bluuebunny/crossref_metadata_2025 huggingface dataset:
Proper motion of water masers near NGC1333-SVS13
Authors: Wootten Alwyn , Claussen Mark , Marvel Kevin , Wilking Bruce
Published: June 2019

VLBA observations of water masers toward the region of NGC1333 near SVS13, the driving source for the well-known Herbig-Haro objects HH7-11, are reported. Maser emission was observed over four epochs spaced by three weeks during late 1998. SVS13 is associated with the millimeter continuum SED Class I source SSV13A1. High resolution CO observations have secured the association of the flow with the continuum object on arc-second scales. A 1998 Aug 12 VLA observation places the blueshifted masers within 80 AU (0.2) of the 2.7 mm position for A1 reported from BIMA. We report observations of two groups of masers, one redshifted by about 6 km s−1 and one blueshifted by about 2-3 km s−1, separated by about 100 AU in projected distance along position angle 21 degrees. Redshifted masers were present only in the latter two epochs. During all epochs, an arclike structure was present with similar morphology; over time this structure moved relative to the southernmost blue maser toward the southeast, roughly along the position angle defined by the Herbig-Haro objects, with a proper motion of about 13 km s−1. Both redshifted and blueshifted masers are clearly part of the same lobe of the flow; their observed Doppler shifts are artifacts of the opening angle of the flow. Our data suggest that the opening angle is about 10°. We measure lower expansion velocities and a wider opening angle than has been found in some other flows near Class 0 SED objects, perhaps indicating that the flows open and slow as they age.
Multiwavelength OH observations of Mon R2 during 4765 MHz OH maser flaring
Authors: Smits Derck P.
Published: June 2019

During the spectacular 4765 MHz excited OH maser flaring episodes observed in Mon R2 from 1994 to 1998 (Smits et al. 1998), observations were made at the line frequencies of other OH transitions. No excited OH lines were detected, nor were any 1612 or 1720 MHz OH masers found in Mon R2. 1665 and 1667 MHz OH masers were present and underwent small changes. With a peak flux of ∼ 75 Jy, the null detections and small variations at other wavelengths put strong constraints on models of OH masers.
The fine spatial structure of methanol masers as an evidence in support of their connection with bipolar outflows
Authors: Slysh Vyacheslav I. , Val'tts Irina E. , Kalenskii Sergei V.
Published: June 2019

We studied class I methanol masers in the transition 70 − 61A+ at the frequency 44 GHz with the VLA. The observations on the VLA were made with the angular resolution 0.1, which was the highest at the moment. It was shown that the masers consist of chains of unresolved spots located on curved lines or arcs. The length of such arcs is from 20 to 1000 AU and the brightness temperature of the strongest masers exceeds 3.6×108 K. The observed location of maser spots is in agreement with their position at the border line between molecular outflows and surrounding molecular clouds. The high brightness temperature implies that the maser condensations have enhanced abundance of methanol due to evaporation of methanol from the surface of dust grains. The mass of maser condensations is less than 4×10−5 M⊙ and corresponds to planetary masses.
CO observations as a diagnostic of possible environmental effects
Authors: Maia Marcio A. G. , de Mello Duilia , Wiklind Tommy
Published: June 2019

We have compared two samples of galaxies in very high and low density environments in order to study their physical properties and stablish any possible relation among them. This paper focus on the CO content as a diagnostic tool to examine galaxy properties such as the amount of molecular gas and the star formation efficiency. The similarities in star formation efficiency of the dense environments and the field galaxies suggest that the physical processes controling the formation of stars from the molecular gas are local rather than global.
Proper motion of a nuclear jet relative to a maser feature in NGC 3079
Authors: Sawada-Satoh Satoko , Inoue Makoto , Shibata Katsunori M. , Kameno Seiji , Nakai Naomasa , Migenes Victor , Diamond Phil J.
Published: June 2019

We present high resolution studies of the nuclear region in NGC 3079 with phase-referenced VLBI monitoring between its water maser and continuum emission. From results of the observations, NGC 3079 showed relative motion between core-jet-like continuum components. One of the components (A) relative to the reference maser feature moved with an apparent subluminal velocity along the SE-NW direction, almost parallel to alignment of the components. On the other hand, the position of the other component (B) did not show such a significant change. If the maser gas is associated with a rotating disk, the maser gas should be gravitationally bound to the central mass. This suggests that B and A are the nucleus and jet, respectively.
A flaring megamaser in Mrk 348
Authors: Peck Alison B. , Falcke Heino , Henkel Christian , Menten Karl M. , Hagiwara Yoshiaki , Gallimore Jack F. , Ulvestad James S.
Published: June 2019

We report new observations of the H2O megamaser in the Seyfert 2 galaxy Mrk 348. Following our initial detection in 2000 March using the Effelsberg 100 m telescope, a re-analysis of previous data on this source indicates that the maser was present but only marginally detectable in late 1997. Monitoring through late 2000 shows that the maser has again decreased to its original level. The H2O line is redshifted by ∼130 km s−1 with respect to the systemic velocity, is extremely broad, with a FWHM of 130 km s−1, and has no detectable high velocity components within 1500 km s−1 on either side of the strong line. Followup VLBA observations show that the maser emission emanates entirely from a region ≤0.25 pc in extent, toward the base of the radio jet.
Merlin water maser observations of the Seyfert 2 galaxy Mrk 348
Authors: Xanthopoulos Emily , Richards Anita M. S. , Diamond Phil J.
Published: June 2019

