bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Energy Galactic Center Gamma Rays from Low Mass X-Ray Binaries
Authors: Kluźniak W. , Ruderman M. , Shaham J. , Tavani M.
Published: June 2019

The hard X-ray and low energy γ-ray emission from the galactic center region (GCR) has four components: a power-law continuum between 20/50 keV and 200/300 keV with a power-law photon index β in the range ~ 2.5 to ~ 3.1; a harder spectrum with β ~ 1.–1.5 between 200/300 keV and ~ 511 keV; a narrow electron-positron annihilation line at 511 keV, reported to disappear in less than < 1/2 yr, although the temporal variation is controversial; and an equally variable continuum emission between 511 keV and several MeV (“MeV bump”). All four have luminosities 1037–1038 erg s−1, if they are located 10 kpc away. We propose non-thermal processes in low mass X-ray binaries (LMXB's) concentrated in the galactic bulge as the direct source of the three continuum components of the emission, as well as of an escaping electron-positron e± wind whose positron annihilation relatively far from the star could be the source of the 511 keV line. We consider a model for energetic emission from LMXB's that reproduces the softer power-law component of the GCR continuum through synchrotron emission of relativistic electrons in the strongly non-uniform (dipolar) magnetic field of the neutron star. We also explain, with less confidence, the variable MeV bump as the result of interaction of harder γ-rays with the power-law photons. The harder power law might be due to Compton scattering of relativistic electrons or photons.
Summary Talk: The Observational Perspective
Authors: Gatley Ian
Published: June 2019

Well, you all look a little tired, and it's getting late; perhaps now is a good time to offer you some oversimplifications…….… – I've been sitting here this week listening to a large number of presentations of a very high caliber. There can be no doubt that this has been a remarkable conference. We've all learned a vast amount; I can't possibly make a coherent explanation of what I've seen and heard, any more than any one of you can. But I want to emphasise a few topics that struck me very forcibly.
The flare activity of AD Leo 1972-1988
Authors: Pettersen B.R. , Panov K.P. , Ivanova M.S. , Ambruster C.W. , Valtaoja E. , Valtaoja L. , Avgoloupis S. , Mavridis L.N. , Seiradakis J.H. , Sundland S.R. , Olah K. , Havnes O. , Olsen Ø. , Solheim J.-E , Aanesen T.
Published: June 2019

Time resolved U-filter lightcurves of stellar flares on the dM4e star AD Leo have been measured to determine the flare frequency for individual observing seasons between 1972 and 1988. This report adds new data for 1984-1988. We use the number of flares with energy larger than 10∗∗30 erg, and the number of flare maxima with amplitudes larger than 0.3 as separate parameters to estimate flare frequencies. Chi-square tests do not reveal statistically significant variations of the flare frequency with time for 1972-1988.
Data filtering in statistical studies of flares recorded in sky fields of stellar aggregates - demonstrated with the example of the

Pleiades
Authors: Szécsényi-Nagy G.
Published: June 2019

Photometric data on flares of cluster flare stars published by different observers were - as a rule - collected during decades by different instruments and amidst various conditions. The uncritical use of these data in global statistical studies is usually unfair since such a collection is an indefinite mixture of high and low quality results. In order to make these investigations more reliable even the best and most complete photometric catalogues have to be filtered.

The first step of the procedure described in the paper is rejecting all flare events having too small amplitudes - seeing that they are under-represented in the catalogue as opposed to medium and large amplitude flares. Then the photographic coverage of the aggregate has to be checked and all events observed in partially covered regions have to be excluded. Next any non-randomness in the time distribution of flares of each active object is to be unveiled and flares of the doubtful stars have to be omitted. Finally some objects are to be rejected for their individual characteristics.

The usefulness of the method is demonstrated with the example of the Pleiades, one of the richest open clusters known. More than 3000 hours of effective observing time has been devoted to flare photometry in fields centered upon Eta Tauri and the outcome of the programme the CPFS - the most complete catalogue of flare stars of the region - contains data of 519 flare stars and their 1532 flare events. Earlier versions of this catalogue or subsets of its data have been used to estimate the probable number of flare stars in the Pleiades region. Results of these attempts range from 600 to 2700 partly owing to the unreliability and incompatibility of the data sets. The method presented here is able to give much more reliable estimates but of course in the limited largest common field (LCF) only. As a result of the filtering the LCF contains 77% of the objects and 67% of the flares listed in the CPFS. Time sequence analysis of the 1026 flare events observed on 402 flare stars and statistical modelling of the phenomena suggested in an earlier paper fit each other almost perfectly.

