A new investigation of the peculiar binary star Epsilon Aurigae

We give results of photoelectric photometry and spectral observations of Aur during its 1982–1984 ingress and total eclipse. Narrow-band light curves and variations in radial velocity within a night resulting from autoregression analysis all indicate short time scale variations in the F supergiant primary on the order of hours or fractions thereof. Fluctuations with an amplitude of ±25 Km/s and a period of 400 d appear to be present in the measured radial velocity of the primary during ingress and totality. Obvious changes in the H profile were also observed: around the second contact of the total eclipse, there was emission in the blue wing; while around the third contact of the atmosphere eclipse, there was emission in the red wing.     

Photometric investigation of the evolved contact binary system DN Aur

We present here the photometric light curve analyses of the eclipsing binary star DN Aur. The CCD photometry, performed at the Behlen observatory using the 0.76 m automated telescope gave 646 individual data points inV andR bandpass filters. From this data we have determined a new epoch and an orbital period of 0.6168891 days. The published spectral classification is F3.The Wilson-Devinney model was used to derive the photometric solutions. DN Aur is a W UMa type contact binary system. The mass ratio, (q=m ₂/m ₁0.210, where star 2 is eclipsed at the primary minimum) suggests that the system has A-type configuration. The computed light curve has a third light of about 22 percent and a total eclipse in the secondary minimum. A solution with a cool spot on the secondary component is also found. We recommend spectroscopic study of DN Aur even though the light curve analysis show it to be a single line spectroscopic system. Generally contact systems of spectral type F3 have periods ranging from 0.25 to 0.5 days. The longer period of DN Aur suggests that it is an evolved contact system with case A mass transfer.     

A study of the eclipsing binary XX Cas

UBV photometry of the eclipsing binary system XX Cas has been presented. Primary eclipse appears to be a total occultation rather than a partial transit (Pierce, 1938). A slightly improved period of 3^d.0671708 has been obtained, and the colour of the system discussed.     

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

We present continuous and time‐resolved R = 55 000 optical échelle spectroscopy of ε Aurigae from 2006–2013. Data were taken with the STELLA Echelle Spectrograph of the robotic STELLA facility at the Observatorio del Teide in Tenerife. Contemporaneous photometry with the Automatic Photoelectric Telescopes at Fairborn Observatory in Arizona is presented for the years 1996–2013. Spectroscopic observations started three years prior to the photometric eclipse and are still ongoing. A total of 474 high‐resolution échelle spectra are analyzed and made available in this paper. We identify 368 absorption lines of which 161 lines show the characteristic sharp disk lines during eclipse. Another 207 spectral lines appeared nearly unaffected by the eclipse. From spectrum synthesis, we obtained the supergiant atmospheric parameters T_eff = 7395 ± 70 K, log g ≈ 1, and [Fe/H] = +0.02 ± 0.2 with ξ_t = 9 km s^–1, ζ_RT = 13 km s^–1, and v sin i = 28 ± 3 km s^–1. The residual average line broadening expressed in km s^–1 varies with a period of 62.6 ± 0.7 d, in particular at egress and after the eclipse. Two‐dimensional line‐profile periodograms show several periods, the strongest with ≈110 d evident in optically thin lines as well as in the Balmer lines. Center‐of‐intensity weighted radial velocities of individual spectral lines also show the 110‐d period but, again, additional shorter and longer periods are evident and are different in the Balmer lines. The two main spectroscopic Hα periods, ≈ 116 d from the line core and ≈ 150 d from the center‐of‐intensity radial velocities, appear at 102 d and 139 d in the photometry. The Hβ and Johnson V I photometry on the other hand shows two well‐defined and phase‐coherent periods of 77 d and 132 d. We conclude that Hα is contaminated by changes in the circumstellar environment while the Hβ and V I photometry stems predominantly from the non radial pulsations of the F0 supergiant. We isolate the disk‐rotation profile from 61 absorption lines and found that low disk eccentricity generally relates to low disk rotational velocity (but not always) while high disk eccentricity always relates to high velocity. There is also the general trend that the disk‐absorption in spectral lines with higher excitation potential comes from disk regions with higher eccentricity and thus also with higher rotational velocity. The dependency on transition probability is more complex and shows a bi‐modal trend. The outskirts of the disk is distributed asymmetrically around the disk and appears to have been built up mostly in a tail along the orbit behind the secondary. Our data show that this tail continues to eclipse the F0 Iab primary star even two years after the end of the photometric eclipse. High‐resolution spectra were also taken of the other, bona‐fide, visual‐binary components of ε Aur (ADS 3605BCDE). Only the C‐component, a K3‐4‐giant, appears at the same distance than ε Aur but its radial velocity is in disagreement with a bound orbit. The other components are a nearby (≈ 7 pc) cool DA white dwarf, a G8 dwarf, and a B9 supergiant, and not related to ε Aur. The cool white dwarf shows strong DIB lines that suggest the existence of a debris disk around this star. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Infrared photometry of the X-ray binary XTE J1118+480 in April 2000

