On the ratio of the total to selective absorption

The ratio of total to selective absorbtion,R, has been found to remain constant as dust is processed in clouds from low to high density, through Hii regions and open clusters, and returned to the interstellar medium.R has the same value in dense dust clouds as it has in Hii regions of different ages. Variations inR values obtained from stars in Hii regions may be due to errors in special type classification. Globular cluster diameters show no tendency to increase with distance from the Sun whenR=3.2 is used. Large grains evidently do not exist in the interstellar medium. There is no evidence for neutral extinction in the Galaxy at large.     

Variability of Fe ii in Two NLS1s, PG 1700+815 and NGC 4051

We analyze the spectral variability for two narrow line Seyfert 1 galaxies, PG 1700+518 and NGC 4051 using the spectral decomposition method. We focus on their optical Fe ii variability to investigate the origin of Fe ii in AGNs. For PG 1700+518, we find that the Fe ii size is about 200 light-days, which is consistent with the Hβ size derived from the empirical R–L relation. For NGC 4051, the [O iii] 5007 Å flux is strongly correlated with continuum flux, suggesting that we should recalibrate the spectral flux on a scale defined by [O iii] flux. The corrected light curves of Fe ii, Hβ, He ii, f _λ (5100 Å) are given here. A detailed analysis will be given in the near future.     

Optical spectral decomposition of NGC 4051

Considering the host galaxy contribution, a spectral decomposition method is used to reanalyzed the archive data of optical spectra for a narrow line Seyfert 1 galaxy, NGC 4051. The light curves of the continuum f _λ (5100 Å), and Hβ, He ii, Fe ii emission lines are given. We find strong flux correlations between line emissions of Hβ, He ii, Fe ii and the continuum f _λ (5100 Å). These low-ionization lines (Hβ, Fe ii, He ii) have “inverse” intrinsic Baldwin effects. Using the methods of the cross-correlation function and the Monte Carlo simulation, we find the time delays, with respect to the continuum, are $3.45^{+12.0}_{-0.5}~\mbox{days}$ with the probability of 34 % for the intermediate component of Hβ, $6.45^{+13.0}_{-1.0}~\mbox{days}$ with the probability of 65 % for the intermediate component of He ii. From these intermediate components of Hβ and He ii, the calculated central black hole masses are $0.86^{+4.35}_{-0.33}\times 10^{6}$ and $0.82^{+3.12}_{-0.45}\times 10^{6}~M_{\odot }$ . We also find that the time delays for Fe ii are $9.7^{+3.0}_{-5.0}~\mbox{days}$ with the probability of 36 %, $8.45^{+1.0}_{-2.0}~\mbox{days}$ with the probability of 18 % for the total epochs and “subset 1” data, respectively. It seems that the Fe ii emission region is outside of the Hβ emission region.     

Direct Measurement Results of the Time Lag of LOS-Velocity Oscillations Between Two Heights in Solar Faculae and Sunspots

We present an investigation of line-of-sight (LOS) velocity oscillations in solar faculae and sunspots. To study the phase relations between chromospheric and photospheric oscillations of the LOS velocity, we measured the time lag of the chromospheric signal relative to the photospheric one for several faculae and sunspots in a set of spectral line pairs. The measured time lags are different for different objects. The mean measured delay between the oscillations in the five-minute band in faculae is 50?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the pair Fe?i 6569?Å?–?Hα 6563?Å the mean delay is 20?s; for the pair Fe?i 4551?Å?–?Ba?ii 4554?Å the mean delay is 7?s; for the pair Si?i 8536?Å?–?Ca?ii 8542?Å the mean delay is 20?s. For the oscillations in the three-minute band in sunspot umbrae the mean delay is 55?s for the Si?i 10?827?Å?–?He?i 10?830?Å pair; for the Fe?i 6569?Å?–?Hα 6563?Å pair it was not possible to determine the delay; for the Fe?i 4551?Å?–?Ba?ii 4554?Å pair the mean delay is 6?s; for the Si?i 8536?Å?–?Ca?ii 8542?Å pair the mean delay is 21?s. Measured delays correspond to the wave propagation speed, which significantly exceeds the generally adopted speed of sound in the photosphere. This raises the question of the origin of these oscillations. The possibility that we deal with slow MHD waves is not ruled out.     

Spectroheliograms in the Mg II line at 2795.5 Å

A rocket-borne spectroheliograph designed to take monochromatic pictures of the sun in the Mgii line at 2795.5 Å was successfully launched from White Sands Missile Range on May 20, 1968. A double ?olc birefringent filter with a spectral bandpass of 2.1 Å was used to select the proper wavelength. Pinhole photographs in the soft X-ray region were also secured in the same flight. The Mgii and X-ray photographs are compared with simultaneous Caii and Hα spectroheliograms, radiomaps at 9.1 cm and 3.3 cm, a Fraunhofer map and a magnetogram and some preliminary results are discussed.     

