be corrected for the effect of crowding which is estimated by generating simulated star fields and comparing the number of stars found using our reduction programmes, with the number used to simulate the fields.

Pulsed high energy X rays from Crab Nebula pulsar NP 0532 measured by balloon-borne X ray telescope

The paper reports partially simultaneous observations of the 'rapid burster' (MXB 1730-335) at X-ray, infrared, and radio wavelengths, covering several hundred hours during 1979 and 1980. None of the authors of this report saw any infrared or radio bursts. On several occasions an absence of infrared bursting was observed during X-ray bursting. On one occasion an absence of X-ray bursting was observed during a radio burst (4.1 GHz) reported by Calla et al. (1979). To date, radio bursts (a total of at least a dozen) have been reported only by Calla et al. (1980). Considering these and other observations summarized here, the reported radio bursts are either unreal or do not bear a simple relation to the X-ray bursts from the 'rapid burster'. The status of the reported infrared bursts also remain ambiguous. Limits to the brightness of any persistent radio source at the position of MXB 1730-335, limits to persistent X-ray emission during an extended X-ray quiet phase, and a measurement of the infrared polarization in the direction of the X-ray source are also reported.

On March 20, 1980, observations of occultations by rings alpha, beta, gamma, delta, and epsilon were observed from Cerro Tololo and Sutherland. A model ring profile was fit to the data to obtain the midtimes of the occultations and the widths of the profiles. A 14-parameter kinematic model, including J sub 2, J sub 4, and some of the orbital elements for rings 4, alpha, beta, and epsilon as free parameters, was fit to these data and previous ring occultation timings. The results yield J sub 2 = (3.396 + or - 0.020) x 10 to the -3 and a 2 sigma upper limit, absolute value of J sub 4 less than 7 x 10 to the -5th. Uniform precession models for rings alpha, beta are established and the dispersion in the values of semimajor axes and eccentricities for rings alpha, beta, and epsilon have been obtained. If self-gravity is the cause of the uniform precession, the mass of the beta ring is estimated at approximately 4 x 10 to the 16th g; the mass of the alpha ring probably is also near this value.

Photoelectric photometer measurements of stellar interferometer fringes strength by light modulation

Balloon-borne proportional counters to measure X rays intensity and spectral distribution from Taurus X-1 and Cygnus X-1