We present the IR photometry of the X-ray binary XTE J1118+480 performed during seven nights in April and two nights in May–June 2000. A significant IR excess has been detected in the object, which may be due to the thermal radiation from a dust envelope/cloud. The observed energy distribution in the range 1.25–3.5 μm can be interpreted in terms of the sum of the fluxes from an accretion disk with a temperature of ～20 000 K and a dust envelope with grains heated to ～900 K. The distance to the X-ray binary estimated from the total flux from the dust envelope is no less than 0.6–3 kpc. The mean optical depth of the dust envelope for the accretion-disk radiation is about 0.06.     

First analysis of eight Algol-type binaries: EI Aur,XY Dra,BP Dra,DD Her,VX Lac,WX Lib,RZ Lyn,and TY Tri

The available photometry from the online databases were used for the first light curve analysis of eight eclipsing binary systems EI Aur, XY Dra, BP Dra, DD Her, VX Lac, WX Lib, RZ Lyn, and TY Tri. All these stars are of Algol-type, having the detached components and the orbital periods from 0.92 to 6.8 days. For the systems EI Aur and BP Dra the large amount of the third light was detected during the light curve solution. Moreover, 468 new times of minima for these binaries were derived, trying to identify the period variations. For the systems XY Dra and VX Lac the third bodies were detected with the periods 17.7, and 49.3 years, respectively.     

UBV photometry of DX Aquarii

U, B, V photometry of the eclipsing binary DX Aqr has been presented for the first time. The period of the system comes out to be nearly half the period given by Strohmeier (1966) and a value of O^d.472502 has been determined. The colour of the system has been discussed. The primary eclipse is a total occulation. The orbit seems to be eccentric. The system belongs to Algol type. DX Aqr may be a very complicated system. The present results are considerably different from those of earlier investigations.     

CoRoT 102931335: a candidate γ Dor in an eclipsing binary

We present an on-going study of CoRoT 102931335. Our preliminary results indicate that the target is an eclipsing binary system with an orbital period of $3{.\!\!\vphantom{0}^{\mathrm{d}}}979$ and a primary component pulsating in the frequency range 0.6–0.8 c/d. The results of a ground-based follow-up program provided four-colour Strömgren photometry and allowed us to infer the spectral class and the primary effective temperature. We devised and applied an iterative procedure to disentangle the effects of binarity from those of pulsations and could test that a detailed binary modelling is essential for the purpose. Our results suggest that the pulsating component of CoRoT 102931335 could be a γ Dor variable, a rare occurrence in an eclipsing system.     

Minimum on the light curve of the classical symbiotic star AS 338 in 1999

We present our UBVRI photometry and spectroscopy of AS 338 performed in 1999–2000. Another eclipse of the hot component in this symbiotic binary system, the deepest one ever observed, occurred in September 1999. The U brightness declined by ～2^m, the Hβflux decreased by a factor of ～2.3, and the [O III]γ5007 flux did not change. The hot component is eclipsed at orbital phases ?≈0.045–0.057. The U-B color index begins to appreciably fluctuate during an eclipse of the hot component and its circumstellar envelope. About 100 days after a strong outburst of 1995, the mean UBV brightness of AS 338 declined linearly in the ensuing five years at the same rate in all bands (ΔU/Δt≈10^?3 mag/day). The brightness of the outer, uneclipsed parts of the circumstellar envelope also decreased, which is attributable to a reduction in the luminosity of the hot component against the rise in its temperature. The appearance of He II lines has not yet been recorded, though the optical brightness of AS 338 has already dropped by ～2^m after the outburst.     

