Search

A spectroscopic and photometric analysis has been carried out for thirty-two candidate SX_Phe variable blue straggler stars in the Kepler-field (Balona & Nemec 2012). Radial velocities (RVs), space motions (U,V,W), projected rotation velocities (v sin i), spectral types, and atmospheric characteristics (T_eff, log g, [Fe/H], xi_t, zeta_RT, etc.) are presented for 30 of the 32 stars. Although several stars are metal-weak with extreme halo orbits, the mean [Fe/H] of the sample is near solar, thus the stars are more metal-rich than expected for a typical sample of Pop.II stars, and more like halo metal-rich A-type stars (Perry 1969). Two thirds of the stars are fast rotators with v sin i > 50 km/s, including four stars with v sin i > 200 km/s. Three of the stars have (negative) RVs > 250 km/s, five have retrograde space motions, and 21 have total speeds (relative to the LSR) > 400 km/s. All but one of the 30 stars have positions in a Toomre diagram consistent with the kinematics of bona fide halo stars (the exception being a thick-disk star). Observed Roemer time delays, pulsation frequency modulations and light curves suggest that at least one third of the stars are in binary (or triple) systems with orbital periods ranging from 2.3 days to more than four years., 43 pages, 23 figures, accepted MNRAS Nov.23,2016

We present the analysis of four first overtone RR Lyrae stars observed with the Kepler space telescope, based on data obtained over nearly 2.5yr. All four stars are found to be multiperiodic. The strongest secondary mode with frequency f_2 has an amplitude of a few mmag, 20 - 45 times lower than the main radial mode with frequency f_1. The two oscillations have a period ratio of P_2/P_1 = 0.612 - 0.632 that cannot be reproduced by any two radial modes. Thus, the secondary mode is nonradial. Modes yielding similar period ratios have also recently been discovered in other variables of the RRc and RRd types. These objects form a homogenous group and constitute a new class of multimode RR Lyrae pulsators, analogous to a similar class of multimode classical Cepheids in the Magellanic Clouds. Because a secondary mode with P_2/P_1 ~ 0.61 is found in almost every RRc and RRd star observed from space, this form of multiperiodicity must be common. In all four Kepler RRc stars studied, we find subharmonics of f_2 at ~1/2 f_2 and at ~3/2 f_2. This is a signature of period doubling of the secondary oscillation, and is the first detection of period doubling in RRc stars. The amplitudes and phases of f_2 and its subharmonics are variable on a timescale of 10 - 200d. The dominant radial mode also shows variations on the same timescale, but with much smaller amplitude. In three Kepler RRc stars we detect additional periodicities, with amplitudes below 1mmag, that must correspond to nonradial g-modes. Such modes never before have been observed in RR Lyrae variables., 21 pages, 18 figures, accepted for publication in MNRAS

High-resolution spectroscopic observation was carried out to find the chemical composition of BE Lyn. The abundances of 25 chemical elements from carbon to neodymium were found. The deficiency of iron appeared to be equal to ΔlogNðFe Þ¼� 0:26 � 0:08 with respect to the solar metallicity, and the abundances of other elements were mainly undersolar. Only nitrogen, sodium, aluminum, and sulfur showed overabundances near 0.2-0.3 dex. The abundance pattern showed no clear signs of accretion or mass transfer events. It is not possible to exclude the classification of BE Lyn as a SX Phe-type star with slightly undersolar abundances of chemical ele- ments. In addition, new differential time-series observations of BE Lyn were secured using V filters, and seven new times of light maximum were identified. We collected 162 times of light maximum from the literature, unpublished data, and an open database, and we proceeded to investigate the pulsational properties of BE Lyn. All five harmonic frequencies were identified using the Fourier decomposition method. Online material: extended tables

Nineteen of the ~40 RR Lyr stars in the Kepler field have been identified as candidate non-Blazhko (or unmodulated) stars. In this paper we present the results of Fourier decomposition of the time-series photometry of these stars acquired during the first 417 days of operation (Q0-Q5) of the Kepler telescope. Fourier parameters based on ~18400 long-cadence observations per star (and ~150000 short-cadence observations for FN Lyr and for AW Dra) are derived. None of the stars shows the recently discovered `period-doubling' effect seen in Blazhko variables; however, KIC 7021124 has been found to pulsate simultaneously in the fundamental and second overtone modes with a period ratio P2/P0 ~ 0.59305 and is similar to the double-mode star V350 Lyr. Period change rates are derived from O-C diagrams spanning, in some cases, over 100 years; these are compared with high-precision periods derived from the Kepler data alone. Extant Fourier correlations by Kovacs, Jurcsik et al. (with minor transformations from the V to the Kp passband) have been used to derive underlying physical characteristics for all the stars. This procedure seems to be validated through comparisons of the Kepler variables with galactic and LMC RR Lyr stars. The most metal-poor star in the sample is NR Lyr, with [Fe/H]=-2.3 dex; and the four most metal-rich stars have [Fe/H] ranging from -0.6 to +0.1 dex. Pulsational luminosities and masses are found to be systematically smaller than L and mass values derived from stellar evolution models, and are favoured over the evolutionary values when periods are computed with the Warsaw linear hydrodynamics code. Finally, the Fourier parameters are compared with theoretical values derived using the Warsaw non-linear convective pulsation code.

