bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infrared Photometric Systems, Standards and Variability
Authors: Leggett S.K. , Smith J.A. , Oswalt T.D. 
Published: July 2016

AbstractThe accuracy with which infrared photometry can be carried out is currently limited by poor definition of the instrumental system and by the accuracy of the available standard stars. We present new colour transformations between the CIT J, H, K photometric system and systems currently in use at Cerro Tololo, Mauna Kea and Kitt Peak. The precision of the J, H, K data for some of the stars observed by Elias et al. is improved and the system extended to fainter stars suitable for use with larger telescopes and/or infrared arrays. Evidence of infrared variability has been detected for one M dwarf star in our programme.
Lessons from Very Long-Term, Very High-Precision Photoelectric Photometry
Authors: Lockwood G.W. , Skiff B.A. , Thompson D.T. 
Published: July 2016

AbstractTraditional photoelectric techniques can achieve millimagnitude precision if a few simple rules are scrupulously followed. We illustrate the practical limits of differential photometry obtained with a dedicated telescope and photometer. Using a highly homogeneous set of measurements of bright F, G, and K solar analog stars, we present the distribution of observational noise and intrinsic stellar variability over a typical observing season and over the entire 8-year program. Finally, we list Strömgren uvby standards which we found to vary slightly.
The Avalanche Photodiode — A Promising Low Light Level Detector for Astronomical Photometry
Authors: Śzécésnyi-Nagy G. 
Published: July 2016

AbstractAstronomical photometry like other scientific methods is always forced to search for up-to-the-minute instruments and the most sophisticated devices. The photomultiplier tube (PMT) is the most widely used photon detector offering high sensitivity and gain with acceptable quantum efficiency and spectral range but it also has some disadvantages. During the past few decades all of these parameters have been improved and it seems likely that possibilities for their continued development are exhausted.In the meantime, technical development — especially micro electronics and semiconductor technology — has produced a new detector, the avalanche photodiode (APD). The APD which is often referred to as a solid-state PMT is just at the start of its career and we may expect its rapid perfection. Although properties of APDs were first discussed almost twenty years ago their mass production did not start until 1990. Early silicon APDs had very limited dimensions compared to PMTs but unfortunately this also implied that their photosensitive area was less than 0.25 mm. One more year of development has been enough to increase the photon collecting surface by a factor of 1000 and APDs may soon become possible rivals of PMTs.Following a brief description of the new device and discussion of its operation a comparison of photodetector performance will be given in order to draw attention to those parameters which are of great promise. Those sections of astronomical photometry which are ready to benefit from the suggested testing and use of this kind of photon detector will be highlighted.
A Bidimensional Photon-counting Microchannel Plate Detector Using a Wedge and Strip Anode
Authors: Drazdys R. , Jukonis J. , Skrebutėnas A. , Vansevičius V. , Vilkaitis G. 
Published: July 2016

AbstractA photon-counting detector with a 45 mm diameter active area has been developed using a microchannel plate (MCP) and the wedge and strip readout system. The detector uses a UV transparent glass input window proximity coupled to a stack of MCP. Quantum efficiency (QE) of the detector photo-cathode is ~ 20%. The resolution of ~ 60 μm FWHM at a gain of 5.107 has been achieved.
The MEKASPEK project — a new step towards the utmost photometric accuracy
Authors: Mantel K. H. , Barwig H. , Kiesewetter S. 
Published: July 2016

AbstractWe present the design of a new 4 channel, fiberoptic spectrophotometer which allows to measure the object, two comparison stars and sky background simultaneously throughout the whole optical wavelength range with high efficiency. The overall spectral resolution of about 50 in combination with over-sampling allows to eliminate colour dependent extinction effects to a high degree and guarantees accurate transformations to other broad band photometric systems.
Correlations between Atmospheric Extinction and Meteorological Conditions
Authors: Reimann H.-G. , Ossenkopf V. 
Published: July 2016

