Scans of Comet Bennett, 19691

We present drift curves through the head and tail of Comet Bennett at λλ5892 (Na) and 6110 Å (continuum) made on 30.5 March 1970 with a 14 arc-sec entrance diaphragm. Quantitative photometry of the sodium emission lines radial profile show a maximum intensity peak offset some 7000 km to the Sun-ward direction of the continuum (dust) maximum. Both the dust and Na distributions on the tail side of Comet Bennett show nearly exponential decays in emission away from the Sun. The interpretation of these data is briefly discussed.     

Anomalous Fe II spectral effects and high H I Lyα temperature in gas blobs near η Carinae

We consider the origin of the anomalously high intensity of the ultraviolet Fe II λλ2507/2509 Å lines observed with high spatial and spectral resolutions from gas blobs (GBs) near η Carinae. This rare effect in stellar spectra is attributable to a combination of several factors: (1) the high hydrogen density(>10⁸ cm^?3) that ensures the blockingof the Lyman continuum by GBs and, accordingly, the formation of a cold H I region with completely ionized Fe atoms; (2) the small distance between the GBs and the central star that ensures a high (>8000–10000 K) Lyα H spectral temperature, which photoexcites Fe II selectively; and (3) the population of Fe II levels and, accordingly, the opening of a stimulated emission channel, which together with spontaneous transitions creates a radiative cycle where a single Fe II ion can multiply absorb Lyα emission.     

Photometric and spectrophotometric observations of the classical symbiotic star YY Her during its return to quiescence

We present new photometric UBVRI and spectroscopic observations of the symbiotic star YY Her during its return to quiescence after a strong outburst in 1993. High-resolution spectra of YY Her at similar phases at outburst maximum ?=0.48) and in quiescence ?=0.37) are presented for the first time. The ephemeris of YY Her has been refined P=586^d). The last two observed minima (in 1999 and 2000) differed radically in shape from the 1997 minimum described previously. Both were sharp and deep $(\Delta U \sim 1\mathop .\limits^m 6, \Delta V \sim 0\mathop .\limits^m 9)$ . To explain this shape of the V light curve, which is only slightly affected by nebular emission, it should be assumed that the cool component of YY Her fills much of its Roche lobe and has a hot spot on the hemisphere facing the hot component. The emission spectrum rich in Fe II lines, which is characteristic of symbiotic stars, was observed during the outburst, but high-ionization lines (He II λ4686) were also observed. The He I λλ5876, 7065 lines exhibit distinct P Cyg profiles; the centers of the absorption components are shifted from the emission ones by V _r≈100 km s^?1, suggesting moderate outflow velocities.     

Temporal and spatial variations in the Io torus

Spectrographic data on the Io torus from 15 nights of observations spread over a 4-month period in 1981 are presented here. The [SII] λλ6716, 6731; [SII] λλ4069, 4076; [OII] λλ3726, 3729; and [SIII] λ3722 lines were simultaneously measured on each spectrogram. An east-west asymmetry was observed in the optical emissions, showing larger western intensities and a more diffuse and radially extensive nebula to the east. Two configurations of [SII] longitudinal asymmetry that were stable over at least 4 days were observed. The magnetic longitudes of ～ 180 and 300° are shown to be of particular interest. Longitudinal structure was not detected in either the [OII] intensity or the plasma density as measured by the [OII] and [SII] doublet ratios. Errors in the line ratios could mask density variations as large as a factor of ～ 1.5. A radial variation in the ratio of OII/SII was observed, with the ratio being largest near Io's orbit. Monthly variabilitywas detected in both the intensity and density of the tours. The [SII] line ratios indicated an increase in n_e over the 4-month period that was accompanied by increased intensities. For single measurements, no correlation between the [SII] intensities and the [SII] λ6716/λ6731 line ratio was detected, but this could be a result of errors in the line ratio determinations. Extremely low values of this same ratio were measured. These appear to indicate errors in the presently accepted [SII] transition probabilities. These [SII] line ratios indicate that very-high-density regions are present in the torus, and it is shown how these regions could have significantly influenced these measurements.     

Oxygen-Rich Cool Stars in the Cepheus Region. New Spectroscopic Observations of Selected Objects from the KP2001 Catalog

Astrophysics - Spectra taken with the 2.6-m telescope at the Byurakan Astrophysical Observatory (BAO) in the λλ4000-7250Å range for eight M giants from the KP2001 catalog confirm...     