DLA abundances in the CUBES’s spectral window

Absorption systems observed along the line of sights to distant quasars are observed at all redshifts and the full range of the electromagnetic spectrum is needed to recover the variety of transitions of different elements. However, some important elements are found within the Lyman forest and their absorption line profiles need to be analyzed against the presence of possible Ly-α contamination. Considering the cosmological evolution of the number density of hydrogen clouds, the probability to detect uncontaminated metal lines is higher in the UV-Optical region exploited by CUBES. The list of these elements includes some important ones such as D, H₂, O?i, N?i, O?vi, Ar?i, P?ii, C?ii, S?ii and B?ii. The determination of some of them in the Damped Ly-α galaxies and their astronomical interest are briefly discussed.     

Lifetimes of some excited states in the rare earths: La ii,Ce ii,Pr ii,Nd ii,Sm ii,Yb i,Yb ii,and Lu ii

Radiative lifetimes for excited states in La ii, Ce ii, Pr ii, Nd ii, Sm ii, Yb i, Yb ii, and Lu ii have been determined by means of the beam-foil technique or the zero-field level-crossing method. The lifetimes for La, Ce, Pr, Nd, Sm, and Yb are shorter than those computed by summing the transition probabilities of Corliss and Bozman by a factor of up to ~5. The large discrepancies between the abundance of La, Ce, Pr, Nd, and Sm in the solar photosphere and in meteorites are eliminated or greatly reduced if the abundance determinations of the solar photosphere are based upon the gf values of Corliss and Bozman, corrected for by the present lifetimes.     

Velocities and Linewidths in the Network and Cell Interiors of a Polar Coronal Hole Compared with the Quiet Sun

The relative Doppler velocities and linewidths in a polar coronal hole and the nearby quiet-Sun region have been obtained from the Solar and Heliospheric Observatory (SOHO)/Coronal Diagnostic Spectrometer (CDS) observations using emission lines originating at different heights in the solar atmosphere from the lower transition region (TR) to the low solar corona. The observed region is separated into the network and the cell interior, and the behavior of the above parameters were examined in the different regions. It has been found that the histograms of Doppler velocity and width are generally broader in the cell interior than in the network. The histograms of Doppler velocities of the network and cell interior do not show significant differences in most cases. However, in the case of the quiet Sun, the Doppler velocities of the cell interior are more blueshifted than those of the network for the lowermost line He?ii 304 Å, and an opposite behavior is seen for the uppermost line Mg?ix 368 Å. The linewidth histograms show that the network–cell difference is more prominent in the coronal hole. The network has a significantly larger linewidth than the cell interior for the lowermost TR line He?ii 304 Å for the quiet Sun. For the coronal hole, this is true for the three lower TR lines: He?ii 304 Å, O?iii 599 Å, and O?v 630 Å. We also obtained the correlations between the relative Doppler velocity and the width. A mild positive correlation is found for the lowermost transition-region line He?ii 304 Å, which decreases even more or become insignificant for the intermediate lines. For the low coronal line Mg?ix 368 Å, the correlation becomes strongly negative. This might be caused by standing waves or waves propagating from the lower to the upper solar atmosphere. The results may have implications for the generation of the fast solar wind and coronal heating.     

Properties of the ionised gas of circumnuclear star-forming regions in early-type spirals

A study of circumnuclear star-forming regions (CNSFRs) in several early-type spirals has been carried out in order to investigate their main properties: stellar and gas kinematics, dynamical masses, ionising stellar masses, chemical abundances and other properties of the ionised gas. Both high resolution (R～20,000) and moderate resolution (R～5000) have been used. In some cases, these regions (about 100–150 pc in size) are composed of several individual star clusters with sizes between 1.5 and 4.9 pc, estimated from Hubble Space Telescope images. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km?s^?1, with the Hβ emission lines being narrower than both the stellar lines and the [Oiii]λ5007 Å lines. The twice ionised oxygen, on the other hand, shows velocity dispersions comparable to those of stars. We have applied the virial theorem to estimate dynamical masses of the clusters, assuming that the systems are gravitationally bounded and spherically symmetric, and using previously measured sizes. The measured values of the stellar velocity dispersions yield dynamical masses of the order of 10⁷ to 10⁸ M_⊙ for the full CNSFRs. We obtain oxygen abundances which are comparable to those found in high-metallicity disc Hii regions from direct measurements of electron temperatures and consistent with solar values within the errors. The region with the highest oxygen abundance is R3+R4 in NGC3504, 12+log(O/H)=8.85, about 1.5 times solar. The derived N/O ratios are, on average, larger than those found in high-metallicity disc Hii regions, and they do not seem to follow the trend of N/O vs. O/H which marks the secondary behaviour of nitrogen. On the other hand, the S/O ratios span a very narrow range—between 0.6 and 0.8 times solar. Compared to high-metallicity disc Hii regions, CNSFRs show values of the O₂₃ and the N2 parameters whose distributions are shifted to lower and higher values, respectively. Hence, even though their derived oxygen and sulphur abundances are similar, higher values would in principle be obtained for the CNSFRs if pure empirical methods were used to estimate abundances. CNSFRs also exhibit lower ionisation parameters than their disc counterparts, as derived from [Sii]/[Siii]. Their ionisation structure also seems to be different, with CNSFRs showing radiation-field properties more similar to Hii galaxies than to disc high-metallicity Hii regions.     