We report the results of our high resolution optical spectroscopic monitoring campaign ($\lambda$ = 3800 -- 8800 A, R = 30000 -- 45000) of the new FU Orionis-type object HBC 722. We observed HBC 722 with the BOES 1.8-m telescope between 2010 November 26 and 2010 December 29 and FU Orionis itself on 2011 January 26. We detect a number of previously unreported high-resolution K I and Ca II lines beyond 7500 A. We resolve the H$\alpha$ and Ca II line profiles into three velocity components, which we attribute to both disk and outflow. The increased accretion during outburst can heat the disk to produce the relatively narrow absorption feature and launch outflows appearing as high velocity blue and redshifted broad features., Comment: accepted for publication in JKAS

We present ground-based and HST optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z = 0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broadband spectral energy distributions (SEDs) of the OT resemble those of local type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB-supernova, and SN1994I, a typical type Ic supernova without a known GRB counterpart, and in both cases the brightness and temporal evolution more closely resemble SN1998bw. We also exploit our extensive optical and radio data for GRB 090618, as well as the publicly-available SWIFT -XRT data, and discuss the properties of the afterglow at early times. In the context of a simple jet-like model, the afterglow of GRB 090618 is best explained by the presence of a jet-break at t-to > 0.5 days. We then compare the rest-frame, peak V -band absolute magnitudes of all of the GRB and X-Ray Flash (XRF)-associated SNe with a large sample of local type Ibc SNe, concluding that, when host extinction is considered, the peak magnitudes of the GRB/XRF-SNe cannot be distinguished from the peak magnitudes of non-GRB/XRF SNe.

We present our analysis of the long cadence Kepler data for the well-studied Blazhko star RR Lyr, gathered during the first two quarters of the satellite's observations and covering a total of 127d. Besides being of great importance for our understanding of RR Lyrae stars in general, these RR Lyr data can be regarded as a case study for observations of bright stars with Kepler. Kepler can perform high-precision photometry on targets like RR Lyr, as the saturated flux is conserved to a very high degree. The Kepler data on RR Lyr are revolutionary in several respects. Even with long-cadence sampling (one measurement per 29.4 min), the unprecedented precision (< mmag) of the Kepler photometry allows the study of the star's extreme light curve variations in detail. The multiplet structures at the main frequency and its harmonics, typical for Blazhko stars, are clearly detected up to the quintuplets. For the first time, photometric data of RR Lyr reveal the presence of half-integer frequencies, linked to a period doubling effect. This phenomenon may be connected to the still unexplained Blazhko modulation. Moreover, with three observed Blazhko cycles at our disposal, we observe that there is no exact repetition in the light curve changes from one modulation cycle to the next for RR Lyr. This may be due to additional periodicities in the star, or to transient or quasi-periodic changes.

The first detection of the period doubling phenomenon is reported in the Kepler RR Lyrae stars RR Lyr, V808 Cyg and V355 Lyr. Interestingly, all these pulsating stars show Blazhko modulation. The period doubling manifests itself as alternating maxima and minima of the pulsational cycles in the light curve, as well as through the appearance of half-integer frequencies located halfway between the main pulsation period and its harmonics in the frequency spectrum. The effect was found to be stronger during certain phases of the modulation cycle. We were able to reproduce the period doubling bifurcation in our nonlinear RR Lyrae models computed by the Florida-Budapest hydrocode. This enabled us to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode and a high-order (9th) radial overtone showing strange-mode characteristics. We discuss the connection of this new type of variation to the mysterious Blazhko effect and argue that it may give us fresh insights to solve this century-old enigma.

