bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Ranging of Orbits for Trans-Neptunian Objects
Authors: Virtanen J. , Muinonen K. , Bowell E. 
Published: March 2016

AbstractWe consider initial determination of orbits for trans-neptunian objects (TNOs), a topical theme because of the rapidly growing TNO population and the challenges in recovering lost TNOs. We apply the method of initial phase-space ranging of orbits to the poorly observed TNOs. The rigorous a posteriori probability density of the TNO orbital elements is examined using a Monte Carlo technique by varying the TNO topocentric ranges corresponding to the observation dates. We can optionally adopt a Bayesian approach to select the region of phase space containing the most plausible orbits. This is accomplished by incorporating semimajor axes, eccentricities, inclinations, and absolute magnitudes of multi-apparition TNOs as a priori information. The resulting a posteriori distributions permit ephemeris and ephemeris uncertainty prediction for TNO recovery observations.
Photometric Evidence for Mixing and Diffusion in GC Stars
Authors: Grundahl Frank 
Published: March 2016

AbstractBased on Strömgren uvby CCD photometry, and UVES spectroscopy we present evidence that possibly all globular clusters show large variations in their abundances of nitrogen, aluminium and sodium, which are not only due to internal mixing processes. Furthermore the evidence for radiative levitation among hot horizontal branch stars is briefly discussed.
Mixing in Magnetized Interiors of Solar-Type Stars: Frequently Asked Questions
Authors: Charbonneau Paul 
Published: March 2016

AbstractThis short paper discusses various issues pertaining to the redistribution of angular momentum and mixing of chemical species in the radiative interior of solar-type stars. Results obtained to date indicate that models combining magnetically-mediated angular momentum transport with turbulent mixing of chemical species offer the best hope of explaining the observed rotation and light element evolution in open clusters, without doing excess violence to seismic measurements of the solar internal differential rotation.
Babylonian Observations
Authors: Brown D.R. 
Published: March 2016

AbstractCuneiform tablets from Babylonia record lunar and solar eclipses, the presence and movement of comets, meteors and meteor showers. These have provided historical astronomers with much valuable data, but caution must be exercised when using such records, for accuracy of observation often ceded to astrological intent. In the future, texts from Assyria may also provide useful data for historical astronomers.
Ancient Eclipses and the Earth’s Rotation
Authors: Morrison L.V. , Stephenson F.R. 
Published: March 2016

AbstractThe analysis of historical eclipses shows that the length of the day is increasing on the average by 1.8 milliseconds per century, as distinct from the value of 2.3 milliseconds per century expected from tidal friction. The difference may be accounted for by the response of the Earth to post-glacial uplift following the end of the last ice-age.
About Some Astronomical Instruments from Batthyanian Observatory in Alba Iulia
Authors: Botez Elvira , Oproiu Tiberiu 
Published: March 2016

AbstractBuilt toward the end of the 18th century on the last floor of a former Trinitarian church, the Astronomical Observatory in Alba Iulia (Romania) was equipped with instruments brought from Vienna and it was in activity until 1860. A description of the astronomical instruments of those existing at present is given.
Characteristics of Flare-Productive Sunspot Groups
Authors: Ishii Takako T. , Kurokawa Hiroki , Takeuchi Tsutomu T. 
Published: March 2016

AbstractThe mechanism of flare energy build-up is one of the most fundamental questions in the solar flare study, but is still to be solved. From the review of the previous studies, we notice that the formation process of the magnetic shear in an active region should be essential for the flare energy build-up mechanism. Based on this idea, we make detailed studies of the active region evolutions using high resolution Hα images obtained with the 60 cm Domeless Solar Telescope at Hida Observatory, Kyoto University.We study sunspot proper motions and evolutionary changes of Hα fine structures and magnetic fields in active regions NOAA 5395 (Ishii et al. 1998) and NOAA 4201 (Ishii et al. 2000). To explain the evolutionary characteristics found from the analysis of these two active regions, we propose schematic models of twisted flux bundles emerging from the convection zone. We also found that the occurrence of high flare activity in each active region was restricted to the rapidly emerging region of the twisted flux bundle. In conclusion, we suggest that the emergence of the twisted flux bundle should be the key to high flare-productivity of the sunspot group, or the flare energy build-up mechanism.
Oxygen in Unevolved Starss
Authors: Boesgaard Ann Merchant 
Published: March 2016

