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).     

Light curve variations of er Vulpeculae in 1984 and 1985 observing seasons

The double-lined spectroscopic and eclipsing binary ER Vul was observed in blue and yellow light during the 1984 and 1985 observing seasons. In 1984 four and in 1985 three different light curves in each colour were obtained. The system sometimes is too active and sometimes too quite. The wave-like distortion has been obtained for each light curve and a period of migration has been estimated to be about 8–9 months. The light fluctuations, which are the main characteristics of ER Vul, seems to be related with the wave minimum, (e.g., spotted regions) of the component(s).     

Light curve variations of the RS CVn-type eclipsing binary ER Vulpeculae

Photoelectric observations of the double-lined spectroscopic and eclipsing binary ER Vul were obtained inB andV colours of Johnson'sUBV system, between 1981 and 1986. The light curves show that the system is sometimes very active and sometimes very quiet and have changes in short time intervals. The were-like distortion, which is superimposed on the light curves, has been obtained. Moreover, small-amplitude light fluctuations in the light curves are noticeable.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.     

Star-Spots Studies for Three Short Period RS CVn-Type Binaries

Light curve analysis for three short-period RS CVn-type binaries were performed, using: a) Fourier analysis techniques for light curve changes in the frequency domain; b) photometric curve fit by means of numerical quadratures to develop theoretical light curves appropriate to RS CVn stars. The two methods were applied to the systems ER Vul, BH Vir, and UV Psc. Improved physical and geometrical parameters are found by taking the average of the results measured by the above two methods.     

The early spectroscopic evolution of nova V458 Vul (Nova Vulpeculae 2007)

The early spectral evolution of the nova V458 Vul has been monitored at the Loiano Observatory, Italy. The nova exhibited a couple of oscillations during the decline from initial maximum. We have performed spectroscopic observations to study the physical properties of the ejected material. The photometric light curve has been used to derive the nova distance and its absolute magnitude at maximum. V458 Vul is a fast nova, with decline rates by two or three magnitudes of 7 and 15 days respectively. The magnitude at maximum is M _V =?8.8. The nova distance is in the range 6.7–10.3 kpc. The spectra secured a few days after initial maximum showed emission lines of H I and Fe II, making V458 Vul a Fe II nova at this stage. After the oscillations V458 Vul came back to a standard decline curve, but evolved towards the He/N class. Thus V458 Vul is a hybrid nova.     

Period studies of classical Algol-type binaries II: UX Leo,RW Mon,EQ Ori,XZ UMa and AX Vul

This study presents an investigation of the orbital period variations of five Algol type binaries, UX Leo, RW Mon, EQ Ori, XZ UMa and AX Vul based on all available minima times. The O–C diagrams of all systems exhibit a periodic variation superimposed on a downward parabolic segment. The mass loss due to magnetic braking effect in the cooler components is assumed to account for the parabolic variation with a downward shape, while it is suggested that the light-time effect (LITE) due to an unseen component around the eclipsing binaries explains the tilted sinusoidal changes in their O–C diagrams. The orbital period decrease rates for the systems are estimated as approximately between about 0.7 and 2.5 s per century. It is clearly seen that mass loss effect is more dominant than the expected mass transfer for classical Algols in this study. The minimum mass of the probable third bodies around the eclipsing pairs was calculated to be ?0.5 M_⊙ except for UX Leo, in which it was estimated to be approximately 0.9 M_⊙. In order to search for third lights in the light curves of five systems, the V-light curves of the systems were analyzed and their physical and photometric parameters were determined. For UX Leo, a significant third light contribution was determined. We found a very small third light that can be tested using multi-color light curves, for RW Mon, EQ Ori and XZ UMa, while a third light for AX Vul could not be exposed.     

激变变星Ⅴ1159 Ori 和BZ UMa 的测光研究

Ⅴ1159 Ori 是SU UMa 型中 ER UMa 亚型激变变星,BZ UMa 介于 U Gem 型和 WZ Sge 型之间,但又具有 SU UMa 的周期特征,存在争议.在2008年2月24日和 25日,用云南天文台 1 米 RCC(Ritchey-Chretien-Coude)望远镜对两者的测光观测显示: Ⅴ1159 Ori 在正常爆发的下降阶段存在 superhump,这为 superhump 现象普遍存在于 ER UMa 型星中提供了观测证据;BZ UMa 观测时处于爆发极大,并未观测到确凿的 superhump 周期,而 AAVSO(American Association of Variable Star Observers)近年的 BZ UMa 观测亦从未发现明确的 superhump;两者均表明 BZ UMa 可能并非 SU UMa 型星.基于星等变化幅度考虑,BZ UMa 较 WZ Sge 更为接近.     