The results of extensive time-series photometry of a new variable star, 2MASS 06451725 + 4122158, are presented. The B, V observations (over 4000 individual measurements) were made over 23 nights between 2006 and 2007. To investigate the star's physical characteristics additional Stromgren photometric observations (uvbyHβ) were made on another four nights in 2007 and 2009. Thirteen frequencies were found from a multifrequency analysis of the V and B photometry. All but two of the frequencies, 19.99716 cycles day-1 (corresponding to the pulsation period of 0.0500071 day) and 25.84662 cycles day-1 (0.0386898 day), have been identified as combination frequencies. The ratio of the two frequencies, f1/f3 = 0.77369, and their pulsation constants, Q(f1) = 0.034 and Q(f3) = 0.026, are well matched with theoretical values of the fundamental and the first-overtone radial modes. But the phase shift of f3 was estimated to be a negative value, in contrast to that of f1 to be positive, suggesting that f3 may be a nonradial mode. The period versus amplitude diagram shows that the star has pulsational properties similar to those of high-amplitude SX Phœnicis stars. We obtained its photometric properties from the Stromgren indices: a metal abundance of [Fe/H] = -0.6 dex, an absolute magnitude of MV = 2.7 mag, a distance of ~1.6 kpc in the direction of the Galactic anticenter from the Sun, and a vertical distance from the Galactic plane of ~0.45 kpc. The tangential velocity of 78 km sec-1, which was estimated from the proper motion and the distance, gives us a hint that the star may have high-space motion. Considering these observational properties, we suggest that this new variable is a field SX Phœnicis-type star, although its metallicity value seems not to be low enough for matching the metallicity versus period relation. Future spectroscopic studies would be required to obtain the metallicity more accurately.

The variable stars in the Large Magellanic Cloud star cluster NGC 2257 are reinvestigated using photometry (to ~20th mag) of over 400 new B, V CCD images taken with the CTIO 0.9 m telescope on 14 nights in 2007 December and 2008 January. New period searches have been made using two independent algorithms (CLEAN, Period04); the resultant periods of most of the stars are consistent with the pulsation periods derived previously, and where there are discrepancies these have been resolved. For the B and V light curves, accurate Fourier coefficients and parameters are given. Six new variable stars have been discovered (V45-50), including a bright candidate long-period variable star showing secondary oscillations (V45) and two anomalously bright RRc stars (V48 and V50), which are shown to be brightened and reddened by nearby red giant stars. Also discovered among the previously known variable stars are three double-mode RR Lyrae stars (V8, V16, and V34) and several Blazhko variables. Archival Hubble Space Telescope images and the photometry by Johnson et al. have been used to define better the properties of the most crowded variable stars. The total number of cluster variable stars now stands at forty-seven: 23 RRab stars, four of which show Blazhko amplitude variations; 20 RRc stars, one showing clear Blazhko variations and another showing possible Blazhko variations; the three RRd stars, all having the dominant period ~0.36 day and period ratios P 1/P 0 ~0.7450; and an LPV star located near the tip of the red giant branch. A comparison of the RRd stars with those in other environments shows them to be most similar to those in IC4499.

We report the discovery of a multiple system with a quadruple-lined spectrum and a double eclipsing feature. Our photometric and high-resolution spectroscopic data show that V994 Herculis (V994 Her; ADS 11373 AB) is composed of two pairs of double-lined eclipsing binaries, which we designate as A and B. System A consists of a B8V+AOV binary with an orbital period of 2.083 264 d and system B of a A2V+A4V binary with 1.420033 d. Our light curves show that both of them have a detached binary configuration. We derive masses and radii of four components (Aa, Ab, Ba and Bb) from the synthetic analyses of light curves and radial velocity curves. The masses of systems A and B are M Aa = 2.83 ± 0.20 M ⊙ , M Ab = 2.30 ± 0.16 M ⊙ , M Ba = 1.87 ± 0.12 M ⊙ and M Bb = 1.86 ± 0.12 M⊙, with radii R Aa = 2.15 ± 0.05 R ⊙ , R Ab = 1.71 ± 0.04R ⊙ , R Ba = 1.59 ± 0.08 R ⊙ and R Bb = 1.50 ± 0.08R ⊙ , respectively. These masses and radii are well consistent with the empirical relation for double-lined eclipsing binaries.

New differential time-series observations of KZ Hya were secured using the V filters, and 28 new times of light maximum were identified. We collected 157 times of light maximum from the literature, unpublished data and open database, and proceeded to investigate the variations of the O–C values for light maxima with the total of 185 times of light maximum. A quasi-sinusoidal character of the O–C diagram was confirmed, and this was interpreted as a light travelling time effect due to a companion moving in an eccentric (e=0.23) orbit with a period of about 24.77 years. The periods of KZ Hya were investigated and nine frequencies were determined using the Fourier decomposition method. All nine were harmonic frequencies and no other frequency was identified.

