Pedro A. Szekely

ESC and KAIT observations of the transitional type Ia SN 2004eo

We present optical and infrared observations of the unusual Type Ia supernova (SN) 2004eo. The light curves and spectra closely resemble those of the prototypical SN 1992A, and the luminosity at ma ...

The Dwarf project: Eclipsing binaries – precise clocks to discover exoplanets

We present a new observational campaign, Dwarf, aimed at detection of circumbinary extrasolar planets using the timing of the minima of low-mass eclipsing binaries. The observations will be performed within an extensive network of relatively small to medium-size telescopes with apertures of similar to 20-200 cm. The starting sample of the objects to be monitored contains (i) low-mass eclipsing binaries with M and K components, (ii) short-period binaries with a sdB or sdO component, and (iii) post-common-envelope systems containing a WD, which enable to determine minima with high precision. Since the amplitude of the timing signal increases with the orbital period of an invisible third component, the timescale of the project is long, at least 5-10 years. The paper gives simple formulas to estimate the suitability of individual eclipsing binaries for the circumbinary planet detection. Intrinsic variability of the binaries (photospheric spots, flares, pulsation etc.) limiting the accuracy of the minima timing is also discussed. The manuscript also describes the best observing strategy and methods to detect cyclic timing variability in the minima times indicating the presence of circumbinary planets. First test observations of the selected targets are presented ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A Wide-Field Kinematic Survey for Tidal Tails around Five Globular Clusters

Using the AAOmega instrument of the Anglo-Australian Telescope, we have obtained medium-resolution near-infrared spectra of 10,500 stars in 2? fields centered on the galactic globular clusters 47 Tuc, NGC 288, M12, M30, and M55. Radial velocities and equivalent widths of the infrared Ca II triplet lines have been determined to constrain cluster membership, which in turn has been used to study the angular extent of the clusters. From the analysis of 140-1000 member stars in each cluster, we do not find extended structures that go beyond the tidal radii. For three cluster we estimate a 1% upper limit of extratidal red giant branch stars. We detect systemic rotation in 47 Tuc and M55.

New clues on outburst mechanisms and improved spectroscopic elements of the black hole binary V4641 Sagittarii

We present spectroscopic observations of the black hole binary V4641 Sagittarii, obtained between 2004 July 4 and 2005 March 28, which cover the minor outburst of the star in early 2004 July and quiescence variations on 19 nights scattered over six months. During the outburst, the star peaked approximately 3 mag brighter than usual, and our spectra were dominated by broad hydrogen, helium and iron emission lines. The very first spectra showed P Cygni profiles, which disappeared within a few hours, indicating rapid changes in matter ejection. The Hα line had multiple components, one being a broad blueshifted wing exceeding 5000 km s -1 . During a simultaneously observed 10-min photometric flare up, the equivalent width of the Ha line temporarily decreased, implying that it was a flare of the continuum. The overall spectral appearance was similar to that observed in the 1999 September active phase, which suggests that similar mass-ejection processes were associated with both eruptions. In quiescence, the spectra were those of the early-type secondary star showing its orbital motion around the primary. By measuring cross-correlation radial velocities, we give an improved set of spectroscopic elements. Whereas we measure the same velocity amplitude (K 2 = 211.3 ± 1.0 km s -1 ), within errors, as Orosz et al., our centre-of-mass velocity (y = 72.7 ± 3.3 km s -1 ) differs significantly from the previously published value (107.4 ± 2.9 km s -1 ). However, we find evidence that the difference is caused by a systematic error in data reduction in the previous study, rather than by gravitational effects of an invisible third component.

CCD photometry of 23 minor planets

Abstract We present CCD photometric observations of 23 main-belt asteroids, of which 8 have never been observed before; thus, the data of these objects are the first in the literature. The majority showed well-detectable light variations, exceeding 0 m . h 1. We have determined synodic periods for 756 Lilliana (9 . h 36), 1270 Datura (3 . h 4), 1400 Tirela (13 . h 36), 1503 Kuopio (9 . h 98), 3682 Welther (3 . h 59), 7505 Furushu (4 . h 14) and 11436 1969 QR (12 . h 3), while uncertain period estimates were possible for 469 Argentina (12 . h 3), 546 Herodias (10 . h 4) and 1026 Ingrid (5 . h 3). The shape of the lightcurves of 3682 Welther changed on a short time-scale and showed dimmings that might be attributed to eclipses in a binary system. For the remaining objects, only lower limits of the periods and amplitudes were concluded.

Radial velocities of five globular clusters obtained with AAOmega

Using the recently commissioned multi-object spectrograph AAOmega on the 3.9m AAT we have obtained mediumresolution near-infrared spectra for 10 500 stars in and around five southern globular clusters. The targets were 47 Tuc, M12, M30, M55 and NGC 288. We have measured radial velocities to ± 1 kms- 1 with the cross correlation method and estimated metallicity, effective temperature, surface gravity and rotational velocity for each star by fitting synthetic model spectra. An analysis of the velocity maps and velocity dispersion of member stars revealed systemic rotation in four of the target clusters. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photometry of SN 2002bo with template image subtraction

VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template frame was necessary to obtain reliable photometry. We used a template frame of NGC 3190 taken during the course of our galaxy imaging project, fortunately, just a few days before SN 2002bo was discovered. The aim of this project is to collect template frames of nearby galaxies that are potential hosts of bright SNe. Subtraction of pre-SN images helped us to exclude the background light contamination of the host galaxy. The maximum occurred at JD 2 452 346, with maximal V brightness of 13: m 58. MLCS analysis led to T0(B)= JD 2 452 346:1 0:8 (fiducial B-