On the complex spatial structure of a gradual microwave burst

We present a discussion of the gradual burst event on May 13,1985 which is based on observations of the RATAN-600 telescope at ten fixed frequencies in the range between 37.5 and 0.95 GHz (0.8 and 31.6 cm wavelength) and on time profiles of patrol observations of the Observatory for Solar Radio Astronomy at Tremsdorf near Potsdam. This up to now most complete data set allows new conclusions on the extended spectral/spatial structure of the source region.There is strong evidence that only less than 24% of the microwave flux from this event is emitted by an excessive small-scale burst source while the bulk of the burst emission comes from a larger region consisting of two major components covered by the source area of the S-component radiation. The different components of the burst and S-component radiation are analyzed.     

On the Red Rectangle optical emission bands

We have observed the Red Rectangle nebula with the Multi-Object Spectrograph on the WIYN telescope. Moderate-resolution spectra (Δ λ =0.4 Å) in the region of 5800 Å were obtained in 3-arcsec apertures at over 50 positions in the nebula. Accurate and precise wavelength calibrations were obtained against a thorium–argon lamp and the sodium lines in the sky and nebula. The peak position and full width at half-maximum of the 5800-Å Red Rectangle band (RRB) were measured to beyond 15 arcsec from the star. The shortest wavelength of the band is found to be 5799.10±0.15 Å in the rest frame of the nebula. None of the emission bands has intensity coincident with the wavelength of the diffuse interstellar band (DIB) at 5797.11±0.05 Å. The 2-Å offset cannot be explained by an instrumental, spectroscopic or photophysical effect. The hypothesis that the same molecule may be the carrier of the RRB and the DIB is contradicted by these observations. As a further test of the hypothesis, absorption has been sought that would be due to a potential DIB carrier in the nebula. Tentative evidence for absorption is found in the RRB spectra taken within 9 arcsec of the star; but any absorption has a peak position essentially coincident in wavelength with the band maximum of the emission band.     

Brightness temperatures of the quiet sun and new moon at the 6 mm wavelength

Absolute brightness temperatures and brightness temperature ratios of a quiet region near the center of the solar disk and the central region of the new moon were measured simultaneously at the 6 mm wavelength. The measured quiet sun/new moon brightness temperature ratios and reported central brightness temperatures of the new moon confirm the measured brightness temperature of the quiet sun at the 6 mm wavelength.Reported central brightness temperatures of the new moon are tabulated and graphed as a function of frequency and wavelength. The equation of a linear regression line for the reported measurements is given for estimating the brightness temperature of the new moon at any millimeter wavelength. Estimated brightness temperatures of the new moon and measured quiet sun/new moon ratios are used to estimate solar brightness temperatures at several millimeter wavelengths. The solar brightness temperatures, the regression line, and the Van de Hulst theoretical model are presented graphically as a function of frequency and wavelength. The regression line equation is given for estimating solar brightness temperatures at any wavelength in the 6 to 1 mm wavelength interval and is solved for the wavelength of the measured ratios.Reported solar brightness temperatures in the millimeter wavelength region are tabulated. The measured temperatures in the 6 to 1 mm wavelength interval and a linear regression line are presented graphically as a function of frequency and wavelength. The regression line equation is given and solved for the solar brightness temperatures at the 6 mm wavelength.This work supported by the U.S. Air Force under Contract No. F04701-69-C-0066.     

Soho Observations of the Connection Between Line Profile Parameters in Active and Quiet Regions and the Net Red Shift in Euv Emission Lines

We present high spatial and spectral resolution observations of one active and one quiet-Sun region, obtained with CDS and SUMER on SOHO. The connections between the line profile parameters are studied and a systematic wavelength shift towards the red with increasing peak line intensity (line broadening) is detected. The large scatter in the data calls for another approach. We apply conditional probability analysis to a series of EUV emission lines and find significant correlations between line profile parameters. For a given interval in wavelength shift we find that: (1) line profiles with large intensities (line widths) and red shifts above the average constitute an increasing fraction of the profiles as the relative wavelength shift increases, (2) line profiles with large intensities (line widths) and blue shifts compared to the average, on the other hand, constitute a decreasing fraction of the profiles as the relative wavelength shift increases. These results extend the findings of an earlier quiet-Sun study from one to several emission lines and expand the validity to include the active region. Interestingly, the active region observations show correlations between peak line intensity and wavelength shift in the coronal lines.The tendency for red-shifted profiles to be more intense than blue-shifted profiles will shift line profiles derived by integrating along the slit towards the red. From the present observations we are not able to determine the fraction of the net red shift that emerges from this correlation. We suggest that the same mechanism is responsible both for the correlation between the line profile parameters and for the differential red shift between the transition region and chromospheric emission lines.     

