bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intermediate Band Photometry of RR Lyrae Variables in ω Cen and 47 Tuc
Authors: Jones D.H.P. 
Published: July 2016

I have recently prepared for publication a study of 100 field RR Lyraes which were measured on the u, k, b, y, β system described by Jones (1971). It is shown that the following indicesβ1 = β − 0.125(k − b) + 0.103(b−y)(u − b)3 = (u − b) − 0.93(b − y) − 0.62(k − b) − 1.95(β − 2.75)(k − b)2 = (k − b) − 0.826(b − y) + 0.25(β − 2.75)correlate strongly with θeff, logg and [Fe/H] respectively. Figures in that paper show the tightness of the correlations.
The RR Lyrae Stars in the Magellanic Clouds
Authors: Graham J. A. 
Published: July 2016

AbstractThe characteristics of the RR Lyrae stars in the Magellanic Clouds are discussed. The existence of numerous RR Lyrae variables in the Large Magellanic Cloud (LMC) cluster NGC 1835 is noted. The variables indicate that this cluster is of Oosterhoff type I. No cluster of Oosterhoff type II has yet been recognized in the Clouds. Some new results of a study of the RRLyrae variables in an LMC field 1° x 1.°3 are discussed. Periods have been determined for 50 out of 72 probable RR lyraes in this field. RR Lyrae ab stars with periods less than 0.d46 are absent. The time averaged and are 19.m56 and 19.m20 with surprisingly small dispersion. First impressions of results for a similar field in the Small Magellanic Cloud (SMC) suggest that the old stellar population of the SMC may have a slightly lower metal abundance than that of the LMC. The best available distance moduli for the Magellanic Clouds indicate a mean absolute visual magnitude M of +0.m5 ±0.2 for the RR Lyrae stars in these systems.
Observational Aspects of Slow Variables in Globular Clusters
Authors: Feast M. W. 
Published: July 2016

AbstractThere are up to 14 known Mira variables in seven globular clusters, though several have not yet been confirmed as radial velocity members. The periods of only 5 are known, all near 200 days. The clusters seem to form a compact group of relatively metal rich clusters. In 3 or 4 cases spectroscopy shows that the giant branches of these clusters penetrate into the M types. The Mira-containing clusters also contain red variables of shorter period and smaller amplitude which are generally also M type stars. Stars apparently evolve to the red of the giant tip as variables of increasing amplitude and period. Effects of TiO blanketing on the (B — V) colours may be anticipated in these clusters.Besides variables at the red giant tip the metal poor globular cluster ω Cen contains variables with strong TiO bands. Photometry, including recent J, H, K, L photometry by Glass shows that these stars are very cool objects. They indicate an extension of the giant branch considerably cooler than previously considered for metal poor clusters.V1, NGC 121 in the Small Magellanic Cloud has a spectrum indicative of an SRd variable. It is not yet clear whether galactic stars similar to this star exist or not.
Narrow-Band Photometry of Red Variables in Globular Clusters
Authors: Wing Robert F. 
Published: July 2016

AbstractFourteen red variables in the southern globular clusters 47 Tuc, ω Cen, and NGC 362 have been observed on an eight-color system of narrow-band photometry in the near infrared. Temperatures are derived from blackbody fits to the calibrated fluxes, and spectral types are given for the M stars. The types observed for the three Mira variables in 47 Tuc range from M3.1 to M7.5; two small-range variables in the same cluster are later than M4. The variables in ω Cen are mostly earlier than K5, but spectra of types M3 and MO were also encountered among radial-velocity members. In both the metal-rich 47 Tuc and the metal-poor ω Cen, the relation between TiO band strength and temperature is approximately normal. Several of these stars fall well above or below the red giant branches of their clusters in diagrams of infrared magnitude against temperature. Comparisons are made with recent results obtained at Radcliffe Observatory on some of the same stars.
The Period-Luminosity Relation for Cepheids in Globular Clusters
Authors: Kukarkin B. V. , Rastorgouev A. S. 
Published: July 2016

