New photometric investigation of the Herbig Ae/Be star HD 52721, a close binary system: Evidence for the existence of large-scale azimuthal inhomogeneities

We present new results of our photometry for the Herbig Be star HD 52721 obtained from January 16 to March 25, 2013. A new data reduction technique is used. Using this technique, we have also reanalyzed the previous results of our photometry for this object pertaining to the period from March 7 to March 28, 2010. The Be star HD 52721 is known as an eclipsing variable with the period P = 1^d. 610. Two photometric minima observed during one period are a peculiarity of its photometric variability. They are separated in phase of the period P by 0.5 and differ from one another in depth by 0 ^m . 04. We have also detected additional minima observed at the phases of maximum brightness. We hypothesize that they can be associated with the existence of local azimuthal inhomogeneities rotating synchronously with the orbital motion of the binary component stars in the circumstellar envelope. When processing our CCD frames, we have applied an efficient CCD-frame rejection method that has allowed the accuracy of observations to be increased considerably. The CCD frames have been further processed using the Apex II software package, which is a universal software platform for astronomical image processing. We justify the need for additional photometric observations of HD 52721 in various color bands to confirm the hypothesis about the existence of azimuthal inhomogeneities in the program binary system and to analyze their physical properties.     

Photometric and spectroscopic investigation of the B2E Herbig star HD52721: First results

We present first results of the photometric and spectroscopic investigation of the B1/B2 Herbig star HD52721 performed in 2009–2010 at three observatories: Mountain Astronomical Station (Kislovodsk)—photometry, CrAO (Crimea, Ukraine)—spectroscopy, Observatory San Pedro Martyr (Ensenada, Mexico)—high-resolution echelle-spectroscopy. We have also used photometric data from the ASAS survey for 2003–2009. Our analysis has shown that a) the object is a close binary system with the orbital period of 1.610 days composed of two components of similar spectral type (B1–B2); b) the system is surrounded by the common disk-like envelope containing azimuthal inhomogeneity rotating with the orbital period of the system. We present preliminary estimates of the system parameters and discuss its possible nature.     

The stellar composition of the star formation region CMa R1 – II. Spectroscopic and photometric observations of nine young stars

We present new high- and low-resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD 52721, HD 53367, LkH α  220 and LkH α  218) show H α emission and we argue that they are Herbig Be stars with discs. Our photometric and spectroscopic observations of these stars reveal new characteristics of their variability. We present first interpretations of the variability of HD 52721, HD 53367 and the two LkH α stars in terms of a partially eclipsing binary, a magnetic activity cycle and circumstellar dust variations, respectively. The remaining five stars show no clear indications of H α emission in their spectra, although their spectral types and ages are comparable with those of HD 52721 and HD 53367. This indicates that the presence of a disc around a star in CMa R1 may depend on the environment of the star. In particular we find that all H α emission stars are located at or outside the arc-shaped border of the H  ii region, which suggests that the stars inside the arc have lost their discs through evaporation by UV photons from nearby O stars, or from the nearby (<25 pc) supernova, about 1 Myr ago.     

An Outburst Detected in the Spectrum of Hd 6226

HD 6226 is a bright binary Be star at visual magnitude 6.81 (Hipparcos database). The emission and absorption phases occur in cycles, which are probably not periodic. The suspected period of about 630 days (derived from photometric measurements) is not confirmed by our spectroscopic survey. The latest emission phase developed in the beginning of 2003, then the emission strength systematically decreased and disappeared between July 21, 2003 and August 4, 2003. The last (absorption) spectrum was exposed on August 25, 2003. Unexpected very strong emission appeared in a spectrum exposed on October 28, 2003. A short-term photometric brightening followed this “outburst”. Long-term spectroscopic RV studies revealed a 2.615 d period modulated by a 29.7 d period (in the He I 6678 line), which perhaps may be interpreted as orbital period of a binary. Nevertheless, the physical nature of the dominant short 2.615 d period is not yet clear. The last detected emission episode has changed considerably our view of the interesting object HD 6226. We hope this study will reveal more details of the physical properties of the Be phenomenon.     