AbstractWe have made observations of 24 unevolved stars of the OH lines in the ultraviolet spectral region at high spectral resolution and high signal-to-noise, typically 60 − 110 with Keck + HIRES. The O abundances have been computed by spectrum synthesis. For these cool, unevolved stars there is a linear relation between [O/H] and [Fe/H] over three orders of magnitude with very little scatter and a slope of +0.66 ±0.02. The relation between [O/Fe] and [Fe/H] is robustly linear with [O/Fe] = −0.35 (±0.03) [Fe/H]. There is no sign of a break at metallicities between −1.0 and −2.0.
Dust Absorption and Emission in Galaxies at High and Low Redshifts
Authors: Fall S. Michael 
Published: March 2016

AbstractThis article reviews three related topics: the extragalactic background light and its sources, evolution models for the dust absorption and emission in galaxies, and empirical constraints on these transfer processes in nearby starburst galaxies. It is intended that the material presented here will serve as an introduction to this Joint Discussion.
Galileo: Close-up Views of Jupiter’s Dynamic Atmosphere
Authors: Vasavada Ashwin R. 
Published: March 2016

AbstractThe Galileo spacecraft’s Solid State Imager (SSI) has been returning mosaics of Jupiter since 1996. The combination of high spatial resolution, broad spectral range, and short mosaic time steps has revealed a dynamic, vertically extended cloud structure not detectable by Voyager. These data have stimulated new analyses of major features such as zonal jets, the Great Red Spot, White Ovals, and the Galileo Probe entry site. Near-infrared images have provided fundamental constraints on the vertical structure of clouds and hazes, including the first imaging of a water cloud. Results from night side imaging include an extensive search for lightning, the first matching of lightning events to day side storm clouds, and the first spectral and spatial measurements of visible-wavelength auroral phenomena (not discussed here, see Vasavada et al. 2000). The identification of several tall, energetic storm systems at specific latitudes has led to new ideas about the role of moist convection in Jupiter’s atmospheric energetics.
Titan’s Atmosphere (Clouds and Composition): New Results
Authors: Griffith Caitlin A. 
Published: March 2016

AbstractTitan’s atmosphere potentially sports a cycle similar to the hydrologic one on Earth with clouds, rain and seas, but with methane playing the terrestrial role of water. Over the past ten years many independent efforts indicated no strong evidence for cloudiness until some unique spectra were analyzed in 1998 (Griffith et al.). These surprising observations displayed enhanced fluxes of 14-200% on two nights at precisely the wavelengths (windows) that sense Titan’s lower altitude where clouds might reside. The morphology of these enhancements in all 4 windows observed indicate that clouds covered ~6-9% of Titan’s surface and existed at ~15 km altitude.Here I discuss new observations recorded in 1999 aimed to further characterize Titan's clouds. While we find no evidence for a massive cloud system similar to the one observed previously, 1%-4% fluctuations in flux occur daily. These modulations, similar in wavelength and morphology to the more pronounced ones observed earlier, suggest the presence of clouds covering ≤1% of Titan's disk. The variations are too small to have been detected by most prior measurements. Repeated observations, spaced 30 minutes apart, indicate a temporal variability observable in the time scale of a couple of hours. The cloud heights hint that convection might govern their evolution. Their short lives point to the presence of rain.
High Resolution Spectroscopy As a Tool for Luminosity Calibration
Authors: Peterson Ruth C. 
Published: March 2016

AbstractRecent results are reviewed for two methods of luminosity calibration based on high-resolution spectroscopy. The first relies on Teff/log g determinations from model-atmosphere analyses based on high-resolution spectra. This method is physically well founded but operationally demanding, and requires advance knowledge of stellar mass. The second, W-B, stems from the empirical relationship between luminosity and the width of chromospheric emission lines first established by Wilson and Bappu. Its physical basis is only partially understood, however, and the calibration depends on stellar metallicity and on the choice of lines.Both Teff/log g and W-B easily distinguish cool dwarfs from cool giants. Generally reasonable agreement is found between distances derived from Hipparcos parallaxes and those inferred from the log g values derived for nearby dwarfs with relatively well-known Hipparcos parallaxes, σ(π)/π < 0.2. Constraining Hipparcos parallaxes star-by-star is not possible at present. Improvements are suggested for both approaches.
The Luminosity Calibration of the uvby — β Photometry
Authors: Jordi C. , Luri X. , Masana E. , Torra J. , Figueras F. , Domingo A. , Gómez A.E. , Mennessier M.O. 
Published: March 2016