The period-luminosity relation for Cepheids in globular clusters has been investigated many times (e.g. Fernie, 1964; Kwee, 1968; Frolov, 1970; Demers, 1971).The method of determination of the apparent distance moduli was recently revised by Kukarkin and Russev (1972). Instead of using a single absolute magnitude for RR Lyrae variables, the magnitudes according to pulsation theory (Christy, 1966, 1971) were adopted. The inhomogeneity of the absolute magnitudes of the RR Lyrae variables had already been established long ago (Pavlovskaya, 1953), but it attracted attention only recently. The different methods for determining the distance moduli of globular clusters were calibrated according to the new absolute magnitudes of the RR Lyrae variables. The problem consisted in the determination of the absolute magnitudes of the Cepheids in globular clusters according to the apparent distance moduli.
On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems
Authors: Castellani V. , Giannone P. , Renzini A. 
Published: July 2016

AbstractThe differences in observational parameters of the RR Lyrae variables and horizontal branch stars of globular clusters and other population II systems are considered. A discontinuous behaviour of some parameters is outlined. The Oosterhoff dichotomy and the HB morphology are discussed with regard to a conjecture of mass loss in the pre-HB phase.
The comet and minor planet program at Lowell Observatory
Authors: Giclas H. L. 
Published: July 2016

The Lowell Observatory has traditionally been involved with the planets, at its inception in 1894 with the bright planet Mars and culminating in 1930 with the discovery of a 15th. magnitude one, Pluto. In the interim and following, many thousands of minor planets and comets have been observed from five separate series of sky surveys and special observing programs.The first program in search of a trans-Neptunian planet, initiated by Percival Lowell, was begun in 1905 and completed in 1907. The entire ecliptic was photographed, using a 5-inch Brashear lens of 35 inches focal length which covered a good usable field of 5 degrees. Many of the 250 plates made in this series were three-hour exposures, in order to reach the 16th. magnitude. The shorter exposures reached the 14th. magnitude. Cramer Iso-Instant and Seed’s 27 plates were used. Each plate pair of this series was laboriously examined by hand magnifier comparing star for star.
The program of observations of minor planets at the Goethe Link Observatory
Authors: Edmondson Frank K. 
Published: July 2016

The Indiana program was started in response to an appeal in 1947 from Dirk Brouwer, President of Commission 20 of the IAU, for cooperation to help overcome the effects of the war-time gap in asteroid observations. The 10-inch Cooke triplet lens which we have used is the property of the Cincinnati Observatory. The scale is 120.̎15/mm. Observations were started in 1948 and continued until the retirement of Mrs. Beryl H. Potter in June 1966. Nearly 6300 plates were taken during this period.A micrometer eyepiece on the guide telescope was used to produce a round image of the asteroid and trailed images of the stars. Prior to 1961 a one hour exposure on Eastman 103a—0 plates would show objects almost to the 18th magnitude. After 1961 the plates were slower and the sky brightness increased with the growth of Indianapolis, 10 miles to the northeast. The plates were taken in pairs in immediate succession, and were blinked by Mrs. Potter. She also did a large part of the measuring and supervised the student assistants who participated in the measuring. By the time Mrs. Potter retired, she had found nearly all of the “critical list” objects which could be reached with our equipment.
Méthode des moindres carrés (erreurs) L’écart sur un point de référence consécutif à une erreur sur sa position, dans la réduction des clichés astrométriques par formules polynomials, peut ne pas être minimum au centre
Authors: Debehogne Henri 
Published: July 2016

Une meilleure compréhension du «méchanisme» de réduction des clichés se trouve assurée par la connaissance des effets d’une erreur sur un point de référence.En ce qui concerne l’effet sur l’ensemble du cliché, nous avons établi graphiquement (Debehogne, 1972), comment1° le degré du polynôme de transformation,2° le nombre d’étoiles de référence,3° la position du point d’application de l’erreur déterminent le nombre et la valeur des extrema.
Total asteroid mass from comet perturbations
Authors: van Flandern T. C. 
Published: July 2016