The Angstrom Project is using a distributed network of two-meter class telescopes to conduct a high cadence pixel-lensing survey of the bulge of the Andromeda Galaxy (M31). With the expansion of global telescope network, the detection efficiency of pixel-lensing surveys is rapidly improving. In this paper, we estimate the detection rate of binary lens events expected from high-cadence pixel-lensing surveys toward M31 such as the Angstrom Project based on detailed simulation of events and application of realistic observational conditions. Under the conservative detection criteria that only high signal-to-noise caustic-crossing events with long enough durations between caustic crossings can be firmly identified as binary lens events, we estimate that the rate would be $\Gamma_{\rm b}\sim (7-15)f_{\rm b}(N/50)$ per season, where $f_{\rm b}$ is the fraction of binaries with projected separations of $10^{-3} {\rm AU}, Comment: 6 pages, 4 figures

We investigated V2314 Oph using high-resolution (R = 45,000) spectral observations. The atmospheric parameters were determined using iron-line abundance analysis. We derived a mean effective temperature of Teff = 7510 K, mean surface gravity of log g = 3.30, metallicity of [Fe/H] = -0.59, and rotation velocity of v sin i = 38 km s-1. The abundances of 19 chemical elements were determined. The abundance pattern of V2314 Oph was found to be similar to that of λ Bootis-type stars. V2314 Oph is also a variable star, as are a majority of λ Bootis stars. A frequency analysis of 10 selected nights of precise differential photometry has preliminarily revealed four pulsational modes. The multiperiodic solution of the light curve is probably more similar to a low-amplitude Population I δ Scuti variable pattern, as is apparent for many λ Bootis stars. For asteroseismic investigations of the star it is necessary to obtain more prolonged, continuous time-series observations. These features, as well as the small proper motion and relatively large rotational velocity of V2314 Oph, specify the star as not likely to be a field SX Phoenicis Population II variable, as was suggested previously.

The Andromeda Galaxy Stellar Robotic Microlensing Project (The Angstrom Project) aims to use stellar microlensing events to trace the structure and composition of the inner regions of the Andromeda Galaxy (M31). We present microlensing rate and timescale predictions and spatial distributions for stellar and sub-stellar lens populations in combined disk and barred bulge models of M31. We show that at least half of the stellar microlenses in and around the bulge are expected to have characteristic durations between 1 and 10 days, rising to as much as 80% for brown-dwarf dominated mass functions. These short-duration events are mostly missed by current microlensing surveys that are looking for Macho candidates in the M31 dark matter halo. Our models predict that an intensive monitoring survey programme such as Angstrom, which will be able to detect events of durations upwards of a day, could detect around 30 events per season within ~5 arcminutes of the M31 centre, due to ordinary low-mass stars and remnants. This yield increases to more than 60 events for brown-dwarf dominated mass functions. The overall number of events and their average duration are sensitive diagnostics of the bulge mass, in particular the contribution of low-mass stars and brown dwarfs. The combination of an inclined disk, an offset bar-like bulge, and differences in the bulge and disk luminosity functions results in a four-way asymmetry in the number of events expected in each quadrant defined by the M31 disk axes. The asymmetry is sensitive to the bar prolongation, orientation and mass.

We report the discovery of an SX Phoenicis type pulsating component in the Algol-type semidetached eclipsing binary QU Sge, in the metal-rich globular cluster M71. QU Sge is only about 80'' from the center of M71 and is located in the blue straggler region in the color-magnitude diagram of M71. It is considered to be a probable member of M71, with a membership probability greater than 60% deduced from a proper-motion study in the literature. From time-series CCD photometry, we find that QU Sge has an orbital period of 3.790818 days and a primary minimum depth of ΔV = 1.333 mag. The eclipsing light curve solution shows that QU Sge has a semidetached binary configuration with the secondary component fully filling its Roche lobe. After subtracting the eclipses from the light curve, we discover an SX Phoenicis type pulsation feature. It is found to have a short period of about 0.03 days and a small amplitude of about 0.024 mag. This is the first eclipsing binary system in a globular cluster to exhibit a pulsating feature. This result supports the model in which the origin of some blue stragglers in globular clusters is mass transfer between two components in the primordial binary systems.

To maximize the number of planet detections, current microlensing follow-up observations are focusing on high-magnification events which have a higher chance of being perturbed by central caustics. In this paper, we investigate the properties of central caustics and the perturbations induced by them. We derive analytic expressions of the location, size, and shape of the central caustic as a function of the star-planet separation, $s$, and the planet/star mass ratio, $q$, under the planetary perturbative approximation and compare the results with those based on numerical computations. While it has been known that the size of the planetary caustic is \propto \sqrt{q}, we find from this work that the dependence of the size of the central caustic on $q$ is linear, i.e., \propto q, implying that the central caustic shrinks much more rapidly with the decrease of $q$ compared to the planetary caustic. The central-caustic size depends also on the star-planet separation. If the size of the caustic is defined as the separation between the two cusps on the star-planet axis (horizontal width), we find that the dependence of the central-caustic size on the separation is \propto (s+1/s). While the size of the central caustic depends both on $s$ and q, its shape defined as the vertical/horizontal width ratio, R_c, is solely dependent on the planetary separation and we derive an analytic relation between R_c and s. Due to the smaller size of the central caustic combined with much more rapid decrease of its size with the decrease of q, the effect of finite source size on the perturbation induced by the central caustic is much more severe than the effect on the perturbation induced by the planetary caustic. Abridged., Comment: 5 pages, 4 figures, ApJ accepted