HD 172189, a Cluster Member Binary System with a δ Scuti Component in the Field of View of COROT

Photometric and spectroscopic results for the star HD 172189, member of the open cluster IC 4756 in the summer field of the space mission COROT, are presented. From photometric observations in the Strömgren system carried out at various epochs, its binary nature as well as the presence of a δ Scuti-type pulsating component have been discovered. The frequency analysis of the whole dataset confirms a dominant frequency of 19.5974 c d^?1 with a maximum amplitude near 0.02 mag plus other frequencies in the range 18–20 c d^?1. A preliminary orbital solution from the light curve and from four FEROS spectra reveals two similar components of around 1.5 M _⊙ orbiting with a period of 5.702 d.     

Results of Photometric and Spectroscopic Observations of the Young Variable Star V730 Cep

We present the results of our photometric (V RI) and spectroscopic observations of the young variable star V730 Cep (MisV1147) classified by Uemura et al. (2004) as a Herbig Be star. Our photometry confirms the conclusion of the above authors that this star has a complex pattern of variability including periodic or quasi-periodic brightness variations with a period of about 14 days and deep Algol-like minima typical for UX Ori stars. Our spectroscopy shows that the classification of V730 Cep as a Herbig Be star is wrong. Actually, this star has a much lower temperature and belongs to the family of T Tauri stars. This allows us to explain the nature of the unusual photometric activity of V730 Cep based on a combination of two well-known models of variable circumstellar extinction applied to young stars: AA Tau- and UX Oritype variability. It follows from our observations that the color tracks on the V ?(V ?I) color–magnitude diagram for these models slightly differ: the AA Tau-type variability of circumstellar extinction is caused by larger grains than the UX Ori-type variability. Such a difference can be due to an increase in the characteristic sizes of circumstellar dust as the star is approached and has a simple explanation: small dust grains evaporate faster than large ones.     

Photometric and spectroscopic variability of the pre‐main sequence star V1184 Tauri (CB 34V)

We present recent results from optical photometric and spectroscopic observations of the pre‐main sequence star V1184 Tau (CB 34V). The star is associated with the Bok globule CB 34 and was considered as a FUOR candidate in previous studies. Our photometric data obtained from October 2000 to April 2003 show that the stellar brightness varies with an amplitude of about 0.m 5 (I ), but from August 2003 the photometric behavior of the star has changed dramatically. Three deep brightness minima (ΔI ∼ 4^m.2) were observed during the past two years. The analysis of available photometric data suggests that V1184 Tau shows two types of variability produced (1) by rotation of large cool spotted surface and (2) by occultation from circumstellar clouds of dust or from features of a circumstellar disk. The behavior of the V – I index indicates that the star becomes redder towards minimum light, but from a certain turning point (V ∼ 18^m.2) it gets bluer and is fading further. Five medium dispersion optical spectra of V1184 Tau were obtained in the period 2001–2004. Signi.cant changes in the profile and strength of the emission lines in the spectrum of V1184 Tau were found. During minimum light the equivalent width of the Hα emission line increases from 4 Å to 9 Å. The [O I] lines (λλ 6003, 6363 Å) are also seen in emission while the sodium doublet keeps its absorption strength and equivalent width. The possibility to reconstruct the historical light curve of V1184 Tau using photographical plate archives is brie.y discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Radial velocity measurements of the chromospherically-active stars (II)

From two sets of the spectroscopic observations covering a ten year period we have obtained 59 radial velocities of the chromospherically-active star HD 28591 = V492 Per. It is a G9III single-lined spectroscopic binary with a period of 21.2910 days and a circular orbit. Thev sini of 24.6 km s^–1, results in a minimum radius 10.3R . We estimate a distance of 165 ± 40 pc and an orbital inclination of 65 ± 25 degrees. The secondary is probably a mid to late-type K dwarf. The star is brighter than the limiting magnitude of theBright Star Catalogue. The mean photometric and the orbital periods are identical within their uncertainties. Since the star fills a significant fraction of its Roche lobe, about 62%, the photometric light curve may be the result of starspots and a modest ellipticity effect.Visiting astronomer, Kitt Peak National Observatory, NOAO, operated by AURA, Inc., under contract with the NSF     