Large-scale ionization fronts and the nature and distribution of light scattering particles in the orion nebula

Image-tube filter photographs calibrated against photoelectric filter photometry have been used to give maps of M42 in absolute flux units over the central 15 arc min of the nebula in Hα, [Nii] (λ 6584 Å), Hβ and continuum at λ 4700 Å. Maps of the ratios Hα/[Nii] and (for the first time) of continuum/Hβ have been produced with unprecedented spatial resolution. These show that the gas to dust ratio is high near the exciting stars and falls strongly in the vicinity of large scale ionization fronts marked by minima in the Hα/[Nii] ratio. These results are interpreted in terms of detailed shell models containing either ice or graphite or silicate scattering particles. In all models there must be a central hole in the distribution of scattering particles. The effect of neutral globules and intrusions is investigated. It is found that all types of grain are trapped inside neutral intrusions near the centre of the nebula by the pressure of the Lα light surrounding the globule, but in the early evolution of the nebula particles can escape into the ionized medium when fronts are R-type. Ice grains escaping at this time will be destroyed for distances to the exciting stars less than 1 pc. These results can explain both the central hole in dust and the underabundance of oxygen in the ionized gas observed earlier. Arguments depending on colour index of the scattered light indicate that mixtures of scattered light from ice in the globules and from ice in the ionized medium can explain the observations, but that the graphite and silicate particles fail. A schematic model of the Orion Nebula is presented to attempt to explain the large scale phenomena observed here. It demonstrates that simple shell models for this nebula are dubious.     

On the origin of the compact H ii regions around massive stellar clusters

The existence of compact H?ii regions around massive stellar clusters with ages exceeding several Myr challenges our understanding of the physical processes occurring inside such clusters, and their impact on the interstellar medium of the host galaxy. Here, we summarize our recent results dealing with the hydrodynamics of matter ejected by massive stars inside the cluster and show that compact H?ii regions found around some massive clusters may indicate that these are evolving in a bimodal hydrodynamic regime. The latter is characterized by the accumulation of the injected matter in the central, thermally unstable zone, and by the ejection of mass supplied by massive stars in the outer regions of the cluster.     

Physical conditions in a quiescent prominence derived from UV spectra obtained with the UVSP instrument on the SMM

A quiescent prominence observed above the north-west limb on November 20, 1980, is analyzed using data obtained with the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM). The spectral data include the lines 1215 Å of Hi, 1401 Å of Oiv, 1402 Å of Siiv, 1548 Å of Civ, 1640 Å of Hei, and 1655 Å of Ci. From an analysis of these lines and their emission patterns we deduce physical characteristics of the prominence plasma, and suggest in particular that the prominence consisted of flux tubes at various temperatures. In the hotter parts of the plasma the number density reached values of about 3 × 10¹¹ cm^#X2212;3.     

The age decay of stellar magnetic activity in MS field solar-type stars

The age decay of two indicators of the stellar magnetic activity (λ 2800 Mgii emission flux and λ 10830 Hei equivalent width) have been studied for field solar-type stars. The Li abundance has been used, in most of the cases, as a stellar age indicator. A calibrated decay law for Mgii has been determined and compared with a similar one, recently published, for the Caii K emission. The greater scatter in the Hei results is atributed to the different rotation rates.     

Ca ii Transient Brightenings Associated with Canceling Magnetic Features

We analyzed transient Ca ii H brightening associated with small-scale canceling magnetic features (CMFs) in the quiet Sun near disk center using Ca ii H filter images and Na D₁ magnetograms of Hinode/SOT. We found that in most Ca ii brightening events related to CMFs the Ca ii H intensity peaks after the magnetic flux cancellation. Moreover, the brightening tends to appear as a pair of bright points of similar size and brightness overlying a magnetic bipole. Then a new opposite polarity fragment moves to them and cancels out. These results imply that magnetic reconnection takes place there and is responsible for CMFs.     

