The Radio Recombination Line Intensities Of Atoms And Ions: Helium,Carbon And Oxygen

The radio recombination line intensities of heavy elements of helium, carbon and oxygen are calculated with accounting for dielectronic recombination. Dielectronic recombination rates are determined accurate to the second order of a perturbation theory and the rates are described as function of principal quantum number for helium-like atom or ion. Balance equations are solved for the departure coefficients from LTE b_n. The collision and spontaneous transition rates are accounted for the balance equations, in which non-equilibrium distribution source is dielectronic recombination. Non-equilibrium amplification coefficients are found as functions of a medium temperature, density and ion charge z = 1–3 for radio recombination lines. Optical depths are calculated for the heavy element low-frequency lines with the numbers 300 > n > 1200. For the chosen electronic temperatures and densities T_e = 0.8× 10⁴–10× 10⁴ K, N_e = 0.05–0.1 cm⁻³ the line optical depth is determined by the values τ_L∼ 0.1× 10⁻⁴–100× 10⁻⁴. Calculated for free-free transition rates, the optical depth is given by using the value τ_ff∼ 10⁻²τ_L.     

No detectable supernova remnant near the pulsar PSR 1930 + 22

No supernova remnant has been found near the third youngest pulsar PSR 1930+22 down to a -limiting brightness temperature of 1·4 K at 610 MHz. This is 6–8 times less than expected of a typical remnant whose age is that of the pulsar (3·60×10⁴ years).     

The imaging and slitless spectroscopy instrument for surveys (ISSIS) for the world space observatory-ultraviolet (WSO-UV)

ISSIS is the Imaging and Slitless Spectroscopy Instrument for the World Space Observatory-Ultraviolet (WSO-UV) mission. ISSIS is a multipurpose instrument designed to carry out high resolution (<0.1 arcsec) imaging in the far UV with fields of view ≥2×2 arcmin². ISSIS has two acquisition channels: the High Sensitivity Channel (HSC) and the Channel for Surveys (CfS). The HSC is equipped with an MCP-type detector to guarantee high sensitivity in the 1150–1750 ? range and high rejection of lower energy radiation. The CfS is equipped with a large CCD detector (4k×4k) to obtain images from the far UV to the red (1150–8500 ?); the CfS is implemented to allow observing UV bright sources such as reflection nebulae or nearby massive star forming regions. The design drivers and the current status of the instrument are described in this contribution.     

Long-wavelength infrared technology for astronomy at the Hughes Technology Center

The Hughes Technology Center (HTC) has developed a family of high-performance Si:As impurity-band conduction (IBC) hybrid focal plane arrays (FPAs) optimized for low background applications: 58×62 pixels (76-m pitch), 128×128 pixels (75- and 120-m pitch), and 256×256 pixels (30-m pitch). These FPAs exhibit state-of-the-art low noise (<100e ^-) achieved by using readout arrays fabricated on HTC's CryoCMOS process line. The IBC detector arrays, also fabricated at HTC, exhibit high quantum efficiency over a wide waveband with operating temperature of 4–12 K. In addition, Hughes is developing a 256×256 Si:As IBC FPA for high background applications as well as a 512×512 FPA. Readout development includes design and fabrication of 256×256 readouts with large well size of 1×10⁷ e ^- for the high-background FPA and 512×512 readouts with moderate well size (1×10⁶ e ^-).     

Orion: A 1–5 Micron Focal Plane for the 21st Century

The Orion program is a project to develop a 2K × 2K infrared focal plane using InSb p-on-n diodes for detectors. It is the natural follow-up to the successful Aladdin 1K × 1K program started in the early 90's. The work is being done at the Raytheon Infrared Operations Division (RIO, previously known as the Santa Barbara Research Center) by many of the same people who created the Aladdin focal plane. The design is very similar to the successful Aladdin design with the addition of reference pixels, whole array readout (no quadrants), two-adjacent-side buttability, and a packaging design that includes going directly to the ultimate focal plane size of 4K × 4K. So far we have successfully made a limited number of hybrid modules with InSb detectors. In this paper we will describe the design features and test data taken from some of these devices. This revised version was published online in July 2006 with corrections to the Cover Date.     