MERLIN images of Mrk 348 at 22 GHz show H2O maser emission at 0.02–0.11 Jy, within ∼ 0.8 pc of the nucleus. This is the first direct confirmation that molecular material exists close to the Seyfert 2 nucleus. Mrk 348 was observed one month after Falcke et al. (2000) first identified the maser in single-dish spectra. The peak maser flux density has increased about threefold. The masing region is ≲ 0.6 pc in radius. The flux density of radio continuum emission from the core has been rising for about 2 years. The maser-core separation is barely resolved but at the 3σ significance level maser and continuum peaks are not coincident along the line of sight. The masers lie in the direction of the northern radio lobes and probably emanate from material shocked by a jet with velocity close to c although direct maser amplification of the core by masers tracing a Keplerian disc is not completely ruled out.
The EVN MkIV recording system and the EVN Data Processor at JIVE
Authors: van Langevelde Huib Jan , Phillips Chris
Published: June 2019

The European VLBI Network (EVN) is involved in a number of projects to enhance its performance and capabilities. The gradual implementation of the MkIV recording standard has introduced a number of new possibilities. As well as wider bandwidth recording, allowing the detection of ever fainter continuum sources, the system has improved flexibility for doing spectral line VLBI. This is especially true when combined with the very large correlation capacity that the EVN MkIV data processor offers. This correlator, at the Joint Institute for VLBI in Europe (JIVE), Dwingeloo, is now providing the main correlator capacity for the EVN, and its capabilities are still being upgraded.
Globular Cluster Systems: Comparison with the Milky Way
Authors: Minniti Dante
Published: June 2019

The Milky Way globular cluster system serves as a reference for the study of more distant galaxies. Here I stress that there are still things we do not know about the globular cluster system of our own galaxy: their total number, their spatial motions and distances, and their IR properties. If our best reference point is not fully known, caution should be exercised when interpreting observations of distant systems. At the same time, when studying distant ellipticals it is not always advisable to rely on the Milky Way as a comparison. For example, only recently the first full calibration of the luminosity function of the globular cluster system of an elliptical galaxy was made, necessary to compare apples with apples.
Kinematics of Globular Clusters in M49 and M87
Authors: Bridges Terry
Published: June 2019

We present recent multi-object spectroscopy of globular clusters in the Virgo gEs M49 and M87. In M49, we have a total of 144 confirmed clusters out to 8 arcmin radius (∼ 6 Reff or 35 kpc). We find that the blue (metal-poor) clusters have both a higher velocity dispersion and rotation than the red (metal-poor) clusters. For the metal-rich population we place an upper limit of (v/σ)proj < 0.34 at 99% confidence. We calculate the velocity dispersion as a function of radius, and show that this is consistent with isotropic cluster orbits and the M49 mass distribution determined from X-ray data. For M87, we combine new CFHT data with previous data to obtain a total sample of 278 clusters out to 10 arcmin radius (∼ 45 kpc). We find a similar global rotation for the metal-poor and metal-rich clusters of 160–170 km/sec. Beyond ⋍ 2 Reff (15 kpc), both the metal-poor and metal-rich clusters appear to rotate about the photometric minor axis. The combined cluster sample is consistent with isotropic orbits, but when considered separately, the metal-poor clusters show significant tangential bias of βcl ⋍ −0.4, while the metal-rich clusters show a radial bias with βcl ⋍ +0.4. In both galaxies, the metal-rich and metal-poor clusters share different kinematics, but there is no clear preference for any one formation scenario.
Density and Velocity Distribution of the Interstellar Gas
Authors: van de Hulst H. C.
Published: June 2019

The interstellar gas shows wide variations in density and in velocity. Common words to describe the existence of these variations are cloudiness for the density and turbulence for the velocity field. These terms have initially been introduced as vague descriptions and were not based on mathematical analysis or dynamical theory. The word cloud as used by astronomers did not always mean a region of large density with relatively sharp boundaries; nor did the word turbulence necessarily imply a velocity field with well-defined statistical regularities and energy dissipation by means of viscosity.
Thermal Inelastic Collision Processes
Authors: Seaton M. J.
Published: June 2019

Section II contains a summary of relevant collision theory methods. Section III is concerned with heavy particle collisions: excitation of H 1s hyperfine structure (hfs) states by H atom impact; excitation of H2 rotation by H and H2 impact; H 2s→2p transitions produced by proton impact; charge exchange reactions; excitation of atomic levels by proton impact. Section IV deals with inelastic collisions between atoms and electrons. Use of the Born and distorted wave approximations is discussed. Calculations of cross sections for excitation of forbidden lines in pq configurations are reviewed and new results presented for O+2, N+, C+, and Si+, both variational and semiempirical methods being used. In Sec. V, concerned with atomic photoionization, new results are given for photoionization from 2pq configurations.
On the Cooling of Interstellar Matter
Authors: Schatzman E.
Published: June 2019

We shall not discuss here in detail the problem of the temperature equilibrium of interstellar matter. Some improvement of our knowledge has been effected by Seaton's results concerning the collisional cross sections of the ions C+, Si+, Fe+, which are important for the temperature equilibrium of the HI regions, and by his results concerning the excitation of the forbidden lines in gaseous nebulae.
On the Stability of Ionization Fronts
Authors: Kahn F. D.
Published: June 2019