We present UBVIabsolute and V-band time-series CCD photometric results for the intermediate-age open cluster NGC 2539. From the empirical zero-age main sequence and theoretical isochrone fitting in color-color and color-magnitude diagrams, we estimated the physical parameters of this cluster as follows: the color excess of E(B − V) = 0.06 ± 0.03, the distance modulus of (V − MV)0 = 10.2 ± 0.1 and the age of logt = 8. 8( ∼630 Myr). By carefully examining the time-series images, we discovered seven new variable stars in the observed cluster field. Considering the light curves, periods and positions on the color-magnitude diagram, we classified them as five eclipsing binary stars, one δ Scuti star and one γ Doradus candidate. The γ Doradus candidate might not be a cluster member because it is located redder by about ∆(B −V) = 0.2 than the cool edge of γ Doradus instability strip.

New differential time-series observations of the distant halo SX Phe variable BQ Psc are reported. We have determined 19 new times of maximum light. The observed minus calculated (O–C) analysis indicates that the period has been increasing with time. We also applied a Fourier decomposition to the data in order to determine the component frequencies of the synthetic light curve. The multiperiodicity of this variable star was not confirmed.

The aberration measurement program has been developed for improving the optical quality of ground-based telescopes. This program is based on the Curvature Sensing Technique (CST) and aberrations are estimated from two defocused stellar images. We used iterative algorithm that simulates closed-loop wave-front compensation in optics. It has been applied to the telescope of Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. The most frequently encountered aberration by misalignment was coma. As a result, the image quality of telescope was improved after adjustment the alignment of secondary mirror.

Cool white dwarf stars often have mysteriously strong magnetic fields (because their coolness suggests that they are old, and magnetic fields should decline in strength with age) and unexplained brightness variations; here the magnetic field is shown to suppress atmospheric convection, inhibiting cooling evolution and causing dark spots. Most stars in the Universe will end their lives as burnt-out cores known as white dwarfs. Many old, isolated white dwarf stars with convecting atmospheres have stronger magnetic fields than young, convection-free ones, which is puzzling because the fields are expected to decay with time. In addition, some white dwarfs with strong fields vary in brightness with their rotation. Gennady Valyavin et al. report optical observations and analysis of the strongly-magnetic white dwarf WD1953-011. They find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. These strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, thereby inhibiting their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs. Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs1,2,3,4, which has been a puzzle because magnetic fields are expected to decay with time5,6 but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate7,8,9,10, which has been variously attributed to surface brightness inhomogeneities similar to sunspots8,9,10,11,12, chemical inhomogeneities13,14 and other magneto-optical effects15,16,17. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

Time-series CCD photometric observations of an intermediate age open cluster NGC 2301 were per- formed to search for variable stars, particularly Dor stars and Sct stars. We also carried outUBVI photometry to study physical properties of variable stars in the cluster. We derived observational parameters of the cluster from UBVI photometric results. The best t of the empirical ZAMS in a color-color diagram gives a reddening value of E(B V )=0 :05 0:03. We also estimated a distance modulus of (V MV )0 =9 :6 0:1 and an age of log t =8 :4 0:1, from the ZAMS and isochrone tting in a color-magnitude diagram. Using V time-series data, we carefully examined light variations of 923 stars fainter than 10: m 0, and discovered nine short-period variable stars; two Dor candidates, ve eclipsing binaries, one Slowly Pulsating B star and one magnetic Chemically Peculiar variable candidate. Two Dor candidates with relatively short periods of around 0.3 days are located in a redder region (about 0: m 1i nB V color) than the red edge of Sct instability strip in the color-magnitude diagram.