FG Sagittae: New observations in the R CrB photometric phase

In 1999–2002, we continued our photometric and spectroscopic observations of FG Sge. This star has been in a new R CrB photometric phase since 1992. We constructed the BV RI light curves and studied the behavior of the color indices as a function of the fading amplitude. As previously, all of the three deep minima observed during this period were found to be blue on the descent; this was interpreted as the result of strong stellar light scattering in dust clouds formed on the line of sight. We analyzed the wavelength dependence of extinction in the circumstellar shell outside fadings, which was similar to Whitford's standard reddening law. Low-resolution spectroscopic observations allowed us to study the changes in the intensities of Swan bands and the Na I D doublet during deep and shallow (up to 1^m) fadings. We confirmed the reversal of the spectrum of the extended stellar envelope on the descending branches of deep minima.     

HD 115781 and HD 116204—two RS CVn binaries

HD 115781 and HD 116204 (BL CVn and BM CVn) are shown to be RS CVn binaries with periods near 20 days. HD 115781 is double-lined; the primary type is about K1III, while the secondary is probably a late-type subgiant. The masses of the two components are equal within observational error. There is substantial photometric variability with a period half the orbital period; it is attributed to ellipsoidal variation. HD 116204 is also of type K1III. It shows exceptionally strong Ca II H and K emission, together with an emission-line spectrum typical of RS CVn stars in theIUE ultraviolet region, but Hα is an absorption line. The secondary star in the HD 116204 system has not been detected. The primary shows photometric variations, presumably due to starspots, with a period 5 per cent longer than the orbital period.     

Photometric investigation of the short period eclipsing binary star V719 Her

The Behlen observatory 0.76 m telescope CCD photometer is used to obtain 347 observations of the short period (P0^d.4) eclipsing binary star V719 Her. The observations done withV andR bandpass filters were made on 6 nights in 1993. Previously published light elements and the present five timings of minimum provide a new epoch and a more accurate orbital period of 0.4009828 days. Our analyses show that the period of the system appears to decrease. We recommend future monitoring of the eclipse minima for this system. No published spectral classification for V719 Her exists. From the color,V-R=0.391, we estimate it to be about F5.The 1993 version of the Wilson Devinney model gave the photometric solutions. The adopted solution indicates that V719 Her is a W UMa type contact binary. The mass ratio,q=(m ₂/m ₁, where star 1 eclipse at the primary minimum)=0.296 suggests that V719 Her is a WUMa system with type-A (transit during primary eclipse) configuration. The secondary minimum shows a total eclipse. V719 Her with period less than 0.5 and spectral class F5, is probably a zero-age contact system. Since our photometric solution shows that the luminosity difference between the components is very large, we suspect that V719 Her is most likely a single line spectroscopic binary. We recommend spectroscopic study of this system.     

Radial velocity measurements of the chromospherically-active stars. i. BD + 25°2511

This paper is the first of a series on radial velocities measures of the chromospherically-active and suspected stars. The chromospherically-active star BD + 25°2511 = HZ Com is found to be double-lined spectroscopic binary with an orbital period of3.558317 days and an eccentricity of0.013 ± 0.006. The orbital period does not differ substantially from the previously determined photometric period. If the photometric period is correct, this system is rotating synchronously and imposes important constraints on theories of synchronization and circularization of binary systems.     