AbstractThe ESA HIPPARCOS satellite has provided astrometry of unprecedented accuracy, allowing us to reassess, improve and refine the pre-Hipparcos luminosity calibrations. We review the “classical” absolute magnitude calibrations with the Strömgren-Crawford intermediate-band photometric system. A small zero point correction of about 2-4% seems necessary, as well as to refine the dependences on metallicity and projected rotational velocity. The need of a rigorous statistical treatment of the extremely precise Hipparcos data to derive definitive dependences of the luminosity on physical parameters is emphasized.
Theoretical Expectations for Clump Red Giants as Distance Indicators
Authors: Girardi Léo 
Published: March 2016

AbstractVariations of ~ 0.4 mag are expected in the I-band absolute magnitude of red clump giants, , as a function of both stellar age and metallicity. This is the case regardless of some potential theoretical uncertainties. The quite large differences in mean ages and metallicities of clump stars among galaxies result in systematic changes (of up to ~ 0.4 mag) in their . These numbers also indicate a distance to the LMC that is not necessarily “short”.
Synthesis of Small and Large Scale Dynamos
Authors: Subramanian Kandaswamy 
Published: March 2016

AbstractUsing a closure model for the evolution of magnetic correlations, we uncover an interesting plausible saturated state of the small-scale fluctuation dynamo (SSD) and a novel anology between quantum mechanical tunnelling and the generation of large-scale fields. Large scale fields develop via the α-effect, but as magnetic helicity can only change on a resistive timescale, the time it takes to organize the field into large scales increases with magnetic Reynolds number. This is very similar to the results which obtain from simulations using the full MHD equations.
Neutrino Properties from Measurements using Astrophysical and Terrestrial Sources
Authors: McDonald A.B. 
Published: March 2016

AbstractThe current knowledge of neutrino properties has been derived from measurements performed with both astrophysical and terrestrial sources. Observations of neutrino flavor change have been made with neutrinos generated in the solar core, through cosmic ray interactions in the atmosphere and in nuclear reactors. A summary is presented of the current knowledge of neutrino properties and a description is provided for future measurements that could provide more complete information on neutrino properties.
Helicity Generation and Signature in Solar Atmosphere
Authors: Pevtsov A. A. 
Published: March 2016

AbstractTo fully understand the origin, evolution and topology of solar magnetic fields, one should comprehend their magnetic helicity. Observationally, non-zero helicity reveals itself in the patterns of electric currents inside active regions, superpenumbral sunspot whirls, the shape of coronal loops and the fine structure of chromospheric filaments. Some patterns may bear information about deep sub-photospheric processes (e.g., dynamo, turbulent convection). Others may originate at or near the photosphere. This presentation reviews the observations of magnetic and current helicity on the Sun, discusses the possible mechanisms of helicity generation, and compares them with the observations.
Magnetic Helicity in Sigmoids, Coronal Mass Ejections and Magnetic Clouds
Authors: Rust D. M. 
Published: March 2016

AbstractSigmoids, coronal mass ejections (CMEs) and magnetic clouds (MCs) all show signatures of twisted and writhing magnetic fields. CMEs are often associated with MCs, whose fields are regularly mapped with sensitive magnetometers. These measurements reveal that MC fields are helical, and each MC carries magnetic helicity away from the sun. It is more difficult to determine the magnetic helicity of the corresponding features on the sun. This presentation surveys recent work on helicity in solar features, focusing especially on the interpretation of sigmoids, which are S-shaped, bright features seen in images from the Yohkoh soft X-ray telescope. Several lines of evidence indicate that sigmoids are twisted and writhing flux ropes that erupt as components of CMEs. CMEs may be initiated by MHD-instable flux ropes. The fact that the ejected flux ropes carry off a large amount of positive helicity from the south and negative helicity from the north each solar cycle implies an equal, compensating flow of helicity through the sun’s equatorial plane.
Prominence Formation Processes
Authors: Welsch B.T. , DeVore C. R. , Antiochos S. K. 
Published: March 2016

AbstractWe summarize our attempts simulate the prominence formation model proposed by Martens & Zwaan (2001, ApJ, 558, 872) in which differential rotation drives reconnection between two initially unconnected bipolar active regions to form helical field lines along the polarity inversion line (PIL) between the flux systems.
New Force-Free Models of Magnetic Clouds
Authors: Vandas M. , Romashets E. P. , Watari S. 
Published: March 2016