Amplification by Stimulated Emission in Rydberg Matter Clusters as the Source of Intense Maser Lines in Interstellar Space

The detailed processes giving maser line radiation from various molecules in space are not well understood, as can be seen from many recent detailed studies of maser line emission with high spatial and velocity resolution, and with polarization measurements. We now propose an improved maser mechanism based on amplification of the original molecular line emission by stimulated emission in Rydberg Matter (RM) clouds in HII regions, containing clusters H _N and (H₂) _N . This mechanism will amplify the molecular lines, depending on the position, velocity, cluster size and state of excitation of the clusters in the RM cloud. RM will only support certain frequencies, corresponding to rotational transitions of the clusters. The bond lengths in the RM clusters are known within 1% from radio frequency emission measurements in the laboratory, and it is now shown that all the commonly studied maser lines agree well with stimulated emission transitions in several types of RM clusters simultaneously. This may explain the strongly varying intensities of neighboring or related maser lines, an important effect that is not well understood previously. It is also pointed out that the magnetic field due to RM is of the same order of magnitude as observed from the Zeeman splitting in maser lines; thus, the molecules that are the original sources of the lines may be embedded in the RM clouds, for example in dense HII regions that are likely to be RM regions.     

ETON 6: A rocket measurement of the O2 Infrared Atmospheric (0-0) band in the nightglow

Co-ordinated rocket measurements of the O₂(a¹Δ_g−X³Σ_g⁻) Infrared Atmospheric (0-0) band emission profile and the atomic oxygen densities in an undisturbed night-time atmosphere are used to investigate the processes responsible for the excitation of O₂(a¹Δ_g) in the terrestrial nightglow. It is shown that three-body recombination of atomic oxygen, and subsequent energy transfer processes, can explain only part of the observed emission profile and that at least two other sources of O₂(a¹Δ_g) emission must exist. One of these additional sources, responsible for most of the emission observed below 90km, is identified as arising from the night-time residual of the very large dayglow ¹Δ_g population. The other additional source is required to explain most of the emission observed above 95km. The processes responsible for this high altitude component cannot be identified but the vertical distribution of the required source function strongly resembles the profile of the atomic oxygen density squared and suggests that a two-body radiative recombination process may be involved. However, the measured zenith emission rates can also be explained without the high altitude source of O₂(a¹Δ_g) if optical emission at 1.27 μm was induced by the rocket as it penetrated the nightglow layer.     

X-ray probes of magnetospheric interactions with Jupiter's auroral zones, the Galilean satellites, and the Io plasma torus

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the jovian system is a source of X-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are both powerful sources of X-ray emission. Chandra observations revealed X-ray emission from the Io plasma torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is due to bombardment of their surfaces by highly energetic magnetospheric protons, and oxygen and sulfur ions. These ions excite atoms in their surfaces leading to fluorescent X-ray emission lines. These lines are produced against an intense background continuum, including bremsstrahlung radiation from surface interactions of primary magnetospheric and secondary electrons. Although the X-ray emission from the Galilean moons is faint when observed from Earth orbit, an imaging X-ray spectrometer in orbit around one or more of these moons, operating from 200 eV to 8 keV with 150 eV energy resolution, would provide a detailed mapping of the elemental composition in their surfaces. Surface resolution of 40 m for small features could be achieved in a 100-km orbit around one moon while also remotely imaging surfaces of other moons and Jupiter's upper atmosphere at maximum regional resolutions of hundreds of kilometers. Due to its relatively more benign magnetospheric radiation environment, its intrinsic interest as the largest moon in the Solar System, and its mini-magnetosphere, Ganymede would be the ideal orbital location for long-term observational studies of the jovian system. Here we describe the physical processes leading to X-ray emission from the surfaces of Jupiter's moons and the properties required for the technique of imaging X-ray spectroscopy to map the elemental composition of their surfaces, as well as studies of the X-ray emission from the planet's aurora and disk and from the Io plasma torus.     