Determination of the elements of eclipsing variables,RW Gem and AY Cam,by Fourier analysis of their light changes

The aim of the present paper has been to present an analysis of the light curve of two eclipsing systems RW Gem and AY Cam by Fourier analysis of the light changes in the frequency domain which was developed by Kopal (1975a, b, c, d, e; 1976).In Section 1, the subject is introduced in a general way, with the intention of laying the foundation of the light curve analysis. Section 2 contains the evaluation of the empirical values of the theoretical momentA _2m is demonstrated, with the equation of the condition given. Then the equations forA _2m in terms of the elements of the total and the annular eclipses, including partial and annular phase of transit eclipse, follow.The analysis of the light curves of the two eclipsing binaries (RW Gem and AY Cam), the results and the discussion of our solution, are outlined in Section 3.     

Orbital period investigation of some short-period sdB-type eclipsing binaries

Analysis of over 15 years of V-band and Wing three filter near-IR photometry of the bright M5Ib-II supergiant has been carried out. Wavelet analysis of these data reveals that the star pulsates with several complicated oscillation modes. Different time scales of variability are identified, and with the aid of discrete Fourier analysis, depending on the filter, up to seven significant pulsation modes are identified and their frequencies and amplitudes extracted. The Long Secondary Period (LSP) with a mean period of ～1343 d has been identified, as well as other periods of the order of ～125 d. The longer period appears to be attributed to the radial pulsational mode, while the various peaks near ～125 d appear to arise from stochastically excited p-modes. After removing the light contribution of the 5th magnitude binary companion and calibrating the intermediate-band photometry to the Wing photometric system, TiO (719 nm) and near-IR (B-C) Wing color indices were formed. These indices have been calibrated with T _eff, while the Wing-C bandpass (1025 nm) serves as a proxy for bolometric magnitude and was transformed to approximate m _bol. Finally, the derivation of the variations in the star’s temperature, luminosity and radius is straightforward.     

Photographic photometry of the eclipsing binary ad bootes

A detailed two colour (BV) photoelectric photometry of the late-type eclipsing binary AD BOO was carried out in 1981 April–May. We found its period to be 2.0688112 d, double what was thought previously. The light curve outside the eclipses is basically flat with Irregular fluctuations of ˜0.075 mag. It is basically an Algol-type curve, with a principal minimum of 0.65 mag and a secondary minimum of 0.40 mag. The O-C diagram of the minimum epoch shows that the period has tended to increase. The photometric solution by the classical Russel-Merrill method gives k = 0.786. The principal minimum corresponds to a partial eclipse of the transit type.     

仙王VV1976—1978年食的UBV光电测光

本文发表1976—1978年食期间,对VVCep进行UBV光电测光的结果。从我们自己观测的B-V和U-B色指数曲线得到了第二,三,四接触时刻,其对应的食甚时刻为JD2443361,与预报的日期相符合。文中,我们用M型子星的气流来解释色指数曲线的下降段和上升段深度不等的现象。从我们解释食的物理模型得到M型超巨星的半径为1860R_⊙,其大气的厚度达450R_⊙,约为半径的四分之一。     

Preliminary Photometric Results for the 2003 Eclipse of Ee Cep

We report multicolour photometric observations of the 2003 eclipse of the long-period (5.6 yr) eclipsing binary EE Cep. Measurements were obtained with ten telescopes at eight observatories in four countries. In most cases, UBV(RI)_C broad band filters have been used. The light curve shape shows that the obscuring body is an almost dark disk around a low-luminosity central object. However, variations of the colour indices during the eclipse indicate that the obscuring body emits a considerable amount of radiation in the near infrared.     

