Recombination emission from protoglobular clouds on high redshifts

Fluxes in hydrogen and helium lines from Proto-Globular Clusters (PGCs) at redshifts z > 1 are estimated. A supernovae remnant in PGCs is considered as a possible source. Intensities in Lyα,Hα and 1640 Å HeI are calculated. It is shown that such PGCs can be detectable for the ongoing and future projects.     

Hα emission objects in Circinus

We present a new survey for Hα emission objects in the Circinus cloud complex and introduce an efficient photometric method for detecting Hα emission via observations in a narrow‐band filter. The observed flux is compared to a blackbody fit of the continuum. Our search strategy reveals 20 stars with strong Hα emission (EW > 10 Å), eight of them being new detections. All Hα stars display infrared excess corroborating their youth. On the other hand, the region contains a number of infrared excess objects that do not show Hα emission. Our results support the picture that accretion – as witnessed by Hα emission – is a highly variable phenomenon. Therefore, Hα surveys can only trace the temporarily active objects. In contrast, infrared excess is a more robust tracer that reveals most of the population of young stellar objects in a star forming region. Our analysis of the general stellar content of the region yields a reliable distance of 450 pc for the Circinus cloud. Moreover, we find a ratio of total‐to‐selective extinction of R^V = 2.8 suggesting that smaller‐than‐normal dust grains may be present. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Motions and magnetic fields in filaments

Based on the developed method of jointly using data on the magnetic fields and brightness of filaments and coronal holes (CHs) at various heights in the solar atmosphere as well as on the velocities in the photosphere, we have obtained the following results:

The upward motion of matter is typical of filament channels in the form of bright stripes that often surround the filaments when observed in the HeI 1083 nm line.

The filament channels observed simultaneously in Hα and HeI 1083 nm differ in size, emission characteristics, and other parameters. We conclude that by simultaneously investigating the filament channels in two spectral ranges, we can make progress in understanding the physics of their formation and evolution.

Most of the filaments observed in the HeI 1083 nm line consist of dark knots with different velocity distributions in them. A possible interpretation of these knots is offered.

The height of the small-scale magnetic field distribution near the individual dark knots of filaments in the solar atmosphere varies between 3000 and 20000 km.

The zero surface separating the large-scale magnetic field structures in the corona and calculated in the potential approximation changes the inclination to the solar surface with height and is displaced in one or two days.

The observed formation of a filament in a CH was accompanied by a significant magnetic field variation in the CH region at heights from 0 to 30000 km up to the change of the predominant field sign over the entire CH area. We assume that this occurs at the stage of CH disappearance.

     

Line Broadening in a Limb Flare：Derivation of Macro—turbulent Velocity Fields

The line profiles of Hα in a limb flare on 1998 November 11 appear to be unusually broadened. It is considered that macro-turbulence (or macroscopic mass motions) may be one of the main causes. We use an inversion technique to extract the probability distribution of the line-of-sight velocity in the flare. There exist some differences between the velocity distributions deduced from Hα and from CaⅡ λ8542, which may be because the two lines depend differently on the temperature and velocity. Since the loop density is high, we obtain a rather short cooling time (several tens of seconds) from the hot X-ray loops to the cool loops visible in Hα. Possible origins of the large scale motions are discussed.     

Spectroscopic analysis of sdB stars from the ESO Supernova Ia Progenitor Survey

We report on the analysis of high-resolution optical spectra for 77 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey. Effective temperature, surface gravity, and photospheric helium abundance are determined simultaneously by spectral line profile fitting of hydrogen and helium lines, and are found to be in agreement with previous studies of sdB stars. Twenty four objects show spectral signs of a cool companion, being either companion absorption lines or a flux contribution at Hα. Five stars with relatively high luminosity show peculiar Hα profiles, possibly indicating stellar winds. Our results are compared to recent theoretical simulations by Han et al. [MNRAS, 341, 669] for the distribution in effective temperature and surface gravity, and are found to agree very well with these calculations. Finally, we present a binary system consisting of two helium-rich hot subdwarfs.     