An Observation of Diffuse Soft X-Ray Background and Distribution of Hot Interstellar Medium

The diffuse soft X-ray background in 0.07∼ 2.0 keV has been observed along a small circle with the angular width of 10– covering b=—57– ∼ 77– and crossing the galactic plane at l=125– and 283–. Observed spectra are well fitted with models emitted from a thin hot gas with two or multi-temperature components and attenuated by a slab or interspersed neutral gas clouds. However the multi-temperature component model has some difficulties to explain the diffuse component expected from observations of OVI absorption lines. The two temperature component model with interspersed clouds consistently interprets a physical state of the hot interstellar medium. It turned out that the hot interstellar medium interspersed with neutral clouds of a representative hydrogen column density of 1× 10²⁰ cm^-2has two temperature components (10^5.8 K,(1.2-4.5)× 10⁶ K) and a disk-like distribution with the thickness of 580(± 100). {(p/k)/10⁴cm^-3 K} ^-2 pc at the pressure of p/k cm^-3 K along the galactic plane. Its pressure (p/k) is obtained to be 1.4(+0.7,-0.5)× 10⁴cm^-3 K, assuming that hot gases responsible for the diffuse soft X-rays and OVI ions are in pressure equilibrium. This interpretation qualitatively agrees with the theoretical prediction proposed by McKee and Ostriker. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solar Polarity Dependence of Cosmic Ray Power Spectra Observed with Mawson Underground Muon Telescopes

Power spectral density (PSD) of cosmic rays has been calculated from hourly averaged counts observed by underground muon telescopes located at Mawson over the low-frequency range 2.7×10⁻⁷ – 1.4×10⁻⁴ Hz. The first two harmonics of the solar daily variation are well defined for even cycles (20 and 22) whereas only the first harmonic is defined in cycle 21. The amplitude of the diurnal variation is lower for even cycles than for the odd cycle. The spectral power of the odd cycle exceeds those of the even cycles. The spectra are flatter and have lower power when the interplanetary magnetic field (IMF) is directed away from the Sun above the current sheet (A>0) than when the IMF is directed toward the Sun above the current sheet (A<0). The spectra imply that heliospheric magnetic turbulence may be more variable on time scales of several years than previously suspected.     

The ion-composition of the plasma produced by impacts of fast dust particles

The composition of the impact plasma produced by fast dust particles (v > 1 km/sec) hitting an Au or W target was measured both with a model of the HELIOS micrometeoroid experiment (low electric field at the target) and a high field detector. The plasma composition and the total plasma charge depend strongly on the impact velocity and the electric field strength at the target. Spectra of 9 different projectile-target combinations were analysed. Two types of spectra could be observed, depending on the projectile material. (1) Spectra of metals and hard dielectrics (Mohs' hardness ? 5). Particle constituents of low ionisation energy (e · u ? 7eV, e.g. Na, K, Al) dominate the spectra of these materials at impact velocities below 10 km/sec. At higher speed the relative intensities change and new ions with higher ionisation energies appear. (2) Spectra of soft dielectrics (Mohs' hardness < 3). Below 9 km/sec these materials produced less total charge than did the others. The highest masses were detected at 74 amu. The relative abundance of ions with low ionization energies such as Li, Na, K, etc. is comparatively small. Negative ions were also observed in the impact plasma. Their total number was found to be approximately 3–6% of that of the positive ions at 6 km/sec particle speed.     

Calibration observations of Fomalhaut with the VLTI

An investigation of the stability of the transfer function of the European Southern Observatory's Very Large Telescope Interferometer has been carried out through observations of Fomalhaut, which was observed over a range in hour angle from 21:50–05:24 on 20 October 2002. No significant variation in the transfer function was found for the zenith angle range 5°–70°. The projected baseline varied between 139.7 m and 49.8 m during the observations and, as an integral part of the determination of the transfer function, a new accurate limb‐darkened angular diameter for Fomalhaut of 2.109 ± 0.013 mas has been established. This has led to improved values for the emergent flux = (3.43 ± 0.10)×10⁸ Wm⁻², effective temperature = 8819 ± 67 K and radius = (1.213 ± 0.011)×10⁹ m (R/R_⊙ = 1.744 ± 0.016). The luminosity has been found to be (6.34 ± 0.20)×10²⁷ W (L/L_⊙ = 16.5 ± 0.5). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Origin of the metamorphosed clasts in the CV3 carbonaceous chondrite breccias of Graves Nunataks 06101, Vigarano,Roberts Massif 04143, and Yamato‐86009