A New Light Curve Analysis of the Eclipsing Binary SX Aur

Using WOOD 's (1972) model, we have analysed BONDARENKO 's (1974) two-colour photoelectric observations – till now unsolved – of the eclipsing binary SX Aur. Our photometric solutions turn out to be in substantial agreement with those derived by CHAMBLISS and LEUNG (1979); they confirm that SX Aur is a post-mass exchange (case A) semi-detached system.     

High-speed energy-resolved STJ photometry of the eclipsing binary UZ For

We present high-time-resolution optical photometry of the eclipsing binary UZ For using a superconducting tunnel junction (STJ) device, a photon-counting array detector with intrinsic energy resolution. Three eclipses of the ∼18-mag 126.5-min orbital binary were observed using a 6×6 array of tantalum STJs at the 4.2-m William Herschel Telescope on La Palma. The detector presently provides individual photon arrival-time accuracy to about 5 μs, and a wavelength resolution of about 60 nm at 500 nm, with each array element capable of counting up to ∼5000 photon s⁻¹. The data allow us to place accurate constraints on the accretion geometry from our time- and spectrally resolved monitoring, especially of the eclipse ingress and egress. We find that there are two small accretion regions, located close to the poles of the white dwarf. The positions of these are accurately constrained, and show little movement from eclipse to eclipse, even over a number of years. The colour of the emission from the two regions appears similar, although their X-ray properties are known to be significantly different: we argue that the usual accretion shock may be absent at the non-X-ray-emitting region, and instead the flow here interacts directly with the white dwarf surface; alternatively, a special grazing occultation of this region is required. There is no evidence for any quasi-periodic oscillations on time-scales of the order of seconds, consistent with relatively stable cyclotron cooling in each accretion region.     

Spectroscopic observations of the eclipsing polar MN Hya (RX J0929–24)

We present low–medium resolution optical spectroscopy of the eclipsing AM Her system MN Hya (RX J0929–24). We determine the magnetic field strength at the primary accretion region of the white dwarf to be 42 MG from the spacing of cyclotron features visible during π ∼ 0.4–0.7. From spectra taken during the eclipse we find that the secondary has an M3–4 spectral type. Combined with the eclipse photometry of Sekiguchi, Nakada &38; Bassett and an estimate of the interstellar extinction we find a distance of ∼300–700 pc. We find unusual line variations at π ∼ 0.9: Hα is seen in absorption and emission. This is at the same point in the orbital phase at which a prominent absorption dip is seen in soft X-rays.     

Catalog of W UMa type binary systems with additional components based on eclipsing time variations

A catalog of W UMa type eclipsing binary systems with tertiary components based on eclipse timing diagrams is presented listing the physical and orbital parameters (including third body parameters) of 150 W UMa type eclipsing binaries.In this study, the (O–C) diagrams of nine sample W UMa type eclipsing binary systems, based on the most reliable timings of minima in the literature, are analyzed to obtain the third-body parameters and significant statistical results are presented from the data in the catalog.     

Photometric study of the variable star population in the globular cluster NGC 6397

We present the results of a photometric survey for variable stars in the central region of the nearby globular cluster NGC 6397. Time-series photometry was obtained for 30 variable objects. The sample includes 12 new objects, of which six show periodic light curves and two are eclipsing binaries of unknown period. Six variables possess certain and three possess likely X-ray counterparts detected with the Chandra observatory. Among them, four are cataclysmic variables and one is a foreground eclipsing binary. The cataclysmic variable CV2 exhibited a likely dwarf nova type outburst in 2003 May. The cataclysmic variable CV3 was observed at  18.5 < V < 20.0  during five observing runs, but went into a low state in 2003 May when it reached   V > 22  . We have found that the light curve of the optical companion to the millisecond pulsar PSR J1740−5340 exhibits noticeable changes of its amplitude on a time-scale of a few months. A shallow eclipse with  Δ V = 0.03 mag  was detected in one of the cluster turn-off stars suggesting the presence of a large planet or brown dwarf in orbit.