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G. Maciejewski,
D. Dimitrov,
M. Seeliger,
St. Raetz,
L. Bukowiecki,
M. Kitze,
R. Errmann,
G. Nowak,
A. Niedzielski,
V. Popov, [......],
G. Corfini,
H. Takahashi,
K. Tachihara,
J. M. Benko,
K. Sarneczky,
Gy. M. Szabo,
T. N. Varga,
M. Vanko,
Y. C. Joshi,
W. P. Chen
[show abstract]
[hide abstract]
ABSTRACT: The transiting planet WASP-12 b was identified as a potential target for
transit timing studies because a departure from a linear ephemeris was reported
in the literature. Such deviations could be caused by an additional planet in
the system. We attempt to confirm the existence of claimed variations in
transit timing and interpret its origin. We organised a multi-site campaign to
observe transits by WASP-12 b in three observing seasons, using 0.5-2.6-metre
telescopes. We obtained 61 transit light curves, many of them with
sub-millimagnitude precision. The simultaneous analysis of the best-quality
datasets allowed us to obtain refined system parameters, which agree with
values reported in previous studies. The residuals versus a linear ephemeris
reveal a possible periodic signal that may be approximated by a sinusoid with
an amplitude of 0.00068+/-0.00013 d and period of 500+/-20 orbital periods of
WASP-12 b. The joint analysis of timing data and published radial velocity
measurements results in a two-planet model which better explains observations
than single-planet scenarios. We hypothesize that WASP-12 b might be not the
only planet in the system and there might be the additional 0.1 M_Jup body on a
3.6-d eccentric orbit. A dynamical analysis indicates that the proposed
two-planet system is stable over long timescales.
Astronomy and Astrophysics 01/2013; · 4.59 Impact Factor
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The YETI Collaboration,
W. P. Chen,
S. C. -L. Hu,
R. Errmann,
Ch. Adam,
S. Baar,
A. Berndt,
L. Bukowiecki,
D. P. Dimitrov,
T. Eisenbeiß, [......],
C. Briceño,
R. Chini,
E. L. N. Jensen,
E. H. Nikogossian,
A. K. Pandey,
J. Sperauskas,
H. Takahashi,
F. M. Walter,
Z. -Y. Wu,
X. Zhou
[show abstract]
[hide abstract]
ABSTRACT: GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an
abrupt variable and to have a circumstellar disk with very active accretion.
Our monitoring observations in 2009-2011 revealed the star to show sporadic
flare events, each with brightening of < 0.5 mag lasting for days. These
brightening events, associated with a color change toward the blue, should
originate from an increased accretion activity. Moreover, the star also
underwent a brightness drop of ~1 mag lasting for about a month, during which
the star became bluer when fainter. Such brightness drops seem to have a
recurrence time scale of a year, as evidenced in our data and the photometric
behavior of GM Cep over a century. Between consecutive drops, the star
brightened gradually by about 1 mag and became blue at peak luminosity. We
propose that the drop is caused by obscuration of the central star by an
orbiting dust concentration. The UX Orionis type of activity in GM Cep
therefore exemplifies the disk inhomogeneity process in transition between
grain coagulation and planetesimal formation in a young circumstellar disk.
The Astrophysical Journal 03/2012; · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Recently, 60Fe was found in the Earth crust formed in a nearby recent
supernova (SN). If the distance to the SN and mass of the progenitor of that SN
was known, then one could constrain SN models. Knowing the positions, proper
motions, and distances of dozens of young nearby neutron stars, we can
determine their past flight paths and possible kinematic origin. Once the birth
place of a neutron star in a SN is found, we would have determined the distance
of the SN and the mass of the SN progenitor star.