AbstractA retrospective investigation covering about twenty years of wide-band and intermediate-band photometry at Jena University observing station allows an analysis of variations of atmospheric extinction at different time scales. A comparison with an earlier investigation by Wempe (1947) permits to draw conclusions about the evolution of air pollution by aerosols over nearly half a century. Complementary weather observations obtained at the meteorological observing station of the Jena University allow to find correlations between the variation of extinction parameters and the changing weather situations. Parallel Mie calculations allow to interpret the variations of the measured extinction data in terms of size variations of water-rich aerosols.
On Improving IR Photometric Passbands
Authors: Young A.T. , Milone E.F. , Stagg C.R. 
Published: July 2016

AbstractThe passbands of the Johnson JHKL broadband photometric system used at a number of major observatories have been compared to the atmospheric window transmissions calculated by MODTRAN, and a family of solar-composition model stellar fluxes from Kurucz (1991 private communication) have been used as input to model the atmospheric extinction under different water vapor content, altitude, and airmass conditions. A figure of merit related to the slope of the extinction curve at zero airmass describes the sensitivity of the response function to atmospheric extinction. We have compared passbands used at several observatories, and have designed an improved set of passbands.
Progress with the Whole Earth Telescope
Authors: O’Donoghue D. , Provencal J. 
Published: July 2016

AbstractA summary of the results from seven global runs using the Whole Earth Telescope is presented, together with an evaluation of the scientific results obtained to date. Factors such as the distance of the target star from the equator, the nature and timescales of its intrinsic variability, etc. are shown to affect the value and quality of the results, as well as the traditional factors such as brightness and long-term coherent behaviour. Experience with the network shows that, taken as a whole, it enjoys far better weather than any one of its sites, and provides unprecedented ‘uncluttered’ resolution of time-series power spectra.
Time-Series Photometry: CCDs vs. PMTs
Authors: Kreidl T.J. 
Published: July 2016

AbstractWith the ability to obtain simultaneous photometry of many objects, CCD time-series photometry is a potentially powerful method for obtaining data, even under non-photometric conditions. In particular, the ability to utilize one or more comparison stars on the same frame without the need to move the telescope to a different field makes for a higher duty cycle than conventional photoelectric photometry. In addition, the ability to determine the local sky in a variety of ways plus the ability to use more complex analysis techniques such as profile fitting and curves of growth permits a variety of analysis options. Some of the advantages of utilizing CCDs and the techniques used in time-series photometry of compact objects are discussed. With the flexibility of modern CCD control systems, possibilities for real-time or near real-time data analysis using readily available computer technology are stressed. Brief discussions of periodicity analysis considerations and other aspects of the data acquisition are presented.
Observation of Multiple Stars with the Digital Speckle Interferometer
Authors: Bonneau D. , Koechlin L. 
Published: July 2016

AbstractSince 1977, the Digital Speckle Interferometer chiefly developed for the study of atmospheric structure in cool supergiant stars, has been used for observing multiple stars. It has provided binary star resolution down to 30 milliarcsec. separation with a precision from 3% to 10%.The incertitude on position angle determination ranges from ± 1° to ± 5°.Working in photon counting mode, we are able to estimate magnitude difference reaching Δ m ~ 3.0 with an uncertainty of about 0.2−0.3 magnitude.On the basis of present experimentation, we think that 17th mag binaries can be resolved with a 3.6 meter telescope.
Le Telsecope Spatial et les Etoiles Doubles
Authors: Couteau Paul , Fulconis Monique 
Published: July 2016

The number of new couples available for the Space Telescope can be estimated through the study of prior surveys and observational selection.Surveys realized at the beginning of this century, as well as actual surveys being recalled, show that couples remain to be discovered. A method is developed showing the importance of instrumental selection by the difference of magnitude between the components, this way can be estimated the number of couples inaccessible by earth observations due to differences of magnitudes.Limiting ourselves to the magnitude 10, we show that the Space Telescope will permit to discoverer mostly close couples with a small difference of magnitude and a short period (P 20 y). They represent several thousands of stars.
Period-K magnitude relations of variable stars in the LMC
Authors: Ita Yoshifusa , Tanabé Toshihiko , Matsunaga Noriyuki , Nakada Yoshikazu ,   The IRSF/SIRIUS team
Published: July 2016