The conclusion of the study is that the most likely number of flare stars in the reach of the telescopes used in this programme is between 520 and 600 in the LCF of the Eta Tauri fields. Their average flare frequency is about 1/2400h and the CPFS lists 70% of these objects. In order to be able to compare the Pleiades field flare stars and those of other aggregates the method of filtering will be carried out throughout the analysis of the most extended data sets available.
Flare stars at radio wavelengths
Authors: Lang Kenneth R.
Published: June 2019

The radio emission from dMe flare stars is discussed using Very Large Array and Arecibo observations as examples. Active flare stars emit weak, unpolarized, quiescent radio radiation that may be always present. Although thermal bremsstrahlung and/or thermal gyroresonance radiation account for the slowly-varying, quiescent radio radiation of solar active regions, these processes cannot account for the long-wavelength quiescent radiation observed from nearby dMe flare stars. It has been attributed to nonthermal gyrosynchrotron radiation, but some as yet unexplained mechanism must be continually producing the energetic electrons. Long-duration (hours), narrow-band (Δv/v < 0.1) radiation is also emitted from some nearby dMe stars at 20 cm wavelength. Such radiation may be attributed to coherent plasma radiation or to coherent electron-cyclotron masers. Impulsive stellar flares exhibit rapid variations (< 100 msec) that require radio sources that are smaller than the star in size, and high brightness temperatures TB > 1015 K that are also explained by coherent radiation processes. Quasi-periodic temporal fluctuations suggest pulsations during some radio flares. Evidence for frequency structure and positive or negative frequency drifts during radio flares from dMe stars is also presented.
X-ray variability in the Orion nebula
Authors: Caillault Jean-Pierre , Zoonematkermani Saeid
Published: June 2019

We have examined each of the 172 EINSTEIN X–ray sources in Orion for both short (100–10,000 seconds) and long (1 day to 2 years) timescale variability. No strong flares were seen in 75,000 total seconds of observations. We compare the Orion variability results with those from the ρ Oph star–forming region, solar X–ray flares and dMe U–band flares.
Flares of radio line emission H2O in Ori A and W49N
Authors: Gosachinskij I.V. , Yudaeva N.A. , Kandalian R.A. , Nazaretian F.S. , Sanamian V.A.
Published: June 2019

The results of observations of H2O maser sources Ori A and W49N at 1.35cm made the RATAN-600 radio telescope from June 1981 till December 1988 are presented. The light curves of these sources showed several outbursts. Duration of the strongest outbursts for the Ori A and W49N are approximately 1 and 1.5yr respectively. The maximum of the total luminosity (assuming isotropic emission) of these sources for the velocity range ±8km.s-1 is egual to 1×1047 ph.s-1 and 2×1049 ph.s-1 respectively. The time behaviour of the water maser source in W49N during more than 7yr is monitored for the first time.
Residual extinction effects in spectra of newly formed stars
Authors: Krelowski Jacek , Papaj Jacek , Wegner Walter
Published: June 2019

Extinction laws observed in spectra of Be stars are shown to be evidently different from the mean extinction curve. They do not contain in many cases the prominent extinction feature - the 2200A bump. The results are derived both from multicolour (ranging from the far-IR until the ultraviolet ANS) photometry and from TD-1 UV spectra. It is strongly suggested that the observed extinction phenomena are originated in circumstellar, disk-shaped shells as the shape of resultant extinction curve suggests both the presence of big, core-mantle grains and continuous infrared emission of circumstellar origin.
The stochastical approach to the modelling of the line profiles in T Tauri stellar winds
Authors: Grinin V.P. , Mitskevich A.S.
Published: June 2019

Line profiles calculations were carried out for spherically-symmetrical stellar wind models with discrete structure. It is shown the possibility to explain two-component emission profiles typical for T Tauri-type stars in the framework of such stochastical approach.
Astrobiology: Process and Discovery
Authors: Blumberg Baruch S.
Published: June 2019

I am very pleased to welcome you to the Fulbright Symposium 2002, Science Education in Partnership, held in conjunction with the Bioastronomy Symposium. I know you will all want to join me in offering our thanks for the beautiful Aboriginal welcoming ceremony. It was particularly meaningful for me. My first trip to this country was in 1966 when I was engaged in medical fieldwork in Western Australia that included members of the Aboriginal community. The ceremony connects this meeting with the earliest human history of this fascinating continent.
A Model for Estimating the Number of Stars for which Terrestrial Planets can be Detected Using Transits
Authors: Koch David
Published: June 2019

Borucki & Summers (1984) have suggested that extrasolar terrestrial planets can be detected by looking for transits. A discussion is presented of a model used to estimate the number and distance of stars for which planets can be detected as a function of spectral type and luminosity class, apparent brightness, planetary size and orbit, and realistic noise sources that must be considered. A choice for an optimum location of the field to search is described given the realistic constraints of a space mission and maximizing the number of available stars.
Terrestrial and Astronomical Sources of Circular Polarisation: A Fresh Look at the Origin of OF Homochirality on Earth
Authors: Wolstencroft Ramon D.
Published: June 2019

In searching for a terrestrial source of circular polarization that could be an agent for homochirality, I have re-discovered earlier work by Ivanoff & Waterman (1958) showing that total internal reflection of sunlight scattered by water or suspended particles can, in calm shallow waters such as tidal pools, yield a degree of circular polarization >10% in favourable directions. A terrestrial source would have the distinct advantage over an astronomical source that the perilous journey to the planetary surface is eliminated. The relative viability of this mechanism is compared with the widely discussed astronomical mechanism of Bailey et al. (1998).
Prebiologically Important Interstellar Molecules
Authors: Kuan Y.-J. , Huang H.-C. , Charnley S. B. , Tseng W.-L. , Snyder L. E. , Ehrenfreund P. , Kisiel Z. , Thorwirth S. , Bohn R. K. , Wilson T. L.
Published: June 2019