AbstractDeviations of Halley’s Comet from its predicted orbit more closely approximate perturbations caused by a gravitational ring of matter, rather than a point source or the usual nongravitational force model for comets. This is especially evident from the perturbations on the perihelion, node, and inclination for this comet. It is hypothesized that the gravitating ring was the asteroid belt. The observed deviations were used to solve for the total mass of the asteroids, giving the result of fifty times the mass of the Earth. Such a large mass can be ruled out by the absence of corresponding secular perturbations on the orbit of Mars, provided that the mean plane and shape of the asteroid belt do not correspond exactly with the orbit of Mars.A mean set of elements for the asteroid belt was determined by averaging the elements of the numbered minor planets, and three short-period comets were then tested with the same hypothesis. It is concluded that there is no correlations between perturbations due to the mean asteroid belt and those exhibited by the three short-period comets.The upper limit for the total mass of the asteroids, set by Mars, is 0.1 Earth mass. The source of the out-of-plane perturbations and of the cause of the secular increase in perihelion distance for Halley’s Comet is still an open question, since these cannot be explained by the usual nongravitational force model for comets.
Flares: the Solar-Stellar Connection
Authors: Byrne P. Brendan 
Published: July 2016

The systematic study of stellar flares in now more than 30 years old. Throughout that time the solar flare paradigm has been used, highly successfully, to understand various aspects of the stellar phenomenon. In this introductory overview I will attempt to justify the use of the solar model in understanding the stellar equivalent. But I will also point out differences between the two which may require extension of the basic solar model and speculate briefly on what these extensions might be.There are many excellent previous reviews of stellar flares in the literature (Haisch 1989, Byrne 1983, 1992), to which the reader is referred, along with the other reviews in this volume, for further reading.
Radio Emission from Flares in Single Late-type Stars
Authors: Benz Arnold O. 
Published: July 2016

AbstractRadio observations provide the most direct information on non-thermal electrons in stellar flares and in the coronae of late-type stars. Radio emissions of single main-sequence F, G, and of many K stars have recently been discovered, in addition to the well-known dwarf M stars. Their long-duration radio flares with low circular polarization, slow variations and broad bandwidth can be attributed to gyrosynchrotron emission of mildly relativistic electrons. The same holds for the low-level (‘quiescent’) radio emission. On the other hand, highly polarized radio flares of M stars have been interpreted by coherent emissions from loss-cone instabilities of magnetically trapped electrons. These conjectures are consistent with recent VLBI observations. The identification of the radio emission process allows to estimate the high-energy component of the flare and compare it to the total flare energy. The weakly polarized radio emission may serve as a proxy for hard X-ray signatures of relativistic electrons. The fraction of primary energy released into energetic electrons then appears to be large and similar to solar flares.
The Red Dwarf Star Population in the Galaxy
Authors: Mirzoyan L.V. 
Published: July 2016

Red dwarf stars in the Galaxy occur in three forms: as flare stars, T Tau stars and red dwarf stars of constant brightness. Haro (1957) suggested that all these stars present regular evolutionary stages of red dwarf stars.The space distribution of UV Cet flare stars in the solar vicinity indicates that these low luminosity stars belong to the disk population of the Galaxy. Therefore one can suppose that all red dwarf stars have a space distribution which is similar to that of the flare stars (Mirzoyan et al. 1988a). Only a small part of them is found in star clusters and associations. The T Tau stars are an exception: because of their very short lifetime, all of them are found in stellar associations.The space distribution of red dwarf stars is determined by the fact that all of them are formed in star clusters and associations and are finally lost from their stellar systems and merge into the general galactic field (Mirzoyan 1995).
New EUV Selected Flare Stars
Authors: Ball Bill , Bromage Gordon 
Published: July 2016

The ROSAT Wide Field Camera all-sky EUV survey of 1990-91 identified over 200 active late-type stars (Pounds et al. 1993). Most of these were not known to be active prior to the survey and follow-up optical spectroscopy has been successful in selecting the most active dMe stars. These stars are characterized by their Balmer line emission which is direct evidence for an active chromosphere. We present photometric monitoring data for 4 new dMe stars, including the discovery of flaring activity on all 4 stars.The observations were made at the South African Astronomical Observatory at Sutherland near Capetown in October 1994, using the 0.5m and 1.9m telescopes for photometry and spectrometry, respectively. The 0.5m telescope is equipped with an automated, pulse-counting photometer. Flare monitoring of all the stars was done in the U-band with either 5 or 10 s integration times. All the stars monitored were between magnitude V = 11 and 13. A total of 15 flares were detected, including at least one on each star (Table 1). Comparison stars were measured in standard UBVRI photometric bands for each star.
Spectral and Photometrical Investigation of EV Lac in Different States with High Time Resolution
Authors: Beskin G.M. , Mitronova S.N. , Panferova I.P. 
Published: July 2016