AbstractWe cross-correlated the OGLE-II database with the SIRIUS JHK survey data in the Large Magellanic Cloud (LMC). After eliminating obvious spurious variables, we determined the pulsation periods for 9 681 stars by applying the Phase Dispersion Minimization (PDM) technique to the OGLE-II data. Based on these data, we studied the period-K magnitude (PK) relations of variable stars in the LMC and found a new sequence. Comparison between the theoretical pulsation model (Wood & Sebo 1996) and observational data suggests that the variable stars on the new sequence are Mira variables pulsating in the first overtone mode.
New results on OGLE Cepheids and PL relations in the LMC and SMC
Authors: Udalski A. 
Published: July 2016

AbstractWe present results of the search for pulsating variable stars in the Magellanic Cloud fields covering central parts of these galaxies. The data were collected during the second phase of the Optical Gravitational Lensing Experiment survey (OGLE-II) from 1997 to 2000. In total, several thousand pulsating stars (Cepheids, RR Lyr) were found in both Magellanic Clouds. The photometric data of all objects are available to the astronomical community from the OGLE Internet archive. We present basic properties of pulsating stars in the Magellanic Clouds including Period–Luminosity relations for Cepheids. We also discuss observational prospects for the pulsating star field in the ongoing third phase of the OGLE project (OGLE-III) which started in 2001.
Dust enshrouded AGB stars in the LMC
Authors: Hinkle Kenneth H. , Joyce Richard R. , Do Tuan 
Published: July 2016

AbstractA near-infrared (J and K) survey of the LMC Bar West region was undertaken with CIRIM on the CTIO 1.5-m telescope to search for obscured carbon stars. A number of very red stars were detected, and from this list five highly reddened, ‘Obscured’ stars were identified. Subsequent to our survey we identified these sources in the 2MASS survey data. Using our J, K photometry as well as J, H, K from 2MASS, 8.28 µm from the MSX satellite, and L photometry from Phoenix on Gemini, we have measured the color temperature and flux of the detected obscured stars. None of these objects is as cool as the bright galactic enshrouded carbon star CW Leo, although the MSX survey does appear to detect objects similar to CW Leo. Using the Phoenix high-resolution infrared spectrograph on Gemini we have observed the first overtone CO spectra of four of the LMC obscured stars. All the spectra are those expected for obscured carbon stars, but a surprising variety of line profiles was found.
AGB variables in globular clusters
Authors: Lebzelter T. , Wood P. , Hinkle K.H. , Joyce R. , Fekel F. 
Published: July 2016

AbstractWith a large number of newly detected red variables in globular clusters we construct a log P – K diagram of these stars and compare it with findings from the LMC. We show the existence of a relation between the location in log P – K diagram and the velocity amplitude in the near infrared.
A census of AGB stars in the Milky Way and M31 subgroups of dwarf-spheroidal galaxies
Authors: Kirschbaum F. , Heiling B. , Nowotny W. , Spindler Ch. , Olofsson H. , Schwarz H.E. 
Published: July 2016

AbstractFrom photometric observations out to the tidal radii of the galaxies, we were able to identify hundreds of new carbon stars, to derive mean absolute magnitudes〈Mi〉, luminosity functions, and the spatial/radial distributions of the carbon stars in these galaxies. For each galaxy this new material will allow estimates of the tips of their RGBs to derive distance moduli, to derive C/M ratios of the AGB populations and bolometric magnitudes Mbol. At the end of our survey a comparison of all quantities of the late-type stars as a function of the properties of the host galaxies will be made possible.
The effect of stellar evolution on the light curves’ shapes of RR Lyrae stars in M3
Authors: Jurcsik Johanna 
Published: July 2016

AbstractThe light curve characteristics of a homogeneous sample of variables in M3 are studied in detail. Accurate light curves and mean magnitudes of about 100 RRab and 50 RRc stars which do not show any type of modulation are analyzed. According to their mean magnitudes and Fourier parameters the variables can be sorted into four groups, representing different stages of the horizontal branch stellar evolution.
Latitude distribution of nonradial pulsations in rapidly rotating B stars
Authors: Jankov S. , Mathias P. , Domiciano de Souza A. , Uytterhoeven K. , Aerts C. 
Published: July 2016

