999 research outputs found
First radial velocity results from the MINiature Exoplanet Radial Velocity Array (MINERVA)
The MINiature Exoplanet Radial Velocity Array (MINERVA) is a dedicated
observatory of four 0.7m robotic telescopes fiber-fed to a KiwiSpec
spectrograph. The MINERVA mission is to discover super-Earths in the habitable
zones of nearby stars. This can be accomplished with MINERVA's unique
combination of high precision and high cadence over long time periods. In this
work, we detail changes to the MINERVA facility that have occurred since our
previous paper. We then describe MINERVA's robotic control software, the
process by which we perform 1D spectral extraction, and our forward modeling
Doppler pipeline. In the process of improving our forward modeling procedure,
we found that our spectrograph's intrinsic instrumental profile is stable for
at least nine months. Because of that, we characterized our instrumental
profile with a time-independent, cubic spline function based on the profile in
the cross dispersion direction, with which we achieved a radial velocity
precision similar to using a conventional "sum-of-Gaussians" instrumental
profile: 1.8 m s over 1.5 months on the RV standard star HD 122064.
Therefore, we conclude that the instrumental profile need not be perfectly
accurate as long as it is stable. In addition, we observed 51 Peg and our
results are consistent with the literature, confirming our spectrograph and
Doppler pipeline are producing accurate and precise radial velocities.Comment: 22 pages, 9 figures, submitted to PASP, Peer-Reviewed and Accepte
Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b
Using the integral field spectrograph OSIRIS, on the Keck II telescope, broad
near-infrared H and K-band spectra of the young exoplanet HR8799b have been
obtained. In addition, six new narrow-band photometric measurements have been
taken across the H and K bands. These data are combined with previously
published photometry for an analysis of the planet's atmospheric properties.
Thick photospheric dust cloud opacity is invoked to explain the planet's red
near-IR colors and relatively smooth near-IR spectrum. Strong water absorption
is detected, indicating a Hydrogen-rich atmosphere. Only weak CH4 absorption is
detected at K band, indicating efficient vertical mixing and a disequilibrium
CO/CH4 ratio at photospheric depths. The H-band spectrum has a distinct
triangular shape consistent with low surface gravity. New giant planet
atmosphere models are compared to these data with best fitting bulk parameters,
Teff = 1100K +- 100 and log(g) = 3.5 +-0.5 (for solar composition). Given the
observed luminosity, log(Lobs/Lsun) ~ -5.1, these values correspond to a radius
of 0.75 Rjup (+0.17, -0.12) and mass ~ 0.72 Mjup (+2.6,-0.6) -- strikingly
inconsistent with interior/evolution models. Enhanced metallicity (up to ~ 10
times that of the Sun) along with thick clouds and non-equilibrium chemistry
are likely required to reproduce the complete ensemble of spectroscopic and
photometric data and the low effective temperatures (< 1000K) required by the
evolution models.Comment: 17 pages, accepted for publication in The Astrophysical Journa
Precise radial velocities of giant stars IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a ~13.6 au eccentric binary system
Context: For over 12 yr, we have carried out a precise radial velocity survey
of a sample of 373 G and K giant stars using the Hamilton \'Echelle
Spectrograph at Lick Observatory. There are, among others, a number of multiple
planetary systems in our sample as well as several planetary candidates in
stellar binaries. Aims: We aim at detecting and characterizing
substellar+stellar companions to the giant star HD 59686 A (HR 2877, HIP
36616). Methods: We obtained high precision radial velocity (RV) measurements
of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in
the RVs, we can assess the nature of companions in the system. In order to
discriminate between RV variations due to non-radial pulsation or stellar spots
we used infrared RVs taken with the CRIRES spectrograph at the Very Large
Telescope. Additionally, to further characterize the system, we obtain
high-resolution images with LMIRCam at the Large Binocular Telescope. Results:
We report the likely discovery of a giant planet with a mass of orbiting at
au from the giant star HD 59686 A. Besides the planetary signal, we discover an
eccentric () binary companion with a mass of
orbiting at a semi-major axis
of just au. Conclusions: The existence of the
planet HD 59686 Ab in a tight eccentric binary system severely challenges
standard giant planet formation theories and requires substantial improvements
to such theories in tight binaries. Otherwise, alternative planet formation
scenarios such as second generation planets or dynamical interactions in an
early phase of the system's lifetime should be seriously considered in order to
better understand the origin of this enigmatic planet.Comment: 14 pages, 11 figures, 2 tables. Accepted for publication in A&A.
Updated version to match the published pape
Optical photometric GTC/OSIRIS observations of the young massive association Cygnus OB2
In order to fully understand the gravitational collapse of molecular clouds,
the star formation process and the evolution of circumstellar disks, these
phenomena must be studied in different Galactic environments with a range of
stellar contents and positions in the Galaxy. The young massive association
Cygnus OB2, in the Cygnus-X region, is an unique target to study how star
formation and the evolution of circumstellar disks proceed in the presence of a
large number of massive stars. We present a catalog obtained with recent
optical observations in r,i,z filters with OSIRIS, mounted on the GTC
telescope, which is the deepest optical catalog of Cyg OB2 to date.
The catalog consist of 64157 sources down to M=0.15 solar masses at the
adopted distance and age of Cyg OB2. A total of 38300 sources have good
photometry in all three bands. We combined the optical catalog with existing
X-ray data of this region, in order to define the cluster locus in the optical
diagrams. The cluster locus in the r-i vs. i-z diagram is compatible with an
extinction of the optically selected cluster members in the 2.64<AV<5.57 range.