Absolute parameters of the Algol binary Z Vul

Spectra in the wavelength range 4230–9150 Å and the first light curves of Z Vul in the infrared J, H and K bands are presented. Our infrared JHK light curves and radial velocities, together with published radial velocity and UBV data are analyzed in order to determine a new set of stellar parameters. This allows us to determine new absolute parameters of the stellar components, the interstellar reddening and the distance to the system. We discuss the rotation of the primary star, finding that must be rotating faster than synchronous. From the visual–infrared photometry we find no evidence of IR excess in the system.     

A Period Study of the Rs CVn-Type Binary ER Vulpeculae

Many available published times of light minima of the late-type binary system ER Vul have been compiled and analyzed using a new method proposed by Kalimeris et al. (1994). It was shown that the orbital period of the system oscillation with a period of about 30.6 years and an amplitude of 3.2×10^-6 days while it undergoes a constant period decrease of about dP /P=7.84× 10^-8 day / year. The prospective physical mechanisms that could have modulated the orbital period behaviour (periodic or non-periodic), have been studied. We found that a combination of a magnetic activity cycle mechanism and an enhanced stellar wind could explain satisfactorily the period change.     

On the possibility of systematizing classical novae by light curve type. I. Type criteria

Nova light curves, plotted on “outburst amplitude-logarithm of main shell radius” axes, have differences that can be systematized. As a result of a survey of over 90 novae, nova groups that are typical in light curve shape have been distinguished: DQ Her, CP Pup, RR Pic, PU Vul, V1974 Cyg, CP Lac, and GQ Mus. The light curve criterion is supplemented by other characteristics. The DQ Her group includes only novae having dust formation in the ejected shell. The GQ Mus group combines certain novae with smooth light curves that are separated into several subgroups with respect to outburst amplitude and the duration of the light curve section before the transitional stage, but for which the linear section of the light curve has the same slope. Translated from Astrofizika, Vol. 42, No. 1, pp. 61–74, January–March, 1999.     

狐狸座BW星的周期分析

利用文[1]中权重5的大量高精度测光数据,用文[2]中的周期分析法,得出BWVul的主要脉动周期P_1=0.21010425d。另有变幅仅为前者十分之一的二倍频P_2=0.10052300d及四倍频P_4=0.05026096d。文[3]求出的变幅更小的P_3、P_5、P_6、P_7、P_8等倍频可信度很低。故多重周期不是引起P_1长期变化及限制脉动变幅的主因。     

Is the semi‐regular variable RU Vulpeculae undergoing a helium‐shell flash?

The semi‐regular variable star RU Vulpeculae (RU Vul) is being observed visually since 1935. Its pulsation period and amplitude are declining since ∼1954. A leading hypothesis to explain the period decrease in asymptotic giant branch (AGB) stars such as RU Vul is an ongoing flash of the He‐burning shell, also called a thermal pulse (TP), inside the star. In this paper, we present a CCD photometric light curve of RU Vul, derive its fundamental parameters, and test if the TP hypothesis can describe the observed period decline. We use CCD photometry to determine the present‐day pulsation period and amplitude in three photometric bands, and high‐resolution optical spectroscopy to derive the fundamental parameters. The period evolution of RU Vul is compared to predictions by evolutionary models of the AGB phase. We find that RU Vul is a metal‐poor star with a metallicity [M/H] = –1.59 ± 0.05 and an effective surface temperature of T_eff = 3634 ± 20 K. The low metallicity of RU Vul and its kinematics indicate that it is an old, low‐mass member of the thick disc or the halo population. The present day pulsation period determined from our photometry is ∼108 d, the semiamplitude in the V ‐band is 0.39 ± 0.03 mag. The observed period decline is found to be well matched by an evolutionary AGB model with stellar parameters comparable to those of RU Vul. We conclude that the TP hypothesis is in good agreement with the observed period evolution of RU Vul. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A model for the infrared brightening of a Nova shell

A model for grain formation in an expanding Nova shell is presented. It is shown that individual grains complete the growth within a very short time interval. In consequence the infrared brightening accompanied with visual darkening observed in several Novae is interpreted in terms of extension of dusty region in the ejected gas shell. Developments of infrared luminosity and visual magnitude are computed on the basis of a model, and compared with the observations of Nova Vul 1976, Nova Ser 1970, and Nova Aql 1975. The constancy and uniformity of grain temperatures for a long period after the infrared maximum observed in Nova Vul 1976 are also discussed.     