Observations of Stellar Winds

The different methods for the study of stellar winds are discussed: (1) P Cygni profiles (2) atomic emission lines (3) infrared and radio free-free emission (4) molecular emission lines (5) infrared radiation by dust. For each of these methods we describe some characteristic observations and we discuss the way in which these data can be used to derive the mass loss rate and the velocity distribution of the wind. We discuss these from the basic physical point of view in order to obtain an understanding of the basic physical processes involved. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solar abundance determination from ultraviolet emission lines

The intensities of far ultraviolet emission lines from the solar corona are analyzed to determine relative coronal abundances for oxygen, silicon, and iron. Dielectronic recombination is included in the formulation of ionization equilibrium. Observations of solar radio emission are used to obtain abundances relative to hydrogen. The absolute coronal abundances appear to be in agreement with their respective photospheric values. General properties of the structure of the chromosphere and corona are deduced from the analysis of observed emission in the ultraviolet and radio wavelength regions.     

Global atomic oxygen density derived from OGO-6 1304 Å airglow measurements

The OGO-6 UV photometer experiment measured the atomic oxygen OI 1304 Å triplet in the Earth's dayglow between 400 and 1100 km. We have analyzed the data for the period 15 September–25 October 1969 by obtaining best-fit models in which the 1304 Å emission is excited by solar resonance scattering and photoelectron excitation. Provided the excitation processes are specified, we find a unique relationship between the vertical column density of atomic oxygen and the zenith 1304 Å intensity. This is essentially independent of the atmospheric temperature. Because of the large numerical uncertainties, the excitation sources are determined from the 1304 Å data and quiet-time in situ measurements of atomic oxygen density. They are found to be in good agreement with recent solar measurements of the 1304 Å lines and with calculations of the photoelectron excitation source. The deduced variations of atomic oxygen column densities over the daytime atmosphere are found to agree well with the Jacchia 1971 models. During the geomagnetic storm, the column density generally increased above a fixed altitude. However, the latitudinal dependence is complex. Following the strong geomagnetic activity between 15 September and 1 October, depletions in atomic oxygen are observed. At times, there is evidence of high-altitude transport of atomic oxygen from high latitude to low latitude.     

Puzzles and potential for gamma-ray line observations of solar flare ion acceleration

The best tool for understanding ion acceleration in solar flares is gamma-ray line emission from nuclear de-excitation, positron annihilation, and neutron capture. These techniques have not yet come close to reaching their potential due to limited counting statistics in the lines. Instruments with focusing optics and large effective areas promise real breakthroughs in understanding high-energy solar processes. I discuss what can be learned from the various lines and the instrumental requirements for future focusing observations.“Mama always told me not to look into the sights of the Sun; oh, but mama, that’s where the fun is...” [1]     

Spectroscopy of candidate metal-deficient galaxies with the 6-m telescope

We present the first results of our program of search for the most metal-deficient blue compact galaxies (BCGs) carried out with the 6-m Special Astrophysical Observatory telescope. The results of spectrophotometry are presented and discussed for ten galaxies from the Case and Hamburg/SAO surveys. The selection of candidates, observations, and data reduction are described in detail. For all the galaxies studied, we measured the intensity of the [O III] λ4363 Å emission line, which allows us to properly determine the temperatures of H II regions and to deduce elemental abundances. We measured the intensities of all the detected emission lines in H II regions of the galaxies under study and determined the abundances of oxygen and neon in them and in some of these galaxies, of other elements (N, S, He, Ar, and Fe). The oxygen abundance log (O/H)+12 in six galaxies was derived with an error ≤0.1 dex. Six of the ten galaxies studied turned out to be metal-poor with an oxygen abundance ≤1/10 of its solar value [i.e., 12+log(O/H)≤7.92]. HS 0837+4717 with 12+log(O/H) ≤7.7 is one of the most metal-poor galaxies in this sample and one of the candidates for young galaxies. Low-contrast, broad emission components of the nebular [O III]λ4959 and 5007 Å lines were detected in its spectrum, suggesting high velocities of gas motions in this galaxy.     

Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter

The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift, and line width simultaneously over a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of the initiation and propagation of coronal mass ejections (CMEs). Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space-weather monitoring.     

活动星系核FeⅡ发发射线的研究进展

FeⅡ发射线是活动星系核光谱从紫外到光学波段的一个重要特征,其不仅与活动星系核的一些基本物理问题紧密相关,而且在宇宙学上有着重要的应用。虽然对FeⅡ发射线的观测和理论研究已有好几十年,但许多问题仍未有定论。主要对FeⅡ发射线近年的研究进展进行综述,包括其与本征向量Ⅰ的关系、它的起源、激发机制、发射区的运动学特征及在宇宙学中的应用等几方面,并指出了一些研究方向。     