We observed metamorphosed clasts in the CV3 chondrite breccias Graves Nunataks 06101, Vigarano, Roberts Massif 04143, and Yamato‐86009. These clasts are coarse‐grained polymineralic rocks composed of Ca‐bearing ferroan olivine (Fa_24–40, up to 0.6 wt% CaO), diopside (Fs_7–12Wo_44–50), plagioclase (An_52–75), Cr‐spinel (Cr/[Cr + Al] = 0.4, Fe/[Fe + Mg] = 0.7), sulfide and rare grains of Fe‐Ni metal, phosphate, and Ca‐poor pyroxene (Fs₂₄Wo₄). Most clasts have triple junctions between silicate grains. The rare earth element (REE) abundances are high in diopside (REE ~3.80–13.83 × CI) and plagioclase (Eu ~12.31–14.67 × CI) but are low in olivine (REE ~0.01–1.44 × CI) and spinel (REE ~0.25–0.49 × CI). These REE abundances are different from those of metamorphosed chondrites, primitive achondrites, and achondrites, suggesting that the clasts are not fragments of these meteorites. Similar mineralogical characteristics of the clasts with those in the Mokoia and Yamato‐86009 breccias (Jogo et al. 2012 ) suggest that the clasts observed in this study would also form inside the CV3 chondrite parent body. Thermal modeling suggests that in order to reach the metamorphosed temperatures of the clasts of >800 °C, the clast parent body should have accreted by ~2.5–2.6 Ma after CAIs formation. The consistency of the accretion age of the clast parent body and the CV3 chondrule formation age suggests that the clasts and CV3 chondrites could be originated from the same parent body with a peak temperature of 800–1100 °C. If the body has a peak temperature of >1100 °C, the accretion age of the body becomes older than the CV3 chondrule formation age and multiple CV3 parent bodies are likely.     

Power law distribution of pressure drops in dust devils: Observation techniques and Earth–Mars comparison

Data from the Pathfinder and Phoenix landers on Mars show transient pressure drops (～1–4 per day) attributed to nearby encounters with dust devils or dust-free vortices. The distribution of pressure drop amplitudes is consistent with a truncated power law distribution with a slope of ?2, similar to that suggested previously for the optical diameters of dust devils. Comparable data from terrestrial field observations are very sparse: the only published dataset is half a century old and lists only 19 pressure drops. That dataset is too small to permit a robust comparison with Mars and likely suffers from a low detection efficiency at small dust devil sizes. Observed pressure drops in these fixed-station Mars datasets (30–300 μbar) are 10× lower than those typically observed on Earth (0.3–3 mbar): some higher drops have been reported for large terrestrial devils sampled by pursuing vehicles. The needed terrestrial data for comparison with Mars in-situ data (soon to be augmented, we hope, by the Mars Science Laboratory mission) is noted. Prospects for obtaining such data via field campaigns using new data acquisition technology, and with microbarographs for nuclear test monitoring, are discussed.     

Rapid neutron capture process in supernovae and chemical element formation

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A > 70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for the production of heavy elements beyond A = 40 with the newest mass values available. The supernova envelopes at a temperature >109 K and neutron density of 10²⁴ cm^?3 are considered to be one of the most potential sites for the r-process. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. We have studied the r-process path corresponding to temperatures ranging from 1.0 × 10⁹ K to 3.0 × 10⁹ K and neutron density ranging from 10²⁰ cm^?3 to 10³⁰ cm^?3. With temperature and density conditions of 3.0 × 10⁹ K and 10²⁰ cm^?3 a nucleus of mass 273 was theoretically found corresponding to atomic number 115. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range.     

Scientific detector workshop 2022 on-sky performance verification of near-infrared e−APD technology for wavefront sensing and demonstration of e−APD pixel performance to improve the sensitivity of large science focal planes

Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e⁻APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is m_k = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10⁻³ e⁻/s have been demonstrated with 1Kx1K e⁻APD arrays and 2Kx2K e⁻APD arrays have already been developed, the possibilities and adaptations of e⁻APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed.     

Primordial magnetic fields in the f2FF model in large field inflation under de Sitter and power law expansion

We use the f²FF model to study the generation of primordial magnetic fields (PMF) in the context of large field inflation (LFI), described by the potential, V ∼ Mϕ^p. We compute the magnetic and electric spectra for all possible values of the model parameters under de Sitter and power law expansion. We show that scale invariant PMF are not obtained in LFI to first order in the slow roll approximation, if we impose the constraint V (ϕ = 0) ∼ 0. Alternatively, if these constraints are relaxed, the scale invariant PMF can be generated. The associated electric field energy can fall below the energy density of inflation, ρ_Inf for the ranges of comoving wavenumbers, k > 8 × 10^–7 Mpc^–1 and k > 4 × 10^–6 Mpc^–1 in de Sitter and power law (PL) expansion. Further, it can drop below ρ_Inf on the ranges, e‐foldings N > 51, p < 1.66, p > 2.03, l₀ > 3 × 10⁵ M_Pl^–1(H_i < 3.3 × 10^–6 M_Pl), and M > 2.8 × 10^–3 M_Pl. All of the above ranges fit with the observational constraints. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cristobalite- and tridymite-bearing clasts in Parnallee (LL3) and Farmington (L5)

