410 research outputs found
Grid Integration of Robotic Telescopes
Robotic telescopes and grid technology have made significant progress in
recent years. Both innovations offer important advantages over conventional
technologies, particularly in combination with one another. Here, we introduce
robotic telescopes used by the Astrophysical Institute Potsdam as ideal
instruments for building a robotic telescope network. We also discuss the grid
architecture and protocols facilitating the network integration that is being
developed by the German AstroGrid-D project. Finally, we present three user
interfaces employed for this purpose.Comment: 4 pages, 5 Figures, refereed proceedings of "Hot-wiring the Transient
Universe", June 2007 (Tucson); version 2 including latex geometry package as
recommended by arXiv and minor changes as requested by AN except removal of
two figure
Robotic observations of the most eccentric spectroscopic binary in the sky
The visual A component of the Gliese 586AB system is a double-lined
spectroscopic binary consisting of two cool stars with the exceptional orbital
eccentricity of 0.976. Such an extremely eccentric system may be important for
our understanding of low-mass binary formation. We present a total of 598
high-resolution echelle spectra from our robotic facility STELLA from 2006-2012
which we used to compute orbital elements of unprecedented accuracy. The orbit
constrains the eccentricity to 0.97608+/-0.00004 and the orbital period to
889.8195+/-0.0003d. The masses of the two components are 0.87+/-0.05 Msun and
0.58+/-0.03 Msun if the inclination is 5+/-1.5degr as determined from
adaptive-optics images, that is good to only 6% due to the error of the
inclination although the minimum masses reached a precision of 0.3%. The flux
ratio Aa:Ab in the optical is betwee n 30:1 in Johnson-B and 11:1 in I. Radial
velocities of the visual B-component (K0-1V) appear constant to within 130 m/s
over six years. Sinusoidal modulations of Teff of Aa with an amplitude of apprx
55 K are seen with the orbital period. Component Aa appears warmest at
periastron and coolest at apastron, indicating atmospheric changes induced by
the high orbital eccentricity. No light variations larger than approximately 4
mmag are detected for A, while a photometric period of 8.5+/-0.2 d with an
amplitude of 7 mmag is discovered for the active star B, which we interpret to
be its rotation period. We estimate an orbital period of approx 50,000 yr for
the AB system. The most likely age of the AB system is >=2 Gyr, while the
activity of the B component, if it were a single star, would imply 0.5 Gyr.
Both Aa and B are matched with single-star evolutionary tracks of their
respective mass
Three years of experience with the STELLA robotic observatory
Since May 2006, the two STELLA robotic telescopes at the Izana observatory in
Tenerife, Spain, delivered an almost uninterrupted stream of scientific data.
To achieve such a high level of autonomous operation, the replacement of all
troubleshooting skills of a regular observer in software was required. Care
must be taken on error handling issues and on robustness of the algorithms
used. In the current paper, we summarize the approaches we followed in the
STELLA observatory
Long-term photometry of three active red giants in close binary systems: V2253 Oph, IT Com and IS Vir
We present and analyze long-term optical photometric measurements of the
three active stars V2253 Oph, IT Com and IS Vir. All three systems are
single-lined spectroscopic binaries with an early K giant as primary component
but in different stages of orbital-rotational synchronization. Our photometry
is supplemented by 2MASS and WISE near-IR and mid-IR magnitudes and then used
to obtain more accurate effective temperatures and extinctions. For V2253 Oph
and IT Com, we found their spectral energy distributions consistent with pure
photospheric emission. For IS Vir, we detect a marginal mid-IR excess which
hints towards a dust disk. The orbital and rotational planes of IT Com appear
to be coplanar, contrary to previous findings in the literature. We apply a
multiple frequency analysis technique to determine photometric periods, and
possibly changes of periods, ranging from days to decades. New rotational
periods of 21.55+-0.03d, 65.1+-0.3d, and 23.50+-0.04d were determined for V2253
Oph, IT Com, and IS Vir, respectively. Splitting of these periods led to
tentative detections of differential surface rotations of delta P/P ~0.02 for
V2253 Oph and 0.07 for IT Com. Using a time-frequency technique based on
short-term Fourier transforms we present evidence of cyclic light variations of
length ~10yrs for V2253 Oph and 5-6yrs for IS Vir. A single flip-flop event has
been observed for IT Com of duration 2-3yrs. Its exchange of the dominant
active longitude had happened close to a time of periastron passage, suggesting
some response of the magnetic activity from the orbital dynamics. The 21.55-d
rotational modulation of V2253 Oph showed phase coherence also with the orbital
period, which is 15 times longer than the rotational period, thus also
indicating a tidal feedback with the stellar magnetic activity.Comment: 13 pages, 14 figures, accepted to A
Lithium enrichment on the single active K1-giant DI Piscium -- Possible joint origin of differential rotation and Li enrichment
We investigate the surface spot activity of the rapidly rotating,
lithium-rich active single K-giant DI Psc to measure the surface differential
rotation and understand the mechanisms behind the Li-enrichment. Doppler
imaging was applied to recover the surface temperature distribution of DI Psc
in two subsequent rotational cycles using the individual mapping lines Ca I
6439, Fe I 6430, Fe I 6421 and Li I 6708. Surface differential rotation was
derived by cross-correlation of the subsequent maps. Difference maps are
produced to study the uniformity of Li-enrichment on the surface. These maps
are compared with the rotational modulation of the Li I 6708 line equivalent
width. Doppler images obtained for the Ca and Fe mapping lines agree well and
reveal strong polar spottedness, as well as cool features at lower latitudes.
