Variations in Gegenschein polarization

Our observations of small scale angular structure and night-to-night variation of the polarized component of the zodiacal light near the anti-solar point have been criticized. We find that these criticisms are unsubstantiated.     

The photometric observations of ER vulpeculae: photometric analysis with the W-D code

The photometric observations of ER Vul were obtained in UBV light in 1994, at Birouni Observatory, University of Shiraz, Iran. The three light curves, which are almost complete, have been analyzed separately by means of Wilson and Devinney method (1971). The light curves include proximity effects, wave-like distortions, mutual eclipses, and short term light fluctuations. The appropriate value of the mass ratio of this system was found after extensive searches. ER Vul has a detached configuration where the two components are very nearly fill their Roche lobe. ER Vul has the characteristic of a RS CVn type system. The absolute dimensions for the primary and secondary of this system were calculated from its spectral types and by combining the photometric solution with inferred component radial velocities (Northcott and Bakos, 1967).     

Measurements of the Gegenschein brightness from the Solar Mass Ejection Imager (SMEI)

The Gegenschein is viewed by the Solar Mass Ejection Imager (SMEI), which has provided near-full-sky broadband visible-light photometric maps for over 5 years. These have an angular resolution of about 0.5° and differential photometric stability of about 1% throughout this time. When individual bright stars are removed from the maps and an empirical sidereal background subtracted, the residue is dominated by the zodiacal light. The unprecedented sky coverage and duration of these measurements enables a definitive characterization of the Gegenschein. This article describes the analysis method for these data, presents a movie with time of the Gegenschein brightness distribution, determines empirical formulae describing its average shape, and discusses its variation with time. These measurements unambiguously confirm previous reports that the Gegenschein surface-brightness distribution has a decided peak in the antisolar point, which rises above a broader background.     

The photometric behaviour of BH Vir

Visible light curves of the RS CVn short-period system BH Vir, collected over 26 years, have been analyzed.B-V colours indicate that the primary minimum is normally redder than one would expect, assuming the spectroscopic classification of the system components, while the secondary yielded bluer. A qualitative comparison of the different light curves, suggests that not only cool starspots are the reason of the observed variability.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

The photometric period of the cataclysmic variable HV Andromedae

We present four nights of time-resolved photometry of the cataclysmic variable star HV And. Our time series analysis has revealed a prominent period at 3.368 ± 0.060 h, as well as some low frequency power. We interpret this signal, from saw-tooth waves in the light curve, as evidence of superhumps in HV And.     

IRAC photometric analysis and the mid-IR photometric properties of Lyman-break galaxies

We present photometric analysis of deep mid-infrared (mid-IR) observations obtained by Spitzer /IRAC covering the fields Q1422+2309, Q2233+1341, DSF2237a,b, HDFN, SSA22a,b and B20902+34, giving the number counts and the depths for each field. In a sample of 751 Lyman-break galaxies (LBGs) lying in those fields, 443, 448, 137 and 152 are identified at 3.6-, 4.5-, 5.8-, 8.0-μm IRAC bands, respectively, expanding their spectral energy distribution to rest-near-IR and revealing that LBGs display a variety of colours. Their rest-near-IR properties are rather inhomogeneous, ranging from those that are bright in IRAC bands and exhibit  [ R ]−[3.6] > 1.5  colours to those that are faint or not detected at all in IRAC bands with  [ R ]−[3.6] < 1.5  colours and these two groups of LBGs are investigated. We compare the mid-IR colours of the LBGs with the colours of star-forming galaxies and we find that LBGs have colours consistent with star-forming galaxies at   z ∼ 3  . The properties of the LBGs detected in the 8-μm IRAC band (rest-frame K band) are examined separately, showing that they exhibit redder  [ R ]−[3.6]  colours than the rest of the population and that although in general, a multiwavelength study is needed to reach more secure results, IRAC 8-μm band can be used as a diagnostic tool, to separate high z , luminous AGN-dominated objects from normal star-forming galaxies at   z ∼ 3  .     