Understanding the organic chemistry of molecular clouds, particularly the formation of biologically important molecules, is fundamental to the study of the processes which lead to the origin, evolution and distribution of life in the Galaxy. Determining the level of molecular complexity attainable in the clouds, and the nature of the complex organic material available to protostellar disks and the planetary systems that form from them, requires an understanding of the possible chemical pathways and is therefore a central question in astrochemistry. We have thus searched for prebiologically important molecules in the hot molecular cloud cores: Sgr B2(N-LMH), W51 e1/e2 and Orion-KL. Among the molecules searched: Pyrimidine is the unsubstituted ring analogue for three of the DNA and RNA bases. 2H-Azirine and Aziridine are azaheterocyclic compounds. And Glycine is the simplest amino acid. Detections of these interstellar organic molecular species will thus have important implications for Astrobiology. Our preliminary results indicate a tentative detection of interstellar glycine. If confirmed, this will be the first detection of an amino acid in interstellar space and will greatly strengthen the thesis that interstellar organic molecules could have played a pivotal role in the prebiotic chemistry of the early Earth.
The Frequency and Predicted Consequences of Cosmic Impacts in the Last 65 Million Years
Authors: Paine Michael , Peiser Benny
Published: June 2019

Sixty five million years ago a huge asteroid collided with the Earth and ended the long reign of the dinosaurs. In the aftermath of this catastrophic event, the mammals arose and eventually mankind came to dominate the surface of the planet. The Earth, however, has not been free from severe impacts since the time of the dinosaur killer. We examine the likely frequency of major impact events over the past 65 million years, the evidence for these impacts and the predicted consequences of various types of impacts. It is evident that the mammals had to survive frequent severe disruptions to the global climate, and it is likely that over the past 5 million years hominids were faced with several catastrophic global events. Smaller but strategically located impact events could bring down our civilisation if they occurred today. Mankind has recently developed the expertise to predict and mitigate future impacts, but political and financial support are lacking.
Photosynthetic Constraints on the Habitable Zone
Authors: Storrie-Lombardi Michael C. , Tsapin A. I. , Mcdonald G. D. , Coleman M. L. , Meadows V. S.
Published: June 2019

The search for extraterrestrial habitable planets will require long observation times and the intelligent selection of appropriate parent stars and target biosignatures. While life can certainly develop in the absence of photosynthesis, such life forms on earth exhibit metabolic rates several orders of magnitude less than the activity accompanying a photosynthetic-driven ecosystem. The most accessible spectral biosignatures are those accompanying a system driven away from thermodynamic equilibrium by photosynthetic activity. For example, the co-existence in a planetary atmosphere of significant amounts of ozone, oxygen, and methane would be a strong indication of biotic activity. Investigating the issue of the Habitable Zone from the standpoint of the constraints inherent in photosynthesis it appears that the absorption characteristics of photosynthetic microorganisms on this planet make it likely that photosynthetic activity can exist on planets orbiting stars to red-ward of the Sun on the H-R diagram. Such a possibility is encouraging for terrestrial planet finder efforts since stars classified red-ward of our sun (G3 to K7) account for more than 55% of our nearest neighbors.
Genetic Differences Between Humans and Great Apes –Implications for the Evolution of Humans
Authors: Varki Ajit
Published: June 2019

At the level of individual protein sequences, humans are 97–100% identical to the great apes, our closest evolutionary relatives. The evolution of humans (and of human intelligence) from a common ancestor with the chimpanzee and bonobo involved many steps, influenced by interactions amongst factors of genetic, developmental, ecological, microbial, climatic, behavioral, cultural and social origin. The genetic factors can be approached by direct comparisons of human and great ape genomes, genes and gene products, and by elucidating biochemical and biological consequences of any differences found. We have discovered multiple genetic and biochemical differences between humans and great apes, particularly with respect to a family of cell surface molecules called sialic acids, as well as in the metabolism of thyroid hormones. The hormone differences have potential consequences for human brain development. The differences in sialic acid biology have multiple implications for the human condition, ranging from susceptibility or resistance to microbial pathogens, effects on endogenous receptors in the immune system, and potential effects on placental signaling, expression of oncofetal antigens in cancers, consequences of dietary intake of animal foods, and development of the mammalian brain.
ROSAT observation of the HII region RCW 49 Possible discovery of a new Wolf-Rayet ring nebula
Authors: Mereghetti S. , Belloni T.
Published: June 2019

We have observed the southern HII region RCW 49 with the ROSAT PSPC instrument. Part of the diffuse X-ray and optical emission present in this region might be associated with the X-ray selected WR star Th35-42 (WR20c). The young star cluster Westerlund 2 (which contains WR20a) is seen in X-rays as a centrally peaked, resolved source, surrounded by fainter diffuse emission.
A clump model for Wolf-Rayet star atmospheres
Authors: Kholtygin A. F.
Published: June 2019

There are many indications for the existence of dense cold clumps in Wolf-Rayet (WR) atmospheres, expanding outwards from the stellar core (e.g., Cherepaschuck et al. 1984, St-Louis et al. 1993). Based on this, we consider a clump model for WR model atmospheres. The main features of the model are described. The mechanism of clump structure formation is outlined. The clump model is used for calculating emission line profiles.
New determinations of the chemical composition of Wolf-Rayet stars
Authors: Nugis T.
Published: June 2019

The formation of the lines of ions He, H, N and C in the WR stars of different spectral subtypes has been studied using clumped wind models. Our new results agree well with the previous results obtained with smooth wind codes which make use of highly excited lines of different ions.
Stellar winds in high-mass X-ray binaries
Authors: Kaper Lex
Published: June 2019