The boundaries between HII and HI regions often have shapes which suggest that the motion of the interstellar gas is unstable there. A characteristic shape of this kind is the so-called “elephant's trunk,” a long tongue of dark material (presumably an HI region) seen superimposed on the luminous HII region, and outlined by a thin rim brighter than the luminous background. A detailed study of these shapes has recently been made by Pottasch; earlier observations had been made by Duncan and by Struve.
Possible Hydromagnetic Simulation of Cosmical Phenomena in the Laboratory
Authors: Bostick Winston H.
Published: June 2019

A technique has been developed whereby ionized gas (plasma) can be projected, by magnetic forces, at speeds of 3X107 cm/sec through a vacuum region free from a magnetic field. The plasma has also been projected across magnetic fields in vacuum at speeds of 107 cm/sec. It is further possible to have present in the magnetic field a background electrically conducting medium in the form of a low-pressure (about one micron) ionized gas. This gas is photoionized by the ultraviolet light from the plasma gun. With the background conducting medium we can calculate, following Spitzer, the electric resistivity η transverse to a strong magnetic field to be η = 1.29X1013(Z lnΛ)T−3/2 emu = 106 emu for T=105 °K (electron temperature), Z=1, lnΛ = 2.3. The magnetic Reynolds number Rm for L =10 cm and V = 107 cm/sec is thus Rm=4πLV/η = 103. Consequently, there is no doubt that with this technique we are producing magnetohydrodynamic phenomena in the laboratory.
Magnetic Fields in X-Ray Binary Systems
Authors: Kemp James C.
Published: June 2019

The case for variable magnetic fields, in the range 1–15 kG, in three of the X-ray binary candidate stars, is discussed. We refer to electronic Zeeman polarimetry by Kemp and Wolstencroft (1973a and b) and by Angel et al. (1973). Our detections in Hβ showed: (1) definite magnetic fields, roughly constant over periods of 2 h, in θ2 Orionis and HD 77581; and (2) complex time behavior in HD 153919, with field reversals over periods of ~ 10 min, but with usually small values (≲ 2 kG) as averaged over times of 1–2 h. (Photographic Zeeman spectroscopy is therefore unlikely to show detectable fields, i.e. > 2 kG, in the latter star.) The essentially null results of Angel et al. (1973) in Hβ, in HD 77581 and HD 153919, indicate that the emission is non-magnetic; only the underlying absorption (which is far weaker than the emission in Hβ) shows Zeeman effects. A plot of the Zeeman measure for HD 77581, against the 8.95-day period, is shown: our points are suggestive of periodicity; and the points of Angel et al. (1973) which unfortunately have larger relative error bars, are consistent with the indicated variation and with the general scale of our results.
Perturbation of the Non-Radial Oscillations of a Gaseous Star by an Axial Rotation, a Tidal Action or a Magnetic Field
Authors: Smeyers P.
Published: June 2019

The study of the linear and adiabatic oscillations of a gaseous star gives rise to an eigenvalue problem for the pulsation σ, if perturbations proportional to eiσt are considered. In the presence of a rotation, a tidal action or a magnetic field, the equations are not separable in spherical coordinates. To get approximate expressions for the influence of these factors on the non-radial oscillations of a star, the author and his collaborators J. Denis and M. Goossens have used a perturbation method (Smeyers and Denis, 1971; Denis, 1972; Goossens, 1972; Denis, 1973). Their procedure corresponds to a generalization of the method proposed by Simon (1969) to study the second order rotational perturbation of the radial oscillations of a star.

Two types of perturbations are taken into account: volume perturbations due to the local variations of the equilibrium quantities and to the presence of a supplementary force in the equation of motion (Coriolis force, Lorentz force); surface perturbations related to the distortion of the equilibrium configuration and to the change of the condition at the surface in the presence of a magnetic field. The resulting expressions are accurate up to the second order in the angular velocity in the case of a rotational perturbation, to the third order in the ratio of the mean radius of the primary to the distance of the secondary in the case of a tidal perturbation, and to the second order in the magnetic field in the case of a perturbing magnetic field. These expressions can in principle be applied to any mode.

Numerical results have been obtained for a homogeneous model and for a polytropic model n = 3. In particular, the splitting of the frequencies of the fundamental radial mode and of the f-mode belonging to l = 2 and m = 0 has been studied for the critical value of y, in the case of a component of a synchronously rotating binary system.
The Art of Fitting P-Mode Spectra
Authors: Appourchaux T. , Gizon L.
Published: June 2019

For deriving p-mode parameters from m, v diagrammes, one has to treat correctly the statistics of the observation. The correct statistical treatment of these diagrammes was first achieved by Schou (1992) (PhD thesis, Aarhus University). Fitting p-mode spectra requires 4 major steps:

1.

Compute the mode leakage matrices

2.

Compute mode covariance matrices from the previous matrices

3.

Compute the noise covariance matrices

4.

