73 research outputs found

    Magnitude-range brightness variations of overactive K giants

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    We study three representative, overactive spotted K giants (IL Hya, XX Tri, and DM UMa) known to exhibit V-band light variations between 0.65-1.05 mags. Our aim is to find the origin of their large brightness variation. We employ long-term phase-resolved multicolor photometry, mostly from automatic telescopes, covering 42 yr for IL Hya, 28 yr for XX Tri, and 34 yr for DM UMa. For one target, IL Hya, we present a new Doppler image from NSO data taken in late 1996. Effective temperatures for our targets are determined from all well-sampled observing epochs and are based on a V-I_C color-index calibration. The effective temperature change between the extrema of the rotational modulation for IL Hya and XX Tri is in the range 50-200 K. The bolometric flux during maximum of the rotational modulation, i.e., the least spotted states, varied by up to 39% in IL Hya and up to 54% in XX Tri over the course of our observations. We emphasize that for IL Hya this is just about half of the total luminosity variation that can be explained by the photospheric temperature (spots/faculae) changes, while for XX Tri it is even about one third. The long-term, 0.6 mag V-band variation of DM UMa is more difficult to explain because little or no B-V color index change is observed on the same timescale. Placing the three stars with their light and color variations into H-R diagrams, we find that their overall luminosities are generally too low compared to predictions from current evolutionary tracks. A change in the stellar radius due to strong and variable magnetic fields during activity cycles likely plays a role in explaining the anomalous brightness and luminosity of our three targets. At least for IL Hya, a radius change of about 9% is suggested from m_bol and T_eff, and is supported by independent vsin(i) measurements.Comment: 13 pages, 8 figures, accepted in A&

    Time-series Doppler images and surface differential rotation of the effectively-single rapidly-rotating K-giant KU Pegasi

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    According to most stellar dynamo theories, differential rotation (DR) plays a crucial role for the generation of toroidal magnetic fields. Numerical models predict surface differential rotation to be anti-solar for rapidly-rotating giant stars, i.e., their surface angular velocity could increase with stellar latitude. However, surface differential rotation has been derived only for a handful of individual giant stars to date. The spotted surface of the K-giant KU Pegasi is investigated in order to detect its time evolution and quantify surface differential rotation. We present altogether 11 Doppler images from spectroscopic data collected with the robotic telescope STELLA between 2006--2011. All maps are obtained with the surface reconstruction code iMap. Differential rotation is extracted from these images by detecting systematic (latitude-dependent) spot displacements. We apply a cross-correlation technique to find the best differential rotation law. The surface of KU Peg shows cool spots at all latitudes and one persistent warm spot at high latitude. A small cool polar spot exists for most but not all of the epochs. Re-identification of spots in at least two consecutive maps is mostly possible only at mid and high latitudes and thus restricts the differential-rotation determination mainly to these latitudes. Our cross-correlation analysis reveals solar-like differential rotation with a surface shear of α=+0.040±0.006\alpha=+0.040\pm0.006, i.e., approximately five times weaker than on the Sun. We also derive a more accurate and consistent set of stellar parameters for KU Peg including a small Li abundance of ten times less than solar.Comment: 13 pages, 12 figures, accepted for publication in A&

    New skeletal tuberculosis cases in past populations from Western Hungary (Transdanubia)

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    The distribution, antiquity and epidemiology of tuberculosis (TB) have previously been studied in osteoarchaeological material in the eastern part of Hungary, mainly on the Great Plain. The purpose of this study is to map the occurrence of skeletal TB in different centuries in the western part of Hungary, Transdanubia, and to present new cases we have found. Palaeopathological analysis was carried out using macroscopic observation supported by radiographic and molecular methods. A large human osteoarchaeological sample (n = 5684) from Transdanubian archaeological sites ranging from the 2nd to the 18th centuries served as a source of material. Spinal TB was observed in seven individuals (in three specimens with Pott's disease two of which also had cold abscess) and hip TB was assumed in one case. The results of DNA for Mycobacterium tuberculosis were positive in seven of the eight cases identified by paleopathology, and negative in the assumed case of hip TB. However, the molecular results are consistent with highly fragmented DNA, which limited further analysis. Based on the present study and previously published cases, osteotuberculosis was found in Transdanubia mainly during the 9th–13th centuries. However, there are no signs of TB in many other 9th–13th century sites, even in those that lie geographically close to those where osteotuberculous cases were found. This may be due to a true absence of TB caused by the different living conditions, way of life, or origin of these populations. An alternative explanation is that TB was present in some individuals with no typical paleopathology, but that death occurred before skeletal morphological features could develop