11/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We try to constrain the Equation-of-State (EoS) of supra-nuclear-density
matter in neutron stars (NSs) by observations of nearby NSs. There are seven
thermally emitting NSs known from X-ray and optical observations, the so-called
Magnificent Seven (M7), which are young (up to few Myrs), nearby (within a few
hundred pc), and radio-quiet with blackbody-like X-ray spectra, so that we can
observe their surfaces. As bright X-ray sources, we can determine their
rotational (pulse) period and their period derivative from X-ray timing. From
XMM and/or Chandra X-ray spectra, we can determine their temperature. With
precise astrometric observations using the Hubble Space Telescope, we can
determine their parallax (i.e. distance) and optical flux. From flux, distance,
and temperature, one can derive the emitting area - with assumptions about the
atmosphere and/or temperature distribution on the surface. This was recently
done by us for the two brightest M7 NSs RXJ1856 and RXJ0720. Then, from
identifying absorption lines in X-ray spectra, one can also try to determine
gravitational redshift. Also, from rotational phase-resolved spectroscopy, we
have for the first time determined the compactness (mass/radius) of the M7 NS
RBS1223. If also applied to RXJ1856, radius (from luminosity and temperature)
and compactness (from X-ray data) will yield the mass and radius - for the
first time for an isolated single neutron star. We will present our
observations and recent results.
11/2011;
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M Moualla,
T ~O ~B Schmidt,
R Neuhäuser,
V ~V Hambaryan,
R Errmann,
L Trepl,
C Broeg,
T Eisenbeiss,
M Mugrauer,
C Marka, [......],
T Pribulla,
S Rätz,
J Schmidt,
A Berndt,
G Maciejewski,
T Röll, M ~M Hohle,
N Tetzlaff,
S Fiedler,
S Baar
[show abstract]
[hide abstract]
ABSTRACT: We present a new flare star, which was discovered during our survey on a
selected field at the edge of the Pleiades cluster. The field was observed in
the period 2007 - 2010 with three different CCD-cameras at the University
Observatory Jena with telescopes from 25 to 90 cm. The flare duration is almost
one hour with an amplitude in the R-band of about 1.08 mag. The location of the
flare star in a color-magnitude diagram is consistent with age and distance of
the Pleiades. In the optical PSF of the flare star there are two 2MASS objects
(unresolved in most images in the optical Jena PSF), so it is not yet known
which one of them is responsible for this flare. The BVRIJHK colors yield
spectral types of M1 and M2 with extinction being A_V=0.231+/-0.024 mag and
A_V=0.266+/-0.020 for those two stars, consistent with the Pleiades cluster.
Astronomische Nachrichten 08/2011; 332:661. · 1.01 Impact Factor
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S Raetz,
M Mugrauer,
T ~O ~B Schmidt,
T Roell,
T Eisenbeiss,
M Vav nko,
A Koeltzsch, M ~M Hohle,
C Ginski,
C Marka,
M Moualla,
N Tetzlaff,
A Reithe,
W Rammo,
S Fiedler,
J Koppenhoefer,
R Neuhäuser
European Physical Journal Web of Conferences; 07/2011
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R. Neuhäuser,
R. Errmann,
A. Berndt,
G. Maciejewski,
H. Takahashi,
W.P. Chen,
D.P. Dimitrov,
T. Pribulla,
E.H. Nikogossian,
E.L.N. Jensen, [......],
E. Schmidt, M.M. Hohle,
M. Kitze,
N. Chakrova,
C. Gräfe,
K. Schreyer,
V.V. Hambaryan,
C.H. Broeg,
J. Koppenhoefer,
A.K. Pandey
[show abstract]
[hide abstract]
ABSTRACT: We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6-m telescopes around the world to monitor continuously young (≤100 Myr), nearby (≤1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e.g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R = 16.5 mag with sufficient precision of 50 millimag rms (5 mmag rms down to R = 14.5 mag) to detect transits, so that we can expect at least about one young transiting object in this cluster. If we observe ∼10 similar clusters, we can expect to detect ∼10 young transiting planets with radius determinations. The precision given above is for a typical telescope