Compute and maximize the likelihood of the observation
Gong Spectra in Three Observables: What is a P-Mode Frequency?
Authors: Harvey J. , Hill F. , Komm R. , Leibacher J. , Pohl B. ,   The Gong
Published: June 2019

The Global Oscillation Network Group (GONG) is an international, community-based helioseismology project conducting a detailed study of the internal structure and dynamics of the Sun. GONG is operating a six-station network of full-disk solar imagers exploring the range from ℓ = 0 to about ℓ = 200. Full network operation began in October 1995. The observation duty cycle has averaged about 87% over the first 684 days of full operation, and single-site data loss due to instrument down time is less than 2%. The data management group is processing the network data at pace with the collection rate. Here we present a comparison of spectra obtained in Doppler velocity, total spectral intensity, and modulation (a mixture of equivalent width and magnetic field strength).
Total Solar Irradiance Variations: The Construction of a Composite and its Comparison with Models
Authors: Fröhlich Claus , Lean Judith
Published: June 2019

Measurements of the total solar irradiance (TSI) during the last 18 years from spacecraft are reviewed. Corrections are determined for the early measurements made by the HF radiometer within the ERB experiment on NIMBUS7 and the factor to refer ACRIM II to the ACRIM I irradiance scale. With these corrections a composite TSI is constructed for the period from 1978-1997. This time series is compared with a model that combines a magnetic brightness proxy with observed sunspot darkening and explains nearly 90% of the observed short and longterm variance. Possible, but still unverified degradation of the radiometers hampers conclusions about irradiance changes on decadal time scales and longer.
Quasi-10-Day and 4-Day Periodicities in Solar Irradiance
Authors: Nikonova M.V. , Klochek N.V. , Palamarchuk L.E.
Published: June 2019

There are many investigations of the total solar irradiance (TSI) variability over the time scales from days to years. Particular emphasis has been placed on the sources of this variability and on the problems concerning stable equipment operation. The investigations made aboard SMM/ACRIM showed a relation between solar variability and various solar activity manifestations. Even then the TSI power spectrum revealed some peculiar periodicity in the range from 9 to 11 days that was not explained and also a well-defined quasi-4-day periodicity (Froelich and Pap, 1989). Their distinctive feature is that they manifest themselves in many processes both on Sun and on Earth. An understanding of their nature is of importance to solar-terrestrial physics. The earlier investigations of Nimbus-7 data pointed out the possible effect of solar sources of unknown nature and also some residual instrumental effects on the behaviour of TSI variations. As a further development of these studies the spectral analysis was made of the TSI variations using the final data set derived over the range from November 1978 to April 1992 aboard Nimbus-7. In our study the data gaps were filled with an artificial noise signal. The autocorrelation function (ACF) was used for detrending and filtering of the data.
Solar Internal Rotation
Authors: Schou Jesper ,   The SOI Internal Rotation team
Published: June 2019

With the flood of high quality helioseismic data from the instruments on the SOHO spacecraft (MDI/VIRGO/GOLF) and ground based instruments (e.g. GONG, LOWL, BiSON, IRIS, MWO-CrAO and TON) we have been able to get increasingly detailed information on the rotation and other large scale flows in the solar interior.

Here we will discuss some of the highlights of what we have learned so far and what we may expect to learn in the near future. Among the recent advances have been tighter constraints on the tachocline at the bottom of the convection zone and detection of details in the surface rotation rate similar to the torsional oscillations found in the surface Doppler shift.
Observation of Seismic Effects of Solar Flares from the SOHO Michelson Doppler Imager
Authors: Kosovichev A.G. , Zharkova V.V.
Published: June 2019

Solar flares are the strongest localized seismic disturbances on the solar surface. During the impulsive phase a high-energy electron beam heats the chromosphere, resulting in explosive evaporation of chromospheric plasma at supersonic velocities. This upward motion is balanced by a downward recoil in the lower part of the chromosphere that excites propagating waves in the solar interior. On the solar surface the outgoing circular flare waves resemble ripples from a pebble thrown into a pond. We report on first observations of the seismic effects of a solar flare from the SOHO Michelson Doppler Imager (MDI) and compare the results with a theoretical model. Observation of flare seismic waves provide important information about the flare mechanism and about the subphotospheric structure of active regions.
The Integrated Magnetic Field of the Sun Seen by the Golf Experiment
Authors: García R.A. , Cortés T. Roca ,   The GOLF Team
Published: June 2019

The secondary objective of the GOLF experiment on-board the SOHO space mission is to measure the line-of-sight component of the disk averaged magnetic field of the Sun. GOLF is an improved disk-integrated sunlight resonant scattering spectrophotometer. Using an extra fixed quarter wave plate placed at the entrance of the instrument, enables a selection of the circularly polarized solar light and therefore, the disk averaged solar line-of-sight component of the magnetic field can be obtained. Unfortunately, due to occasional malfunction of the rotating mechanisms, only a series of 26 continuous days are available. Here, the analysis of this series is presented including the value of the averaged magnetic field.
Temporal Behavior of Solar P-Modes from Gong and Golf Experiments
Authors: Gavryusev V.G. , Gavryuseva E.A.
Published: June 2019

We used the measurements of solar oscillations taken by GONG and GOLF experiments. The first set of data are the integrated images obtained from the complex GONG observations taken from June 10 of 1995 to January 7 of 1997, 578 days in total, referenced below as ts0 time series. Radial, dipole and quadrupole modes are well visible in this time series. The second data set is the GOLF time series obtained on-board SOHO mission from April 11, 1996 to June 22, 1997. GOLF observes the “Sun as a star”. This time series is similar to ts0 of GONG but of a better quality (better signal-to-noise ratio; uniform, practically uninterrupted data). Both experiments are significantly overlapped in time. Because of this the direct comparison between them is possible, and the effects visible in both observations support each other.
The EC14026 Stars - Pulsating Hot Subdwarfs
Authors: Koen C. , O'Donoghue D. , Kilkenny D. , Stobie R.S.
Published: June 2019