Context. The Vista Variables in the V\'ia L\'actea (VVV) ESO Public Survey is a variability survey of the Milky Way bulge and an adjacent section of the disk carried out from 2010 on ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV will eventually deliver a deep near-IR atlas with photometry and positions in five passbands (ZYJHK_S) and a catalogue of 1-10 million variable point sources - mostly unknown - which require classifications. Aims. The main goal of the VVV Templates Project, that we introduce in this work, is to develop and test the machine-learning algorithms for the automated classification of the VVV light-curves. As VVV is the first massive, multi-epoch survey of stellar variability in the near-infrared, the template light-curves that are required for training the classification algorithms are not available. In the first paper of the series we describe the construction of this comprehensive database of infrared stellar variability. Methods. First we performed a systematic search in the literature and public data archives, second, we coordinated a worldwide observational campaign, and third we exploited the VVV variability database itself on (optically) well-known stars to gather high-quality infrared light-curves of several hundreds of variable stars. Results. We have now collected a significant (and still increasing) number of infrared template light-curves. This database will be used as a training-set for the machine-learning algorithms that will automatically classify the light-curves produced by VVV. The results of such an automated classification will be covered in forthcoming papers of the series., Comment: 12 pages, 16 figures, 3 tables, accepted for publication in A&A. Most of the data are now accessible through http://www.vvvtemplates.org/

The KMTNet (Korea Microlensing Telescope Network) was completed on October 2nd in 2015. There are three 1.6 m telescopes in Chile (CTIO), Australia (SSO) and South Africa (SAAO). The field of view of the CCD camera is 2 degree × 2 degree. We are monitoring and observing the bulge region for 24-hour continuous observations using the KMTNet telescopes. I present the characteristics of CCD camera and telescope, and the status of observation programs. We are still developing CCD cameras to accurate photometry. From the KMTNet data, we can obtain accurate 24-hour continuous time-series data for many variable stars.

We present our successful program using Chandra for identifying the X-ray afterglow with sub-arcsecond accuracy for the short GRB 111117A d iscovered by Swift and Fermi. Thanks to our rapid target of opportuni ty request, Chandra clearly detected the X-ray afterglow, whereas no optical afterglow was found in deep optical observations. Instead, we clearly detect the host galaxy in optica; and also in near-infrared b ands. We found that the best photometric redshift fitofthe host is z = 1.31:(+0.46/-0.23) (90% confidence), making it one of the highest redshift short GRBs. Furthermore, we see an offset of 1.0+/-O.2 arcseco nds, which corresponds to 8.4+/-1.7 kpc aSBuming z= 1.31, between the host and the afterglow position. We discuss the importance of using Chandra for obtaining sub-arcsecond localization of the afterglow in X -rays for short GRBs to study GRB environments in great detail.

Massive black holes are believed to reside at the centres of most galaxies. They can be- come detectable by accretion of matter, either continuously from a large gas reservoir or impulsively from the tidal disruption of a passing star, and conversion of the gravitational energy of the infalling matter to light. Continuous accretion drives Active Galactic Nuclei (AGN), which are known to be variable but have never been observed to turn on or off. Tidal disruption of stars by dormant massive black holes has been inferred indirectly but the on- set of a tidal disruption event has never been observed. Here we report the first discovery of the onset of a relativistic accretion-powered jet in the new extragalactic transient, Swift J164449.3+573451. The behaviour of this new source differs from both theoretical models of tidal disruption events and observations of the jet-dominated AGN known as blazars. These differences may stem from transient effects associated with the onset of a powerful jet. Such an event in the massive black hole at the centre of our Milky Way galaxy could strongly ionize the upper atmosphere of the Earth, if beamed towards us.

We present and interpret simultaneous new photometric and spectroscopic observations of the peculiar magnetic white dwarf WD1953-011. The flux in the V-band filter and intensity of the Balmer spectral lines demonstrate variability with the rotation period of about 1.45 days. According to previous studies, this variability can be explained by the presence of a dark spot having a magnetic nature, analogous to a sunspot. Motivated by this idea, we examine possible physical relationships between the suggested dark spot and the strong-field magnetic structure (magnetic "spot", or "tube") recently identified on the surface of this star. Comparing the rotationally-modulated flux with the variable spectral observables related to the magnetic "spot" we establish their correlation, and therefore their physical relationship. Modeling the variable photometric flux assuming that it is associated with temperature variations in the stellar photosphere, we argue that the strong-field area and dark, low-temperature spot are comparable in size and located at the same latitudes, essentially overlapping each other with a possible slight longitudinal shift. In this paper we also present a new, improved value of the star's rotational period and constrain the characteristics of the thermal inhomogeneity over the degenerate's surface., Comment: accepted to the ApJ

Time-series CCD photometric observations of the intermediate-age open cluster NGC 2099 were performed to search for variable stars. We also carried out BV photometry to study physical properties of variables in the cluster. Using V-band time-series data, we carefully examined light variations of about 12,000 stars in the range of 10 < V < 22 mag. A total of 24 variable stars have been identified; seven stars are previously known variables and 17 stars are newly identified. On the basis of observational properties such as light curve shape, period, and amplitude, we classified the new variable stars as nine delta Scuti-type pulsating stars, seven eclipsing binaries, and one peculiar variable star. Judging from the position of delta Scuti-type stars in the color-magnitude diagram, only two stars are likely to have the cluster membership. One new variable KV10 shows peculiar light variations with a delta Scuti-type short period of about 0.044 day as well as a long period of 0.417 day., 26 pages, 9 figures, 4 tables, accepted for publication in PASP