Optical, X-ray and radio observations of HD 61396: a probable new RS CVn-type binary

We have carried out BVR photometric and H spectroscopic observations of the star HD 61396 during 1998 March 20 to 1999 April 3. We have discovered regular optical photometric variability from this star, with an inferred period of 31.95±0.10 d, and an amplitude of 0.18 mag. A possible period of 35.34±0.12 d, as determined with Hipparcos , cannot be completely ruled out, however. Modelling of its photometric light curve with two circular spots indicates that 521 per cent of the stellar surface is covered by dark starspots which are 830 K cooler than the surrounding photosphere, and produce the observed rotational modulation of the optical flux. Optical spectroscopy reveals a variable H emission feature, indicating that it is an unusually active star.
In addition, we have analysed archival X-ray data of HD 61396, obtained from serendipitous observations with the ROSAT X-ray observatory, and we also discuss the radio properties of this star, based on both published Green Bank and unpublished VLA observations. The strong photometric variability and H emission, the relatively hard X-ray spectrum, and the high X-ray and radio luminosities imply that HD 61396 is most likely to be a member of the RS CVn class of evolved active binary stars. Its X-ray and radio luminosities place it among the five most luminous active binaries detected so far.     

New CCD photometry for the extreme lower mass-ratio binary AW Ursae Majoris

This paper presents charge-couple device (CCD) photometric observations for the eclipsing binary AW UMa. The V-band light curve in 2007 was analyzed using the 2003 version of the Wilson–Devinney code. It is confirmed that AW UMa is a total eclipsing binary with a higher degree of contact f=80.2% and a lower mass ratio of q=0.076. From the (O−C) curve, the orbital period shows a continuous period decrease at a rate of dP/dt=−2.05×10⁻⁷ d yr⁻¹. The long-term period decrease suggested that AW UMa is undergoing the mass transfer from the primary component to the secondary one, accompanied by angular momentum loss due to mass outflow L ₂. Weak evidence indicates that there exists a cyclic variation with a period of 17.6 yr and a small amplitude of A=0. ^d 0019, which may be attributed to the light-time effect via the third body. If the existence of an additional body is true, it may remove a great amount of angular momentum from the central system. For this kind of contact binary, as the orbital period decreases, the shrinking of the inner and outer critical Roche lobes will cause the contact degree f to increase. Finally, this kind of binary will merge into a single rapid-rotation star.     

Remarks on erratic period fluctuations of detached close binaries and the constancy of the orbital period of XY UMa

It is shown that the erratic changes of the orbital period, which are observed in some detached eclipsing binary systems, cannot be interpreted as real if their light curves show changing anomalies with asymmetric minimum profiles. In this case the photometrically determined times of the minima do not coincide with the ideal geometric ones, which are unobservable. This fact and the applied reduction methods for deriving the photometric times of minima cause systematic period errors of cumulative character. The discussion of six photoelectrically-determined minima obtained within the last 20 yr, and earlier photographic ones of the 0^d.479 period eclipsing binary XY UMa yields a constant period. The long cyclic light curve variations due to starspot activity of the larger and hotter component of this system are reflected in corresponding period oscillations. Dedicated to Dr. Ida Noddack on the occasion of her eightieth birthday.     

Spectral variability of LBV star V 532 (Romano’s star)

We present the results of studying the spectral and photometric variability of the luminous blue variable star V532 in M33. The photometric variations are traced from 1960 to 2010, spectral variations—from 1992 to 2009. The star has revealed an absolute maximum of visual brightness (1992–1994, high/cold state) and an absolute minimum (2007–2008, low/hot state) with a brightness difference of ΔB ≈ 2.3 ^m . The temperature estimates in the absolute maximum and absolute minimum were found to be T ∼ 22000 K and T ∼ 42000 K, respectively. The variability of the spectrum of V532 is fully consistent with the temperature variations in its photosphere, while both permitted and forbidden lines are formed in an extended stellar atmosphere. Broad components of the brightest lines were found, the broadening of these components is due to electron scattering in the wind parts closest to the photosphere. We measured the wind velocity as a difference between the emission and absorption peaks in the PCyg type profiles. The wind velocity clearly depends on the size of the stellar photosphere or on the visual brightness, when brightness declines, the wind velocity increases. In the absolute minimum a kinematic profile of the V532 atmosphere was detected. The wind velocity increases and its temperature declines with distance from the star. In the low/hot state, the spectral type of the star corresponds to WN8.5h, in the high/cold state—to WN11. We studied the evolution of V532 along with the evolution of AGCar and the massive WR binary HD5980 in SMC. During their visual minima, all the three stars perfectly fit with the WNL star sequence by Crowther and Smith (1997). However, when visual brightness increases, all the three stars form a separate sequence. It is possible that this reflects a new property of LBV stars, namely, in the high/cold states they do not pertain to the bona fide WNL stars.     