AbstractMagnetic clouds are thought to be large flux ropes propagating through the heliosphere. Their twisted magnetic fields are mostly modeled by a constant-alpha force-free field in a circular cylindrical flux rope (the Lundquist solution). However, the interplanetary flux ropes are three dimensional objects. In reality they possibly have a curved shape and an oblate cross section. Recently we have found two force-free models of flux ropes which takes into account the mentioned features. These are (i) a constant-alpha force-free configuration in an elliptic flux rope (Vandas & Romashets 2003, A&A, 398, 801), and (ii) a non-constant-alpha force-free field in a toroid with arbitrary aspect ratio (Romashets & Vandas 2003, AIP Conf Ser. 679, 180). Two magnetic cloud observations were analyzed. The magnetic cloud of October 18-19, 1995 has been fitted by Lepping et al. (1997, JGR, 102, 14049) with use of the Lundquist solution. The cloud has a very flat magnetic field magnitude profile. We fitted it by the elliptic solution (i). The magnetic cloud of November 17-18, 1975 has been fitted by Marubashi (1997) with use of a toroidally adjusted Lundquist solution. The cloud has a large magnetic field vector rotation and a large magnetic field magnitude increase over the background level. We fitted it by the toroidal solution (ii). The both fits match the rotation of the magnetic field vector in a comparable quality to the former fits, but the description of the magnetic field magnitude profiles is remarkable better. It is possible to incorporate temporal effects (expansion) of magnetic clouds into the new solutions through a time-dependent alpha parameter as in Shimazu & Vandas (2002, EP&S, 54, 783).
Of Tilt and Twist
Authors: Holder Zachary A. , Canfield Richard C. , McMullen Rebecca A. , Howard Robert F. , Pevtsov Alexei A. 
Published: March 2016

AbstractUsing Mees Solar Observatory active-region vector magnetograms and Mt. Wilson Observatory full-disk longitudinal magnetograms, we measure both the twist and tilt of the magnetic fields of 368 active regions. This dataset clearly shows two well-known phenomena, Joy’s law and the hemispheric helicity rule, as well as a lesser-known twist-tilt relationship, which is the point of this work. Those regions that closely follow Joy’s law show no twist-tilt relationship, which is a predicted consequence of convective buffeting of initially untwisted and unwrithed flux tubes through the Σ effect. Those regions that strongly depart from Joy’s law show significantly larger than average twist and a very strong twist-tilt relationship. These properties suggest that the twist-tilt relationship in these regions is due to kinking of flux tubes that are highly twisted but not strongly writhed.
The Evolution of NGC 5128: Globular Clusters and Field Stars
Authors: Peng Eric W. 
Published: March 2016

AbstractAs the nearest giant elliptical galaxy, NGC 5128 (Centaurus A) is an excellent place to use globular clusters (GCs) and host galaxy field stars to study galaxy evolution. We have performed a detailed investigation of this galaxy, comparing field star kinematics with the metallicities, ages, and kinematics of GCs. We used our sample of 780 planetary nebulae (PNe) to trace the kinematics of the field star population. Our survey for GCs bring the total number of confirmed GCs to 215. Using spectra of the brightest GCs to determine ages, we find that the metal-rich GCs have a mean age of approximately 4-5 Gyr, and that their kinematics are similar to those of the PNe. The metal-poor GCs have old ages similar to the Galactic GCs, and show a weaker kinematic correlation with the field stars. It is possible that NGC 5128 was formed by the merger of two or more disk galaxies at the time that the metal-rich clusters were formed.
The Dynamical Mass of the Young Cluster W3 in NGC 7252: Heavy-Weight Globular Cluster or Ultra-Compact Dwarf Galaxy?
Authors: Maraston Claudia , Bastian N. , Saglia R. P. , Kissler-Patig Markus , Schweizer François , Goudfrooij Paul 
Published: March 2016