High-mass X-ray binaries (HMXBs) represent an important stage in the evolution of massive binary systems. The compact object (in most cases an X-ray pulsar) not only provides information on the orbital and stellar parameters, but also probes the stellar wind of the massive companion, an OB supergiant or Be star. The X-ray luminosity directly depends on the density and the velocity of the wind at the orbit of the X-ray source. Important constraints on the stellar-wind structure can be set by studying the orbital modulation of UV P-Cygni profiles. In this paper different aspects of the interactive wind-accretion process are highlighted, such as the highly variable X-ray luminosity, the influence of the X-rays on the radiative acceleration of the wind inside the ionization zone, and the large-scale structures that trail the X-ray source in its orbit.
UBV photometry of the Wolf-Rayet stars WR137 and WR140
Authors: Panov K. P. , Stegert J. , Seggewiss W.
Published: June 2019

Photometric observations between 1991 and 1993 of the Wolf-Rayet object WR137 show no evidence of an eclipse but some small intrinsic variability. The light-curve for WR140 shows a clear dip in this period, probably as a result of an eclipse.
The Sunyaev-Zeldovich Effect Imaging and Interferometry: BIMA-CBI-OVRO State of the Art and Future Prospects
Authors: Myers Steven T.
Published: June 2019

This talk presents a summary of the most recent results from microwave and millimeter-wave surveys of the Sunyaev-Zeldovich Effect (SZE) in massive clusters of galaxies. The SZE is caused by Compton scattering of low-energy CMB photons off high-temperature ionized gas in cluster atmospheres, and is a direct measurement of the baryon content of the intracluster medium. New results from the Chicago-BIMA SZE survey of Carlstrom et al., the Penn-OVRO SZE program of Mason et al., and the Caltech-CBI SZE project of Padin et al. are discussed, along with prospects for future imaging and interferometric studies of clusters to pin down the astrophysical properties of cluster baryons and dark matter as well as possible constraints on cosmological parameters.
Comparative CMBology: Putting Things Together
Authors: Lineweaver Charles H.
Published: June 2019

I present a series of diagrams which illustrate why the cosmic microwave background (CMB) data favor certain values for the cosmological parameters. Various methods to extract these parameters from CMB and non-CMB observations are forming an ever-tightening network of interlocking constraints. I review the increasingly precise constraints in the Ωm - ΩΛ plane and show why more cosmologists now prefer ΛCDM cosmologies to any other leading model.
Cosmic Data Fusion
Authors: Bridle S. L.
Published: June 2019

We compare and combine likelihood functions of the cosmological parameters Ωm, h and σ8 from the CMB, type Ia supernovae and from probes of large scale structure. We include the recent results from the CMB experiments BOOMERANG and MAXIMA-1. Our analysis assumes a flat ACDM cosmology with a scale-invariant adiabatic initial power spectrum. First we consider three data sets that directly probe the mass in the Universe, without the need to relate the galaxy distribution to the underlying mass via a “biasing” relation: peculiar velocities, CMB and supernovae. We assume a baryonic fraction as inferred from Big-Bang Nucleosynthesis and find that all three data sets agree well, overlapping significantly at the 2σ level. This therefore justifies a joint analysis, in which we find a joint best fit point and 95% confidence limits of Ωm = 0.28 (0.17, 0.39), h = 0.74 (0.64, 0.86), and σ8 = 1.17 (0.98,1.37). Secondly we extend our earlier work on combining CMB, supernovae, cluster number counts, IRAS galaxy redshift survey data to include BOOMERANG and MAXIMA-1 data and to allow a free Ωbh2. We find that, given our assumption of a scale invariant initial power spectrum (n = 1), we obtain the robust result of Ωbh2 = 0.031 ± 0.03, which is dominated by the CMB constraint.
Concluding Remarks
Authors: Peebles P. J. E.
Published: June 2019

I review the reason for considering the prime purpose of the program of measurements of the fundamental parameters of cosmology to be the tests of cosmological models. I comment on the philosophy by which we are approaching this goal, offer an assessment of where we stand, and present some thoughts on where the tests may be headed.
H0 determinations via the S-Z & X-ray route
Authors: Grainger William F.
Published: June 2019

A new H0 determination via the S-Z & X-ray route from cluster 0016+16 is presented. Potential sources of errors, in particular the effect of temperature profiles, are discussed.
The Galaxy Environment of Quasars in the z ⋍ 1.3 Clowes-Campusano Large Quasar Group
Authors: Haines C. P. , Clowes R. G. , Campusano L. E.
Published: June 2019

We report significant associated clustering in the field of a z = 1.226 quasar from the Clowes-Campusano LQG in the form of both a factor ˜ 11 overdensity of I - K > 3.75 galaxies, and red sequences of 15-18 galaxies at I - K ⋍ 4.3, V - K ⋍ 6.9 indicative of a population of massive ellipticals at the quasar redshift. The quasar is located between two groups of these galaxies, with further clustering extending over 2-3 Mpc. A band of V - I < 1 galaxies bisects the two groups of red sequence galaxies, and we suggest that the merging of these two groups has triggered both this band of star-formation and the quasar.
Cosmic Acceleration: A Natural Remedy For Horizon and Flatness Problems
Authors: Mitra Abhas.
Published: June 2019

