Photometry of BD −7° 3007

Photometric observations of BD –7° 3007 in B and V filters are reported. Rapid flickering appears to be present at all phases, implying an unfavourable angle of inclination of orbit for seeing eclipse effects. A modulation of the light curve of period about an hour is present only on one night. The continuum energy distribution agrees with that of Com (GO V) in the longer wavelength region only.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Realization of X-ray telescopes–from design to performance

For more than 45 years the building of X-ray telescopes for solar and astronomical observations has been practised with significant performance improvement. The various techniques applied are reviewed emphazising the impact of proper mirror material choice, grinding and polishing improvements and the role of metrology.     

Preface: Key technologies for enhancing the performance of FAST

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)passed its national acceptance inspection on 2020 January 11.This special issue includes a total of 15 papers,which are selected to introduce the status of FAST’s performance and demonstrate the key technologies applied to FAST.The presented performance parameters can provide an important reference for scientists to propose observations with FAST.The key technologies presented in these papers include design and implementation in the measurement and control system,electromagnetic compatibility system,and receiver system.Finally,scientific achievements obtained by FAST during the commissioning phase are also reported.     

Science performance of Gaia, ESA’s space-astrometry mission

Gaia is the next astrometry mission of the European Space Agency (ESA), following up on the success of the Hipparcos mission. With a focal plane containing 106 CCD detectors, Gaia will survey the entire sky and repeatedly observe the brightest 1,000 million objects, down to 20^th magnitude, during its 5-year lifetime. Gaia’s science data comprises absolute astrometry, broad-band photometry, and low-resolution spectro-photometry. Spectroscopic data with a resolving power of 11,500 will be obtained for the brightest 150 million sources, down to 17^th magnitude. The thermo-mechanical stability of the spacecraft, combined with the selection of the L2 Lissajous point of the Sun-Earth/Moon system for operations, allows stellar parallaxes to be measured with standard errors less than 10 micro-arcsecond (μas) for stars brighter than 12^th magnitude, 25 μas for stars at 15^th magnitude, and 300 μas at magnitude 20. Photometric standard errors are in the milli-magnitude regime. The spectroscopic data allows the measurement of radial velocities with errors of 15 km s⁻¹ at magnitude 17. Gaia’s primary science goal is to unravel the kinematical, dynamical, and chemical structure and evolution of the Milky Way. In addition, Gaia’s data will touch many other areas of science, e.g., stellar physics, solar-system bodies, fundamental physics, and exo-planets. The Gaia spacecraft is currently in the qualification and production phase. With a launch in 2013, the final catalogue is expected in 2021. The science community in Europe, organised in the Data Processing and Analysis Consortium (DPAC), is responsible for the processing of the data.     

Om diagnostic of dilaton dark energy with two-parameter ω in potential [1+(σ−A)2]e (−Bσ)

Based on a new geometric diagnostic method-Om, we consider a new independent-model parametrization . When we work in potential W _σ [1+(σ−A)²]e ^(−Bσ), we investigate the evolutional behavior of Om with respect to red-shift z and the influence of coupling parameter α on the trajectory of Om with respect to z. We get that phantom model of Dilaton dark energy can avoid the future singularity “Big Rip”. The numerical results give current value of EOS which fits the latest observational data WMAP5+BAO+SNe very well.     

The fundamental performance of FAST with 19-beam receiver at L band

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) has passed national acceptance and finished one pilot cycle of ‘Shared-Risk’ observations. It will start formal operation soon. In this context, this paper describes testing results of key fundamental parameters for FAST, aiming to provide basic support for observation and data reduction of FAST for scientific researchers. The 19-beam receiver covering 1.05–1.45 GHz was utilized for most of these observations. The fluctuation in electronic gain of the system is better than 1% over 3.5 hours, enabling enough stability for observations. Pointing accuracy,aperture efficiency and system temperature are three key parameters for FAST. The measured standard deviation of pointing accuracy is 7.9′′, which satisfies the initial design of FAST. When zenith angle is less than 26.4°, the aperture efficiency and system temperature around 1.4 GHz are ~0.63 and less than 24 K for central beam, respectively. The sensitivity and stability of the 19-beam backend are confirmed to satisfy expectation by spectral HI observations toward NGC 672 and polarization observations toward 3 C 286. The performance allows FAST to take sensitive observations for various scientific goals, from studies of pulsars to galaxy evolution.     