The Edinburgh-Cape Blue Object Survey (Stobie et al. 1997a) is a southern hemisphere survey to discover hot, blue stellar objects brighter than B=18 at galactic latitudes more than 30° from the galactic plane. The main categories of object detected are hot subdwarfs, white dwarfs, blue horizontal branch stars, apparently normal B stars, cataclysmic variables and (stellar-like) active galactic nuclei. Over 50% of the EC Survey comprises hot subdwarfs.
Infall in Protostellar Envelopes
Authors: Ohashi Nagayoshi
Published: June 2019

We summarize recent progress of observational studies of infall in protostellar envelopes, with great emphasis on results obtained using millimeter and submillimeter interferometers. Interferometric observations allow us to spatially resolve kinematical structures of protostellar envelopes, enabling us to detect infalling motions in the envelope directly. High angular resolution observations of infalling envelopes having compact disks sufficiently bright in continuum show inverse P-Cygni profiles, which are the least ambiguous evidence for infall. Observations of infalling envelopes using the Submillimeter Array (SMA) may allow us to study the innermost infalling envelopes, where infalling motions most probably transform to Keplerian motions, leading to formation of Keplerian or protoplanetary disks around protostars.
Formation and Early Evolution of Intermediate Mass Stars
Authors: Testi Leonardo
Published: June 2019

In this paper I discuss our current understanding of the formation of intermediate mass stars and the evolution of their circumstellar material. The results of the search for clusters around Herbig Ae/Be stars are discussed in the context of the possible relationship of the formation of massive stars via coalescence process. Current surveys are not able to offer a definite answer on whether there is a physical relationship between the most massive intermediate mass stars and the presence of clusters. The present day stellar densities in these clusters is too low to allow for frequent stellar collisions, but do not exclude the possibility of coalescence at earlier cluster ages. I review the evidence for and properties of circumstellar disks around Herbig Ae stars, as well as recent observational evidence for dust evolution within these disks. Evidence is presented for the presence of evolved dust in some of these disks, with grain growth to sizes as large as a few centimeters. The status of the search for the more elusive disks around Herbig Be stars is also discussed. Current observations show that disks around Herbig Be stars progenitors may have been common and massive in the protostellar phase, but optically visible Herbig Be stars, albeit very young, are never found to be surrounded by conspicuous dusty disks, suggesting dispersion timescales as short as 1 Myr.
Subaru AO Coronagraphic and Direct Imaging of YSOs
Authors: Tamura Motohide , Fukagawa Misato , Hayashi Masahiko ,   SDPS/CIAO teams
Published: June 2019

A cold near-infrared stellar coronagraph combined with adaptive optics (CIAO) is introduced. As an open-use instrument on the Subaru 8.2-m telescope, it has been used for several star formation studies with high spatial resolutions (from natural seeing of about 0.6 arcsec down to 0.07 arcsec with adaptive optics). A brief explanation is described of the instrument as well as its current main project of systematic surveys of disks and young companions around T Tauri stars and Herbig Ae/Be stars. In particular, observations of HL Tau are presented in some details. Our images of HL Tau show several new circumstellar features including the presence of a red H - K color region of ∼150 AU, probably corresponding to the small circumstellar disk. The observations of a high density stellar cluster of MWC 137 are also reported. It appears to be a cluster of very low-mass stars around Herbig Be star or a cluster of B stars around a super giant.
Modeling Outflows from Young Stars
Authors: Shang Hsien
Published: June 2019

We have constructed the foundations to a series of diagnostics methods to probe the jet phenomena in young stars as observed at various optical forbidden lines and radio wavelengths. We calculate and model in a self-consistent manner the physical and radiative processes, which arise within an inner disk-wind driven magnetocentrifugally from the circumstellar accretion disk of a sun-like star. Comparing with real data taken at high angular resolution, our approach will provide the basis of systematic diagnostics for jets and their related young stellar objects, to attest the emission mechanisms of such phenomena. Such approach can help bring first-principle theoretical predictions to confront actual multi-wavelength observations, and will bridge the link between complex numerical simulations and observational data. Analysis methods discussed here are immediately applicable to new high-resolution data obtained with HST, Adaptic Optics, and radio interferometry.
Herbig Ae/Be Star Disks at High Angular Resolution
Authors: Dullemond C. P. , Dominik C. , van Boekel R. , Waters R. , van den Ancker M.
Published: June 2019

We show that there exists a simple geometric picture for the geometries of protoplanetary disks around Herbig Ae/Be stars that explains the two main kinds of spectral energy distributions found for these objects, and that makes predictions that are qualitatively in agreement with currently available spatially resolved images and/or interferometric measurements. Also it qualitatively explains the phenomenon of UX Orionis variability.
Star Formation by Future Millimetre and Radio Interferometers
Authors: Knee Lewis B.G.
Published: June 2019