Rocket observations of the extreme ultraviolet dayglow

The ultraviolet dayglow in the wavelength region 750–1050 Å was investigated over the altitude range 100–800 km using a thin film filter photometer. From the airglow spectrum obtained by Carruthers and Page, one of the dominant features in this wavelength range is OII 834 Å. It is pointed out that the major excitation mechanism for this transition is photoionization excitation of atomic oxygen. Solution of the radiative transfer problem for this excitation process shows good agreement with the observed dayglow in the 300–800 km region. At lower altitudes additional components are present and are interpreted as the N₂, OI and possibly HI emissions observed by Carruthers and Page.     

Observations of Saturn at a wavelength of 49.5 cm

Radio emission from the planet Saturn was detected and measured by an unusually efficient observing technique at a wavelength of 49.5cm. The corresponding equivalent disk brightness temperature was hence determined to be 390 ± 65°K, providing further evidence for a mild enhancement in the emission at long wavelengths. It is pointed out that the currently available measurements of the disk brightness temperature in the wavelength range 1mm-1m are, as a whole, inadequate for estimating with confidence the detailed shape of the spectrum and that the exiguous, long wavelength observations should be supplemented with more and accurate measurements.     

Observation of the solar eclipse 1966 May 20 in the region between 3.2 cm to 2.7 m wavelength

The solar eclipse 1966 May 20 was observed at 3.2, 10, 15, 20, 54, 59 cm, 1.05, 1.34 and 2.7 m wavelength by the observatories of the Heinrich-Hertz-Institut. The meter-wavelength observations were superposed by a noise storm. The result shows a region of enhanced radiation from the plages near the central meridian at the short wavelengths. Consulting additionally the observations made at Kiel, NERA, and Ondejov in the region of about 1.2 m wavelength it is possible to localize the source of the noise storm.     

The relation between the intensities of umbra and penumbra of large sunspots

Based on pinhole photometer observations in 4–6 wavelength regions we have searched for a connection between the intensities of the umbra and the penumbra of sunspots. For the 1.67 μm wavelength region it is apparent that spots with dark umbrae also have dark penumbrae. In the other wavelength regions similar relations are found. The darkness of the spot is probably connected with the degree of complexity of the spot.     

Rotational and vibrational temperatures of BaO from a barium release at 170 km, and the synthetic spectrum of BaO in the region 4700 Å to 15,500 Å

Band spectra of BaO covering a total wavelength region of 5050 Å-9300 Å were recorded from the ground with a scanning spectrophotometer at 7.1 Å resolution during a series of barium rocket releases at College, Alaska in the Spring of 1969. Rotational and vibrational temperatures, both equal to approximately 850°K at the release altitude of 170 km, were inferred by matching the release spectra with calculated synthetic spectra. This temperature persisted throughout the observing period, from release + 20 sec to 14 min after release.

Analysis of the BaO band spectrum over a large wavelength region reveals that rotational temperatures are best determined at wavelengths below 5500 Å, and that vibrational temperatures should be measured at wavelengths greater than 5500 Å. Comparisons with synthetic spectra show that several broad emission features in the release spectra, located at about 7900 Å 8400 Å and 9000 Å, may be identified as clusters of overlapping BaO bands. A synthetic spectrum of BaO extending from 4700 Å to 15,000 Å is included for general reference and to facilitate future studies in that wavelength region.     