By assuming that the recently found cosmic acceleration is a genuine and ever present effect, we show that, the resultant modified Friedman model is free from the horizon and flatness problems; and there is no need to invoke the additional “inflationary” initial phase as a separate ingredient.
Limits On The Core Radii Of JVAS/CLASS Gravitational Lenses
Authors: Norbury M. , Jackson N. J. , Browne I. W. A. , Wilkinson P. N. , Rusin D.
Published: June 2019

Gravitational lenses typically consist of either two or four images (doubles and quads) of the background source. However, it has been shown that gravitational lensing by transparent extended matter distributions should produce an odd number of images. An upper limit for the flux of the missing ‘odd image’ can be obtained using high sensitivity radio observations, such as 5GHz MERLIN (Multi-Element Radio Linked Interferometer Network) data. Limits on the ‘odd image’ flux can then be converted into an upper limit on the core radius of the lensing galaxy.
A collimated molecular jet in W 43A traced by water maser emission
Authors: Imai Hiroshi , Sasao Tetsuo , Obara Kumiko , Omodaka Toshihiro , Diamond Philip J.
Published: June 2019

We present the spatial and velocity distributions of water masers in W 43A. Most of the maser features are spatially and kinematically collimated to a surprising extent. It is very likely that the jet in W 43A is predominantly composed of warm molecules traced by water maser emission. The position angle of the spatial collimation of the maser clusters is slightly different from the directions of both the cluster separation and the proper motions. We propose a model involving a precessing jet to explain the axis offsets. The discovery of a molecular jet with precession in W 43A provides important information on our understanding of the formation of collimated molecular jets and may provide clues on specific stages of stellar evolution.
Interstellar methanol masers
Authors: Menten Karl M.
Published: June 2019

The asymmetric rotor molecule methanol (CH3OH) has hundreds of transitions at centimeter-, millimeter-, and submillimeter wavelengths. Many of these are excited in the hot (T ≳ 150 K), dense (n ≳ 106 cm−3) molecular cloud cores surrounding newly formed massive stars or protostars. The high temperatures in these cores cause evaporation of icy grain mantles, releasing copious amounts of complex molecules, such as methanol, in the gas phase, which in hot cores has abundances (up to 10−6 relative to H2) that are two or more orders of magnitude higher than in cold dark clouds.
Polarization properties of 6.7 GHz methanol masers in NGC6334F
Authors: Ellingsen Simon
Published: June 2019

The Australia Telescope Compact Array (ATCA) has been used to make the first full polarization observations of 6.7 GHz methanol masers. Linear polarization was detected towards all four sources observed, at levels between a few and 10%, while none of the sources show circular polarization stronger than approximately 1.5%. Linear polarization appears to be more common in the 6.7 GHz methanol maser transition than it is for the 12.2 GHz transition, consistent with the hypothesis that the 6.7 GHz masers are more saturated.
The circumstellar environment of methanol masers
Authors: Phillips Chris , Bock Douglas , van Langevelde Huib Jan , Minier Vincent
Published: June 2019

We present VLBI and BIMA observations of the Class II methanol maser source G 59.783+0.065. The methanol emission arises from the centre of a compact molecular core, supporting the view that methanol masers trace an early stage of massive star formation. The velocity spread of the masers is significantly larger than that of the parent molecular cloud, which is consistent with the methanol coming from a rotating structure within the molecular core. However, there is also weak evidence that the methanol is aligned with an outflow.
Maser and thermal methanol emission in the millimeter wave range: new masers at 1.3 mm and 2.8 mm
Authors: Kalenskii Sergei V. , Slysh Vyacheslav I. , Val'tts Irina E.
Published: June 2019

Results of a survey of Galactic star-forming regions in the lines of methanol 8−1 − 70E at 229.8 GHz, 3−2 − 4−1E at 230.0 GHz, 00 − 1−1E at 108.9 GHz, and a series of methanol lines J1 − J0E near 165 GHz are presented. Two masers, DR 21 (OH) and DR 21 West, and two maser candidates, L 379 IRS3 and NGC 6334I(N), as well as 16 thermal sources are found at 229.8 GHz. This is the first detection of methanol masers at a wavelength as short as 1 mm. At 108.9 GHz, masers were found towards G345.01 + 1.79 and probably, towards M 8E. Thermal emission is found towards 28 objects. Only thermal emission was found at 165 and 230.0 GHz (20 and 7 sources, respectively). The masers at 229.8 GHz belong to class I, whereas those at 108.9 GHz belong to class II, according to the classification by Menten (1991). The masers in DR 21 (OH) and DR 21 West can be roughly fitted by models with the gas kinetic temperature of the order of 50 K. The detection of the 108.9 GHz masers towards G345.01 + 1.79 and M 8E may indicate on a specific geometry of these objects. The combination of the existence of the class II J0 - J−1E masers towards W 3(OH), G345.01 + 1.79, W 48, and Cep A and our non-detection of the 3−2 − 4−1E and J1 - J0E lines is an evidence that the class II masers in these objects are pumped by the radiation of hot dust rather than by that of UC HII-regions.
NLTE NH3(J,K) = (1,1) observations towards southern hemisphere compact regions
Authors: Roman Lopes Alexandre , Abraham Zulema , Caproni Anderson , Lépine Jacques R. D. , Vilas-Boas Jose W. S.
Published: June 2019