of the YETI network, namely the 60/90-cm Jena telescope (similar brightness limit, namely within ±1 mag, for the others) so that planetary transits can be detected. For targets with a periodic transit-like light curve, we obtain spectroscopy to ensure that the star is young and that the transiting object can be sub-stellar; then, we obtain Adaptive Optics infrared images and spectra, to exclude other bright eclipsing stars in the (larger) optical PSF; we carry out other observations as needed to rule out other false positive scenarios; finally, we also perform spectroscopy to determine the mass of the transiting companion. For planets with mass and radius determinations, we can calculate the mean density and probe the internal structure. We aim to constrain planet formation models and their time-scales by discovering planets younger than ∼100 Myr and determining not only their orbital parameters, but also measuring their true masses and radii, which is possible so far only by the transit method. Here, we present an overview and first results (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 06/2011; 332(6):547 - 561. · 1.01 Impact Factor
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R. Neuhäuser,
R. Errmann,
A Berndt,
G. Maciejewski,
H Takahashi,
W P Chen,
D. P. Dimitrov,
T. Pribulla,
E. H. Nikogossian,
E. L. N. Jensen, [......],
E Schmidt, M. M. Hohle,
M. Kitze,
N. Chakrova,
C. Gräfe,
K. Schreyer,
V. V. Hambaryan,
C. H. Broeg,
J. Koppenhoefer,
A. K. Pandey
[show abstract]
[hide abstract]
ABSTRACT: We present the Young Exoplanet Transit Initiative (YETI), in which we use
several 0.2 to 2.6m telescopes around the world to monitor continuously young
(< 100 Myr), nearby (< 1 kpc) stellar clusters mainly to detect young
transiting planets (and to study other variability phenomena on time-scales
from minutes to years). The telescope network enables us to observe the targets
continuously for several days in order not to miss any transit. The runs are
typically one to two weeks long, about three runs per year per cluster in two
or three subsequent years for about ten clusters. There are thousands of stars
detectable in each field with several hundred known cluster members, e.g. in
the first cluster observed, Tr-37, a typical cluster for the YETI survey, there
are at least 469 known young stars detected in YETI data down to R=16.5 mag
with sufficient precision of 50 milli-mag rms (5 mmag rms down to R=14.5 mag)
to detect transits, so that we can expect at least about one young transiting
object in this cluster. If we observe 10 similar clusters, we can expect to
detect approximately 10 young transiting planets with radius determinations.
The precision given above is for a typical telescope of the YETI network,
namely the 60/90-cm Jena telescope (similar brightness limit, namely within
+/-1 mag, for the others) so that planetary transits can be detected. For
planets with mass and radius determinations, we can calculate the mean density
and probe the internal structure. We aim to constrain planet formation models
and their time-scales by discovering planets younger than 100 Myr and
determining not only their orbital parameters, but also measuring their true
masses and radii, which is possible so far only by the transit method. Here, we
present an overview and first results. (Abstract shortened)
06/2011;
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St. Raetz,
G. Maciejewski,
M. Mugrauer,
T. O. B. Schmidt,
T. Roell,
T. Eisenbeiss,
A Berndt, M. M. Hohle,
Ch. Ginski,
R. Errmann,
M. Seeliger,
Ch. Adam,
T. Pribulla,
N. Tetzlaff,
M. Vaňko,
J. Koppenhoefer,
M. Raetz,
R. Neuhäuser
[show abstract]
[hide abstract]
ABSTRACT: We report on our ongoing search for timing, duration, and depth variations in the exoplanet TrES-2. In Raetz et al. (2009) we already presented ten different transits obtained at the University Observatory Jena. Between November 2008 and August 2010 twelve additional transits could be observed. The timing, depth and duration of each individual event was analyzed and is presented here.