The formation of plessite in meteoritic metal

Abstract— Plessite is a mixture of body‐centered cubic (bcc) kamacite (α), face‐centered cubic (fcc) taenite (γ), and/or ordered FeNi‐tetrataenite (γ“) phases and is observed in the metal of iron, stony‐iron, and chondritic meteorites. The formation of plessite was studied by measuring the orientation of the bcc and fcc phases over large regions of plessite using electron backscatter diffraction (EBSD) analysis in five ataxites, the Carlton IAB‐IIICD iron, and zoneless plessite metal in the Kernouve H6 chondrite. The EBSD results show that there are a number of different orientations of the bcc kamacite phase in the plessite microstructure. These orientations reflect the reaction path γ (fcc)→α₂ (bcc) in which the α₂ phase forms during cooling below the martensite start temperature, M_s, on the close‐packed planes of the parent fcc phase according to one or more of the established orientation relationships (Kurdjumov‐Sachs, Nishiyama‐Wasserman, and Greninger‐Troiano) for the fcc to bcc transformation. The EBSD results also show that the orientation of the taenite and/or tetrataenite regions at the interfaces of prior α₂ (martensite) laths, is the same as that of the single crystal parent taenite γ phase of the meteorite. Therefore, the parent taenite γ was retained at the interfaces of martensite laths during cooling after the formation of martensite. The formation of plessite is described by the reaction γ→α₂ + γ→α + γ. This reaction is inconsistent with the decomposition of martensite laths to form γ phase as described by the reaction γ→α₂→α + γ, which is the classical mechanism proposed by previous investigators. The varying orientations of the fine exsolved taenite and/or tetrataenite within decomposed martensite laths, however, are a response to the decomposition of α₂ (martensite) laths at low temperature and are formed by the reaction α₂→α + γ.     

The continuous absorption coefficient of a stellar atmosphere

It is pointed out that, when calculating the continuous absorption coefficient in a stellar atmosphere, it is advantageous to use the coefficient per particle of the most abundant element instead of the usual coefficient per gram of matter. The sources of continuous opacity considered are 1) absorption by H^-, HI, H₂^-, H ₂⁺, HeI, HeII, CI, CII, CIII, NI, NII, OI, OII, NaI, MgI, MgII, AlI, AlII, SiI, SiII, ClI, KI, CaII; and 2) Rayleigh scattering by HI, HeI, CI, NI, OI, H₂, and 3) Thomson scattering of free electrons. The calculations are illustrated by the results for a solar-type photosphere.     

Airglow from Jupiter's nightside and crescent: Ultraviolet spectrometer observations from Voyager 2

The Voyager Ultraviolet Spectrometer has made extensive observations of airglow from Jupiter's dark-side equatorial latitudes. The brightness of H Lyman α (Lyα), the only emission detected, varies between 700 and 1000 rayleighs (R) as a function of lungitude. The dark side of Jupiter is illuminated by sky background Lyα arising from resonance scattering of the solar Lyα line by the neutral hydrogen of the interstellar medium. Calculations show that resonance scattering of this sky background by hydrogen in Jupiter's thermosphere will produce about 300 R of Lyα emission. The additional Lyα observed is probably excited by electrons and protons precipitating at equatorial latitudes. Based on the 500-R upper limit set here on the dark-side H₂ Lyman and Werner bands, and the Lyα measurements, the exciting particles are thought to have a soft energy spectrum and deposit about 0.04 erg cm^?2 sec^?1 in the atmosphere. There is evidence for an asymmetrical precipitation pattern associated with the longitudinal variation in Ly α emission, and a suggestion of a strong day-night difference in precipitation as well.     

Optical spectra of supernova remnant candidates in the Sculptor Group galaxy NGC 300

We present moderate-resolution (<5 Å) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [S?ii]_Total:Hα≥0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [S?ii]_Total:Hα of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [S ii]_Total:Hα criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.     

Synchronous <Emphasis Type="Italic">UBVR</Emphasis> photometry and spectroscopy of DI Cephei

We present our synchronous spectroscopy and photometry of DI Cep, a classical T Tauri star. The equivalent widths and radial velocities of the individual components and Hα, Hβ, D1 and D2 Na I, and HeI λ5876 Å emission line profiles exhibit variability. We have found a clear positive correlation between the brightness and equivalent width for the Hα and Hβ emission lines. The photometric and spectroscopic data are satisfactorily described in phases of a 9-day period. The expected magnetic field of the star has been estimated using existing magnetospheric models to be 655–1000 G. The star is suspected to be a binary.     

DOT Tomography of the Solar Atmosphere VII. Chromospheric Response to Acoustic Events

We use synchronous movies from the Dutch Open Telescope sampling the G band, Ca?ii?H, and Hα with five-wavelength profile sampling to study the response of the chromosphere to acoustic events in the underlying photosphere. We first compare the visibility of the chromosphere in Ca?ii?H and Hα, demonstrate that studying the chromosphere requires Hα data, and summarize recent developments in understanding why this is so. We construct divergence and vorticity maps of the photospheric flow field from the G-band images and locate specific events through the appearance of bright Ca?ii?H grains. The reaction of the Hα chromosphere is diagnosed in terms of brightness and Doppler shift. We show and discuss three particular cases in detail: a regular acoustic grain marking shock excitation by granular dynamics, a persistent flasher, which probably marks magnetic-field concentration, and an exploding granule. All three appear to buffet overlying fibrils, most clearly in Dopplergrams. Although our diagnostic displays to dissect these phenomena are unprecedentedly comprehensive, adding even more information (photospheric Doppler tomography and magnetograms along with chromospheric imaging and Doppler mapping in the ultraviolet) is warranted.     