We present NH3(J,K) = (1,1) observations toward CS(2,1) sources in the southern hemisphere, obtained with the Itapetinga Radio Telescope, that exhibit departure from LTE conditions. The mechanism of selective trapping in the hyperfine transitions of NH3(J, K) =(2,1)-(1,1) is invoked to explain the non-thermal population in the NH3(J, K) = (1,1) hyperfine states. This effect is relevant only when the width of the hyperfine lines lie between 0.3 and 0.6 km s−1. Due to this restriction, the assumption that the molecular cloud is formed by clumps, which produce spectra within this line-width interval seems to be a natural explanation for the non-thermal population. The observed spectra can be the result of the superposition of individual clump spectra with different central velocities. This model was applied to determine the physical conditions of the observed regions, providing satisfactory results for most of them. However, for some sources the model is not adequate to reproduce the observations, indicating that some other effects should be included, such as IR continuum, that was neglected in the radiative transfer calculations.
IR properties of H2O megamaser galaxies, pumping mechanisms, and central sources
Authors: Zhi-yao Yu
Published: June 2019

The IR-properties of all the host galaxies which exhibit H2O megamaser emission have been studied in this paper. The most striking feature is the anticorrelation of the log[S(60)/S(100)] vs. log[S(12)/S(25)] and log[S(25)/S(60)] vs. log[S(12)/S(25)], and the correlation of log[S(60)/S(100)] vs. log[S(25)/S(60)]. These anticorrelations and the correlation in the flux density ratios can be explained by the coexistence of large and very small dust particles. The relationship between the luminosity of the H2O megamaser and the infrared luminosity vs. the flux density ratio of S(60)/S(100), S(25)/S(60), and S(12)/S(25) have been studied. The correlation of the luminosity vs. S(60)/S(100) and the luminosity vs. S(25)/S(60), and the anticorrelation of the lumonosity vs. S(12)/S(25) are obtained, respectively. The pumping mechanism of the H2O megamaser is discussed according to the these results. The characteristics of the central sources are also studied, according to these relationships.
The VERA project
Authors: Honma Mareki
Published: June 2019

I present an overview of the VERA (VLBI Exploration of Radio Astrometry) project. I summarize the properties of the VERA array and its observational system as well as the current construction status, and I also present a brief overview of the science targets of VERA, including dynamics of the Galaxy and internal kinematics of maser sources.
Relative Ages from Horizontal-Branch Morphology: Revisited
Authors: Lee Young-Wook , Lee Hyun-chul , Yoon Suk-Jin , Rey Soo-Chang , Chaboyer Brian
Published: June 2019

We present our recent revision of model constructions for the horizontal-branch (HB) morphology of globular clusters, which suggests the HB morphology is more sensitive to age compared to our earlier models. We also present our high precision CCD photometry for the classic second parameter pair M3 and M13. The relative age dating based on this photometry indicates that M13 is indeed older than M3 by 1.7 Gyr. This is consistent with the age difference predicted from our new models, which provides a further support that the HB morphology is a reliable age indicator in most population II stellar systems.
Extragalactic Globular Cluster Systems in the Near-IR
Authors: H. Puzia Thomas , Kissler-Patig Markus , Brodie Jean , Goudfrooij Paul , Hilker Michael , Minniti Dante , Zepf Steve
Published: June 2019

Extragalactic Globular Clusters are useful tracers of galaxy formation and evolution. Photometric studies of globular cluster systems beyond the Local Group are still the most popular method to investigate their physical properties, such as their ages and metallicities. However, the limitations of optical photometry are well known. The better wavelength sampling of the underlying cluster's SED using K-band photometry combined with optical passbands allows us to create colors which reduce the age-metallicity degeneracy to the largest extent. Here we report on the very first results of our near-IR photometric survey of globular cluster systems in early-type galaxies outside the Local Group.
Super Stellar Clusters in HII Galaxies
Authors: Telles Eduardo
Published: June 2019

Stellar Clusters are identified in images and in the spectra of these star forming dwarf galaxies. These Stellar Clusters have properties similar to those observed in other violent star forming galaxies and may the elementary entities of a starburst.
IFS and IR Observations of Star Clusters in the Antennae
Authors: Mengel Sabine , D. Lehnert Matthew , Thatte Niranjan , Genzel Reinhard
Published: June 2019

Over the past decade, it has become clear that interaction induced formation of compact young star clusters is a ubiquitous pheonomenon, and the understanding of this process is thought to also shed light on galaxy evolution in general, because these young clusters are widely believed to be the progenitors of a part of the globular cluster systems seen in local elliptical galaxies. We have observed the prototypical merger NGC 4038/4039 using near-infrared broad- and narrow band imaging, integral field spectroscopy and medium and high resolution spectroscopy. We find that all of the bright star clusters are young (<20 Myrs), but the “overlap region” hosts the youngest clusters (∼5 Myrs), while the nuclear starbursts started ∼100 Myrs ago. Photometric and dynamical masses range from 105 to a few x106M⊙. However, mass-to-light ratios vary from cluster to cluster and suggest differences in the contribution of low-mass stars. While clusters with a deficiency in low-mass stars are likely to evaporate before they are a Hubble time old, those with a high mass-to-light-ratio could represent young globulars.
Open, Massive and Globular Clusters — Part of the Same Family?
Authors: Larsen Søren S.
Published: June 2019