The Low Frequency Array (LOFAR), the Atacama Large Millimetre Array (ALMA), and the Square Kilometre Array (SKA) will be the largest and most capable aperture synthesis facilities of the next few decades. The advances in our knowledge of star formation that ALMA will permit are well known to the star formation community, but the potential of the SKA has so far attracted less attention. I will outline the star formation science cases of these upcoming facilities, with an emphasis on the SKA.
The Milky Way from antiquity to modern times
Authors: Hoskin Michael
Published: June 2019

The paper outlines the history of attempts to explain the Milky Way, from Antiquity to the early-twentieth century, with special reference to the eighteenth and nineteenth centuries. Also discussed is the relationship of the Galaxy to other star systems, and particularly the question of whether there are other galaxies in the visible universe.
Infrared scanning of the Galactic bulge
Authors: Catchpole R. M. , Whitelock P. A. , Glass I. S.
Published: June 2019

We find values of the interstellar absorption from J, H and K scans of a 6.8 × 200 arcmin strip of sky extending from the Sgr I field to the Galactic Centre. The visual absorption, excluding dark clouds, increases from 3 to 30 magnitudes in this region.
The carbon monoxide distribution in the inner Galaxy
Authors: Bania T. M.
Published: June 2019

The latitude distribution of the emission from the 12CO J=1→0 rotational transition has been surveyed for the region 350° ≤ 1 ≤ 25° at b = 0′, ±10′ and ±20′. Most of the 12CO emission in the inner Galaxy, the region extending from the galactic center to 4 kpc radius, is produced by three large and massive objects: the nuclear disk/bar, the 3-kpc arm and the “+135 km s-1 feature”. These structures all have observed HI counterparts and each shows extremely large deviations (50–180 km s-1) from circular motion. Observations of 13CO in selected directions show that the two structures outside the nuclear disk each span at least 2 kpc in length and that together they imply ≥ 1055 ergs in kinetic energy of expansion away from the galactic nucleus.
A bisymmetric spiral magnetic field in the Milky Way
Authors: Sofue Y. , Fujimoto M.
Published: June 2019

The distribution of Faraday rotation measure (RM) of extragalactic radio sources shows that a large-scale magnetic field in the Galaxy is oriented along the spiral arms. The field lines change direction from one arm to the next in the inter-arm region.
Determination of Galactic spiral structure at radiofrequencies
Authors: Liszt H. S.
Published: June 2019

We consider some results of attempts to trace the pattern of galactic spiral structure in HII regions, HI, and CO. There is really no adequate method available for solving this problem, a fact reflected in the lack of consensus regarding the “correct” spiral pattern. The newly-begun process of deriving galactic structure in CO seems to be recapitulating the history laid down by HI observers.
Interpretation of the apparent anomalies of the Galactic structure
Authors: Jaakkola T. , Holsti N. , Teerikorpi P.
Published: June 2019

In maps of the galactic structure based on the kinematical method (Fig. 1) several systematically heliocentric anomalies are found: 1. Assuming purely circular motion, the spiral arms are more tightly wound and the extent of neutral hydrogen is smaller in the northern galactic hemisphere than in the southern one. 2. With separate rotation curves for the north and the south, the arms become anomalously circular. 3. Consequently, there is a striking discrepancy with the stellar spiral structure. 4. There are long straight portions in the arms pointing towards the Sun. 5. There are abrupt knee-like features in the south. 6. Some arms seem to affect the structure of other, outer arms. 7. Conspicuously strong curvature of the arms is found in the north. 8. The HI-density is enhanced at symmetric longitudes on the far side. 9. With the northern rotation model HII-regions and HI avoid the southern tangential circle. 10. The Perseus Arm is displaced at 1 = 180°.
The Galactic Nucleus
Authors: Oort J. H.
Published: June 2019

The ionized gas within 2 parsec from the centre region is distributed in spiral-like features which appear to emanate from a nucleus. This nucleus is close to the ultra-compact radio source and the infrared source IRS 16, but does not exactly coincide with either. The spiral is strongly inclined to the galactic plane. The arms are clumpy. The spiral appears to rotate, but there appear to be also large radial motions.

The phenomena show some resemblance to what is observed on a very much larger scale in the nuclei of radio galaxies and quasars.

An exceptionally powerful, variable source of hard X- and gamma-rays, GCX, has been found in the direction of the centre. This may be the true galactic nucleus. Strong, variable emission of the 511-keV electron-positron annihilation line has also been observed to come from the central region.

The evidence for a central black hole is discussed. It is not compelling. The energy required for the strong infrared radiation emitted by the central few parsecs is probably coming from a large number of luminous stars, and due to a recent burst of star formation. The observed state of ionization indicates the burst to have occurred about one million years ago.