Observations and analysis of the Southern binary R Arae

This paper investigates the nature of the relatively bright ( 7th magnitude) eclipsing variable R Arae (HD 149730A), which has an orbital period of 4^d.42509, from the analysis of photometricUBV observations. The main objective behind such an analysis is to determine whether the system qualifies for a classical Algol of semi-detached status.An analysis has been performed twice on each of theUBV curves as well as the light curve due to Gaposchkin, utilising a light curve optimisation procedure. In the first analysis the presence of the visual companion (HD 1497330B) to R Arae (angular separation = 3'.6), whose light was present in all observations, was not accounted for. The second analysis attempts to account for this third light source.All the analyses indicate the relative radius of the secondary star, is of the order of 0.20. This value is well below the limit which would classify the system as a semi-detached binary.These results do, however, seem to be somewhat discordant with the spectroscopic and general photometric nature of the system, all of which suggest mass transfer processes to be occuring (therefore a possible semi-detached status). This is seen in several features, especially a marked increase in the system's mean orbital period, which tends to corroborate mass transfer from the secondary star.     

Correlated V/R and infrared photometric variations in the Be/X-ray binary LS I +61° 235/RX J0146.9+6121

We report on the long-term variability of the Be/X-ray binary LS I +61° 235/RX J0146.9+6121. New optical spectroscopic and infrared photometric observations confirm the presence of global one-armed oscillations in the circumstellar disc of the Be star, and allow us to derive a V R band quasi-period of 1240±30 d. Pronounced shell events, reminiscent of the spectacular variations in Be stars, are also seen. We have found that the J , H and K infrared photometric bands vary in correlation with the spectroscopic V R variations, implying that the one-armed disc oscillations are prograde. The effect of the oscillations is not only seen in the H α line but is also seen in the He  i λ 6678 and Paschen lines. As these lines are formed at different radii in the equatorial disc of the Be star, such effects confirm the global nature of the perturbation. The Keplerian disc has been found to be denser than the average for a sample of isolated Be stars, which may be indicative of some kind of interaction with the compact companion. Finally, from a Rossi X-ray Timing Explorer observation we derive a spin period of the neutron star of 1404.5±0.5 s.     

The (O–C) diagram problem of triple pre-cataclysmic system V471 Tau solved

V471 Tau was discovered as a spectroscopic binary by Wilson (General Catalogue of Stellar Radial Velocities, p. 44, 1953). It is the prototype of a post-common envelope system and a progenitor of a cataclysmic binary. The system consists of a cool red dwarf, K2 V, very probably a main sequence star and a hot white dwarf. The object was classified as a close binary with an orbital period of around 0.5 days. Moreover, on the light curve are observed light variations with a period of 191 days, which are connected with an ellipsoidal shape of the red dwarf as well as with the migration of spots on the surface of this cool component. The eclipse of the white dwarf in the binary remains 49 minutes and declines to the minimum and the increase from the minimum takes only 55 s. Such photometric behaviour hinders obtaining good eclipses. In this paper we have obtained during four years seven eclipses with high time resolution with all four contacts to reach precise times of minima. Fortunately these times of the minima show a change of trend in the (O–C) diagram, and we were able to decide about the physical processes responsible for the behaviour of the (O–C) diagram. We showed that this behaviour is caused by a third body in the system with an orbital period of 33.2 years, and its physical and geometrical parameters are presented. For an inclination larger than 35° we get the mass of this body below the stable hydrogen-burning limit and thus most probably the candidate would be a brown dwarf.     

Photometric study of the FUor star V 1735 Cyg (Elias 1-12)

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1_⋅^m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0_⋅^m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1_⋅^m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.