V-band time-series CCD photometric observations of the intermediate-age open cluster M11 were performed to search for variable stars. Using these time-series data, we carefully examined light variations of all stars in the observing field. A total of 82 variable stars were discovered, of which 39 stars had been detected recently by Hargis et al. (2005). On the basis of observational properties such as variable period, light curve shape, and position on a color-magnitude diagram, we classified their variable types as 11 delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries, and 16 eclipsing binaries with long period. Cluster membership for each variable star was deduced from the previous proper motion results (McNamara et al. 1977) and position on the color-magnitude diagram. Many pulsating stars and eclipsing binaries in the region of M11 are probable members of the cluster., Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PASP

The Angstrom Project is undertaking an optical survey of stellar microlensing events across the bulge region of the Andromeda Galaxy (M31) using a distributed network of two-meter class telescopes. The Angstrom Project Alert System (APAS) has been developed to identify in real time candidate microlensing and transient events using data from the Liverpool and Faulkes North robotic telescopes. This is the first time that real-time microlensing discovery has been attempted outside of the Milky Way and its satellite galaxies. The APAS is designed to enable follow-up studies of M31 microlensing systems, including searches for gas giant planets in M31. Here we describe the APAS and we present a few example light curves obtained during its commissioning phase which clearly demonstrate its real-time capability to identify microlensing candidates as well as other transient sources., 4 pages, submitted to ApJ Letters

We have investigated the characteristics of B2H6 plasma doping (PLAD) process used to convert the n+ doped poly‐Si gate to the p+ poly‐Si gate for pMOS. The throughput of the PLAD process is much higher than a conventional beam line implantation process at low energy and high dose ranges. The B2H6 plasma counter‐doping on the n+ poly‐Si were performed in the energy range of 5kV ∼ 9kV and dose of ∼E16♯/cm2. The B2H6 Plasma doped poly‐Si layers were characterized by TDS, SIMS, AFM, and TEM.The TDS analysis showed hydrogen desorption from the B2H6 plasma doped p+ poly‐Si layer at a low temperature. The surface concentration of PLAD doped boron was much higher compared to the conventional beam line implantation. However, a serious loss of surface dopant was also observed during photoresist strip and post cleaning. The surface dopant loss could be suppressed by 10% with optimization of the cleaning condition, leading to improve characteristics of PLAD doped p+ poly‐Si pMOS, compared to the beam line implantati...

Results of a CCD study of the variability of the cataclysmic variable BG CMi obtained at the Korean 1.8m telescope in 2002-2005 are presented. The "multi-comparison star" method had been applied for better accuracy estimates. The linear ephemeris based on 19 mean maxima for 2002--2005 is HJD 2453105.31448(6)+0.01057257716(198)(E-764707). The period differs from that predicted by the quadratic ephemeris by Pych et al. (1996) leading to a possible cycle miscount. The statistically optimal ephemeris is a fourth-order polynomial, as a quadratic or even a cubic ephemeris leads to unaceptably large residuals: Min.HJD=$ 2445020.28095(28)+0.0105729609(57)E -1.58(32)\cdot10^{-13}E^2-5.81(64)\cdot10^{-19}E^3+4.92(41)\cdot10^{-25}E^4.$ Thus the rate of the spin-up of the white dwarf is decreasing. An alternative explanation is that the spin-up has been stopped during recent years. The deviations between the amplutudes of the spin variability in V and R, as well as between phases are not statistically significant. However, the orbital light curves exhibit distinct difference; the corresponding color index shows a nearly sinusoidal shape with a maximum at orbital phase $\sim0.2.$ The variations of the amplitude of spin waves shows a short maximum at the phase of the orbital dip. The corrected ephemeris for orbital minima is Min.HJD=$2448368.7225(12)+0\fd13474841(6)\cdot(E-24849)$ with a narrow dip occuring 0.07P later. The rate of the spin period variation seems to be changed, justifying the necessity of regular observations of intermediate polars., Comment: 13 pages, 9figures, accepted in 2005 issue of Astronomy and Astrophysics