A study of solar radio emission in the light of Sengupta's model of coronal active regions

Daily solar radio flux at six different frequencies in dm, cm and mm wavelength regions has been studied for 182 days from December 1, 1970 to May 30, 1971. It is found that the slowly varying component of the centimeter wave emission correlates well with the physical model of the coronal active regions derived by Sengupta (Sengupta, 1971b) from which, as he showed earlier, most of the solar soft X-rays of wavelength less than 20 Å comes. It is also found that the cm wave emission is consistent with the assumption that the emitting regions are optically thin in this wavelength range.Emissions in dm and mm wavelength ranges, however, show poor correlation with the physical model of the soft X-ray emitting regions.It is concluded that the preferred regions of cm wave emission are located in the same region of solar corona from where most of the soft X-rays comes, but are different from the preferred regions of mm and dm emission.     

自引力磁均分和磁守恒吸积盘模型的稳定性分析

对自引力磁均分和磁守恒两种模型的径向振荡稳定性的研究表明：在同时考虑自引力和磁场作用的情况下,吸积盘在磁均分和磁守恒模型中均存在着三种振荡模式,其中粘滞模式总是稳定的,磁声模式是不稳定的,中性模式在图中较长波段范围趋于稳定,在较短波段范围是不稳定的．这些结果有利于解释活动天体的Mark421和Pks2155—304的长周期光变现象．同时阐明了自引力在两种模型中对三种模式的影响有相同的趋势,而对磁场则分别起着相反的作用．这个结论表明磁均分吸积盘模型在解释光变现象时更为有利．     

More evidence for an oscillation superimposed on the Hubble flow

In a recent investigation evidence was presented for a low-level sinusoidal oscillation superimposed on top of the Hubble flow. This oscillation was in V _CMB , in a sample of type Ia Supernovae sources with accurate distances, and it was found to have a wavelength close to 40 Mpc. It became easily visible after the removal of several previously identified discrete velocity components. Its amplitude like that of the Hubble velocity showed an increase with distance, as would be expected for a constant-amplitude space oscillation. Here we report that this oscillation is also present in distance clumping in these sources, with the same wavelength, but in phase quadrature. The discrete velocity components do not play a role in detecting the distance clumping wavelength. Assuming that time proceeds from high cosmological redshift to low, the blue-shifted velocity peaks, which represent the contraction stage of the velocity oscillation, then lead the density peaks. With the discrete velocity components removed we also find evidence for at least one other, weaker velocity oscillation. It is found to have a wavelength similar to one reported in density clumping by previous investigators. In those cases the source samples were much larger.     

Relative umbral intensity of a large sunspot

Simultaneous observations of relative umbral intensities in four wavelength regions are presented. In the visual wavelength region the umbral intensities show lower values than given by most authors. By observing the same spot during different seeing conditions the method of correction for stray light is found to be consistent within the accuracy of the method. In addition, a new simple correction method is suggested.     

Coronal emission line profile observations at total solar eclipses

High resolution spectra of the coronal emission line Fe xiv at 530.3 nm obtained at the 30 May 1965 total solar eclipse are analyzed and interpreted. Deconvolution techniques that preserve the line intensity vs wavelength profile shape are developed to obtain further resolution improvement. The west limb coronal enhancement is determined to have temperatures less than 3 MK and turbulent velocities of ～25 km s^-1 decreasing with altitude. Temperature gradients provide evidence for marginal solar wind flow from this enhancement. Above the quiet photosphere in the southwest quadrant the comparison of line and continuum intensities and consideration of line width suggest to us the coronal region is filled with inhomogeneous plasma, dense enough in localized regions to maintain collisional excitation. Solar wind flow from this region obtains when turbulent velocities are assumed to contribute to the line broadening. We identify this region as a coronal hole and suggest that coronal material is heated by the quiet photosphere below.     

A comparison of the ultraviolet to near-infrared spectral properties of Mercury and the Moon as observed by MESSENGER

Measurements of the disk-integrated reflectance spectrum of Mercury and the Moon have been obtained by the MESSENGER spacecraft. A comparison of spectra from the two bodies, spanning the wavelength range 220-1450 nm, shows that the absolute reflectance of Mercury is lower than that of the nearside waxing Moon at the same phase angle with a spectral slope that is less steep at visible and near-infrared wavelengths. We interpret these results and the lack of an absorption feature at a wavelength near 1000 nm as evidence for a Mercury surface composition that is low in ferrous iron within silicates but is higher in the globally averaged abundance of spectrally neutral opaque minerals than the Moon. Similar conclusions have been reached by recent investigations based on observations from both MESSENGER and Mariner 10. There is weak evidence for a phase-reddening effect in Mercury that is slightly larger in magnitude than for the lunar nearside. An apparent absorption in the middle-ultraviolet wavelength range of the Mercury spectrum detected from the first MESSENGER flyby of Mercury is found to persist in subsequent observations from the second flyby. The current model of space weathering on the Moon, which also presumably applies to Mercury, does not provide an explanation for the presence of this ultraviolet absorption.     