AbstractWe have measured the dynamical mass of the highly luminous star cluster W3 in the young merger remnant galaxy NGC 7252. The value is Mdyn = (8 ± 2) × 107M⊙, and represents the highest dynamically-confirmed mass for an extra-galactic star cluster so far. The dynamical mass is in excellent agreement with the luminous mass (Maraston et al. 2001). This results from the use of stellar population models that include correctly the brightest AGB stellar phase, dominant in young stellar populations. To classify W3, we employ the fundamental plane of stellar systems (Bender, Burstein & Faber 1992), for the first time in these kinds of studies. We find that W3 lies far from typical Milky Way globular clusters, but it is also far from the heavyweights ωCen in the Milky Way and G1 in M31, because it is too extended for its mass, and from dwarf elliptical galaxies because it is much more compact for its mass. Instead W3 lies close to the ultra-compact Fornax objects (Drinkwater et al. 2003) and to the compact elliptical M32, possibly shedding light on the still mysterious nature of these objects. A previously deserted region of the fundamental plane starts to be populated.
Dynamical Evolution of Globular Cluster Systems in Clusters of Galaxies: The Case of NGC 1404 in the Fornax Cluster
Authors: Bekki Kenji , Couch Warrick J. , Forbes Duncan A. , Beasley M. A. 
Published: March 2016

AbstractWe investigate, via numerical simulations, the tidal stripping and accretion of globular clusters (GCs). In particular, we focus on creating models that simulate the situation for the GC systems of NGC 1404 and NGC 1399 in the Fornax cluster, which have poor (specific frequency
SN ~ 2) and rich (SN ~ 10) GC systems respectively. We initially assign NGC 1404 in our simulation a typical SN (~ 5) for cluster ellipticals, and find that its GC system can only be reduced through stripping to the presently observed value, if its orbit is highly eccentric (with orbital eccentricity of > 0.5) and if the initial scale length of the GCs system is about twice as large as the effective radius of NGC 1404 itself. These stripped GCs can be said to have formed a ‘tidal stream’ of intra-cluster globular clusters (ICGCs) orbiting the center of Fornax cluster (many of which would be assigned to NGC 1399 in an imaging study). The physical properties of these GCs (e.g., number, radial distribution, and kinematics) depend on the orbit and initial distribution of GCs in NGC 1404. Our simulations also predict a trend for 5N to rise with increasing cluster-centric distance – a trend for which there is some observational support in the Fornax cluster. We demonstrate that since the kinematical properties of ICGCs formed by tidal stripping in the cluster tidal field depend strongly on the orbits of their previous host galaxies, observations of ICGC kinematics provides a new method for probing galaxy dynamics in a cluster.
The Spectra of Bright Near-IR Clusters in M82
Authors: Lançon A. , Mouhcine M. , Chané E. , Smith L.J. , Gallagher J.S. , Schreiber N. Förster , Vacca W. , de Grijs R. , O’Connell R.W. 
Published: March 2016

AbstractBased on new spectra spanning wavelengths from 0.8 to 2.4μm, we study the properties of bright near-IR clusters in M82. We focus on age and extinction, which are critical parameters when one uses dynamical masses to constrain the stellar IMF. The modelling of red supergiant evolution by various authors leads to very significant differences in synthetic cluster spectra. Near-IR fluxes alone therefore do not rule out a normal IMF for cluster F, previously found to be deficient in low mass stars. Combined optical and near-IR studies are being undertaken.
Multicolor Photometry and Age Estimates of Globular Clusters in M31
Authors: Ma Jun 
Published: March 2016

AbstractWe present CCD multicolor photometry for 172 globular clusters (GCs), taken from the Bologna catalog (Battistini et al. 1987), in the nearby spiral galaxy M31. The observations were performed by using the National Astronomical Observatories 60/90 cm Schmidt Telescope in 13 intermediate-band filters, which covered a range of wavelength from 3800 to 10000 Å. This provides a multicolor map of M31 in pixels of 1.7 × 1.7 arcminutes. By aperture photometry, we obtain the spectral energy distributions (SEDs) for these GCs. Using the relationship between the Beijing-Arizona-Taiwan-Connecticut (BATC) intermediate-band system used for the observations and the UBVRI broad-band system, the magnitudes in the B and V bands are derived. The computed V and B–V are in agreement with the values given by Battistini et al. (1987) and Barmby et al. (2000). Finally, by comparing the photometry of each GC with theoretical stellar population synthesis models of Bruzual & Chariot (1996, hereafter BC96), we estimate ages of the sample GCs for different metallicities. The BC96 models provide the evolution in time of the spectrophotometric properties of simple stellar populations for a wide range of stellar metallicity. The results show that nearly all our sample GCs have ages more than 109 years, and most of them are around 1010 years old. At the same time, we find that GCs fitted by the metal-poor model are generally older than ones fitted by the metal-rich model.