EPJ Web of Conferences. 01/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Traditionally, runaway stars are O- and B-type stars with large peculiar velocities. We would like to extend this definition to young stars (up to ≈50 Myr) of any spectral type and to identify those present in the Hipparcos catalogue by applying different selection criteria, such as peculiar space velocities or peculiar one-dimensional velocities. Runaway stars are important for studying the evolution of multiple star systems or star clusters, as well as for identifying the origins of neutron stars. We compile the distances, proper motions, spectral types, luminosity classes, V magnitudes and B−V colours, and we utilize evolutionary models from different authors to obtain star ages. We study a sample of 7663 young Hipparcos stars within 3 kpc from the Sun. The radial velocities are obtained from the literature. We investigate the distributions of the peculiar spatial velocity and the peculiar radial velocity as well as the peculiar tangential velocity and its one-dimensional components and we obtain runaway star probabilities for each star in the sample. In addition, we look for stars that are situated outside any OB association or OB cluster and the Galactic plane as well as stars for which the velocity vector points away from the median velocity vector of neighbouring stars or the surrounding local OB association/cluster (although the absolute velocity might be small). We find a total of 2547 runaway star candidates (with a contamination of normal Population I stars of 20 per cent at most). Thus, after subtracting these 20 per cent, the runaway frequency among young stars is about 27 per cent. We compile a catalogue of runaway stars, which is available via VizieR.
Monthly Notices of the Royal Astronomical Society 12/2010; 410(1):190 - 200. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Traditionally runaway stars are O and B type stars with large peculiar velocities.We want to extend this definition to young stars (up to ~50 Myr) of any spectral type and identify those present in the Hipparcos catalogue applying different selection criteria such as peculiar space velocities or peculiar one-dimensional velocities. Runaway stars are important to study the evolution of multiple star systems or star clusters as well as to identify origins of neutron stars. We compile distances, proper motions, spectral types, luminosity classes, V magnitudes and B-V colours and utilise evolutionary models from different authors to obtain star ages and study a sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Radial velocities are obtained from the literature. We investigate the distributions of the peculiar spatial velocity, the peculiar radial velocity as well as the peculiar tangential velocity and its one-dimensional components and obtain runaway star probabilities for each star in the sample. In addition, we look for stars that are situated outside any OB association or OB cluster and the Galactic plane as well as stars of which the velocity vector points away from the median velocity vector of neighbouring stars or the surrounding local OB association/ cluster although the absolute velocity might be small. We find a total of 2547 runaway star candidates (with a contamination of normal Population I stars of 20 per cent at most). Thus, after subtraction of those 20 per cent, the runaway frequency among young stars is about 27 per cent. We compile a catalogue of runaway stars which will be available via VizieR. Comment: 12 pages, 8 figures, 7 tables, accepted for publication in MNRAS old version replaced due to change of the title after journal proof-reading
07/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Massive stars are of interest as progenitors of supernovae, i.e. neutron stars and black holes, which can be sources of gravitational waves. Recent population synthesis models can predict neutron star and gravitational wave observations but deal with a fixed supernova rate or an assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernova progenitors, i.e. with O- and early B-type stars, and also all supergiants within 3 kpc. We restrict our sample to those massive stars detected both in 2MASS and observed by Hipparcos, i.e. only those stars with parallax and precise photometry. To determine the luminosities we calculated the extinctions from published multi-colour photometry, spectral types, luminosity class, all corrected for multiplicity and recently revised Hipparcos distances. We use luminosities and temperatures to estimate the masses and ages of these stars using different models from different authors. Having estimated the luminosities of all our stars within 3 kpc, in particular for all O- and early B-type stars, we have determined the median and mean luminosities for all spectral types for luminosity classes I, III, and V. Our luminosity values for supergiants deviate from earlier results: Previous work generally overestimates distances and luminosities compared to our data, this is likely due to Hipparcos parallaxes (generally more accurate and larger than previous ground-based data) and the fact that many massive stars have recently been resolved into multiples of lower masses and luminosities. From luminosities and effective temperatures we derived masses and ages using mass