Hydrology and hydrogeology of Sakaryabaşı Karstic springs, Çifteler, Turkey

The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements.     

Non-Radial Pulsations in Components of Symbiotic Stars

Photometric observations of symbiotic stars in the blue and in the red spectral regions make it possible to reveal non-radial oscillations both of the cool and of the hot components. Light variations of red giants in the symbiotic systems CI Cyg and AG Peg show several periods in the 10–80^d range, interpreted as p-mode pulsations. These modes are excited by a bright spot produced by radiation flux from the hot component. The spot moves on the red giant’s photosphere at a velocity close to the sound speed. During the active phase of the symbiotic star CH Cyg, at least 25 frequencies of oscillations in the 150–6000 s range of periods were found in the light of the white dwarf. Their features correspond to non-radial g-modes. In the frame of 2D gas dynamical non-adiabatic models, the interaction between gas flows and the accretion disk leads to formation of a system of shock waves propagating towards the compact object, which is one of possible mechanisms to excite non-radial pulsations of white dwarfs in symbiotic systems.     

LO Pegasi: an investigation of multiband optical polarization

We present BVR polarimetric study of the cool active star LO Pegasi (LO Peg) for the first time. LO Peg was found to be highly polarized among the cool active stars. Our observations yield average values of polarization in LO Peg:   P_B = 0.387 ± 0.004 per cent, θ_B= 88°± 1°; P_V = 0.351 ± 0.004 per cent, θ_V= 91°± 1°  and   P_R = 0.335 ± 0.003 per cent, θ_R= 91°± 1°  . Both the degree of polarization and the position angle are found to be variable. The semi-amplitude of the polarization variability in B, V and R bands is found to be  0.18 ± 0.02, 0.13 ± 0.01  and  0.10 ± 0.02  per cent, respectively. We suggest that the levels of polarization observed in LO Peg could be the result of scattering of an anisotropic stellar radiation field by an optically thin circumstellar envelope or scattering of the stellar radiation by prominence-like structures.     

Detection of superhumps in the cataclysmic variable V378 Peg (PG 2337+300)

The cataclysmic variable V378 Peg is known since 15 years. Although V378 Peg is a rather bright star (14 mag), it underwent no detailed study. We performed photometric observations of V378 Peg during 75 h with the goal to detect periodic brightness variations. The obtained light-curves clearly showed changes with a period of about 3 h. The Fourier analysis reveals that this oscillation occurs with a period of 3.238 h and a semiamplitude of 0.07 mag. Although the detected oscillation possesses certain coherence, it appears to have a slightly unstable period or phase. Therefore, the detected period cannot be the orbital period of the V378 Peg system. Because such instability is typical of superhumps, we must consider the detected oscillation as superhumps. Furthermore, V378 Peg shows no outbursts and has to be a nova-like variable rather than a dwarf nova. Hence, the detected superhumps have to be regarded as permanent superhumps. Because superhump periods in cataclysmic variables are close to orbital periods, we can find the place of V378 Peg in the orbital period distribution of cataclysmic variables. V378 Peg is a permanent superhump system above the upper edge of the 2-3 h period gap in the orbital period distribution.     

A spatially resolved 'inside-out' outburst of IP Pegasi

We present a comprehensive photometric data set taken over the entire outburst of the eclipsing dwarf nova IP Peg in 1997 September/October. Analysis of the light curves taken over the long rise to the peak-of-outburst shows conclusively that the outburst started near the centre of the disc and moved outwards. This is the first data set that spatially resolves such an outburst. The data set is consistent with the idea that long rise times are indicative of such 'inside-out' outbursts. We show how the thickness and the radius of the disc, along with the mass transfer rate, change over the whole outburst. In addition, we show evidence of the secondary and the irradiation thereof. We discuss the possibility of spiral shocks in the disc; however, we find no conclusive evidence of their existence in this data set.     

Time‐series photometric spot modelling – VI. A new computer code and its application to 23 years of photometry of the active giant IM Pegasi

We present and apply a new computer program named SpotModeL to analyze single and multiple bandpass photometric data of spotted stars. It is based on the standard analytical formulae from Budding and Dorren. The program determines the position, size, and temperature of up to three spots by minimizing the fit residuals with the help of the Marquardt‐Levenberg non‐linear least‐squares algorithm. We also expand this procedure to full time‐series analysis of differential data, just as real observations would deliver. If multi‐bandpass data are available, all bandpasses can be treated simultaneously and thus the spot temperature is solved for implicitly. The program may be downloaded and used by anyone. In this paper, we apply our code to an ≈23 year long photometric dataset of the spotted RS CVn giant IM Peg. We extracted and modelled 33 individual light curves, additionally, we fitted the entire V dataset in one run. The resulting spot parameters reflect the long term light variability and reveal two active longitudes on the substellar point and on the antipode. The radius and longitude of the dominant spot show variations with 29.8 and 10.4 years period, respectively. Our multicolour data suggests that the spot temperature is increasing with the brightening of the star. The average spot temperature from V, I_C is 3550 ± 150 K or approximately 900 K below the effective temperature of the star.     

Aussiedler migration and its impact on Braşov's ethnic German population and built environment

The expression of different ethnic identities in the landscape is a product of the creation, destruction and preservation of the built environment. This may illustrate the changing processes over the evolution of a landscape. In the case of Braşov, Romania, it is possible to see in the urban landscape a reflection of the changing nature of the relationship between the ethnic German and Romanian populations, and the German and Romanian governments. This paper will demonstrate the persistence of ethnic German culture in the built environment and social organisation of Braşov in spite of the exodus of the ethnic German population. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photometric Solution of the Eclipsing Binary V351 Pegasi

BVR light curves of the recently discovered eclipsing binary V351 Peg were studied to derive the preliminary physical parameters of the system. The light curves were obtained at the TüBİTAK* – Turkish National Observatory (TUG) during three nights in August, 2003. The solutions were made using Djurašević’s inverse problem method. V351 Peg is a system in an overcontact configuration (f _over∼ 21 %) with a relatively small temperature difference between the components ΔT ≈ 20 K. The results suggest a significant mass and energy transfer from the more massive primary onto the less massive secondary. The hot area on the less massive star, near the neck region, can be considered as a consequence of this mass and energy exchange between the components through the connecting neck of the common envelope. TüBİTAK: The Scientific and Technical Research Council of Turkey.     

On the nature of the purported common proper motion companions to the exoplanet host star 51 Peg

Greaves (2006) proposed that three red, high proper motion stars within 10° of 51 Peg (NLTT 54007, 54064, and 55547) are co‐moving companions to this famous exoplanet host star. While the stars clearly have proper motions similar to 51 Peg, the inferred kinematic parallaxes for these stars produce extremely inconsistent color‐magnitude positions 2 to 4 magnitudes below the main sequence. All three stars are likely to be background stars unrelated to 51 Peg (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Erratum: Spiral structure in the accretion disc of the binary IP Pegasi

The paper 'Spiral structure in the accretion disc of the binary IP Pegasi' was published in Mon. Not. R. Astron. Soc. 290 , L28–L32 (1997). Figs 1 and 2 of the paper (grey-scale images) did not reproduce well, and are reprinted here (Fig. 1 overleaf). Colour versions of the images are available on the World Wide Web:http://www-star.st-and.ac.uk/^∼ds10/spirals.html