521 research outputs found
SAOLIM, a prototype of a low cost System for Adaptive Optics with Lucky Imaging
A prototype of a low cost Adaptive Optics (AO) system has been developed at
the Instituto de Astrofisica de Andalucia (CSIC) and tested at the 2.2m
telescope of the Calar Alto observatory. We present here the status of the
project, which includes the image stabilization system and compensation of high
order wavefront aberrations with a membrane deformable mirror. The image
stabilization system consists of magnet driven tip-tilt mirror. The higher
order compensation system comprises of a Shack-Hartmann sensor, a membrane
deformable mirror with 39 actuators and the control computer that allows
operations up to 420Hz in closed loop mode. We have successfully closed the
high order AO loop on natural guide stars. An improvement of 4 times in terms
of FWHM was achieved. The description and the results obtained on the sky are
presented in this paper.Comment: Accepted for publishing in PASP, 11 pages, 14 figures, 6 table
Lunar impact flashes from Geminids, analysis of luminous efficiencies and the flux of large meteoroids on Earth
We analyze lunar impact flashes recorded by our team during runs in December
2007, 2011, 2013 and 2014. In total, 12 impact flashes with magnitudes ranging
between 7.1 and 9.3 in V band were identified. From these, 9 events could be
linked to the Geminid stream. Using these observations the ratio of luminous
energy emitted in the flashes with respect to the kinetic energy of the
impactors for meteoroids of the Geminid stream is estimated. By making use of
the known Geminids meteoroid flux on Earth we found this ratio to be
2.1x10 on average. We compare this luminous efficiency with other
estimations derived in the past for other meteoroid streams and also compare it
with other estimations that we present here for the first time by making use of
crater diameter measurements. We think that the luminous efficiency has to be
revised downward, not upward, at least for sporadic impacts. This implies an
increase in the influx of kilogram-sized and larger bodies on Earth that has
been derived thus far through the lunar impact flash monitoring technique
PYRAMIR: Calibration and operation of a pyramid near-infrared wavefront sensor
The concept of pyramid wavefront sensors (PWFS) has been around about a
decade by now. However, there is still a great lack of characterizing
measurements that allow the best operation of such a system under real life
conditions at an astronomical telescope. In this article we, therefore,
investigate the behavior and robustness of the pyramid infrared wavefront
sensor PYRAMIR mounted at the 3.5 m telescope at the Calar Alto Observatory
under the influence of different error sources both intrinsic to the sensor,
and arising in the preceding optical system. The intrinsic errors include
diffraction effects on the pyramid edges and detector read out noise. The
external imperfections consist of a Gaussian profile in the intensity
distribution in the pupil plane during calibration, the effect of an optically
resolved reference source, and noncommon-path aberrations. We investigated the
effect of three differently sized reference sources on the calibration of the
PWFS. For the noncommon-path aberrations the quality of the response of the
system is quantified in terms of modal cross talk and aliasing. We investigate
the special behavior of the system regarding tip-tilt control. From our
measurements we derive the method to optimize the calibration procedure and the
setup of a PWFS adaptive optics (AO) system. We also calculate the total
wavefront error arising from aliasing, modal cross talk, measurement error, and
fitting error in order to optimize the number of calibrated modes for on-sky
operations. These measurements result in a prediction of on-sky performance for
various conditions
An All Sky Transmission Monitor: ASTMON
We present here the All Sky Transmission MONitor (ASTMON), designed to
perform a continuous monitoring of the surface brightness of the complete
night-sky in several bands. The data acquired are used to derive, in addition,
a subsequent map of the multiband atmospheric extinction at any location in the
sky, and a map of the cloud coverage. The instrument has been manufactured to
afford extreme weather conditions, and remain operative. Designed to be fully
robotic, it is ideal to be installed outdoors, as a permanent monitoring
station. The preliminary results based on two of the currently operative units
(at Do\~nana National Park - Huelva- and at the Calar Alto Observatory -
Almer\'ia -, in Spain), are presented here. The parameters derived using ASTMON
are in good agreement with previously reported ones, what illustrates the
validity of the design and the accuracy of the manufacturing. The information
provided by this instrument will be presented in forthcoming articles, once we
have accumulated a statistically amount of data.Comment: 12 Figures, Accepted for publishing in PAS
CAFE: Calar Alto Fiber-fed Echelle spectrograph
We present here CAFE, the Calar Alto Fiber-fed Echelle spectrograph, a new
instrument built at the Centro Astronomico Hispano Alem\'an (CAHA). CAFE is a
single fiber, high-resolution (70000) spectrograph, covering the
wavelength range between 3650-9800\AA. It was built on the basis of the common
design for Echelle spectrographs. Its main aim is to measure radial velocities
of stellar objects up to 13-14 mag with a precision as good as a few
tens of . To achieve this goal the design was simplified at maximum,
removing all possible movable components, the central wavelength is fixed, so
the wavelentgth coverage; no filter wheel, one slit and so on, with a
particular care taken in the thermal and mechanical stability. The instrument
is fully operational and publically accessible at the 2.2m telescope of the
Calar Alto Observatory.