Rotation curves of luminous spiral galaxies

We have investigated the stellar light distribution and the rotation curves of high‐luminosity spiral galaxies in the local Universe. The sample contains 30 high‐quality extended Hα and H I rotation curves. The stellar disk scale‐length of these objects was measured or taken from the literature. We find that in the outermost parts of the stellar disks of these massive objects, the rotation curves agree with the Universal Rotation Curve (Salucci et al. 2007), however a few rotation curves of the sample show a divergence (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-Wavelength Signatures of Magnetic Reconnection of a Flare-Associated Coronal Mass Ejection

The evolution of an X2.7 solar flare, that occurred in a complex β γ δ magnetic configuration region on 3 November 2003 is discussed by utilizing a multi-wavelength data set. The very first signature of pre-flare coronal activity is observed in radio wavelengths as a type III burst that occurred several minutes prior to the flare signature in Hα. This type III burst is followed by the appearance of a loop-top source in hard X-ray (HXR) images obtained from RHESSI. During the main phase of the event, Hα images observed from ARIES solar tower telescope, Nainital, reveal well-defined footpoint (FP) and loop-top (LT) sources. As the flare evolves, the LT source moves upward and the separation between the two FP sources increases. The co-alignment of Hα with HXR images shows spatial correlation between Hα and HXR footpoints, whereas the rising LT source in HXR is always located above the LT source seen in Hα. The evolution of LT and FP sources is consistent with the reconnection models of solar flares. The EUV images at 195 Å taken by SOHO/EIT reveal intense emission on the disk at the flaring region during the impulsive phase. Further, slow-drifting type IV bursts, observed at low coronal heights at two time intervals along the flare period, indicate rising plasmoids or loop systems. The intense type II radio burst at a time in between these type IV bursts, but at a relatively greater height, indicates the onset of CME and its associated coronal shock wave. The study supports the standard CSHKP model of flares, which is consistent with nearly all eruptive flare models. More importantly, the results also contain evidence for breakout reconnection before the flare phase.     

Structure and physical conditions in the Hα loops of an M7.7 solar flare

The M7.7 solar flare on July 19, 2012, is the most dramatic example of a “Masuda” flare with a well-defined second X-ray above-the-loop-top source. The behavior of the system of loops accompanying this flare has been studied comprehensively by Liu et al. based on Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data. We have performed spectroscopic and filter observations of the Hα loops in this flare with the Large Solar Vacuum Telescope. The basic physical parameters in the loops of this peculiar flare generally coincide with the known data in Hα loops. However, the electron density, 10¹¹ cm_?3, and the integrated disk-center continuum intensity, 12%, are quite high, given that the observations were obtained almost 3 h after the flare onset.We have estimated the ascending velocity of the loop arcade (~3.5 km s^?1) and the height difference between the Hα and 94 Å loops (~2 × 10⁴ km).     

Studies of K line filtergrams

High resolution filtergrams made with a 0.3 Å K line filter at Big Bear are discussed. The dark K3 clouds noted in spectra by Bappu and Sivaraman (1971) are confirmed; they cover about 1/3 of the inside of supergranule cells, and oscillate (mainly horizontally) with 3–4 min period. Their vertical extent of about 3000 km produces a sharp broadening of K3 at the extreme limb and obscuration of bright features. Spicules also produce K3 absorption, but they occur in emission more often than in Hα, particularly near the limb. Apart from these differences the structures seen in Hα and K generally correspond. A fine structure of granule size, also oscillating with 3–4 min period, is seen in K1. This structure is also obscured near the extreme limb, possibly by the same clouds seen in K1. The bright K232 network does not appear to oscillate significantly in brightness, except through covering and uncovering by the overlying dark clouds. Some bright spicules, and many dark ones, are seen over all elements of the K network, as in Hα. In active regions the structure in K is very close to Hα; all plagettes and plages are bounded by systems of strongly inclined bright and dark fibrils apparently marking the lines of force. The fibrils are the same (bright or dark) in Hα and K3; they are not seen in K2. Umbral flashes are much less visible in Hα. There is, however, a finer, granular umbral structure in Hα which does not oscillate. Running penumbral waves are not seen in K. The penumbra and surrounding areas are bright in K3. Every bright point in K3 corresponds to a magnetic field spot, except for the intranetwork area, where the magnetograms cannot detect possible fields. Flares are the same in K and Hα. The formation of the K double reversal at the limb is exhaustively discussed.     

