Szoláris és asztrofizikai magnetohidrodinamika = Solar and astrophysical magnetohydrodynamics

A pályázat az ELTE Csillagászati Tanszékén muködo szoláris magnetohidrodinamikai kutatócsoport működésének fo finanszírozási forrása. Itt két fontos eredményünket emeljük ki a 2007--2011 évekből. A naplégkör felső rétegeibe irányuló mechanikai energiatranszport és fűtés kérdése a mai napig nem tisztázott. Fontos empirikus megkötést sikerült adnunk ehhez a problémához azáltal, hogy keskenysávú, nagy felbontású H-alfa felvételek alapján oszcillációkat mutattunk ki a Nap fotoszférájában mágneses elemek egy csoportjában. Gondos elemzéssel kimutattuk, hogy az oszcillációk csak torziós Alfvén-hullámokként értelmezhetőek, melyek szögamplitúdója 22 fok. Ez az ilyen típusú hullámok jelenlétének eddigi legmeggyőzőbb bizonyítéka a Nap légkörében. Energiafluxusuk elegendő lehet a napkorona fűtéséhez is. A Nap-dinamó lehetséges működési mechanizmusai közül az egyik legnépszerűbb az ún. határfelületi dinamó. Ennek legegyszerűbb, s így a fontosabb effektusok kölcsönhatásába leginkább betekintést engedő leírása a Parker-féle analitikus határfelületi dinamómodell. Ennek további általánosításaként levezettük és grafikusan megoldottuk a felületi hullám viselkedését leíró diszperziós relációkat arra az esetre, ha a tachoklína véges vastagságú (szemben az eredeti modellel, ahol két félvégtelen réteg szerepel). Azt találtuk, hogy a véges rétegmélység hatása igen összetett, és a véges mélységű vízrétegen terjedő felületi hullámok analógiája nem alkalmazható. | The project has been the principal source of funding for the solar and astrophysical research group at the Department of Astronomy of Eötvös University. In this summary we just mention two key results of our research. The flow of energy through the solar atmosphere and the heating of the Sun's outer regions are still not understood. We could impose an important empirical constraint on this problem by detecting oscillatory phenomena associated with a large bright-point group. With careful analysis we have demontrated that these oscillations are the signature of Alfvén waves produced by a torsional twist of ±22 degrees. This is the most convincing evidence to date for the presence of such waves in the solar atmosphere. The energy flux associated with this wave mode is sufficient to heat the solar corona. One of the most widely duscussed scenarios for the solar dynamo is the so-called interface dynamo. We generalized Parker's analytic Cartesian interface dynamo to the case of a shear layer of finite thickness and low resistivity (""tachocline""), bounded by a perfect conductor (""radiative zone"") on the one side, and by a highly diffusive medium (""convective zone"") supporting an alpha-effect on the other side. We have found that the ffect of finite layer depth is quite complex and the analogy with surface waves on shallow water is not applicable

Lymphomatoid papulosis type B in a patient with Crohn\u27s disease treated with TNF-alpha inhibitors infliximab and adalimumab

No abstract availabl

A search for tight hierarchical triple systems amongst the eclipsing binaries in the CoRoT fields

We report a comprehensive search for hierarchical triple stellar system candidates amongst eclipsing binaries (EB) observed by the CoRoT spacecraft. We calculate and check eclipse timing variation (ETV) diagrams for almost 1500 EBs in an automated manner. We identify five relatively short-period Algol systems for which our combined light curve and complex ETV analyses (including both the light-travel time effect and short-term dynamical third-body perturbations) resulted in consistent third-body solutions. The computed periods of the outer bodies are between 82 and 272 days, (with an alternative solution of 831 days for one of the targets). We find that the inner and outer orbits are near coplanar in all but one case. The dynamical masses of the outer subsystems determined from the ETV analyses are consistent with both the results of our light curve analyses and the spectroscopic information available in the literature. One of our candidate systems exhibits outer eclipsing events as well, the locations of which are in good agreement with the ETV solution. We also report another certain triply eclipsing triple system which, however, is lacking a reliable ETV solution due to the very short time range of the data, and four new blended systems (composite light curves of 2 eclipsing binaries each), where we cannot decide whether the components are gravitationally binded or not. Amongst these blended systems we identify the longest period and highest eccentricity eclipsing binary in the entire CoRoT sample