    HAT-P-13: a multi-site campaign to detect the transit of the second planet in the system

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    A possible transit of HAT-P-13c has been predicted to occur on 2010 April 28. Here we report on the results of a multi-site campaign that has been organised to detect the event. CCD photometric observations have been carried out at five observatories in five countries. We reached 30% time coverage in a 5 days interval centered on the suspected transit of HAT-P-13c. Two transits of HAT-P-13b were also observed. No transit of HAT-P-13c has been detected while the campaign was on. By a numerical experiment with 10^5 model systems we conclude that HAT-P-13c is not a transiting exoplanet with a significance level from 65% to 72%, depending on the planet parameters and the prior assumptions. We present two times of transit of HAT-P-13b ocurring at BJD 2455141.5522 +- 0.0010 and BJD 2455249.4508 +- 0.0020. The TTV of HAT-P-13b is consistent with zero within 0.001 days. The refined orbital period of HAT-P-13b is 2.916293 +- 0.000010 days.Comment: 5 pages, 4 figures, to be accepted by A&

    EI Eridani: a star under the influence -- The effect of magnetic activity in the short and long term

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    We use our photometric time series of more than forty years to analyze the long-term behaviour of EI Eri. Flare activity is investigated using space-borne photometric data obtained with TESS. The MUSICOS campaign aimed to achieve high-resolution spectroscopic observations from many sites around the globe, so that uninterrupted phase coverage of EI Eri became available. We use these data to reconstruct successive surface temperature maps of the star in order to study the changes of starspots on a very short timescale. We use long-term, seasonal period analysis of our photometric time series to study changes in the rotational period. Short-term Fourier-transform is also applied to look for activity cycle-like changes. We also study the phase and frequency distribution of hand-selected flares. We apply our multi-line Doppler imaging code to reconstruct four consecutive Doppler images. These images are also used to measure surface differential rotation by our cross-correlation technique. In addition, we carry out tests to demonstrate how Doppler imaging is affected by the fact that the data came from several different instruments with different spectral resolutions. Seasonal period analysis of the light curve reveals a smooth, significant change in period, possibly indicating the evolution of active latitudes. Temperature curves from B−VB-V and V−IV-I show slight differences, indicating the activity of EI Eri is spot dominated. Short-term Fourier transform reveals smoothly changing cycles between 4.5--5.5 and 8.9--11.6 years. The time-resolved spotted surface of EI Eri from Doppler imaging enabled us to follow the evolution of the different surface features. Cross-correlating the consecutive Doppler maps reveal surface shear of α=0.036±0.007\alpha=0.036\pm0.007. Our tests validate our approach and show that the surface temperature distribution is adequately reconstructed by our method.Comment: 14 pages, 13 figures, A&A accepte

    Antisolar differential rotation with surface lithium enrichment on the single K-giant V1192  Ori

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    Context: Stars with about 1−-2 solar masses at the red giant branch (RGB) represent an intriguing period of stellar evolution, i.e. when the convective envelope interacts with the fast-rotating core. During these mixing episodes freshly synthesized lithium can come up to the stellar surface along with high angular momentum material. This high angular momentum may alter the surface rotation pattern. Aims: The single rapidly rotating K-giant V1192 Ori is revisited to determine its surface differential rotation, lithium abundance, and basic stellar properties such as a precise rotation period. The aim is to independently verify the antisolar differential rotation of the star and possibly find a connection to the surface lithium abundance. Methods: We applied time-series Doppler imaging to a new multi-epoch data set. Altogether we reconstructed 11 Doppler images from spectroscopic data collected with the STELLA robotic telescope between 2007--2016. We used our inversion code iMap to reconstruct all stellar surface maps. We extracted the differential rotation from these images by tracing systematic spot migration as a function of stellar latitude from consecutive image cross-correlations. Results: The position of V1192 Ori in the Hertzsprung-Russell diagram suggests that the star is in the helium core-burning phase just leaving the RGB bump. We measure A(Li)NLTE=1.27A({\rm Li})_{\rm NLTE}=1.27, i.e. a value close to the anticipated transition value of 1.5 from Li-normal to Li-rich giants. Doppler images reveal extended dark areas arranged quasi-evenly along an equatorial belt. No cool polar spot is found during the investigated epoch. Spot displacements clearly suggest antisolar surface differential rotation with α=−0.11±0.02\alpha=-0.11\pm0.02 shear coefficient. Conclusions: The surface Li enrichment and the peculiar surface rotation pattern may indicate a common origin.Comment: Accepted for publication in Astronomy and Astrophysic