The incidence of metabolic syndrome is increasing globally, as the prevalence of obesity continues to rise. However, the basic mechanisms of metabolic syndrome are not completely known yet. Therefore, animal disease models are required for the study of metabolic syndrome. The overexpression of 11 β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in mice leads to metabolic syndrome; thus, we attempted to produce pigs with overexpression of 11β-HSD1 gene by somatic cell nuclear transfer (SCNT). However, low transgenic (TG) efficiency has been an obstacle to the production of TG pigs. A SCNT method in which somatic cells derived from TG pig are used as the nuclear donor (re-cloning method) is an effective technique for TG pig production. In this study, we attempted to increase TG efficiency by the re-cloning method. Pregnancy efficiency, production efficiency, and TG efficiency were compared with sources of donor cells (transfected TG fetal fibroblast v. TG fibroblast derived from newborn TG cloned pig). A total of 1382 and 881 TG SCNT embryos were produced from fetal fibroblast v. cloned fibroblast, and then transferred to 13 and 10 recipients. The pregnancy rate was not significantly different (30.8% v. 20.0%). Seventeen live piglets and 5 stillborn piglets were born from 4 recipients in the fetal fibroblast group, and 8 live piglets, 2 stillborn piglets, and 3 mummies were born from 2 recipients in the cloned fibroblast group. There were no significant differences in the production efficiency (3.7% v. 5.0%). All of the 13 re-cloned piglets showed reporter and target gene integration. But, of 22 fetal fibroblast-cloned piglets, reporter gene integration was confirmed in 9, but only 3 clone piglets showed reporter gene integration. Efficiency of TG was significantly increased in re-cloning group (13.6% v. 100.0%). In this study, TG efficiency of 11β-HSD1 overexpressed pigs was improved by re-cloning method. These results indicate that re-cloning is an efficient method for production of TG cloned pigs.This work was supported by a grant from the Next-Generation Bio Green 21 Program (No. PJ009563032014), Rural Development Administration, Republic of Korea.

Homogeneous B, V photometry is presented for 19,324 stars in and around 5 Magellanic Cloud globular clusters: NGC 1466, NGC 1841, NGC 2210, NGC 2257, and Reticulum. The photometry is derived from eight nights of CCD imaging with the Cerro Tololo Inter-American Observatory 0.9 m SMARTS telescope. Instrumental magnitudes were transformed to the Johnson B, V system using accurate calibration relations based on a large sample of Landolt-Stetson equatorial standard stars, which were observed on the same nights as the cluster stars. Residual analysis of the equatorial standards used for the calibration, and validation of the new photometry using Stetson's sample of secondary standards in the vicinities of the five Large Magellanic Cloud clusters, shows excellent agreement with our values in both magnitudes and colors. Color-magnitude diagrams reaching to the main-sequence turnoffs at V ∼ 22 mag, sigma-magnitude diagrams, and various other summaries are presented for each cluster to illustrate the range and quality of the new photometry. The photometry should prove useful for future studies of the Magellanic Cloud globular clusters, particularly studies of their variable stars.

Through time-series CCD photometry of the globular cluster M 53, we have discovered eight new SX Phoenicis type stars. All the new SX Phoenicis stars are located in the blue straggler star region in the color-magnitude diagram of M 53. In addition, we have obtained light curves for 45 known RR Lyrae stars.

The Tibetan Mastiff is the oldest dog breed in the world, and it is at the edge of extinction. Li et al. (2008) believe that protection of and research on the Tibetan Mastiff is extremely urgent, yet few studies have been carried out, particularly at the molecular level. Somatic cell nuclear transfer (SCNT) is an efficient technique for the conservation of endangered animals because it can increase the number of individuals within a population. Considering the virtually unlimited value of cloned canids in critical biotechnology applications, including gene conservation of endangered canids and disease models, the effect of cell-cycle synchronization methods, including the use of cycling canine adult skin fibroblasts (CASF), on the cell-cycle stage and viability of donor nuclei was analyzed. To improve the efficiency of cloned dog production, optimal conditions of donor cells were analyzed by culture duration (Days 1, 2, 3, and 4), passages (2, 4, 7, 10, and 11 passages) and mitotic regulator Plk-1/-4 gene expression. Simerly et al. (2003) reported that the depletion of microtubule motors and centrosomal proteins during enucleation of SCNT procedures caused abnormal development of SCNT embryos. We therefore analyzed Plk-1/-4-induced centriole biogenesis in CASF at different passages of donor cells. In this study, somatic cells were collected from a purebred 9-month-old male Mastiff and an 11-month-old female mastiff. In vivo-matured oocytes were retrieved from outbreed dogs by operation. Cycling cells cultured at Day 4 showed a similar effect to that of cells that were artificially synchronized (contact inhibition or serum starvation). It was also confirmed that fresh and short-term culture (

A time-series CCD photometric survey of variable stars in open clusters has been in progress using 1.8-m telescope at the Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We present preliminary results of time series photometry for the intermediate-age open cluster NGC 2301.