The FORS Deep Field: the photometric catalog

The FORS Deep Field project is a multi-colour, multi-object spectroscopical investigation of a ∼ 7′ × ′' region near the south galactic pole based mostly on observations carried out with the FORS instruments attached to the VLT telescopes. It includes the QSO Q 0103-260 (z = 3.36). The goal of this study is to improve our understanding of the formation and evolution of galaxies in the young Universe. In this contribution, the photometric observations are presented. In particular, a combined B and I selected UBgRIJKs photometric catalog of 8753 objects in the FDF is presented and its content is briefly described. The formal 50% completeness limits for point sources, derived from the coadded images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and 21.57in U, B, g, R, I, J and Ks, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

The photometric function for Saturn's rings

An inhomogeneous vertical distribution of matter in Saturn's rings is capable of producing the tilt effect which is observed in ring B. In this model the effective thickness of the rings is 8 to 9 times the radius of the particles.     

The photometric period of 39 AY Ceti

Photoelectric photometry obtained in 1971 and 1972 is compared with that obtained in 1980–81 and 1981–82 to derive a photometric period of 77 ^d .65. JD 2444636.0 is an epoch of minimum light. The full amplitude has been as large as 0 ^m .18 inV. Curiously, the mean light level has dropped by almost 0 ^m .2 over the last ten years. This binary is additionally interesting because of the recently discovered white dwarf secondary component and because unpublished radial velocity measures of Fekel show a large (0.1) eccentricity and an orbital period (57 ^d .1) very different from our photometric period.     

The photometric solution of cc com by use of the

The contact binary system CC Com (=12^h09^m33^s.8, =+22°4339, (1950);V _max=11.31, (B-V)_max=1.24) is a W UMa-type system with the shortest known period. The photometric solution of CC Com is presented using the Wilson and Devinney method. The results show that the CC Com belongs to the late-type eclipsing binary with the spectral type K5V and K6V, low temperatureT ₁=4300 K,T ₂=4265 K, the mass ratioq=0.5873±0.0021, and the inclinationi=87°.719±1°.44. The best regions of the gravity darkening exponents , the bolomotric albedov, and the limb-darkening coefficients are tested. It is found that 0.1250.065, 0.1v0.5, =0.5 are better regions for CC Com. The third body ofl ₃ is not found to be significant. The results are combined with the spectroscopic results of Rucinski to provide an estimate of the absolute parameters.     

The photometric method of detecting other planetary systems

The photometric method detects planets orbiting other stars by searching for the reduction in the light flux or the change in the color of the stellar flux that occurs when a planet transits a star. A transit by Jupiter or Saturn would reduce the stellar flux by approximately 1% while a transit by Uranus or Neptune would reduce the stellar flux by 0.1%. A highly characteristic color change with an amplitude approximately 0.1 of that for the flux reduction would also accompany the transit and could be used to verify that the source of the flux reduction was a planetary transit rather than some other phenomenon. Although the precision required to detect major planets is already available with state-of-the-art photometers, the detection of terrestrial-sized planets would require a precision substantially greater than the state-of-the-art and a spaceborne platform to avoid the effects of variations in sky transparency and scintillation. Because the probability is so small of observing a planetary transit during a single observation of a randomly chosen star, the search program must be designed to continuously monitor hundreds or thousands of stars. The most promising approach is to search for large planets with a photometric system that has a single-measurement precision of 0.1%. If it is assumed that large planets will have long-period orbits, and that each star has an average of one large planet, then approximately 10⁴ stars must be monitored continuously. To monitor such a large groups of stars simultaneously while maintaining the required photometric precision, a detector array coupled by a fiber-optic bundle to the focal plane of a moderate aperture (≈ 1 m), wide field of view (≈50°) telescope is required. Based on the stated assumptions, a detection rate of one planet per year of observation appears possible.     