Spectroscopic and photometric monitoring of the flare star EV Lac was carried out with the 6-m telescope of the Special Astrophysical Observatory on the following 3 nights: 1993 September 10 (18:54-20:16 UT), 11 (17:46-20:03 and 21:25-22:16 UT) and 12 (19:46-20:08 and 21:23-22:21 UT).We used the observation method described in detail by Berdyugin et al. (1994) and Alekseev et al. (1994). Observations were carried out with the 1024 channel TV scanner (Drabek et al. 1986) installed on the spectrograph SP-124 at the Nasmyth focus which covered a wavelength range 3480-5530Å with a spectral resolution 2Å per channel. Exposure times were 3 — 5 minutes, the signal/noise ratio was 20 at 3500Å and 40 at 5500Å and dead time between exposures was 10 — 15 sec. 92 spectra were obtained in total.
Photoelectric Observations of AD Leo: 1989-1994
Authors: Konstantinova-Antova R. , Antov A.P. 
Published: July 2016

An investigation of the activity of the flare star AD Leo was made using U-band patrol observations. 60 cm computer-controlled telescopes with identical single channel photon-counting photometers at the National Astronomical Observatory at Rozhen and at the Belogradchik Observatory were used. The integration time was 1 sec. Differential photometry was carried out, the AD Leo measurements were made relative to BD+20°2475. The data was reduced with the program package APR (Kirov et al. 1991).Two simultaneous observing runs were made. The results of the first have already been published (Antov etal. 1991). The other was part of the observational campaign in May, 1991 with the ROSAT satellite. In Bulgaria, the observations were carried out at Rozhen in the U-band and at Belogradchik in the B-band. Four flares were detected by both.
Flares Detected on Some Late Giants: Are They Real?
Authors: Konstantinova-Antova R. , Ivanov M.M. , Antov A.P. 
Published: July 2016

Recently, some apparently single red giants with evidence of chromospheric activity were reported. In this work we observed those single late giants with reported flares, referenced by Pettersen (1989) and Schaefer (1989), as part of a program for investigation of the chromospheric activity in G and K giants.According to Simon & Drake (1989), active single G and K giants may be first crossing stars that have just entered the phase of rapid spin-up as their convection zones advance upon their more rapidly rotation radiative cores. These stars are situated on the base of the red giant branch on the HR diagram. As a result they may possess dynamo driven activity at this stage of evolution.
CCD Monitoring of Flare Stars in Stellar Aggregates
Authors: Kurtanidze Omar M. 
Published: July 2016

After Haro’s fundamental discovery of flare stars in stellar associations and young clusters, their importance was fully recognized. The flare star system provides one of the most important records of the stellar aggregate’s history. This record can be used to establish the chronology of these systems and to test theories of star and aggregate formation.Unfortunately, the observational material contains an unavoidable strong selection with respect to the statistics and the physical characteristics of flare stars in aggregates. This explains the difficulties which arise when one tries to compare physical and statistical characteristics of flare stars in aggregates and in the solar neighborhood, since the latter objects are studied almost exclusively by photoelectric methods. The flare frequency in aggregates is more than one order of magnitude smaller than that of flare stars in the solar neighbourhood. This is probably a selection effect, since the photographic observations in aggregates have been carried out with exposure times 5-10 min. Small amplitude flares cannot be recorded at all. Flare stars in aggregates are usually objects whose recorded flares have amplitudes > 0m.6 − 0m.7, and which last for at least 5 min. The long exposure masks the true amplitude of the flare.
Flare Stars Database: Present Status
Authors: Tsvetkova K.P. , Tsvetkov M.K. , Stavrev K.Y. 
Published: July 2016

AbstractAn updated data collection for UV Cet type stars and their registered flare events in stellar aggregates and in the solar neighbourhood during more than 9580 hours observing time is described. The Flare Stars Database (FSDB) presently includes 3127 entries for 1622 stars.
Optical Observations on Milli-, Micro-, and Nanosecond Timescales
Authors: Dravins D. , Lindegren L. , Mezey E. 
Published: July 2016