Late-time emission of the type II Supernovae powered by the radioactive decay56Ni−56Co−56Fe

A one-zone model for the late time SN II energized by the radioactive decay⁵⁶Ni–⁵⁶Co–⁵⁶Fe is presented. The model succeeds in reproducing for the late time evolution of H and [Oi] 6300 emission lines in SN1970g for the reasonable set of parameters: mass of ejecta 4M , boundary velocityv ₀=4000 km s^–1 and amount of⁵⁶NiM _Ni=0.02M . However, a one-zone model does not account for the late time continuum. In the case of SN1980k the radioactive model fits H and [Oi] 6300 emissions att250 day satisfactory but fails at very late time, e.g.,t=670 day when the predicted value of the ratioL(H)/L(6300) is two orders of magnitude smaller than the observed one. We suggest that the strong H emission in SN1980k on the 670th day is due to the interaction of the supernova envelope with the pre-SN wind. The radioactive model for the late time SN II predicts strong Mgii 2800 line and detectable Hei 10830 line in emission and absorption.     

Chemical and Isotope Composition of Comet 67P/Churyumov−Gerasimenko: The Rosetta−Philae Mission Results Reviewed in the Context of Cosmogony and Cosmochemistry

Solar System Research - The studies of the composition and structure of comet 67P/Churyumov–Gerasimenko—a short-period comet of Jupiter’s family—which was an object of the...     

Simulation of FAST EM performance for both the axial and lateral feed defocusing

Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the world’s largest single dish radio telescope,which is located in Guizhou Province,in southwest China.The FAST feed cabin is supported and positioned by six steel cables.The deviation of the feed position and orientation would lead to loss in the telescope efficiency.In this paper,a series of electromagnetic(EM)simulations of the FAST facility with varying feed positions and orientation offsets was performed.The maximum gain of FAST is about 82.3 dBi and the sibelobe is–32 dB with respect to the main beam at 3 GHz.The simulation results have demonstrated that the telescope efficiency loss is more sensitive to the lateral feed deviation compared with the axial deviation.The telescope efficiency would decrease by 8.2%due to the FAST feed position deviation of 10 mm rms when the observing frequency is 3 GHz.The FAST feed deviation basically has no effect on the sidelobes and cross polarization characteristic according to the simulations.     

Astrometric Observations of the Galilean Moons of Jupiter at the Pulkovo Normal Astrograph in 2016−2017

We present the results of observations of the Galilean moons of Jupiter carried out at the Normal Astrograph of the Pulkovo Observatory in 2016?2017. We obtained 761 positions of the Galilean moons of Jupiter in the system of the Gaia DR1 catalog (ICRF, J2000.0) and 854 differential coordinates of the satellites relative to each other. The mean errors in the satellites’ normal places and the corresponding root-mean-square deviations are ε_α = 0.0020′′, ε_δ = 0.0027′′, σ_α = 0.0546′′, and σ_δ = 0.0757′′. The equatorial coordinates of the moons are compared to the motion theories of planets and satellites. On average, the (O–C) residuals in the both coordinates relative to the motion theories are less than 0.031′′. The best agreement with observations is achieved by a combination of the EPM2015 and V. Lainey-V.2.0|V1.1 motion theories, which yields the average (O–C) residuals of approximately 0.02″. Peculiarities in the behavior of the (O–C) residuals and error values in Ganymede have been noticed.     