Cross-correlating the consecutive maps yields antisolar differential rotation
with shear coefficient -0.083 +- 0.021. The difference of the average and the
Li maps indicates that the lithium abundance is non-activity related. There is
also a significant rotational modulation of the Li equivalent width.Comment: 8 pages, 7 figures, accepted in A&
Reading Immanence
The following text opened the conference, “The Concept of Immanence in Philosophy and the Arts”, held in Vienna in May 2016. It is a reader consisting of key passages on immanence by Gilles Deleuze, Baruch de Spinoza, Giorgio Agamben, Henri Bergson, François Laruelle, Antonin Artaud and Friedrich Nietzsche. The reader was put together by Arno Böhler and Elisabeth Schäfer, and a collage of its content arranged by Susanne Valerie Granzer, who read out these text fragments at the start of the conference. Her reading was sporadically interrupted by Alice Lagaay, whose comments served to draw lines of connection between the dense theoretical texts and the performative immanent context in which they were being read and digested—the context of the conference. We present here the readings and their lighthearted—and at times deadly serious—commentary as performed. Readers are invited to imagine and re-enact the live-ness of this event, letting their own comments, questions and musings interrupt the proposed interruptions of reading
Reading Immanence
The following text opened the conference, “The Concept of Immanence in Philosophy and the Arts”, held in Vienna in May 2016. It is a reader consisting of key passages on immanence by Gilles Deleuze, Baruch de Spinoza, Giorgio Agamben, Henri Bergson, François Laruelle, Antonin Artaud and Friedrich Nietzsche. The reader was put together by Arno Böhler and Elisabeth Schäfer, and a collage of its content arranged by Susanne Valerie Granzer, who read out these text fragments at the start of the conference. Her reading was sporadically interrupted by Alice Lagaay, whose comments served to draw lines of connection between the dense theoretical texts and the performative immanent context in which they were being read and digested—the context of the conference. We present here the readings and their lighthearted—and at times deadly serious—commentary as performed. Readers are invited to imagine and re-enact the live-ness of this event, letting their own comments, questions and musings interrupt the proposed interruptions of reading
Stellar rotation, binarity, and lithium in the open cluster IC4756
An important aspect in the evolutionary scenario of cool stars is their
rotation and the rotationally induced magnetic activity and interior mixing.
Stars in open clusters are particularly useful tracers for these aspects
because of their known ages. We aim to characterize the open cluster IC4756 and
measure stellar rotation periods and surface differential rotation for a sample
of its member stars. Thirty-seven cluster stars were observed continuously with
the CoRoT satellite for 78 days in 2010. Follow-up high-resolution spectroscopy
of the CoRoT targets and deep Str\"omgren and H photometry
of the entire cluster were obtained with our robotic STELLA facility and its
echelle spectrograph and wide-field imager, respectively. We determined
high-precision photometric periods for 27 of the 37 CoRoT targets and found
values between 0.155 and 11.4 days. Twenty of these are rotation periods.
Twelve targets are spectroscopic binaries of which 11 were previously unknown;
orbits are given for six of them. Six targets were found that show evidence of
differential rotation with in the range 0.04-0.15. Five
stars are non-radially pulsating stars with fundamental periods of below 1d,
two stars are semi-contact binaries, and one target is a micro-flaring star
that also shows rotational modulation. Nine stars in total were not considered
members because of much redder color(s) and deviant radial velocities with
respect to the cluster mean. H photometry indicates that the cluster
ensemble does not contain magnetically over-active stars. The cluster average
metallicity is -0.080.06 (rms) and its logarithmic lithium abundance for
12 G-dwarf stars is 2.390.17 (rms). [...]Comment: A&A, in pres
Recommended from our members
Three years of experience with the STELLA robotic observatory
Since May 2006, the two STELLA robotic telescopes at the Izaa observatory in Tenerife, Spain, delivered an almost uninterrupted stream of scientific data. To achieve such a high level of autonomous operation, the replacement of all troubleshooting skills of a regular observer in software was required. Care must be taken on error handling issues and on robustness of the algorithms used. In the current paper, we summarize the approaches we followed in the STELLA observatory. Copyright © 2010 Thomas Granzer et al
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