AbstractWe present a method for the analysis of latitude distribution associated with temperature and/or velocity perturbations of the stellar surface due to non-radial pulsation (NRP) modes in rapidly rotating B stars. The technique is applied together with Fourier Doppler Imaging (FDI) to high resolution and high signal-to-noise ratio spectroscopic observations of ϵ Per. The main advantage of this approach is that it decomposes complex multi-periodic line profile variations into single components, allowing the detailed analysis of each mode separately. We study the 10.6-d−1 frequency that is particularly important for modal analysis of non-radial pulsations in the star.
Pulsational velocity fields in the atmospheres of two roAp stars HR1217 and γ Equ
Authors: Sachkov M. , Ryabchikova T. , Kochukhov O. , Weiss W.W. , Reegen P. , Landstreet J.D. 
Published: July 2016

AbstractWe discuss spectroscopic observations of pulsations in the roAp stars γ Equ and HR 1217. In both stars we observe strong variations of rare-earth lines and detect running magneto-acoustic waves, but do not find evidence for a standing pulsational wave. In γ Equ we find strong pulsational variations across line profiles, characteristic of l ≥ 2 modes.
Chemical abundances ofβCephei stars from low- and high-resolution UV spectra
Authors: Daszyńska-Daszkiewicz Jadwiga , Niemczura Ewa 
Published: July 2016

AbstractWe determined the stellar parameters (Teff, [m/H],θ) andE(B – V)for allβCephei stars observed during the IUE satellite mission. All parameters were derived using an algorithmic procedure of fitting theoretical flux distributions (Kurucz 1996) to the IUE observations.
Multiperiodicity in pulsating red giants
Authors: Percy J.R. , Bakos A.G. , Besla G. , Hou D. , Velocci V. , Henry G.W. 
Published: July 2016

AbstractWe describe several aspects of the variability of bright pulsating red giant (PRG) stars, with emphasis on the determination of pulsation modes and pulsation masses by using observed multiperiodicity and pulsation constants (Q- values). Our studies of bright PRGs provide a model for the analysis and interpretation of the thousands of PRGs being discovered in surveys of Local Group galaxies.
The Period-Radius Relation: Classical Cepheids and RR Lyrae stars
Authors: Marconi M. , Bono G. , Nordgren T.E. 
Published: July 2016

Abstract We present the period-radius relations predicted by nonlinear convective models of Classical Cepheids and RR Lyrae stars. For the former variables we show that the metallicity effect is negligible for both fundamental and first overtone pulsators. This confirms the power of the period-radius relation to estimate Cepheid radii and in turn distances. For the latter class of variables we show that the dispersion of the period-radius relation of both fundamental and first overtone pulsators is significantly reduced once the metallicity dependence is taken into account. This provides a robust method to evaluate the radius of observed RR Lyrae with measured period and metal abundance.
VINCI/VLTI Interferometric Observations of Cepheids
Authors: Nardetto N. , Kervella P. , Mourard D. , Bersier D. , Coudé du Foresto V. 
Published: July 2016

AbstractWe report the angular diameter measurements of seven classical Cepheids, X Sgr, η Aql, W Sgr, ζ Gem, β Dor, Y Oph, and l Car, that we have obtained with the VLT Interferometer Commissioning Instrument, installed at ESO’s VLT Interferometer. For four of these stars, η Aql, W Sgr, β Dor, and l Car, we detect the pulsational variation of their angular diameter. This enables us to compute directly their distances using a modified version of the Baade-Wesselink method. For X Sgr, ς Gem, and Y Oph, we apply a hybrid method that makes use of published estimates of their linear diameters to derive their distances.
The Study of δ Scuti Stars in The Transition Era from Ground-Based to Space Photometry
Authors: Garrido Rafael , Poretti Ennio 
Published: July 2016