Polarization measurement and study of thirty RS CVn stars

We made polarization measurement on 30 RS CVn systems using the Berger polarimeter of McDonald Observatory in July-December 1984, of which 26 systems were measured for the first time. The results are given here. They show that for most RS CVn systems, the optical linear polarization is weak, generally below 0.45%, averaging about 0.20%. Some systems, like AR Lac, HR 5110, HD 8357, HK Lac, HR 7275 and HR 7428 have polarization above 0.03%, which showed time variations by factors between 10 and 30. For HD 8357 and ER Vul, there is a clear connection between the polarization and the orbital phase.     

Photometric observation and light curve analysis of binary system ER-Orionis

Photometric observations of the over-contact binary ER ORI were performed during November 2007 and February to April 2008 with the 51 cm telescope of Biruni Observatory of Shiraz University in U, B and V filters (Johnson system) and an RCA 4509 photomultiplier. We used these data to obtain the light curves and calculate the newtimes of minimum light in each filter and plot the O-C diagram of ER ORI. Using theWilson’s computer code with the help of an auxiliary computer program to improve the optimizations, the light curve analyses were carried out to find out the photometric elements of the system.     

Detection of optical circular polarization in the Herbig Ae star WW Vul

UBVRI observations of circular polarization in WW Vul are presented. A positive polarization of ～0.1% was detected with a signal-to-noise ratio from 3 to 5 in each of the bands and more than 5 when averaged over all five bands. This observed polarization roughly corresponds to a 1% circular polarization of the radiation scattered in a circumstellar disk, which is most likely attributable to the significant alignment of scattering nonspherical dust grains. Since grain alignment is possible only in a magnetic field, this result provides circumstantial evidence for the existence of a magnetic field in the circumstellar disk of WW Vul.     

A comprehensive study of six Algol type binaries

CCD light curves of the Algol type eclipsing binaries DP Cep, AL Gem, FG Gem, UU Leo, CF Tau and AW Vul were analysed using the Wilson–Devinney code and new geometric and absolute parameters were derived. Due to cyclic apparent orbital period changes of the systems, probably caused by the Light-Time Effect, the contribution of a third light was taken into account in the light curve solution. All the reliable timings of minima found in the literature were used to study the period variations and search for the presence of a tertiary component in the systems. A comparison between the parameters of the third body derived from the light curve and orbital period analyses is also discussed. Moreover, the absolute parameters of the eclipsing binary components were also used to determine their current evolutionary state.     

Photometry of the Cataclysmic Variables V1159 Ori and BZ UMa

V1159 Ori is an ER UMa sub-type cataclysmic variable belonging to the SU UMa type, and the controversial BZ UMa lies between the U Gem type and the WZ Sge type, but it possesses also the periodicity characteristics of SU UMa. We have made photometric observations of these two cataclysmic variables with the 1m RCC optical telescope in Yunnan Astronomical Observatory from Feb. 24th to 25th, 2008. The obtained light curves of V1159 Ori exhibit superhumps in the descending stage of a normal outburst, this provides an observational evidence for the universal existence of superhumps in ER UMa-type stars. During our observations BZ UMa was at the maximum of an outburst, but no evident superhump period was detected. The previous observations made by AAVSO (American Association of Variable Star Observers) also have never found any definite superhump. This demonstrates that BZ UMa probably is not a SU UMa-type variable. According to the range of its magnitude variations, BZ UMa is closer to WZ Sge.     

Application of a probabilistic neural network in radial‐velocity curve analysis of the spectroscopic binary stars HD 152218, HD 143511, HD 27149, and ER Vul

We use an Artificial Neural Network (ANN) to derive the orbital parameters of spectroscopic binary stars. Using measured radial velocity data of four double‐lined spectroscopic binary systems HD 152218, HD 143511, HD 27149, and ER Vul, we find corresponding orbital and spectroscopic elements. Our numerical results are in good agreement with those obtained by others using more traditional methods (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthetic direct impact light curves of the ultracompact AM CVn binary systems V407 Vul and HM Cnc

The interacting binary white dwarf (AM CVn) systems HM Cnc and V407 have orbital periods of 5.4 and 9.5 min, respectively. The two systems are characterized by an 'on/off' behaviour in the X-ray light curve, and optical light curves that are nearly sinusoidal and which lead the X-ray light curves in phase by about 0.2 in both systems. Of the models that have been proposed to explain the observations, the one that seems to require the least fine-tuning is the direct impact model of Marsh & Steeghs. In this model, the white dwarf primary is large enough relative to the semimajor axis that the accretion stream impacts the surface of the primary white dwarf directly without forming an accretion disc. Marsh & Steeghs proposed that in this situation there could be a flow setup around the equator with a decreasing surface temperature, the further one measured from the impact point. In this study, we estimate the light curves that might result from such a temperature distribution, and find them to be reasonable approximations to the observations. One unexpected result is that two distinct X-ray spots must exist to match the shape of the X-ray light curves.