Comments on the observability of coronal variations

We discuss the observable variability of spectral lines in the soft X-ray and XUV region. Rapid variability of coronal emission, both in flaring and non-flaring structures has been reported and is particularly prominent when high spatial resolution is available. Examination of the ionization and recombination time-scales for the formation and removal of ions with prominent solar emission lines shows that, even though ionization equilibrium generally prevails, the observable variability time-scales are often limited by these atomic processes, independent of the physical process which is causing the change in the solar atmosphere. Rapid heating can lead to an initial freezing-in of abundances of some ions; observations of at least one low- and one high-excitation line from such an ion would permit studies of the time evolution of the emission measure and temperature. In a very limited number of cases, rapid cooling leads to freezing-in of the abundance of an ion and observations of a low-excitation line of this ion will not yield accurate information about the thermal evolution. Thus, future observations of Mgx 609 Å should be augmented by simultaneous observation at another wavelength, such as 63 Å. In addition, with the ability to produce images in isolated spectral lines it becomes possible to select those for which rapid variability is observable, such asOvii, rather than lines which were selected on the basis of previous hardware constraints, such asOvii.     

Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer

The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940–1350 Å range as well as the 470–630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a few lines, but electron collisional excitation produces most of the lines observed. Resonance, intercombination and forbidden lines are seen, and their relative line intensities are diagnostics for the ionization state and elemental abundances of the coronal gas. The elemental composition of the solar corona and solar wind vary, with the abundance of each element related to the ionization potential of its neutral atom (First Ionization Potential–FIP). It is often difficult to obtain absolute abundances, rather than abundances relative to O or Si. In this paper, we study the ionization state of the gas in two coronal streamers, and we determine the absolute abundances of oxygen and other elements in the streamers. The ionization state is close to that of a log T = 6.2 plasma. The abundances vary among, and even within, streamers. The helium abundance is lower than photospheric, and the FIP effect is present. In the core of a quiescent equatorial streamer, oxygen and other high-FIP elements are depleted by an order of magnitude compared with photospheric abundances, while they are depleted by only a factor of 3 along the edges of the streamer. The abundances along the edges of the streamer (‘legs’) resemble elemental abundances measured in the slow solar wind, supporting the identification of streamers as the source of that wind component.     

Emission stratification in two-component HII regions with stellar wind

To explain the variety of observed optical emission stratification in the shells around Wolf-Rayet stars, we have calculated the nonstationary cooling of a homogeneous gas layer heated to a temperature (0.4–2) × 10⁵ K. We have assumed that the nebula is ionized by its central star and consists of a rarefied gas and a set of clouds with different densities through which adiabatic shock waves produced by the stellar wind propagate. Based on this model, we have determined the sequence in which the emission in Hα and in nebular oxygen lines appears. The Hα emission attributable to the electron-collision excitation of hydrogen atoms is produced earliest on the periphery of nebulae, the [O III] line emission follows next, and, finally, the Hα recombination emission is produced. The results obtained are in good agreement with the observational data.     

部分遮蔽类星体SDSS J151653.22+190048.2的紫外波段中等宽度发射线起源

类星体SDSS J151653.22+190048.2 (简称J1516+1900)在紫外-光学-近红外波段展现出奇特的光谱性质:其光学Hα、Hβ和近红外的Paα、Paβ等发射线的半高全宽(full width at half maximum intensity, FWHM)均超过5000 km/s,等值宽度接近类星体平均值;而紫外波段光谱的常见发射线Lyβ、OVI、Lyα、NV、Si IV和CIV等,由FWHM1700 km/s的中等宽度成分主导.这种现象很可能是由于紫外发射线的宽线成分经尘埃消光,强度严重削弱,从而使得中等宽度成分凸显出来;在光学和近红外波段,尘埃消光减弱,发射线由宽线成分主导,潜在的中等宽度成分不容易被看到.根据中等宽度成分的线宽和J1516+1900中央超大质量黑洞的质量MBH5.75×108M⊙,在维里化假设下,估计中等宽度发射区到中央黑洞的距离约为1.6 pc.另一方面,利用J1516+1900丰富的观测谱线,结合光致电离模型计算,可以限定J1516+1900的中等宽度发射线区气体密度1012cm-3、电离参数10-0.65.据此估计该发射线区到中心黑洞距离0.016 pc,只有维里化距离的1%.这一矛盾结果预示着中等宽度发射区可能具有较为复杂的物理结构,未来需要观测更多类似J1516+1900的部分遮蔽类星体并进行系统的分类和研究.