tracks and isochrones from different authors. From masses and ages we estimated lifetimes and derived a lower limit for the supernova rate of ≈20 events/Myr averaged over the next 10 Myr within 600 pc from the sun. These data are then used to search for areas in the sky with higher likelihood for a supernova or gravitational wave event (like OB associations) (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 03/2010; 331(4):349 - 360. · 1.01 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Since the first optical detection of RX J0720.4–3125 various observations have been performed to determine astrometric and photometric data. We present the first detection of the isolated neutron star in the V Bessel filter to study the spectral energy distribution and derive a new astrometric position. At ESO Paranal we obtained very deep images with FORS 1 (three hours exposure time) of RX J0720.4–3125 in the V Bessel filter in January 2008. We derive the visual magnitude by standard star aperture photometry. Using sophisticated resampling software we correct the images for field distortions. Then we derive an updated position and proper motion value by comparing its position with FORS 1 observations of December 2000. We calculate a visual magnitude of V = 26.81 ± 0.09 mag, which is seven times in excess of what is expected from X-ray data, but consistent with the extant U, B, and R data. Over about a seven year epoch difference we measured a proper motion of μ = 105.1 ± 7.4 mas yr–1 towards θ = 296.951° ± 0.0063° (NW), consistent with previous data (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 02/2010; 331(3):243 - 249. · 1.01 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Young isolated radio-quiet neutron stars are still hot enough to be detectable at X-ray and optical wavelengths due to their thermal emission and can hence probe cooling curves. An identification of their birth sites can constrain their age.For that reason, we try to identify the parent associations for four of the so-called Magnificent Seven neutron stars for which proper motion and distance estimates are available. We are tracing back in time each neutron star and possible birth association centre to find close encounters. The associated time of the encounter expresses the kinematic age of the neutron star which can be compared to its characteristic spin-down age. Owing to observational uncertainties in the input data, we use Monte Carlo simulations and evaluate the outcome of our calculations statistically.RX J1856.5−3754 most probably originated from the Upper Scorpius association about 0.3 Myr ago. RX J0720.4−3125 was either born in the young local association TW Hydrae about 0.4 Myr ago or in Trumpler 10 0.5 Myr in the past. Also RX J1605.3 + 3249 and RBS 1223 seem to come from a nearby young association such as the Scorpius-Centraurus complex or the extended Corona-Australis association. For RBS 1223 also a birth in Scutum OB2 is possible.We also give constraints on the observables as well as on the radial velocity of the neutron star. Given the birth association, its age and the flight time of the neutron star, we estimate the mass of the progenitor star.Some of the potential supernovae were located very nearby (<100 pc) and thus should have contributed to the 10Be and 60Fe material found in the Earth's crust.In addition, we reinvestigate the previously suggested neutron star/runaway pair PSR B1929+10/ζ Ophiuchi and conclude that it is very likely that both objects were ejected during the same supernova event.
Monthly Notices of the Royal Astronomical Society 02/2010; 402(4):2369 - 2387. · 4.90 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Among a sample of 140 OB associations and clusters, we want to identify probable parent associations for the Guitar pulsar (PSR B2224+65), which would then also constrain its age. For this purpose, we are using an Euler–Cauchy technique, treating the vertical component of the Galactic potential to calculate the trajectories of the pulsar and each association into the past. To include errors, we use Monte Carlo simulations varying the initial parameters within their error intervals. The whole range of possible pulsar radial velocities is taken into account during the simulations.We find that the Guitar pulsar most probably originated from the Cygnus OB3 association ≈0.8 Myr ago, inferring a current radial velocity of vr≈−30 km s−1, consistent with the inclination of its bow shock.
Monthly Notices of the Royal Astronomical Society Letters 11/2009; 400(1):L99 - L102.
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[show abstract]
[hide abstract]
ABSTRACT: We determine the Galactic production rate of strangelets as a canonical input to calculations of the measurable cosmic ray flux of strangelets by performing simulations of strange star mergers and combining the results with recent estimates of stellar binary populations. We find that the flux depends sensitively on the bag constant of the MIT bag model of QCD and disappears for high values of the bag constant and thus more compact strange stars. In the latter case, strange stars could coexist with ordinary neutron stars as they are not converted by the capture of cosmic ray strangelets. An unambiguous detection of an ordinary neutron star would then not rule out the strange matter hypothesis.
