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Structure and variability in the corona of the ultrafast rotator LO Pegasi
Schmitt, J. H. M. M.; Singh, K. P.; Lalitha, S.
Context. Low-mass ultrafast rotators show the typical signatures of magnetic activity and are known to produce flares, probably as a result of magnetic reconnection. As a consequence, the coronae of these stars exhibit very large X-ray luminosities and high plasma temperatures, as well as a pronounced inverse FIP effect.
Aims: To probe the re…
Young, active radio stars in the AB Doradus moving group
Ros, E.; Hormuth, F.; Ortiz, J. L. +5 more
Context. Precise determination of stellar masses is necessary to test the validity of pre-main-sequence (PMS) stellar evolutionary models, whose predictions are in disagreement with measurements for masses below 1.2 M⊙. To improve such a test, and based on our previous studies, we selected the AB Doradus moving group (AB Dor-MG) as the …
Gaia and VLT astrometry of faint stars: Precision of Gaia DR1 positions and updated VLT parallaxes of ultracool dwarfs
Sahlmann, J.; Lazorenko, P. F.
Aims: We compared positions of the Gaia first data release (DR1) secondary data set at its faint limit with CCD positions of stars in 20 fields observed with the Very Large Telescope (VLT) FORS2. We aim at an independent verification of the DR1 astrometric precision taking advantage of the FORS2 position uncertainties which are smaller than o…
Reconstructing the cosmic Horseshoe gravitational lens using the singular perturbative approach.
Alard, C.
The reconstruction of the cosmic horseshoe gravitational lens using the perturbative method reveals the presence of significant third-order terms. The presence of these higher order terms is apparent in the numerical expansion of the perturbative fields in Fourier series. The expansion of the fields at order 2 produces a higher value of the chi-sq…
Formation of Radio Type II Bursts During a Multiple Coronal Mass Ejection Event
Valtonen, Eino; Pohjolainen, Silja; Al-Hamadani, Firas
We study the solar event on 27 September 2001 that consisted of three consecutive coronal mass ejections (CMEs) originating from the same active region, which were associated with several periods of radio type II burst emission at decameter-hectometer (DH) wavelengths. Our analysis shows that the first radio burst originated from a low-density env…
Photometric and spectroscopic variability of the B5IIIe star HD 171219
Poretti, E.; Rainer, M.; Uytterhoeven, K. +11 more
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show, or have shown at some epoch, Balmer lines in emission and an infrared excess.…
Statistical survey of day-side magnetospheric current flow using Cluster observations: magnetopause
Fornaçon, Karl-Heinz; Glassmeier, Karl-Heinz; Liebert, Evelyn +2 more
We present a statistical survey of current structures observed by the Cluster spacecraft at high-latitude day-side magnetopause encounters in the close vicinity of the polar cusps. Making use of the curlometer technique and the fluxgate magnetometer data, we calculate the 3-D current densities and investigate the magnetopause current direction, lo…
Dual E × B flow responses in the dayside ionosphere to a sudden IMF By rotation
Trattner, K. J.; Eriksson, S.; Baker, J. B. H. +3 more
We report for the first time a dual transition state in the dayside ionosphere following a sudden rotation of the interplanetary magnetic field (IMF) in the upstream magnetosheath from IMF <fi>B</fi><fi>y</fi> < 0 to <fi>B</fi><fi>y</fi> > 0 during <fi>B</fi>
The dusty silhouette jet HH 1019 in the Carina Nebula
Smith, Nathan; Bally, John; Reiter, Megan +1 more
We report the discovery in Hubble Space Telescope (HST) images of the new Herbig-Haro jet, HH 1019, located near the Tr 14 cluster in the Carina Nebula. Like other HH jets in the region, this bipolar collimated flow emerges from the head of a dark dust pillar. However, HH 1019 is unique because - unlike all other HH jets known to date - it is iden…
A deep staring campaign in the σ Orionis cluster. Variability in substellar members
Eislöffel, J.; Scholz, A.; Jayawardhana, R. +2 more
Context. The young star cluster near σ Orionis is one of the primary environments to study the properties of young brown dwarfs down to masses comparable to those of giant planets.
Aims: Deep optical imaging is used to study time-domain properties of young brown dwarfs over typical rotational timescales and to search for new substellar and pl…