Gaia Data Release 2 Variable stars in the colour-absolute magnitude diagram

Context. The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ≲ 21 mag. Aims: We showcase stellar variability in the Galactic colour-absolute magnitude diagram (CaMD). We focus on pulsating, eruptive, and cataclysmic variables, as well as on stars that exhibit variability that is due to rotation and eclipses. Methods: We describe the locations of variable star classes, variable object fractions, and typical variability amplitudes throughout the CaMD and show how variability-related changes in colour and brightness induce "motions". To do this, we use 22 months of calibrated photometric, spectro-photometric, and astrometric Gaia data of stars with a significant parallax. To ensure that a large variety of variable star classes populate the CaMD, we crossmatched Gaia sources with known variable stars. We also used the statistics and variability detection modules of the Gaia variability pipeline. Corrections for interstellar extinction are not implemented in this article. Results: Gaia enables the first investigation of Galactic variable star populations in the CaMD on a similar, if not larger, scale as was previously done in the Magellanic Clouds. Although the observed colours are not corrected for reddening, distinct regions are visible in which variable stars occur. We determine variable star fractions to within the current detection thresholds of Gaia. Finally, we report the most complete description of variability-induced motion within the CaMD to date. Conclusions: Gaia enables novel insights into variability phenomena for an unprecedented number of stars, which will benefit the understanding of stellar astrophysics. The CaMD of Galactic variable stars provides crucial information on physical origins of variability in a way that has previously only been accessible for Galactic star clusters or external galaxies. Future Gaia data releases will enable significant improvements over this preview by providing longer time series, more accurate astrometry, and additional data types (time series BP and RP spectra, RVS spectra, and radial velocities), all for much larger samples of stars. A movie associated to Fig. 11 is available at http://https://www.aanda.org.Data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A11

Absolute Distances to Nearby Type Ia Supernovae via Light Curve Fitting Methods

We present a comparative study of absolute distances to a sample of very nearby, bright Type Ia supernovae (SNe) derived from high cadence, high signal-to-noise, multi-band photometric data. Our sample consists of four SNe: 2012cg, 2012ht, 2013dy and 2014J. We present new homogeneous, high-cadence photometric data in Johnson-Cousins BVRI and Sloan g' r' i' z' bands taken from two sites (Piszkesteto and Baja, Hungary), and the light curves are analyzed with publicly available light curve fitters (MLCS2k2, SNooPy2 and SALT2.4). When comparing the best-fit parameters provided by the different codes, it is found that the distance moduli of moderately reddened SNe Ia agree within less than or similar to 0.2 mag, and the agreement is even better (less than or similar to 0.1 mag) for the highest signal-to-noise BVRI data. For the highly reddened SN 2014J the dispersion of the inferred distance moduli is slightly higher. These SN-based distances are in good agreement with the Cepheid distances to their host galaxies. We conclude that the current state-of-the-art light curve fitters for Type Ia SNe can provide consistent absolute distance moduli having less than similar to 0.1-0.2 mag uncertainty for nearby SNe. Still, there is room for future improvements to reach the desired similar to 0.05 mag accuracy in the absolute distance modulus

The continuing story of SN IIb 2013df: new optical and IR observations and analysis

This work has been supported by the Hungarian Scientific Research Fund (OTKA) Grants NN107637, K104607, K83790, and K113117. TS is supported by the OTKA Postdoctoral Fellowship PD112325. JCW’s Supernova group at the UT Austin is supported by NSF Grant AST 11-09881 grant. JMS is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1302771. KS and AP are supported by the ‘Lend¨ulet-2009’ Young Researchers Program and the LP2012-31 grant of the Hungarian Academy of Sciences, respectively; KS is also supported by the ESA PECS Contract no. 4000110889/14/NL/NDe.SN 2013df is a nearby Type IIb supernova that seems to be the spectroscopic twin of the well-known SN 1993J. Previous studies revealed many, but not all interesting properties of this event. Our goal was to add new understanding of both the early- and late-time phases of SN 2013df. Our spectral analysis is based on six optical spectra obtained with the 9.2 m Hobby-Eberly Telescope during the first month after explosion, complemented by a near-infrared spectrum. We applied the SYNAPPS spectral synthesis code to constrain the chemical composition and physical properties of the ejecta. A principal result is the identification of 'high-velocity' He i lines in the early spectra of SN 2013df, manifest as the blue component of the double-troughed profile at ~5650 Å. This finding, together with the lack of clear separation of H and He lines in velocity space, indicates that both H and He features form at the outer envelope during the early phases. We also obtained ground-based BVRI and g'r'i'z' photometric data up to +45 d and unfiltered measurements with the ROTSE-IIIb telescope up to +168 d. From the modelling of the early-time quasi-bolometric light curve, we find Mej ~ 3.2-4.6 M⊙ and Ekin ~ 2.6-2.8 × 1051 erg for the initial ejecta mass and the initial kinetic energy, respectively, which agree well with the values derived from the separate modelling of the light-curve tail. Late-time mid-infrared excess indicates circumstellar interaction starting ~1 yr after explosion, in accordance with previously published optical, X-ray, and radio data.Publisher PDFPeer reviewe

Activity of 50 Long-Period Comets Beyond 5.2 AU

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by afrho values >3--4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets