Showing papers by "European Southern Observatory published in 1981"
179 citations
TL;DR: In this article, a period and bolometric magnitudes for Miras in the Large Magellanic Cloud (LMC) are reported, which show a period-luminosity relation with very small scatter.
Abstract: Mira variables are very bright objects in the IR (∼2µm) so that they can be seen to large distances and through heavy interstellar absorption. Provided that they have well defined luminosities they should therefore be ideal indicators of galactic and extragalactic distances. Luminosities are also essential for understanding the physical state and pulsational characteristics of these stars which may be at the final stage of stellar evolution before planetary nebula formation1–3. A period–luminosity relation has been established for galactic Miras4 but the intrinsic scatter in the relation is largely unknown. We report here periods and bolometric magnitudes for Miras in the Large Magellanic Cloud (LMC) which show a period–luminosity relation with very small scatter.
123 citations
48 citations
TL;DR: In this article, an analysis of average optical properties yields values for the typical companion star masses and orbital periods of low-mass X-ray binaries of about 0.6 solar masses and 6 hours, respectively.
Abstract: The characterization of X-ray burst sources and other, non-bursting galactic bulge X-ray sources as low-mass close binary systems is generally accepted. The companion stars of the transient burst sources Aql X-1 and Cen X-4 are of spectral types G7-K3V and K3-7V, respectively. If these stars fill their Roche lobe, their orbital periods are in the range of 5-8 hr. X-ray observations offer evidence for a Cen X-4 orbital period of about 8 hr. An analysis of average optical properties yields values for the typical companion star masses and orbital periods of this class of low-mass X-ray binaries of about 0.6 solar masses and 6 hr, respectively.
30 citations
29 citations
Journal Article•
TL;DR: In this paper, photoelectric and time-resolved spectroscopic observations of the short-period eruptive binary AE Aqr are presented, where the system has a period of 0.4116537 days, and emission and absorption-line components equal to 135 km/sec and 159 km /sec, respectively.
Abstract: Photoelectric and time-resolved spectroscopic observations of the short-period eruptive binary AE Aqr are presented. The system has a period of 0.4116537 days, and emission and absorption-line components equal to 135 km/sec and 159 km/sec, respectively. The spectral type of the absorption-line component is found to be K5V, from which M1 = 0.82 solar mass, M2 = 0.69 solar mass, and i = 64 deg. A predominantly Ca II emission region occurs on the hemisphere of the K5V star facing the broad emission-line component, whose center of light is located 0.64 of the way from the inner Lagrangian point to the center of mass of the K star. This emission appears to be associated with the transfer of mass from the K5V star to the accretion disk surrounding the primary. In the absence of flare activity, the light of the system is variable in the orbital period with a range in V of about 0.16 mag; maxima occurs near the times of maximum recession velocity and during the approach of each of the two components of the system (0.25 P and 0.80 P).
26 citations
TL;DR: In this article, the energy per decade of frequency emitted by 3C 273 is nearly constant between 6000 A and 500 MeV and is ∼20 × 1046 erg s-1 for H = 50 km s − 1 Mpc-1.
Abstract: 3C 273 is the most extensively studied quasar both from the ground and from space. Recent satellite observations have given important information on the overall electromagnetic spectrum of 3C 273 in the γ-ray, X-ray, and UV ranges. The most salient results are: (i) the energy per decade of frequency emitted by 3C 273 is nearly constant between 6000 A and 500 MeV and is ∼20 × 1046 erg s-1 for H = 50 km s-1 Mpc-1; (ii) there is no absorption in the soft X-ray range in contrast to the X-ray spectrum of Seyfert nuclei; (iii) the optical and UV spectra cannot be fitted by power-law spectra only, and the energy distribution in this range suggests that a substantial fraction of the energy in the UV is emitted as back-body radiation at ≈20 000 K. If the peculiar shape of the UV spectrum is indeed caused by black-body radiation, then an estimate of the energy emitted under this form is 2.5 × 1046erg s-1, corresponding to an optically thick disk of ∼1016 cm in diameter.
22 citations
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TL;DR: For ω 1∶ω2 = 4∶1, the characteristic of the central periodic orbits is broken into two and each part is joined with a resonant characteristic as discussed by the authors.
Abstract: We study the resonance ω1∶ω2 = 4∶1 and some near-resonance cases. The main peculiarity of this resonance is that for ω1∶ω2 < 4 the characteristic of the central periodic orbits is broken into two and each part is joined with a resonant characteristic. This behaviour is described theoretically by means of the ‘third’ integral. It seems that there are infinite families of simple periodic orbits near the escape region. Finally, a comparison is made with the cases near the ω1∶ω2 = 2∶1 resonance.
14 citations
13 citations
8 citations
TL;DR: In this article, the authors consider a family of simple periodic orbits and show that for small values of h this family is stable, but as h increases beyond a table I, it becomes unstable and a new table family appears for h > h.
Abstract: DO SUCCESSIVE BIFURCATIONS IN HAMILTO1NIA1N SYSTEMS ETC. 4 ~ consider the fami ly of per iodic orbits (3) q~ = 2~q~, for different values of h. Fo r small values of h this fami ly is stable. A t a par t icu lar va lue h = h 1 (table I) a new fami ly of simple periodic orbits bifurcates f rom i t ; the fami ly (3) becomes unstable for h larger t h a n hx, while the new fami ly is stable. As h increases beyond a TABLE I. -Bifurcations o] the straight-line solutions o] Hamiltonian (2). 1 0.111 361 163 61 9.382 16 0.115 289 767 88 9.542 57 2 0.123 546 301 252 9.25635 O. 123 982 430 124 9.266 78 3 0.124 842 951 250 9.226 57 0.124 890 191 665 9.227 05 4 0.124 982 978 639 9.221 48 0.124 988 099 306 9.220 69 5 0.124 998 154 162 9.220 75 0.124 998 709 459 9.218 40 6 0.124 999 799 816 996 9.220 47 0.124 999 860 038 637 9.220 84 7 0.124 999 978 289 277 9.221 97 0.124 999 984 821 187 9.218 49 8 0.124 999 997 645 762 0.124 999 998 353 438 va lue h = hi (> hi) the fami ly (3) becomes again stable and a new uns table fami ly appears for h > hi. The fami ly (3) becomes again unstable at h = h~ (> hi) etc. There is an inf ini ty of successive t ransi t ions f rom stabi l i ty to ins tabi l i ty at hi, h2, ha ... and f rom ins tabi l i ty to s tabi l i ty at hi, h~, h~, ... such tha t (4) h i c~ is the escape energy h~ = 0.125. I n the fol lowing we define the va lue h ~ h k (5) a~ = h ~ h~+l and a similar va lue 0rl~" The values of hk, hl, 6k, (5~ are g iven in table I. The error of the numbers g iven is at most about one in the last digit . W e notice tha t the b i furcat ion rat ios O k, Of t end to the number 9.22. The accuracy is no t so good as in de te rmina t ions of s imilar rat ios g iven by o ther authors. However , i t is obvious t h a t the difference f rom the (~ universal ~> n u m b e r for conservat ive systems = 8.7210972 is significant, a l though bo th numbers are of the same order. (6) R . C . CHUROttlLL, G. PEOELZI a n d D. L . ROD : i n Stochastic Bshaviour in Classical and Quantum Hamiltonian Sysiems, e d i t e d b y G. CASATI a n d J . FORD (Ber l in , 1979) , p . 76.
TL;DR: In this article, the 165.5-day spectroscopic period of SS433 was used to show that the jets, rather than a highly reddened O star, are a major source of the IR radiation.
Abstract: SS433 shows X-ray, optical and radio variability and evidence of material moving at one-quarter the speed of light1. We report here the presence of the 165.5-day spectroscopic period in our extensive JHKL (1.2–3.4 µm) photometry. This indicates that the jets, rather than a highly reddened O star, are a major source of the IR radiation. We also show that the (J–H) colour index becomes redder as SS433 brightens but find no evidence for the 11.8-day period reported by Giles et al.2.
01 Jan 1981
TL;DR: In this article, the mass loss of early type stars in the infrared has been studied and a broad band photometry of 70 southern OB stars of various luminosity classes has been secured.
Abstract: In this paper we report briefly on a study of the mass loss of early type stars in the infrared. Up to now near infrared (1.25 – 4.8 µ) broad band photometry of 70 southern OB stars of various luminosity class has been secured. Program stars have been selected, among those bright enough in the infrared to give a suitable photometric accuracy, in order to cover a wide range of spectral types (Fig. 1).
01 Jan 1981
TL;DR: The ESO CCD camera system as discussed by the authors is based on an 11-processor, programmable in FORTH, which allows a great deal of flexibility in driving the CCD chip.
Abstract: This paper describes the CCD camera system that is currently operating at ESO, the perfor-mance characteristics of this camera, and presents some test results. The system has beendeveloped with the philosophy that it will be important to be able to utilize a widevariety of CCD chips since chip development is proceeding rapidly. Thus, the system isbased around a 11-processor, programmable in FORTH, which allows a great deal of flexibilityin driving the CCD chip. One feature of interest is the ability to do on chip summing ofadjacent pixels. Test results in the laboratory used a thinned, special version of the RCASID 52501 chip are encouraging, but the chip itself is far from optimized, having about80 electrons /pixel of noise. However, this is considered sufficient for many directimaging applications where sky noise will dominate.IntroductionAround the end of 1978, it became increasingly obvious that CCD chips of exceptionalquality were going to be widely available to the astronomical community and that anobservatory such as ESO should move rapidly to keep pace with this development. Alsoaround the same time it was obvious that the disruptions of the technical developmentsthat would accompany the transfer of ESO from Geneva to Munich would make the timescalefor an internal CCD observing system development unacceptably long. Therefore, it wasdecided to search for a vendor who could supply a "ready- to -no" system suitable forastronomical applications.Two firms responded to our tender and Princeton Scientific Instrument was selected onthe basis of price and performance. A contract was negotiated in December 1979 and thefinished product was delivered in early April 1981. The system has been designed so thatit can be used both at the telescope and in the laboratory to test various CCD's. So far,we have used only the RCA chips SID 52501 and have made only rather limited tests of thesystem in the laboratory. We had hoped to be able to report on our first observing runat this meeting but due to a six week delay in the program, this observing run will onlyoccur after this meeting.We describe below the hardware, some laboratory tests and our future plans.Hardware DescriptionThe system consists of the camera head and head electronics, the control and video pro-cessing unit and a micro processor. Figure
Journal Article•
TL;DR: In this article, the authors obtained high-speed broad-band optical photometry of the X-ray pulsar 4U 1626-67 from the ESO 3.6m telescope.
Abstract: High-speed broad-band optical photometry of the X-ray pulsar 4U 1626-67 has been obtained on five nights in May 1978. May 1979 and June 1980 with the ESO 3.6m telescope. These observations yield a pulse period and pulse derivative consistent with the X-ray data. The average pulse, of 4% amplitude, shows a broad, flat maximum and a narrow, deep minimum, much like the HEAO-1 low-energy X-ray pulse. The time-averaged flux is seen to vary by 15-50% on time scales of 10-15 minutes and by 15% on time scales down to 1 minute. Results of a search on 5 June 1980 for the down-shifted frequency component reported by Middleditch et al. (1981) shows no detectable signal at the expected frequency. The 90% confidence upper limit on the power at this frequency is P/Po≤ 1.5, where Po is the local noise power level. Since for the main peak P/Po ≃ 53, this means that the side-lobe was at least a factor of 35 times weaker than the main peak at the time of these observations.
Journal Article•
01 Jan 1981
TL;DR: In this paper, data on Wolf-Rayet (WR) stars in extragalactic H II regions and emission line galaxies are presented and discussed, and two cases are apparently observed, one in which only WN, the other in which both WN and WC are present.
Abstract: Data on Wolf-Rayet(WR) stars in extragalactic H II regions and emission line galaxies are presented and discussed. The sample is still limited and inhomogeneous but two important points appear to be already established: a) The WR stars are more numerous than the blue super-giants at least in same phase of the evolution of the stellar clusters which ionize the giant H II regions, b) when the WR stars are detected, two cases are apparently observed, one in which only WN, the other in which both WN and WC, are present.
TL;DR: The X-ray source H2155-304, identified with the radiosource PKS 2155 and with a 14 mag star-like object, is commonly believed to be a BL Lac object, on the basis of the blue featureless continuum, the presence of optical polarization and the violent variability, with mB varying from 12.8 to 14.2 on a time scale of months.
Abstract: The X-ray source H2155-304, identified with the radiosource PKS 2155 and with a 14 mag star-like object (Wade, Szkody and Cordova 1978; Schwartz et al. 1979; Agrawal and Riegler, 1979) is commonly believed to be a BL Lac object, on the basis of the blue featureless continuum, the presence of optical polarization and the violent variability, with mB varying from 12.8 to 14.2 on a time scale of months (Griffiths et al, 1979). Its X-ray emission has been observed to vary by a factor 2 on a time scale of 6 hours which is among the shortest found in extragalactic objects (Snyder et al, 1980). An X-ray flare of 2 sec duration, which would be hardly consistent with the BL Lac interpretation, has been reported by Agrawal and Riegler (1979).
01 Jan 1981
TL;DR: V 861 Sco (HD 152667) is a well known single line binary (1, 2) and its proposed association with a variable X-ray source has triggered renewed interest in the system.
Abstract: V 861 Sco (HD 152667) is a well known single line binary (1, 2). The proposed association with a variable X-ray source (3, 4) has triggered renewed interest in the system. Recent optical, infrared and ultraviolet observations (5 – 12) have provided a better knowledge of its char acteristics. A first estimate of the mass loss was given by Hutchings.(13)
TL;DR: In this article, a detailed account of the data collected from February 1978 to January 1979 is given, and three more papers devoted to the continuum, the emission and the absorption lines based on all IUE data up to May 1980 are in preparation.
Abstract: The nucleus of the Seyfert galaxy NGC 4151 has been extensively monitored with the International Ultraviolet Explorer (IUE) in the wave- length range 1200–3000 A, a region of the spectrum where the contamination by the stellar component of the nuclear light is negligible. A first detailed account of the data collected from February 1978 to January 1979 is given in Penston et al (1981), and three more papers devoted to the continuum, the emission and the absorption lines based on all IUE data up to May 1980 are in preparation. This note is a summary of the paper on the continuum, which includes also optical and X-ray observations (Perola et al, 1981).