Physical Review Letters 08/2009; 103(1):011101. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this work we present detailed photometric results of the trapezium like galactic nearby OB clusters NGC 1502 and NGC 2169 carried out at the University Observatory Jena. We determined absolute BVRI magnitudes of the mostly resolved components using Landolt standard stars. This multi colour photometry enables us to estimate spectral type and absorption as well as the masses of the components, which were not available for most of the cluster members in the literature so far, using models of stellar evolution. Furthermore, we investigated the optical spectrum of the components ADS 2984A and SZ Cam of the sextuple system in NGC 1502. Our spectra clearly confirm the multiplicity of these components, which is the first investigation of this kind at the University Observatory Jena (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 05/2009; 330(5):511 - 517. · 1.01 Impact Factor
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St. Raetz,
M. Mugrauer,
T.O.B. Schmidt,
T. Roell,
T. Eisenbeiss, M.M. Hohle,
N. Tetzlaff,
M. Vaňko,
A. Seifahrt,
Ch. Broeg,
J. Koppenhoefer,
R. Neuhäuser
[show abstract]
[hide abstract]
ABSTRACT: We report on observations of transit events of the transiting planets XO-1b and TrES-1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO-1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)-Project- and Exoplanet Transit Database (ETD)-data, including our own I -band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R -band photometry of two transits of TrES-1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 05/2009; 330(5):475 - 481. · 1.01 Impact Factor
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St. Raetz,
M. Mugrauer,
T.O.B. Schmidt,
T. Roell,
T. Eisenbeiss, M.M. Hohle,
A. Koeltzsch,
M. Vaňko,
Ch. Ginski,
C. Marka,
M. Moualla,
N. Tetzlaff,
A. Seifahrt,
Ch. Broeg,
J. Koppenhoefer,
M. Raetz,
R. Neuhäuser
[show abstract]
[hide abstract]
ABSTRACT: We report on observations of several transit events of the transiting planet TrES-2 obtained with the Cassegrain-Teleskop-Kamera at the University Observatory Jena. Between March 2007 and November 2008 ten different transits and almost a complete orbital period were observed. Overall, in 40 nights of observation 4291 exposures (in total 71.52 h of observation) of the TrES-2 parent star were taken. With the transit timings for TrES-2 from the 34 events published by the TrES-network, the Transit Light Curve project and the Exoplanet Transit Database plus our own ten transits, we find that the orbital period is P = (2.470614 ± 0.000001) d, a slight change by ∼0.6 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we found a second dip after the transit which could either be due to a blended variable star or occultation of a second star or even an additional object in the system. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 05/2009; 330(5):459 - 468. · 1.01 Impact Factor
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T. Eisenbeiss,
M. Moualla,
M. Mugrauer,
T.O.B. Schmidt,
St. Raetz,
R. Neuhäuser,
Ch. Ginski, M.M. Hohle,
A. Koeltzsch,
C. Marka,
W. Rammo,
A. Reithe,
T. Roell,
M. Vaňko
[show abstract]
[hide abstract]
ABSTRACT: We have performed deep, wide-field imaging on a ∼0.4 deg2 field in the Pleiades (Melotte 22). The selected field was not yet target of a deep search for low mass stars and brown dwarfs. Our limiting magnitudes are R ∼ 22 mag and I ∼ 20 mag, sufficient to detect brown dwarf candidates down to 40 MJ. We found 197 objects, whose location in the (I, R – I) color magnitude diagram is consistent with the age and the distance of the Pleiades. Using CTK R and I as well as JHK photometry from our data and the 2MASS survey we were able to identify 7 new brown dwarf candidates. We present our data reduction technique, which enables us to resample, calibrate, and co-add many images by just two steps. We estimate the interstellar extinction and the spectral type from our optical and the NIR data using a two-dimensional χ2 fitting (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Astronomische Nachrichten 05/2009; 330(5):439 - 458. · 1.01 Impact Factor