In this article we describe (i) the design, summarizing its manufacturing
phase; (ii) characterize the main properties of the instrument; (iii) describe
the reduction pipeline; and (iv) show the results from the first light and
commissioning runs. The preliminar results indicate that the instrument fulfill
the specifications and it can achieve the foreseen goals. In particular, they
show that the instrument is more efficient than anticipated, reaching a
20 for a stellar object as faint as 14.5 mag in 2700s
integration time. The instrument is a wonderful machine for exoplanetary
research (by studying large samples of possible systems cotaining massive
planets), galactic dynamics (high precise radial velocities in moving groups or
stellar associations) or astrochemistry.Comment: 12 pages, 23 figures; Acepted for publishing in A&A, 201
The initial human settlement of Northwest South America during the Pleistocene/Holocene transition: Synthesis and perspectives
The northwestern corner of South America, represented by the current territory of Colombia, is a key region to asses some relevant issues linked with the initial human peopling of the area, including population dispersals, cultural diversity, and early adaptations to the changing environmental conditions experienced by lowland and highland north-Andean Neotropical ecosystems at the Pleistocene/Holocene transition. The aim of this paper is to present a synthesis of the archaeological research about early peopling carried out in Northwest South America during the last four decades. Specifically, it will focus on the adaptive strategies and the cultural diversity patterns exhibited by the early hunter-gatherer groups that entered the region since late Pleistocene times. The classic ideas about the time of arrival of the first settlers, the dispersal routes, the incidence of the climate change in on the rate of dispersal and colonization of different habitats, and the role of the megafauna in the subsistence will be reviewed, prior to the formulation of new hypotheses about the meaning of the apparent intraregional diversity of the archaeological record and the evolution of economic strategies over time.Fil: Aceituno, Francisco J.. Universidad de Antioquia; ColombiaFil: Loaiza, Nicolás. Universidad de Antioquia; Colombia. Temple University; Estados UnidosFil: Delgado Burbano, Miguel Eduardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Barrientos, Gustavo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin
No variations in transit times for Qatar-1 b
The transiting hot Jupiter planet Qatar-1 b was presented to exhibit
variations in transit times that could be of perturbative nature. A hot Jupiter
with a planetary companion on a nearby orbit would constitute an unprecedented
planetary configuration, important for theories of formation and evolution of
planetary systems. We performed a photometric follow-up campaign to confirm or
refute transit timing variations. We extend the baseline of transit
observations by acquiring 18 new transit light curves acquired with 0.6-2.0 m
telescopes. These photometric time series, together with data available in the
literature, were analyzed in a homogenous way to derive reliable transit
parameters and their uncertainties. We show that the dataset of transit times
is consistent with a linear ephemeris leaving no hint for any periodic
variations with a range of 1 min. We find no compelling evidence for the
existence of a close-in planetary companion to Qatar-1 b. This finding is in
line with a paradigm that hot Jupiters are not components of compact
multi-planetary systems. Based on dynamical simulations, we place tighter
constraints on a mass of any fictitious nearby planet in the system.
Furthermore, new transit light curves allowed us to redetermine system
parameters with the precision better than that reported in previous studies.
Our values generally agree with previous determinations.Comment: Accepted for publication in A&
The night-sky at the Calar Alto Observatory II: The sky at the near infrared
We present here the characterization of the night sky-brightness at the
near-infrared, the telescope seeing, and the fraction of useful time at the
Calar Alto observatory. For this study we have collected a large dataset
comprising 7311 near-infrared images taken regularly along the last four years
for the ALHAMBRA survey (J, H and Ks-bands), together with a more reduced
dataset of additional near-infrared images taken for the current study. In
addition we collected the information derived by the meteorological station at
the observatory during the last 10 years, together with the results from the
cloud sensor for the last ~2 years. We analyze the dependency of the
near-infrared night sky-brightness with the airmass and the seasons, studying
its origins and proposing a zenithal correction. A strong correlation is found
between the night sky-brightness in the Ks-band and the air temperature, with a
gradient of ~ -0.08 mag per 1 C degree. The typical (darkest) night
sky-brightness in the J, H and Ks-band are 15.95 mag (16.95 mag), 13.99 mag
(14.98 mag) and 12.39 mag (13.55 mag), respectively. These values show that
Calar Alto is as dark in the near-infrared as most of the other astronomical
astronomical sites in the world that we could compare with. Only Mauna Kea is
clearly darker in the Ks-band. The typical telescope seeing at the 3.5m is
~1.0" when converted to the V-band, being only slightly larger than the
atmospheric seeing measured at the same time by the seeing monitor, ~0.9".
Finally we estimate the fraction of useful time based on the relative humidity,
gust wind speed and presence of clouds. This fraction, ~72%, is very similar to
the one derived in Paper I, based on the fraction of time when the extinction
monitor is working.Comment: 15 pages, 6 figures, accepted to be published in PAS
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