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9 papers found.
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Study of FK Comae Berenices - VII. Correlating photospheric and chromospheric activity

Aims. We study the connection between the chromospheric and photospheric behaviour of the active late-type star FK Comae. Methods. We use spot temperature modelling, light curve inversion based on narrow- and wide-band photometric measurements, Hα observations from 1997−2010, and Doppler maps from 2004−2010 to compare the behaviour of chromospheric and photospheric features...

High frame rate imaging based photometry - Photometric reduction of data from electron-multiplying charge coupled devices (EMCCDs)

Context. The EMCCD is a type of CCD that delivers fast readout times and negligible readout noise, making it an ideal detector for high frame rate applications which improve resolution, like lucky imaging or shift-and-add. This improvement in resolution can potentially improve the photometry of faint stars in extremely crowded fields significantly by alleviating crowding...

Strömgren photometry of the open clusters NGC 6134 and NGC 3680

We present Strömgren photometry of the two southern open clusters NGC 6134 and NGC 3680. The field of NGC 6134 was observed with different shifts of the telescope and rotations of the CCD camera in order to detect and remove any large scale flat field errors using the technique described by Andersen et al. (1995). By using calibrations of the Ström gren indices we find the...

Cam A: a new dwarf low-surface-brightness galaxy on the Local Group outskirts?

We present a deep I-band image of the nearby dwarf irregular galaxy Cam A obtained with the Nordic Optical Telescope with 0.6-arcsec seeing (FWHM). The distance to Cam A, DMW=1.9 Mpc, is estimated from the tip of the red giant branch seen at I=22.8±0.2 mag. The youngest stellar population of the galaxy seems to be of age about 100 Myr. Relying on its barycentric distance, DLG=1.6...

GRB afterglow studies at the Nordic Optical Telescope

Using the 2.56-m Nordic Optical Telescope (NOT) on La Palma we have observed most of the known optical afterglows to gamma-ray bursts (GRBs). We here briefly report on the discoveries of the optical afterglows of two recent SAX GRBs (GRB 980519 and GRB 980613) and the detection of their host galaxies. GRB 980519 was bright upon discovery () and occurred in a faint () galaxy...

Constraints on the optical afterglow emission of the short/hard burst GRB 010119

We report optical observations of the short/hard burst GRB 010119 error box, one of the smallest error boxes reported to date for short/hard GRBs. Limits of and are imposed by observations carried out 20.31 and 20.58 hours after the gamma-ray event, respectively. They represent the most constraining limits imposed to date on the optical emission from a short/hard gamma-ray burst...

An HST study of three very faint GRB host galaxies

A&A Astronomy & Astrophysics A. O. Jaunsen 3 M. I. Andersen 0 1 J. Hjorth 7 J. P. U. Fynbo 6 7 S. T. Holland 5 B. Thomsen 6 J. Gorosabel 4 8 9 B. E. Schaefer 2 G. Bjo¨ rnsson 11 P. Natarajan 12

GRB 090313: X-shooter's first shot at a gamma-ray burst

. Hjorth 10 R. A. M. J. Wijers 14 S. D'Odorico 9 F. Hammer 15 L. Kaper 14 P. Kjaergaard 4 S. Randich 5 M. I. Andersen 10 L. A. Antonelli 12 L. Christensen 9 P. D'Avanzo 8 F. Fiore 12 P. J. Groot 2 E