The Structure and the Partial Opacity of the Spiral Shocks on the Novalike Cataclysmic Variables

V347 Pup is the first novalike system with clear spiral arms in its accretion disc, as evidenced from its HeI Doppler maps. Combining the Doppler maps of the various lines of the system V347 Pup a more complex structure is revealed on the first arm. On the Doppler maps of HeI λ5875 emission line the first arm splits to two smaller and thinner structures. The Doppler map of HeI λ6678 emission line shows that this line dominates the region of thin structure with higher velocities that we met on the Doppler map of HeI λ5875 emission line. On the contrary the Hα emission line dominates the region of thin structure with lower velocities. We therefore observe, that the Hα emission line dominates on the exterior of the first arm, and the emission line of HeI on the interior. Most of NaI is probably emanated from the white dwarf or from the interior of the disc, and then being absorbed by the spiral shocks.     

Measurements of Filament Height in Hα and EUV 304 Å

In this study, we present the three-dimensional (3D) configuration of a filament observed by STEREO and the Global High Resolution H-alpha Network (GHN) in EUV 304 Å and Hα line center, respectively. This was the largest filament located close to the active region NOAA 10956 that produced a small B9.6 flare and two Coronal Mass Ejections (CMEs) on 19 May 2007. The 3D coordinates of multiple points traced along this filament were reconstructed by triangulation from two different aspect angles. The two STEREO (A and B) spacecraft had a separation angle α of 8.6 degree on 19 May 2007. The “true” heights of the filament were estimated using STEREO images in EUV 304 and Hα images, respectively. Our results show that EUV emission of the filament originates from higher locations than the Hα emission. We also compare the measured reconstructed heights of the filaments in EUV with those reported in previous studies.     

Calibrated H I Lyman α Observations with TRACE

Since shortly after launch in April 1998, the Transition Region and Coronal Explorer (TRACE) observatory has amassed a collection of H?i Lα (1216 Å) observations of the Sun that have been not only of high spatial and temporal resolution, but also span a duration in time never before achieved. The Lα images produced by TRACE are, however, composed of not only the desired line emission, but also local ultraviolet continuum and longer wavelength contamination. This contamination has frustrated attempts to interpret TRACE observations in H?i Lα. The Very Advanced Ultraviolet Telescope (VAULT) sounding rocket payload was launched from White Sands Missile range 7 May 1999 at 20:00 UT. The VAULT telescope for this flight was a dedicated H?i Lα imaging spectroheliograph. We use TRACE observations in the 1216 Å and 1600 Å channels along with observations from the VAULT flight to develop a method for removing UV continuum and longer wavelength contamination from TRACE Lα images.

     

Study of galaxies in the Lynx-Cancer void. II. Element abundances

In the framework of study of the evolutionary status of galaxies in the nearby Lynx-Cancer void, we present the results of the SAO RAS 6-m telescope spectroscopy for 20 objects in this region. The principal faint line [Oiii]λ4363 Å, used to determine the electron temperature and oxygen abundance (O/H) by the classicalmethod, is clearly detected in only about 2/3 of the studied objects. For the remaining galaxies this line is either faint or undetected. To obtain the oxygen abundances in these galaxies we as well apply the semi-empirical method by Izotov and Thuan, and/or the empirical methods of Pilyugin et al., which are only employing the intensities of sufficiently strong lines. We also present our O/H measurements for 22 Lynx-Cancer void galaxies, for which the suitable Sloan Digital Sky Survey (SDSS) spectra are available. In total, we present the combined O/H data for 48 Lynx-Cancer void galaxies, including the data adopted from the literature and our own earlier results. We make a comparison of their locations on the (O/H)-M_B diagram with those of the dwarf galaxies of the Local Volume in the regions with denser environment. We infer that the majority of galaxies from this void on the average reveal an about 30% lower metallicity. In addition, a substantial fraction (not less than 10%) of the void dwarf galaxies have a much larger O/H deficiency (up to a factor of 5). Most of them belong to the tiny group of objects with the gas metallicity Z ⊙/20 or 12+log(O/H)?7.35. The surface density of very metal-poor galaxies (Z ⊙/10) in this region of the sky is 2–2.5 times higher than that, derived from the emission-line galaxy samples in the Hamburg-SAO and the SDSS surveys. We discuss possible implications of these results for the galaxy evolution models.     

Properties of the magnetic fields of coronal holes with active regions

We determine the structure of the magnetic fields of coronal holes (CHs) and investigate its change in connection with the emergence of active regions (ARs) in CHs. Based on our observations in the HeI 1083 nm line performed with the CrAO TST-2 telescope, we have selected CHs of two types: without (15 CHs) and with (28 CHs) ARs. Magnetograms obtained at the Kitt Peak National Solar Observatory have been used to calculate the magnetic fields of the same objects.