    A case of spinal tuberculosis from the Middle Ages in Transylvania (Romania)

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    Study Design: Case report. Objective: To characterise the paleopathology presented in the skeleton of a 45-50-year-old male indicative of tuberculous spondylitis and to confirm by the detection of ancient DNA. Summary of Background Data: Tuberculosis (TB) is an infectious disease prevalent in both present and ancient human populations. The disease is primarily located within the lungs, so although characacteristic bone lesions can lead to a clear diagnosis, skeletal TB occurs in only 5-6% of TB infections, even in historical cases. In addition, the visual appearance of human skeletal remains may be influenced by the environmental conditions at the burial site. However, it is important to recognise ancient skeletal TB, because this can provide important data on the history of Mycobacterium tuberculosis and gives an unique opportunity for physicians to observe the natural outcome of the infection from the pre-antibiotic era. Methods: Paleopathological analysis was carried out using careful visual observation supported by ancient DNA analysis. Approximately 60 mg of bone powder from rib fragments was examined and DNA from the M. tuberculosis complex was detected by PCR targeting specific genetic loci of the IS6110 and IS1081 regions. Results: The skeleton is part of a human osteoarchaeological collection (n=274) from the 12th-13th century Transylvanian archaeological site of Peteni, in modern-day Romania. The individual, a 45-50-year-old male, showed gross pathology typical of tuberculous spondylitis. The paleopathological diagnosis was supported by analysis for M. tuberculosis complex ancient DNA. Conclusions: This case demonstrates that TB was present in Transylvania (Romania) during the 12-13th century and adds to the growing body of knowledge on the history of this disease

    Hungarian Psychotherapists’ Experiences of the Cooperation with Spiritual Directors and Pastoral Counselors : A Qualitative Study

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    There has been a constantly growing interest towards the themes of psychotherapy and spirituality in the past decades. The questions and experiences concerning spirituality can come up and play an important role in the psychotherapeutic relationship. Often another helping relationship, spiritual direction or pastoral counseling is already present in religious people’s life, before or at the time of starting psychotherapy. In our research we tried to find answers to the question of how psychotherapists approach cooperation with spiritual directors and pastoral counselors, what attitudes and experiences they have in this regard. In the research semi-structured in-depth interviews were carried out with 31 Hungarian psychotherapists, and they were analyzed with the method of Grounded Theory. Four main categories evolved during the analysis of the interviews. In the first main category, where there is no cooperation between the helping professionals, codes refer to the attitudes, whether the psychotherapists would be open to cooperate, what professional considerations they would follow, and in what framework the cooperation could be realized. In the second main category the psychotherapist and the spiritual director work parallel with the patient, without contacting each-other, in the third the psychotherapist is in contact with the spiritual director/pastoral counselor, and in the fourth the psychotherapist evaluates the experiences of the cooperation

    Magnetic activity of the young solar analog V1358 Orinis

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    Context. Young, fast-rotating single stars can show dramatically different magnetic signatures and levels of magnetic activity as compared with the Sun. While losing angular momentum due to magnetic breaking and mass loss through stellar winds, the stars gradually spin down resulting in decreasing levels of activity. Studying magnetic activity on such solar analogues plays a key role in understanding the evolution of solar-like stars and allows a glimpse into the past of the Sun as well. Aims: In order to widen our knowledge of the magnetic evolution of the Sun and solar-like stars, magnetic activity of the young solar analog V1358 Ori is investigated. Methods: Fourier analysis of long-term photometric data is used to derive rotational period and activity cycle length, while spectral synthesis is applied to high-resolution spectroscopic data in order to derive precise astrophysical parameters. Doppler imaging is performed to recover surface-temperature maps for two subsequent intervals. Cross-correlation of the consecutive Doppler maps is used to derive surface differential rotation. The rotational modulation of the chromospheric activity indicators is also investigated. Results: An activity cycle of 1600 days is detected for V1358 Ori. Doppler imaging revealed a surface-temperature distribution dominated by a large polar cap with a few weaker features around the equator. This spot configuration is similar to other maps of young solar analogs from the literature, and supports recent model predictions. We detected solar-like surface differential rotation with a surface shear parameter of α = 0.016 ± 0.010, which is in close agreement with our recently proposed empirical relation between rotation and differential rotation. The chromospheric activity indicators showed rotational modulation
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