The different research teams involved in the study of δ Sct stars have slightly changed their strategy in the past years. The observational effort to secure worldwide coverage of case studies has been continued, but the requirements have become more severe, especially about target characterization and frequency resolution.After the successful launch of the Canadian satellite MOST, which will be the pioneer of asteroseismology from space, the future missions are programmed to properly take into account the need for adequate frequency resolution: COROT will spent 30 and 150 d (additional and core programs, respectively) on the target, while EDDINGTON will spend up to 3yr. Such a requirement is a direct consequence of the observational results on δ Sct, γ Dor, SPB, and other stars obtained from ground. It should be noted that without these results (see Poretti 2000 for a review about δ Sct stars) the scientific background of the space missions would be much less defined and the risks of incomplete results (owing to inaccurate selection of targets, insufficient resolution, underestimate of the influence of the rotation) much higher.
The Absolute Magnitudes of RR Lyrae Stars and the Age of the Galaxy
Authors: Sandage Allan 
Published: July 2016

AbstractIt is shown that the intrinsic spread in the absolute magnitudes of the RR Lyrae variables in a given globular cluster can reach 0.5 magnitudes at a given period or at a given color, due to luminosity evolution away from the zero age horizontal (ZAHB). The size of this intrinsic luminosity spread is largest in clusters of the highest metallicity.The absolute magnitude of the ZAHB itself also differs from cluster to cluster as a function of metallicity, being brightest in clusters of the lowest metallicity. Three independent methods of calibrating the ZAHB RR Lyrae luminosities each show a strong variation of MV(RR) with [Fe/H]. The pulsation equation of P<ρ>0.5 = Q(M,Te, L) used with the observed periods, temperatures, and masses of field and of cluster RR Lyraes gives the very steep luminosity-metallicity dependence of dMv(RR)/d[Fe/H] = 0.42. Main sequence fitting of the color-magnitude diagrams of clusters which have modern main-sequence photometry gives a confirming steep slope of 0.39. A summary of Baade-Wesselink MV(RR) values for field stars determined in four independent recent studies also shows a luminosity-metallicity dependence, but less steep with a slope of dMV(RR)/d[Fe/H] = 0.21.Observations show that the magnitude difference between the main sequence turn-off point and the ZAHB in a number of well observed globular clusters is independent of [Fe/H], and has a stable value of dV = 3.54 with a disperion of only 0.1 magnitudes. Using this fact, the absolute magnitude of the main sequence turn-off is determined in any given globular cluster from the observed apparent magnitude of the ZAHB by adopting any particular MV(RR) = f([Fe/H]) calibration.Ages of the clusters are shown to vary with [Fe/H] by amounts that depend upon the slopes of the MV(RR) = f([Fe/H]) calibrations. The calibrations show that there would be a steep dependence of the age on [Fe/H] if MV(RR) does not depend on [Fe/H]. No dependence of age on metallicity exists if the RR Lyrae luminosities depend on [Fe/H] as dMV(RR)/d[Fe/H] = 0.37. If Oxygen is not enhanced as [Fe/H] decreases, the absolute average age of the globular cluster system is 16 Gyr, independent of [Fe/H], using the steep MV(RR)/[Fe/H] calibration that is favored. If Oxygen is enhanced by [O/Fe] = – 0.14 [Fe/H] + 0.40 for [Fe/H] < –1.0, as suggested from the observations of field subdwarfs, then the age of the globular cluster system decreases to 13 Gyr, again independent of [Fe/H], if the RR Lyrae ZAHB luminosities have a metallicity dependence of dMV(RR)/d[Fe/H] = 0.37.
The Globular Cluster ω Centauri and its RR Lyrae Variables
Authors: Dickens R.J. 
Published: July 2016

AbstractThe significance of some of the unusual characteristics of the globular cluster ω Centauri in various fundamental problems is explored. Interest is centred on the properties of the cluster RR Lyraes, and what they can contribute to studies of early cluster chemical enrichment, stellar pulsation, the distance scale, stellar evolution, stellar ages and the Oosterhoff period-shift problem. This article, which is intended to highlight problems and progress rather than give a comprehensive review, includes new results based on photometry of the RR Lyraes, red giants, subgiants, horizontal-branch and main sequence stars in the cluster.