The distribution of the dense molecular clouds within 300 pc from the centre is very asymmetric: practically all lie at positive longitudes. Their motions differ radically from circular motions. The layer of clouds is tilted relative to the galactic plane. The so-called “+40-km/s cloud” lies in front of the nuclear spiral, and is therefore moving towards the centre. Different interpretations of the systematic motions are considered. The outspoken asymmetry excludes a static condition. If the “molecular ring” at R ~ 150 parsec is actually an expanding feature, its origin might be sought in the same burst of star formation proposed to explain the state of ionization and the infrared radiation of the nuclear region.
Distribution and motion of CO in M31
Authors: Stark Antony A.
Published: June 2019

M31 is among the few galaxies whose solid angle is more than 100 times the beam area of currently operational millimeter-wave telescopes. Roughly 10% of its area has been mapped in the J=1→0 line of CO with the 7-m telescope at Bell Laboratories. The data lie on the major and minor axes and in a filled 20′ by 15′ field. The average CO emissivity is less than 1/5 that of the Milky Way Galaxy, and the inferred H2 column densities are less than 10% of the HI column densities at the same positions. Thus M31 has a predominantly atomic interstellar medium, whereas our Galaxy seems to have a predominantly molecular interstellar medium. The molecular emission is strongly concentrated in spiral-arm segments, with greater than 25:1 contrast between arm and interarm regions. Overall, the CO emission is well correlated with the HI emission, but shows greater concentration to the spiral arms. There is no evidence for a spatial separation of the HI and CO arms to within our resolution (~1′): all the spiral-arm tracers are spatially coincident. Almost all the gas on the minor axis exhibits non-circular velocities of about 20 km s-1. There are systematic streaming motions as large as 80 km s-1 associated with spiral arms.
Warps and heavy halos
Authors: Sparke Linda S.
Published: June 2019

The outer gas disk of our Galaxy (and many others) is warped, bending away from the plane defined by the inner disk. The bend begins just outside the solar circle; gas at longitudes ℓ ≃ 80° reaches highest above the plane, while material at ℓ ≃ 260° lies below it. Shortwavelength ripples are superposed. The orbit of a free particle inclined to the galactic disk precesses at a rate which depends on galactocentric radius; warped structures will tend to do the same, winding the warp into a tight spiral. The large-scale galactic warp has no sense of spirality, and is not obviously of recent origin - why then has it survived?
Stochastic star formation and spiral structure
Authors: Seiden Philip E.
Published: June 2019

Most approaches to explaining the long-range order of the spiral arms in galaxies assume that it is induced by the long-range gravitational interaction. However, it is well-known in many fields of physics that long-range order may be induced by short-range interactions. A typical example is magnetism, where the exchange interaction between magnetic spins has a range of only 10 ångströms, yet a bar magnet can be made as large as one likes. Stochastic self-propagating star formation (SSPSF) starts from the point of view of a short-range interaction and examines the spiral structure arising from it (Seiden and Gerola 1982). We assume that the energetic processes of massive stars, stellar winds, ionization-front shocks and supernova shocks, in an OB association or open cluster can induce the creation of a new molecular cloud from cold interstellar atomic hydrogen. In turn this new molecular cloud will begin to form stars that will allow the process to repeat, creating a chain reaction. The differential rotation existing in a spiral galaxy will stretch the aggregation of recently created stars into spiral features.
Archaeology in Greece, 1895–6. II. Melos
Authors: Smith Cecil
Published: June 2019

The operations at Melos of the British School, between March 20th and the end of May, were mainly tentative in character; the island contains evidently a large number of ancient sites, but unfortunately, in most of them, a great deal of unsystematic and unrecorded digging has been for a long time carried on. It seemed, therefore, desirable to ascertain, first, whether it would be necessary to continue for more than one season; and, secondly, what sites would best repay investigation. Our first researches were directed to the shore of the little bay of Klima, which lies at the foot of the hill on which the theatre and many other traces of the old town are still distinguishable. The fact that part of this ground (the property of the Government) was said to have yielded the celebrated statue of Poseidon, now in the National Museum, as well as other statues (one of which is still lying in situ), and was otherwise said to be unexcavated, seemed to warrant our choice; the more so as the Government had made this excavation a condition of their permission. Here, then, on March 20th, we began (site A, fig. 2); at the same time I received permission to break ground at another promising site (site B) in the opposite side of the delta, where the gardener, in sinking a well-shaft, had come upon traces of a marble pavement with two bases resting upon it.
A Psychological Look at Some Problems of Perception
Authors: Farrell B. A.
Published: June 2019

I shall attempt something rash in this paper. I shall draw your attention to some past and current work on perception by psychologists and others. I shall concentrate on work in vision and hearing. This outline will occupy the first part of my lecture. I shall then go on, in the second part, to suggest that this scientific work has certain philosophical implications. This whole attempt is a bit rash for obvious reasons. It is not easy to outline fairly and accurately past and current work in any branch of science. I am very liable, therefore, to do an injustice to the efforts of psychologists and others in this field. What makes matters more difficult for me is that I also have to show that this work is of philosophical interest. What has led me to embark on this perilous enterprise is a hunch I have developed in recent years. I have the hunch that philosophers who are interested in perception would do well to pay rather more attention than (perhaps) they have been wont to do in the past to the work and discourse coming out of the scientific laboratory and similar places.
I/ Geography of the Mogollon Area
Authors: Wheat Joe Ben
Published: June 2019

In cultural terms, the Southwest has never been satisfactorily defined. This is particularly true of the southern boundaries. Archeologists usually include the territory occupied by the groups we term Anasazi, Hohokam, Mogollon, and Patayan; it is this area that will be considered here.