Populations of young star clusters show significant differences even among “normal” disk galaxies. In this contribution I discuss how properties of young cluster systems are related to those of their host galaxies, based on a recent study of clusters in a sample of 22 nearby spiral galaxies. Luminous young clusters similar to the “super” star clusters observed in starbursts and mergers exist in several of these galaxies, and it is found that the luminosity of the brightest star cluster as well as the specific luminosity of the cluster systems both correlate well with the host galaxy star formation rate. When considering star clusters in different environments the traditional distinction between “open”, “massive” and “globular” clusters breaks down, underscoring the need for a universal physical description of cluster formation.
The Early Stages of Extragalactic Star Cluster Evolution: New Results From Gemini
Authors: E. Johnson Kelsey , D. Vacca William , S. Conti Peter , A. Kobulnicky Henry
Published: June 2019

As part of an ongoing program to better understand the early stages of massive star cluster evolution and the physical conditions required for their formation, we have obtained 10 μm (N-band) images with Gemini North of the nuclear region of the starburst galaxy He 2-10. Five massive star clusters still enshrouded in their natal cocoons with no optical counterparts were previously discovered by Kobulnicky & Johnson (1999) as optically thick thermal radio sources. Three of these five radio sources have strong 10 μm detections in only 10 minutes of integration time with Gemini. The blackbody temperatures of the dust cocoons are estimated to range from ∼ 40 — 150 K at their outer and inner edges, and the mass of these dust shells is ∼ 107 M⊙. The ages of the embedded stellar clusters must be < 106 years. The bolometric luminosities of the exciting clusters can be constrained to ∼ 108–9 L⊙, and the implied masses are > 106 M⊙. These three embedded clusters are responsible for at least 60% of the IRAS flux of the entire galaxy He 2-10.
The Life and Death of Globular Clusters
Authors: Lee Hyung Mok
Published: June 2019

Globular clusters are embedded in galactic potential. Various processes such as dynamical friction, steady tidal field, and shocks by disk and bulge contribute to the dissolution of globular clusters. Most of them are closely coupled with internal dynamical processes. The tidal shock is very effective during the initial phase of the cluster evolution while steady tidal field becomes more important in the later phase. Recent studies revealed that the rotation of the cluster could significantly accelerate the evolution and evaporation. We emphasize that the lifetime of the clusters could be much shorter than the previous estimates of ∼ 20trhfor more realistic models.
The Lick Northern Proper Motion Program
Authors: Klemola A.R. , Hanson R.B. , Jones B.F.
Published: June 2019

The Lick Northern Proper Motion (NPM) Program will provide absolute proper motions (referred to faint galaxies), equatorial coordinates, and two-color photographic photometry for some 300,000 stars with 8 < B < 18 covering the 70% of the sky north of declination −23°. Part 1 of the NPM program (NPM1), recently completed, covers the 72% of the northern sky (899 of 1,246 fields) outside the Milky Way. Two catalogs result from NPM1: The NPM1 Catalog (Klemola et al. 1993a, Hanson 1993a) contains 149,000 stars. The NPM1 Reference Galaxy List (Klemola et al. 1993b, Hanson 1993b) contains 50,000 faint galaxies. Klemola et al. (1987, 1994, 1995) describe the NPM program. Hanson et al. (1994) describe the NPM1 Catalogs.
Stellar Astrophysics with Sub-Milliarcsecond Optical Interferometry
Authors: Stee Ph. , Bonneau D. , Mourard D. , Lawson P. , Morand F. , Tallon I. , Vakili F.
Published: June 2019

Although stellar interferometers are capable of measuring the angular diameters of stars, with longer baselines they may also be used to measure brightness variations across a star's surface and to provide constraints on models of stellar envelopes. In this paper we will look at the interpretation of visibility data and some of the more exciting prospects within the reach of current interferometers.
Accurate Binary Mass Determinations: Goals, Limitations, and Prospects
Authors: Andersen J.
Published: June 2019

The state of the art in accurate mass determination for binary stars is reviewed, and the angular sizes and their errors are computed for a typical system from the existing high-precision sample. It appears that sub-μas (microarcsecond) absolute astrometry will be needed in order to improve the accuracy substantially by astrometry alone. The types of system, and the kinds of data, where precision astrometry appears most promising are outlined. Finally, astrophysical applications of such accurate stellar masses, and the auxiliary data required in them, are briefly reviewed.
Astrometric Tests of Galactic Evolution
Authors: Gilmore Gerard
Published: June 2019

There are many fundamental aspects of Galactic structure and evolution which can be studied best or exclusively with high quality three dimensional kinematics. Amongst these we note as examples determination of the orientation of the stellar velocity ellipsoid, and the detection of structure in velocity-position phase space. The first of these is the primary limitation at present to reliable and accurate measurement of the Galactic gravitational potential. The second is a critical test of current standard models of Galactic formation and evolution.
Earth Rotation Velocity in Relation with Different Reference Frames
Authors: Brumberg V. A.
Published: June 2019