Spatial profiles of lines in active region loops

From the statistical treatment of magnetohydrodynamically turbulent plasma, a steady-state density, temperature and magnetic field structure is derived for a coronal loop emitting in UV and EUV range. Spatial variation of line flux is presented for the lines C ii, C iii, O iv, O vi, Ne vii, and Mgx. It is found that the hotter lines which are emitted near the surface of the loop have larger spatial extents compared to the lines originating in the cool core of the loop, in agreement with the observations.     

Rosat and EUVE observations of B stars

Recent observations of the X-ray and EUV emission of non-supergiant B stars are summarized. As compared with O stars, the X-rays of most of the near-main-sequence B stars are soft, and the stars show a departure from theL _x = 10^?7 L _bol relation. Using line driven wind models to provide an estimate of the density distribution, it is concluded that a major fraction of the wind emission measure is hot, whereas in shocked wind theory less than 10 percent of the wind emission measure should be hot. The X-ray observations suggest that all of the B stars are X-ray emitters with a basal X-ray luminosity of about 10^?8.5 L _bol . A hard component dominates the X-ray emission of τ Sco, and possible causes are discussed. For the Be stars, the X-ray emission is that which is expected from a normal B-star wind coming from the poles, as in the Wind Compressed Disk (WCD) model of Be stars. None of the stars, including theβ Cep stars, show noticeable variability in their X-rays.EUVE observations of∈ CMa B2 II, find it to be the brightest object in the EUV sky at 500 to 700 Å. It shows a Lyman continuum flux that is a factor of 30 higher than line blanketed model atmospheres. The continuum is seen on both sides of the He I 504 Å edge, and the discrepancy with model atmospheres is even greater shortward of 504 Å. TheEUVE spectra show emission lines both from high stages of ionization ( Feix to Fexvi) and from low stages (Heii and Oiii). The Heii Lymanα results from recombination following X-ray photoionization in the wind, and the Oiii resonance line is found to be present because of the Bowen fluorescence mechanism. Thus, there is and interesting coupling between the wind production by the EUV photospheric emission, the production of X-ray and line EUV emission by winds, and the production of fluorescence by recombination in the wind; all of these processes are now observable in B stars.     

Spectrophotometric studies of star HD 157978

Examination of the stellar spectrum of this star reveals that it has a composite spectrum. It could be classified as (A7V+G5V). It contains three forbidden [Feii] lines which are of the essential features of η Carinae stars. The spectrum also contains H, Hei, Feii, Mni, Tiii, and other different lines. The K-line seems to be sharp double line while other lines appear single ones which suggest early component may be double. This also seems to be true according to radial velocity measurements.     

Integral-field high spatial resolution spectroscopy of the giant Hii region NGC5461

We present preliminary results obtained from integral-field (IFU) data of the giant extragalactic Hii region NGC5461, located in a spiral arm (RA=14^h03^m41.4^s, dec=+54°19′05″) of M101. The spatial and spectral information obtained with IFUs allows us to decompose the Hii region and analyze it at high resolution.     

Emission features in the solar corona after the perihelion passage of Comet 1979 XI

On the coronograph spectrophotographic records taken on 31.372 UT, August 1979, some faint emission features were found which can be ascribed to Siii and Niii. These emissions were obviously a transient phenomena which were detected only 10 hr after the supposed fall of Comet 1979 XI in the Sun's photosphere. It cannot be excluded that the appearance of Si and Ni lines was triggered by the evaporation of dust particles with a high abundance of heavier elements in the solar corona. This assumption is also supported by intensity distribution of the Fex coronal line around the Sun's limb. The maximum coincide with the position angle of the projected path of the comet.     

The work of the diode array: He 10 830 observations of spicules and subflares

At a spatial resolution of 1″ and with spectral passbands of 0.25–0.47 Å, the chromospheric fine structure was studied with an array of 512 silicon photodiodes. The high quantum efficiency of the diodes in the near infrared allowed low noise spectroheliograms to be constructed from observations in the lines of H i, Ca ii, and He i. Magnetograms of the underlying photosphere were obtained simultaneously. Tachograms in the He 10830 Å line revealed 1″ points and elongated features that are interpreted as spicules seen against the disk. Active regions and filaments at 10830 are compared with Hα and Ca ii (8542 Å) features. Filament contrast increases with the proximity of bright plage. Twelve subflares were studied and in eight cases, 3–5″ kernels of He I emission appeared over small, growing pores or over 5″ patches of magnetic field emerging through the photosphere. All the subflares showed 10830 emission, contrary to established belief that the 10830 line goes into emission only in the largest flares. All the subflares included at least one emission kernel over regions where the photospheric magnetic field, as seen with a resolution of 1–2″, broke down into a mosaic of both polarities with 3–5″ diam. elements.