Physiographically (Atwood 191+0; Darton 1925; Fenneman 1931), the northern and eastern parts of this area belong primarily to the Colorado Plateaus Province; the southern and western parts comprise a portion of the Basin and Range Province. Physiographers subdivide these major provinces into lesser units having more significance for the archeologist. The Colorado Plateaus Province is marked primarily by high mesas and plateaus underlain by nearly horizontal strata of strong, cliff-producing rocks locally covered by volcanic features or domed by igneous intrusions. This extensive area is drained largely by the Colorado River and its tributaries. Among the distinguishing features are the hundreds of deeply entrenched canyons and great retreating cliffs or escarpments.
VII / Minor Handicrafts of the Mogollon
Authors: Wheat Joe Ben
Published: June 2019

One of the principal characteristics of the Mogollon culture pattern is the relative abundance of ground and pecked stone artifacts, for the most part of a rather rough-and-ready nature. There can be little doubt that this is, in large measure, a heritage from their Cochise forebears, for often the same tool types are continued, almost without change, from preceramic into ceramic Mogollon horizons. Examples of such continuation are basin and slab metates and associated mano types, grinding slabs, pestles and boulder mortars, abrading stones, stone balls, and the universal hammer stones. Some of these artifacts are widespread in the Southwest in both time and space; others are specifically southern in their distribution. Data concerning the time and branch distribution of Mogollon ground stone artifacts are presented in Table 11 and Figure 8
Astrophysics in the 1890s – The Dawn of a New Age in Astronomy
Authors: Hearnshaw J. B.
Published: June 2019

The Konkoly Observatory was established as a public institution in Hungary in 1899, when Nicholas von Konkoly Thege (1842–1916) bequethed his private observatory at Ógyalla to the state. Konkoly himself was one of the pioneers in the new science of astrophysics, and he was an expert in astronomical instruments used for photometry and spectroscopy.

In this paper I review, from a global perspective, the 1890s decade as ten years of prodigious achievements in stellar astronomy, with many huge programmes being launched and undertaken in spectral classification, radial velocities, photometry and astrometry. New astrophysical observatories were founded in America and Europe and new large telescopes designed and built, and the first international conferences were held in astronomy.

Astrophysics was still a largely qualitative science in the 1890s, but this was soon to change in the early years of the present century. I review the development of astrophysics in the 1890s, its interaction with new discoveries in physics, and comment on some of the large projects in stellar photometry, spectroscopy and astrometry and especially the influence of photography on observational astrophysics. The place of Nicholas von Konkoly in this overall endeavour is discussed and I pay tribute to his considerable influence and to the observatory he founded. A century of state-funded astronomy in Hungary has been the result.
Impact of the Sloan Digital Sky Survey on Variable Star Research
Authors: Ivezić Željko , Goldston Josh , Finlator Kristian , Knapp Jill , Yanny Brian ,   the SDSS Collaboration
Published: June 2019

We present the results of a preliminary search for variable objects in about 100 deg2 of SDSS commissioning data surveyed twice with Δt=1.99462 days. In particular, we find that the density of RR Lyrae star candidates abruptly ends at a galactocentric radius of 50–60 kpc.
Red Variables from the MOA Database
Authors: Takeuti Mine , Noda Sachiyo , Bond I. A. , Rattenbury N. J. , Abe F. , Carter B. S. , Dodd R. J. , Hearnshaw J. B. , Honda M. , Jugaku J. , Kabe S. , Kilmartin P. M. , Masuda K. , Matsubara Y. , Muraki Y. , Nakamura T. , Reid M. , Rumsey N. J. , Saito To. , Sato H. , Sekiguchi M. , Sullivan D. J. , Sumi T. , Watase Y. , Yanagisawa T. , Yock P. C. M. , Yoshizawa M.
Published: June 2019

The red variables whose amplitude is larger than 1.3 mag in the MOA database are studied for the LMC. Among 3 196 such stars, 532 stars are likely to be Miras or red semiregular variables. The period–colour relation of these stars is shown.
Pulsation of the AGB Variable in the Symbiotic Nova PU Vulpeculae
Authors: Chochol D. , Pribulla T.
Published: June 2019

Analysis of the 1993–4 eclipse in the slow symbiotic nova PU Vul (4900-d binary orbital period) and 1995-9 photoelectric observations in V and R bandpasses show that the cool component of this object is pulsating AGB variable with a 215-d pulsation period. Basic properties of the components of the system are discussed.
Optical and Radio Monitoring of a Sample of Late-Type Variables
Authors: Esipov V. F. , Lekht E. E. , Pashchenko M. I. , Rudnitskij G. M.
Published: June 2019

Results of regular observations of about 20 Miras and semiregular variables (∘ Cet, R Leo, R Aql, U Her, χ Cyg, R Tri, and others) in 1994–1999 are presented. The monitoring includes optical spectroscopy, optical (UBV) and infrared (JHKLM) photometry, high-resolution radio spectroscopy in the 1.35-cm water-vapour maser line (on the 22-m radio telescope in Pushchino). Optical spectroscopy shows that the appearance of strong Balmer emission lines in Miras may be a rare event, and the presumed shock waves are thus weak. The H2O maser flux generally correlates with visual light curves of the stars with some delay Δφ = 0.1 – 0.4P (P is the variability period). For R Leo, R Cas, and U Aur strong flares in the Hφ line, observed in 1997–1998, were followed by corresponding outbursts of the H2O maser emission about 2P later. This sequence of events is probably caused by a shock wave propagating outward in the stellar atmosphere and consecutively initiating the Hα emission and, later, the maser flare at a larger distance from the stellar surface.