First Byurakan Spectral Sky Survey. Stars of late spectral types. −11° ≤ δ ≤ −7° belt

A 10th list of late-type M and C stars found on plates of the First Byurakan Spectral Sky Survey in the − 11° ≤ δ ≤ − 7° belt with an area of about 1070 deg² is given. The list contains data on 169 red stars, 117 of which were found for the first time: 8 are new C stars, 3 are Cstar candidates, 104 are M stars, 1 is either an M or an S star, and 1 object on the survey plate cannot be classified. Of the 117 objects, 47 are unidentified IRAS sources. A statistical analysis of the objects that are and are not identified with IRAS sources shows that the identified stars are, with a high probability, brighter and have relatively more massive envelopes. Two stars were found to have fairly large brightness variability (with an amplitude of at least 6^m.O). Gasdust shells are assumed to exist around nine of the IRAS sources. The equatorial coordinates, spectral types, and stellar magnitudes, determined on Palomar E maps, are given for the selected objects. Translated from Astrofizika, Vol. 41. No. 4, pp. 545–559, October–December, 1998.     

Shock ionization of line-emitting gas in the radio galaxy PKS 0349−27

The FR II radio galaxy PKS 0349−27 contains a luminous emission-line nebula, extending over several tens of kpc around its host galaxy. We investigate the spatial distribution of the kinematics, line ratios and total emission-line flux of the gas by means of a detailed series of long-slit spectra that cover its entire extent. We show that the physical properties of the line-emitting gas, in particular its ionization properties, excitation state, dynamics and energetics, suggest a scenario involving auto-ionizing shocks as the dominant ionization mechanism.     

Lineaments on the Surface of the Consolidated Material of the Comet 67P/Churyumov−Gerasimenko Nucleus

Morphologic analysis of the fragments (500 × 500 pixels) of images of comet 67P/Churyumov? Gerasimenko obtained with the OSIRIS camera for 18 regions, where the consolidated material is exposed on the surface, has been carried out. In terms of resolution, the images form a series from 0.04 to 1.29 m/pixel; consequently, the areas covered by these fragments vary from 400 to ~400000 m². In all of the regions, lineaments resembling tension fractures—several dozens of structures per region—are seen; and their number scarcely changes when passing from high-resolution images to lower-resolution ones. It is clear that relatively small lineaments cease to be reliably distinguished when the image resolution worsens, but the largest and well-defined ones remain observable, while the number of larger lineaments grows proportionally to the survey area increasing. Undoubtedly, this is an observational effect, which was demonstrated by examples with an artificially worsened resolution. However, on the other hand, this means that the tension fractures of the consolidated nucleus material represent a hierarchic population of smaller (meters long) to larger (decameters and longer) features. The lineaments seen in the analyzed fragments of images were counted, their lengths were measured, and the spacings (the mean distances between lineaments) and, from them, the depths of penetration of fractures into the nucleus material were estimated. It has been shown that the mean length of lineaments within each studied region depends on its area (which here correlates with the image resolution) and the depths of fracture penetration into the nucleus body depends on the mean length of lineaments. Both dependences are close to a power law. In the images of four regions covering the areas from 100000 to 400000 m² with a resolution of 0.66?1.29 m/pixel, the structures that look like layering or sheet jointing are seen in addition to fracture lineaments. The tension fractures are apparently formed due to seasonal and diurnal variations of the temperature, while the nature of the formation of the layer-like structures is not yet fully understood.     

The Chandra X-ray galaxy clusters at z<1.4: constraints on the evolution of L X −T−M g relations

We analyzed the luminosity-temperature-mass of gas (L _X ?T?M _g ) relations for a sample of 21 Chandra galaxy clusters. We used the standard approach (β?model) to evaluate these relations for our sample that differs from other catalogues since it considers galaxy clusters at higher redshifts (0.4<z<1.4). We assumed power-law relations in the form $L_{X} \sim(1 +z)^{A_{L_{X}T}} T^{\beta_{L_{X}T}}$ , $M_{g} \sim(1 + z)^{A_{M_{g}T}} T^{\beta_{M_{g}T}}$ , and $M_{g} \sim(1 + z)^{A_{M_{g}L_{X}}} L^{\beta_{M_{g}L_{X}}}$ . We obtained the following fitting parameters with 68 % confidence level: $A_{L_{X}T} = 1.50 \pm0.23$ , $\beta_{L_{X}T} = 2.55 \pm0.07$ ; $A_{M_{g}T} = -0.58 \pm0.13$ and $\beta_{M_{g}T} = 1.77 \pm0.16$ ; $A_{M_{g}L_{X}} \approx-1.86 \pm0.34$ and $\beta_{M_{g}L_{X}} = 0.73 \pm0.15$ , respectively. We found that the evolution of the M _g ?T relation is small, while the M _g ?L _X relation is strong for the cosmological parameters Ω _m =0.27 and Ω _Λ =0.73. In overall, the clusters at high-z have stronger dependencies between L _X ?T?M _g correlations, than those for clusters at low-z. For most of galaxy clusters (first of all, from MACS and RCS surveys) these results are obtained for the first time.     