Abstract— A set of cristobalite- and tridymite-rich igneous clasts (CB1 to CB8) have been found in Parnallee (LL3.6). They consist of clinoenstatite, minor feldspathic mesostasis and cristobalite veined by endiopsideaugite. The largest clast, CB8, is 1.6 cm in diameter and contains veined tridymite and cristobalite, clinoenstatite (zoned to ferroaugite and pyroxferroite Fs_75.6Wo_20.0) and plagioclase. Compared to bulk ordinary chondrites (OC), the bulk clasts are depleted in Al (0.02–0.8× OC), Na and K and enriched in Si (1.6–2.0× OC) and Ca (1.3–4.5× OC). Bulk CB8 has LREE > HREE (La/Lu = 1.6) with a positive Eu anomaly (Eu/Eu^* = 2.4). Textural observations suggest that the clasts cooled rapidly (24–420 °C/h) above 1200 °C. Clasts CB1—CB8 contain the isotopically heaviest O yet found in ordinary chondrites (up to δ¹⁷O = +8.7%_o, δ¹⁸O = +11.6%_o). Enrichment in the heavy isotopes of O is dependent on the proportion of cristobalite (or tridymite) in the clasts. A regression line CRIL (Cristobalite Line), with slope 0.77, is defined by the isotopic compositions of CB1—CB8, the Farmington clast and ordinary chondrite chondrules. An ¹⁶O-poor gas reservoir, whose composition must lie at some point along the extension of CRIL, has undergone varying degrees of isotopic exchange with most ordinary chondrite material. Silica polymorphs have undergone the greatest degree of exchange because of their open, framework structures. Silicon in CB1—CB8 has normal isotopic ratios. A model is proposed that involves differentiation of H-group material through extraction of volatile elements in a vapour phase, loss of an Fe-Ni-S melt and metastable crystallisation (60–70%) of olivine. The calculated residual liquid is silica-oversaturated and its subsequent predicted crystallisation sequence resembles that preserved in CB1—CB8. This model may require two stages of heating, the second one prior to cristobalite crystallisation (if the silica polymorph crystallises within its predicted stability field of > 1500 °C). Isotopic exchange took place either when CB1—CB8 were ejected from their parent body due to impact or near the surface of the parent body, perhaps in an ejecta blanket setting. The latter option is preferred because it is more consistent with our igneous model.     

The Ooty synthesis radio telescope: First results

A 4-km synthesis radio telescope has recently been commissioned at Ootacamund, India for operation at 327 MHz. It consists of the Ooty Radio Telescope (530 m × 30 m) and 7 small antennas which are distributed over an area of about 4 km × 2 km. It has a coverage of about ± 40‡ in declination δ. The beam-width is about 40 arcsec × 90 arcsec at δ = 0‡ and about 40 arcsec × 50 arcsec at δ = 40‡. The sensitivity attained for a 5:1 signal-to-noise ratio is about 15 m Jy after a 10-hour integration. The observational programmes undertaken and some of the results obtained recently are summarized. The radio halo around the edge-on spiral NGC 4631 is found to have a larger scale-height at 327 MHz than is known at higher frequencies. Mapping of interesting radio galaxies at 327 MHz is being carried out; preliminary results for 0511-305 (∼2 Mpc) and 1333-337 (∼750 kpc) are summarized. The very-steep-spectrum radio source in the Abell cluster A85 is found to be resolved; since it has no obvious optical counterpart, it is conceivable that it is a remnant of past activity of a galaxy that has drifted away in about 10⁹ years.     

Radio emission from the quiet sun and local sources at wavelengths 5, 10.7, 12, and 95 cm from observations of the January 4, 2011 eclipse in Crimea