Comments on the quiet Sun brightness distribution at 1.2 mm wavelength

A re-analysis of the brightness distribution of the quiet Sun at 1.2 mm wavelength is made. It is concluded that there is no evidence for uniform or limb-brightened distribution at this wave-length.     

An investigation of Fe xvi emission lines in solar and stellar extreme-ultraviolet and soft X-ray spectra

New fully relativistic calculations of radiative rates and electron impact excitation cross-sections for Fe  xvi are used to determine theoretical emission-line ratios applicable to the 251–361 and 32–77 Å portions of the extreme-ultraviolet (EUV) and soft X-ray spectral regions, respectively. A comparison of the EUV results with observations from the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS) reveals excellent agreement between theory and experiment. However, for emission lines in the 32–49 Å portion of the soft X-ray spectral region, there are large discrepancies between theory and measurement for both a solar flare spectrum obtained with the X-Ray Spectrometer/Spectrograph Telescope (XSST) and for observations of Capella from the Low-Energy Transmission Grating Spectrometer (LETGS) on the Chandra X-ray Observatory . These are probably due to blending in the solar flare and Capella data from both first-order lines and from shorter wavelength transitions detected in second and third order. By contrast, there is very good agreement between our theoretical results and the XSST and LETGS observations in the 50–77 Å wavelength range, contrary to previous results. In particular, there is no evidence that the Fe  xvi emission from the XSST flare arises from plasma at a much higher temperature than that expected for Fe  xvi in ionization equilibrium, as suggested by earlier work.     

Spectral averaging of the point spread function for Yohkoh's SXT

The point spread function of the soft X-ray telescope (SXT) aboard the Yohkoh spacecraft is a Moffat function with elliptical characteristics. This function has two parameters, a and b, that are wavelength dependent in the X-ray region of interest. Since most SXT data analysis is performed with respect to plasma temperature rather than wavelength, it is useful to spectrally average these two parameters over wavelength with temperature as the free variable. The results of this spectral averaging are given here for users of SXT data.     

Polarization at 4430Å

The wavelength dependence of polarization in the region of the interstellar absorption band at 4430 Å is investigated theoretically by variation of the relevant parameters over a wide range. Comparison is made with observations, and the suggestion that the 4430 Å band is produced by impurities in a silicate matrix is found to be not inconsistent.     

Polarization models of young stellar objects – II. Linear and circular polarimetry of R Coronae Australis

Near-infrared linear imaging polarimetry of the young stellar objects R CrA and T CrA in the J , H and K n bands, and circular imaging polarimetry in the H band, is presented. The data are modelled with the Clark and McCall scattering model. The R CrA and T CrA system is shown to be a particularly complex scattering environment. In the case of R CrA there is evidence that the wavelength dependence of polarization changes across the nebula. MRN dust grain models do not explain this behaviour. Depolarization by line emission is considered as an alternative explanation. The dust grain properties could also be changing across the nebula.
Although surrounded by reflection nebulosity, there is a region of particularly low polarization surrounding R CrA that is best modelled by the canonical bipolar outflow being truncated by an evacuated spherical cavity surrounding the star. The symmetry axis of the nebula appears inclined by 50° to the plane of the sky.
The H -band circular polarimetry of R CrA clearly shows a quadrupolar structure of positive and negative degrees of circular polarization that reach peak magnitudes of ∼5 per cent within our limited map. It is shown that spherical MRN grains are incapable of producing this circular polarization given the observed linear polarization of the R CrA system. Instead, scattering from aligned non-spherical grains is proposed as the operating mechanism.
T CrA is a more archetypical bipolar reflection nebula, and this object is modelled as a canonical parabolic reflection nebula that lies in the plane of the sky. The wavelength independence of linear polarization in the T CrA reflection nebula suggests that the scattering particles are Rayleigh sized. This is modelled with the MRN interstellar grain size distribution.