AbstractInstrumentation and observing methods are developed for optical high-speed astrophysics, aiming at exploring milli-, micro-, and nanosecond variability. Such rapid fluctuations can be expected from instabilities in accretion flows, and in the fine structure of photon emission. For the optical, we have constructed a dedicated instrument, whose first version was tested on La Palma to study atmospheric scintillation on very short timescales. A second version is now under development, using photon-counting avalanche photodiodes as detectors.
Physical Processes During Impulsive Solar and Stellar Flares
Authors: Katsova Maria , Livshits Moissei 
Published: July 2016

Investigations of impulsive flares on both the Sun and red dwarf stais during more than 30 years allow us to arrive at quite definite conclusions. Here we will consider impulsive events; on the Sun the impulsive phase of a flare is observed as a hard X-ray burst with the emission of photons with energies E > 30 keV up to the γ-ray range. At the same time microwave radio bursts, and sometimes UV and optical continuum bursts are registered. Typical durations of these processes are ∼l-3 min. In this time interval other kinds of flare emission like soft X-ray (2-10 keV) emission, meter radio bursts and Balmer line emission begin to rise, but their maxima occur later on, in the gradual (thermal) phase of the flare.Impulsive stellar flares are often observed as a significant increase in optical continuum, especially in the U-band, of similar duration (1-3 min), and this time interval is, like in the solar case, the rise phase of the soft X-ray emission.Modern observations demonstrate that both the impulsive phase of a flare or an impulsive flare develops in low-lying loops. Earlier only indirect evidence existed in optical and radio data. Recently, however, the heights of the hard X-ray sources in impulsive solar events were determined directly from YOHKOH’s HXT (Kosugi 1994, Masuda 1994) (Fig. 1a). Statistically, the height of the hard X-ray source in the 14-23 keV range is 9700 ± 2000 km above the photosphere, and this height reduces to 6500 km in the 53-93 keV range. Besides two hard X-ray sources in the loop footpoints, a third hard X-ray source exists at the top of the loop at least in some cases. The authors of this experiment suppose that the appearance of this loop-top source is due to reconnection in the impulsive phase. Note that the reconnection begins close to the apex of the loop, when this loop is filled by hot plasma that evaporated from both footpoints.
A Very Active T Tauri Star in NGC 7129
Authors: Semkov Evgeni 
Published: July 2016

The star forming region NGC 7129 was first studied by Herbig (1960), who discovered two bright (BD+65° 1637 and LkHα234) and some weaker Hα emission stars. Subsequent investigations in this region led to the detection of five Herbig-Haro objects (Strom et al. 1974, Gyulbudaghian et al. 1978, Eiroa et al. 1992) and one T Tauri star, V350 Cep (Gyulbudaghian & Sarkissian 1977). Some non-stable stars in NGC 7129 are surrounded by reflection and cometary nebulae.Our Hα-emission survey (Semkov &: Tsvetkov 1986) revealed an interesting irregular variable star in the dark clouds near the emission nebulae. On objective prism plates the star shows very strong Hα-emission and was included in our list of such stars as No. 7. An identification chart and the coordinates can be found in Semkov (1993a). The observations reported here include long-time photographic photometry and CCD spectroscopic and photometric observations.
Flares and Flickering in the Cataclysmic Variable AE Aquarii
Authors: Welsh William F. , Horne Keith , Gomer Richard 
Published: July 2016

Detected from the radio to the γ-ray bands, AE Aquarii is an extraordinary cataclysmic variable. It is a relatively bright (V ∼11.4), non-eclipsing binary with an orbital period of 9h.9. The mass-donor secondary star is of approximate spectral type K5V and contributes about ∼ 80% of the total flux in the optical. While the mass ratio is well determined at q = M2/M1 = 0.646, the individual stellar masses are poorly known since the inclination is unknown. AE Aqr’s flickering behavior is unique among CVs, alternating from periods of very violent activity to near total quiescence. Large amplitude flares have been detected in the radio, optical and UV. Previous work has shown the optical flare spectrum to be similar to stellar flare spectra.Four nights of exactly simultaneous Hα spectroscopy and photometry were obtained on the 2.5 and 1.5m telescopes at Mt. Wilson on 27-30 July 1982. The simultaneity allowed us to renomalize the spectroscopy to agree with the photometry, giving us spectrophotometric data (spectral resolution ∼ 50 km s−, time resolution ∼ 68). A total of ∼ 17h of data were obtained, resulting in 10,098 spectra.