The high precision of present observations makes it reasonable to clear up a question about GRT (general relativity theory) corrections in the problem of Earth's rotation. The answer is that one may almost forget about GRT corrections when dealing in an adequate reference system (RS). The problem of Earth's rotation may be related to the relativistic hierarchy of RS started in (Brumberg and Kopejkin, 1989) and completed in (Klioner, 1993). Let letters B, G and T be related to barycentric, geocentric and topocentric RS, respectively. Let DRS and KRS be dynamically nonrotating or kinematically nonrotating RS, respectively. From the dynamical equations of rotation it follows that the most adequate system for studying the Earth's rotation is DGRS. Apart from the geophysical factors the rotation of the Earth in this system is fairly well approximated by the rigid-body rotation with some angular velocity . The same rotation of the Earth as considered in BRS and DTRS may be also approximated by the rigid-body rotation but with some additive relativistic corrections and with other angular velocities ωi and , respectively. Substituting these three rotation relations into four-dimensional BRS-DGRS and DGRS-DTRS transformations one may express ωi and in terms of and determine the additive relativistic corrections in BRS and BTRS. These corrections are of importance for treating kinematics problems in various coordinate systems and for obtaining physically meaningful solutions of the dynamical equations of rotation in the barycentric reference system.

The complete text will be published in Journal of Geodynamics.
The General Relativistic Potential of Astrometric Studies at Microarcsecond Level
Authors: Zhdanov V. I.
Published: June 2019

The relativistic effects in positioning of distant objects at microarcsecond level are studied. The main points are: statistics of random variations of the image position of a distant radiation source due to the gravitational field of moving stars, motion of the image due to individual invisible gravitators, and possibilities to obtain information on their masses and velocities. The gravitators shifting the object image may be stars of our Galaxy or of a lensing galaxy.
A New Era of Global Astrometry. II: A 10 Microarcsecond Mission
Authors: Høg E.
Published: June 2019

A ground-based project for a small telescope about 20 cm aperture is proposed. It would be able to obtain 500 million astrometric observations per year of all stars between V=7 and 18 mag, based on the Hipparcos-Tycho reference net of one million stars. In addition, V and I magnitudes for all stars from V=7 to 17 mag would be obtained. — A new space mission is proposed, capable of obtaining 10 microarcsecond (μas) precision for parallaxes and proper motions of stars of V = 11 mag, and a precision of 0.5 millimagnitude (mmag) for intermediate-band photometry. The mission is here called Roemer Plus (or Roemer+) and the design is derived from Hipparcos and Roemer, but a larger telescope aperture and high-precision metrology is applied. At magnitude V = 20 a precision of 1.0 milliarcsecond (mas) would be achieved.
The Atmospheric Limitation on the Precision of Ground-Based Astrometry
Authors: Guseva I.S.
Published: June 2019

Anomalous refraction remains to be the most critical problem in the meridian astrometry measuring large angles on the sky. I study slow quasi-periodical variations of refraction caused by the processes in the middle and upper atmosphere, such as gravity waves, etc., which can not be detected and calibrated out by use of any on-ground meteorological measurements. For this study, very old observations at large zenith distances of 80 to 90 degrees made by V. Fuss at Pulkovo Observatory in 1867-1869 [1] were used. The Deeming's method [2] of spectral analysis of data was applied to examine the characteristic variations of refraction in a wide range of periods. Very powerful quasi-periodical processes with periods of 7-8, 11-14, 18-22, 36-44 minutes and with amplitudes of 0.3 to 0.5 arcsec in the zenith were found when short sets of observations (1-5 days) were considered. They increase random errors of astrometric observations with meridian circles, transit instruments, astrolabes, etc. The periods of very slow variations — 152, 122, 93, 82.5, 73, 61 and 50 days, – are close to the well known periods discovered in other astronomical phenomena, for instance, in solar activity and in Earth rotation. I note also, that some of the long-period variations of refraction may cause quasi-systematic errors in astrometric measurements and catalogues.
MACHO Photometry and Astrometry
Authors: Høg E. , Novikov I.D. , Polnarev A.G.
Published: June 2019

MACHOs (Massive Astrophysical Compact Halo Objects) have been discovered by their relativistic amplification of light from distant stars as they crossed very near to the line-of-sight. The very few events were detected from more than a billion photometric measurements of millions of stars in the LMC. – A mathematical theory of analysis of astrometric and photometric measurements of microlensing events is presented. It is shown that three photometric measurements and three one-dimensional astrometric measurements during an event are, in principle, sufficient to determine the – precisely – six observable physical parameters of the MACHO, including the proper motion and distance of the dark body, provided the position, motion and distance of the undeflected star has been determined from observations outside the event. The practical possibility of such observations is discussed by comparison with the proposed ROEMER satellite, an instrument concept with the potential for obtaining the many billions of photometric and astrometric observations of the required quality. At least 300 photometric amplifications of light from stars brighter than V = 16.5 mag could de detected during a ROEMER mission, but the prospects for significant astrometric observations are meagre.
Velocities of Escapers from Unstable Hierarchical Triple Stars
Authors: Kiseleva L. , Anosova J. , Colin J.
Published: June 2019

We consider unstable hierarchical triple stars which are disrupted by the straightforward ejection and escape of the distant companion. The main aim of the present work is the study of velocities of escaping stars from these unstable systems, and the dependence of these velocities on the masses of the stars and on the distances of the escapers from the centers of mass of the remaining binary and of the triple system as a whole. Velocities of escapers are estimated for actual star systems. It is shown that in the triple star λ Tau, when it becomes unstable as a result of mass transfer in its close semi-detached binary, the velocity of the escaping distant companion with mass M ≈ 0.7M⊙ can be about 100 km/s. A possible application of these results to the problem of anomalous high-velocity stars in the Galaxy is discussed.