Survival of yeast spores in hypervelocity impact events up to velocities of 7.4 km s−1

We report on the survivability in hypervelocity impacts of yeast in spore form, and as mature cultures, at impact velocities from 1 to 7.4 km s^?1, corresponding to an estimated peak shock pressure of ～43 GPa. Spores from a yeast strain (BY4743), deficient in an enzyme required for uracil production, were fired into water (to simulate oceanic impact from space) using a light gas gun. The water was then retrieved and filtered and the resulting retentate and filtrate cultured to determine viability and survival rates of remnant spores. Yeast growth (confirmed as coming from the original sample as it had the same enzyme deficiency) was found in recovered samples at all impact speeds, albeit in smaller quantities at the higher speeds. The survival probabilities were measured as ～50% at 1 km s^?1, falling to ～10^?3% at 7.4 km s^?1. This follows the pattern observed in previous work on survival of microbial life and spores exposed to extreme shock loading, where there is reasonable survival at low peak shock pressures with more severe lethality above a critical shock pressure at the GPa scale (here between 2 and 10 GPa). These results are explained in the context of a general model for survival against extreme shock and are relevant to the hypotheses of panspermia and litho-panspermia, showing that extreme shocks during transfer across space are not necessarily sterilising.     

The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions.     

Model Estimates of Non-Hydrostatic Stresses in the Martian Crust and Mantle: 2−Three-Level Model

Regions of maximum shear and tension-compression stresses in the Martian interior have been revealed using the three-level compensation model. Nonequilibrium relief, density anomalies at the crust?mantle boundary, and density anomalies at the base of the lithosphere are the sources of the anomalous gravitational field. The thickness of elastic lithosphere positioned on a weak layer that has partially lost its elastic properties varies from 150 to 500 km. The weakening of the layer under the lithosphere is simulated by a tenfold lower value of the shear modulus down to the core boundary. In general, the stresses for the threelevel compensation model differ from the values obtained for the two-level model (nonequilibrium relief and density anomalies at the crust?mantle boundary are the sources of the anomalous gravitational field) by 5?10%. Considerable differences between the models of two-level and three-level compensation are revealed beneath Hellas and Argyre regions.     

Chirikov diffusion in the asteroidal three-body resonance (5, −2, −2)

The theory of diffusion in many-dimensional Hamiltonian system is applied to asteroidal dynamics. The general formulation developed by Chirikov is applied to the Nesvorny-Morbidelli analytic model of three-body (three-orbit) mean-motion resonances (Jupiter-Saturn-asteroid). In particular, we investigate the diffusion along and across the separatrices of the (5, −2, −2) resonance of the (490) Veritas asteroidal family and their relationship to diffusion in semi-major axis and eccentricity. The estimations of diffusion were obtained using the Melnikov integral, a Hadjidemetriou-type sympletic map and numerical integrations for times up to 10⁸ years.     

The X-ray spectrum of the bright galactic bulge source X1813−14=GX17+2

The spectral analysis of the persistent X-ray flux from the bright galactic bulge X-ray source and an X-ray burster X1813–14=GX17+2 is presented. A model with a single thermal bremsstrahlung continuum plus iron emission line at 6.7 keV fits the lower and higher intensity state data reasonably well. The line feature observed here is reproduced by a single emission line at 6.7 keV with intrinsic line width less than 0.7 keV. The equivalent width of the line ranges between 52 and 43 eV, depending on the intensity state of the source. This implies that the observed line is mostly due to helium-like iron (Fexxv). The properties of the line suggest that line-emitting matter is located far outside the neutron star.