The radio radii of the Sun at wavelengths of 5, 10.7, 12, and 95 cm have been determined from eclipse observations as R₅ ?? (1.0 ± 0.015)R _??, R _10,12 = (1.05 ± 0.003)R _??, and R ₉₅ = (1.2 ± 0.02)R _??. The bright-ness temperatures of quiet solar disk areas at these wavelengths have turned out to be Td ₅ = (22 ± 2) × 10³, Td ₁₀ = (44 ± 3) × 10³, Td ₁₂ = (47 ± 3) × 10³, and Td ₉₅ = (1000 ± 30) × 10³ K. There were local sources of radio emission with angular sizes from 1.9 to 2.4 arcmin and brightness temperatures from 80 × 10³ to 1.75 × 10⁶ K above sunspot groups at short wavelengths of 5, 10.7, and 12 cm. The radio flux from the local sources at 95 cm turned out to be below the detection threshold of 1.0 × 10^?22 W m^?2 Hz^?1. Comparison of the values obtained with the results of observations of another eclipse on August 1, 2008, occurred at the epoch of minimum of the 11-year solar cycle has shown that the radio radius of the Sun at 10.7 and 12 cm increased from 1.016 R _?? to 1.05 ± 0.003R _??, the height of the emitting layer at these wavelengths moved from 11 × 10³ km to (30 ± 7) × 10³ K, and the brightness temperature of the quiet Sun rose from (35.8 ± 0.4) × 10³ K to (44 ± 3) × 10³ K at 10.7 cm and from (37.3 ± 0.4) × 10³ K to (47 ± 3) × 10³ K at 12 cm. Consequently, the parameters of the solar atmosphere changed noticeably in 2 years in connection with the beginning of the new solar cycle 24. The almost complete absence of local sources at the longest wavelength of 95 cm suggests that the magnetic fields of the sunspot groups on January 4, 2011, were weak and did not penetrate to the height from where their emission could originate. If this property is inherent in most sunspot groups of cycle 24, then it can be responsible for its low flare activity.     

Wide-band high linearity active dipole for low frequency radio astronomy

We have developed an active dipole that is intended for use in new generation low frequency array applications. The preamplifier of the active dipole has very high linearity (input IP2 = 70 dBm, input IP3 = 31 dBm) and low noise temperature (100?C360 K). The frequency dependence of the dipole impedance and the match between the dipole and preamplifier have been optimized to achieve Galactic noise limited operation. The ratio between the antenna temperature due to Galactic noise and the noise temperature of the preamplifier is 10 ± 1.5 dB over the whole 10 to 70 MHz range. The total cost of the active cross-dipole is 220 euro.     

The 1985 outburst of RS Ophiuchi: Spectroscopic results

Optical spectroscopic data on the recurrent nova RS Ophiuchi obtained between 32 and 108 days after its last outburst on 1985 January 27 are presented. RS Oph was in the coronal-line phase at that time. The widths of the permitted as well as coronal-lines decreased continuously. Assuming that the ejected envelope decelerated due to its interaction with circum stellar matter, its size is deduced as a function of time. Observed fluxes in permitted lines would then imply that the electron density decreased from 3 × 10⁹ cm^#x2212;3 on day 32 to 1.8 × 10⁸ cm^-3 on day 108, for an assumed filling factor of 0.01. The helium abundance in the ejecta is estimated to be n(He)/n(H) ∼ 0.16. The mass of the unshocked ejecta was 3 × 10-6 (Φ/0.01)^1/2 M_⊙, (at this stage, where f is the filling factor. Observed fluxes in coronal-lines imply that the temperature of coronal-line region decreased from 1.5 × 10⁶ K on day 32 to 1.1 × 10⁶ K on day 108. Most of the coronal line emission, as well as He n emission arises in shocked and cooling ejecta. This region is not isothermal, but contains material at a wide range of temperatures. Mass of the shocked ejecta is estimated to be in the range 10⁻⁷−10⁻⁶ M⊙ Based on the number of H- and He-ionizing photons, we estimate that the ionizing source evolved from a radius and temperature of (2 × l0¹² cm, 3 × 10⁴ K) on day 32 to (6 × l0⁹ cm, 3.6 × 10⁵K) on day 204. We also present the spectra of RS Oph recorded in quiescent phase, 2 and 3 years after outburst, for comparison. The spectrum is dominated by that of M2 giant secondary, with superposed emission lines of H and He I     

Isotopic r-process abundances produced by supernova explosions

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A>70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for production of heavy elements beyond A=40 with the newest mass values available. The supernovae envelopes at a temperature >10⁹ K and neutron density of 10²⁴ cm⁻³ are considered to be one of the most potential sites for the r-process. We investigate the r-process in a site-independent, classical approach which assumes a chemical equilibrium between neutron captures and photodisintegrations followed by a β-flow equilibrium. We have studied the r-process path corresponding to temperatures ranging from 1.0×10⁹ K to 3.0×10⁹ K and neutron density ranging from 10²⁰ cm⁻³ to 10³⁰ cm⁻³. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. The abundances obtained are compared with supernova explosion condition and found in good agreement. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range.