The SAGE photometric survey: technical description

To investigate a huge sample of data related to the Stellar Abundance and Galactic Evolution(SAGE) survey in more detail, we are performing a northern sky photometric survey named SAGES with the SAGE photometric system.This system consists of eight filters: Str?mgren-u, SAGE-v, SDSS g, r, i, DDO-51, Hα_(wide) and Hα_(narrow), including three Sloan broadband filters, three intermediateband filters, two narrow-band filters and one newly-designed narrow-band filter.SAGES covers～12 000 square degrees of the northern sky with δ -5°, excluding the Galactic disk(|b| 10°) and the sky area 12 h RA 18 h.The photometric detection limit depth at signal-to-noise ratio 5σ can be as deep as V～20 mag.SAGES will produce a photometric catalog with uniform depth for～500 million stars with atmospheric parameters including effective temperature T_(eff), surface gravity log g and metallicity[Fe/H], as well as interstellar extinction to each individual target.In this work, we will briefly introduce the SAGE photometric system, the SAGE survey and a preliminary test field of the open cluster NGC 6791 and its surroundings.     

The photometric reflection effect in close binaries

A method for evaluating the photometric consequences of the reflection effect in close binaries is described. There is no restriction on the extent of the penumbra and the conversion to monochromatic radiation avoids the ambiguity of the approach based on application of a luminous efficiency factor. The reflected radiation is taken to have a phase law of the form (1–u _r+u _rcos) where represents the angle between the local normal and the observer's line of sight.An estimate of the accuracy of the method is made; it is found that it is suitable for the reduction of light curves of high precision for all systems except those where the components are in contact or almost so.     

The photometric reflection effect in close binaries

Some earlier statistical investigations of the reflection effect are repeated using a more precise theory. The conclusions of earlier workers are reversed: it is found that the albedos of earlytype binaries are broadly in agreement with the theory, but that those of cooler systems are substantially less than unity.Various hypotheses to account for this phenomenon are investigated. It is concluded that the observations verify a prediction by Rucinski: cool secondary components possess deep convective envelopes whose structure is altered by the incident radiation in such a way as to depress the radiation from the far interior of the reflecting star.     

The photometric method of extrasolar planet detection revisited

We investigate the geometry concerning the photometric method of extrasolar planet detection, i.e., the detection of dimunition of a parent star's brightness during a planetary transit. Under the assumption that planetary orbital inclinations can be defined by a Gaussian with a of 10° centered on the parent star's equatorial plane, Monte Carlo simulations suggest that for a given star observed at an inclination of exactly 90°, the probability of at least one Earth-sized or larger planet being suitably placed for transits is approximately 4%. This probability drops to 3% for a star observed at an inclination of 80°, and is still 0.5% for a star observed at an inclination of 60°. If one can select 100 stars with a pre-determined inclination 80°, the probability of at least one planet being suitably configured for transits is 95%. The majority of transit events are due to planets in small-a orbits similar to the Earth and Venus; thus, the photometric method in principle is the method best suited for the detection of Earthlike planets.The photometric method also allows for testing whether or not planets can exist within binary systems. This can be done by selecting binary systems observed at high orbital inclinations, both eclipsing binaries and wider visual binaries. For a real-world example, we look at the Centauri system (i = 79°.2). If we assume that the equatorial planes of both components coincide with the system's orbital plane, Monte Carlo simulations suggest that the probability of at least one planet (of either component) being suitably configured for transits is approximately 8%.In conclusion, we present a non-exhaustive list of solar-type stars, both single and within binary systems, which exhibit a high equatorial inclination. These objects may be considered as preliminary candidates for planetary searches via the photometric method.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.     

The first CCD photometric study of the open cluster NGC 744

We present the first CCD photometric observations of open cluster NGC 744, as part of the 50 BiN Open Cluster Survey. The color-magnitude diagrams of this cluster were derived from absolute BV RI photometry on a good photometric night. A brief isochrone fitting gives a distance modulus of(m-M)V= 11.58±0.2 and a reddening of E(B-V) = 0.35±0.05 with an age of log t = 8.30±0.05.By carefully examining the BV time-series data, we discovered four new variable stars in a 20′×20′field around the cluster. We classified them as three eclipsing binary stars and one δ Scuti pulsating star,mainly based on the light-curve shape, the detected periods and the positions on the color-magnitude diagrams.