We derive an extinction map of the region, finding a median value of AV=4.33 in
the center of the association, decreasing toward the north-west. In the
color-magnitude diagrams, the shape of the distribution of main sequence stars
is compatible with the presence of an obscuring cloud in the foreground at
about 850+/-25 pc from the Sun.Comment: Accepted for publication ApJS 201
Distributed Job Scheduler
Since Cron was released for Unix operating systems in 1975, it became a useful tool for making developers and system administrators’ life easier by programming tasks to be launched autonomously. Although Cron is a simple and powerful tool, it has some problems associated with it, such as lack of visibility, and complexity, because scheduling tasks using crontab’s notation can sometimes be difficult. As times wore on, new approaches of job scheduling systems emerged, most of them providing a user friendly interface to manage jobs/tasks scheduling and reports or statistics about job’s execution. Every day Jumia dispatches millions of marketing campaigns which include emails, newsletters, push notifications, SMS, and other types of channels to engage its customers to visit the e-commerce online store and other Jumia applications. In Jumia Marketing and Digital Services team’s systems a job scheduler is also used, it’s called Eye Of Sauron (EOS). EOS is very useful, however it wasn’t designed very well when it begun and, nowadays, it’s considered a problem for Jumia’s business because it’s not reliable. It’s Eye Of Sauron’s duty to trigger the dispatch process for all the marketing campaigns for Jumia’s users, so it needs to be well designed and provide trust to Jumia’s business stakeholders. With this project the problems from the original service were addressed. A new distributed job scheduler named Eye of Sauron v2 was designed and developed. It is composed by several components that are capable of being scaled horizontally and/or vertically. The new system also uses a message broker for asynchronous communication and a relational database as storage solution. The new job scheduler was considered successful because it was evaluated with a quality percentage of eighty-seven points using a Quantitative Evaluation Framework (QEF) model that considers numerous aspects not only related with functionality, but also with user interface and experience.Desde que o Cron foi lançado para sistemas operativos Unix em 1975, este tornou-se uma ferramenta muito útil para facilitar a vida de programadores e administradores de sistemas ao possibilitar o agendamento de tarefas a serem lançadas de forma autónoma. Embora o Cron seja uma ferramenta simples e poderosa, ele possui alguns problemas associados, como a falta de visibilidade e complexidade, pois o agendamento de tarefas usando a notação do crontab às vezes pode ser difícil. Com o passar do tempo, surgiram novas abordagens de sistemas de agendamento de tarefas, a maioria delas fornecendo uma interface amigável para promover a manutenção do agendamento de tarefas e relatórios ou estatísticas sobre a execução dessas tarefas. Todos os dias a Jumia envia milhões de campanhas de marketing que incluem e-mails, newsletters, notificações push, SMS e outros tipos de canais para aliciar os seus clientes a visitar a loja online de comércio eletrónico e outras aplicações da Jumia. Nos sistemas da equipa Jumia Marketing and Digital Services também é usado um agendador de tarefas, chamado Eye Of Sauron (EOS), ou “Olho de Sauron”. Este sistema é muito útil, porém não foi adequadamente projetado, o que fez com que hoje em dia seja considerado considerado um problema para o negócio da Jumia por não ser confiável. É dever do Eye Of Sauron chamar o processo de envio de todas as campanhas de marketing para os utilizadores da Jumia, por isso precisa fornecer confiança aos executivos da Jumia. Com este projeto os problemas do serviço original foram solucionados. Um novo agendador de tarefas distribuído chamado Eye of Sauron v2 foi projetado e desenvolvido. É composto por vários componentes que podem ser escláveis horizontalmente e/ou verticalmente. O novo sistema também utiliza um message broker para comunicação assíncrona e uma base de dados relacional como solução de armazenamento. O novo agendador de tarefas foi considerado bem sucedido porque foi avaliado com uma percentagem de qualidade de oitenta e sete pontos usando um modelo Quantitative Evaluation Framework (QEF). Este modelo considera inúmeros aspectos, não apenas relacionados à funcionalidade, mas também com a interface e a experiência do utilizador
They are Small Worlds After All: Revised Properties of Kepler M Dwarf Stars and their Planets
We classified the reddest () stars observed by the NASA
mission into main sequence dwarf or evolved giant stars and determined the
properties of 4216 M dwarfs based on a comparison of available photometry with
that of nearby calibrator stars, as well as available proper motions and
spectra. We revised the properties of candidate transiting planets using the
stellar parameters, high-resolution imaging to identify companion stars, and,
in the case of binaries, fitting light curves to identify the likely planet
host. In 49 of 54 systems we validated the primary as the host star. We
inferred the intrinsic distribution of M dwarf planets using the method of
iterative Monte Carlo simulation. We compared several models of planet orbital
geometry and clustering and found that one where planets are exponentially
distributed and almost precisely coplanar best describes the distribution of
multi-planet systems. We determined that M dwarfs host an average of
planets with radii of 1-4 and orbital periods of
1.5-180 d. The radius distribution peaks at and is
essentially zero at , although we identify three giant planet
candidates other than the previously confirmed Kepler-45b. There is suggestive
but not significant evidence that the radius distribution varies with orbital
period. The distribution with logarithmic orbital period is flat except for a
decline for orbits less than a few days. Twelve candidate planets, including
two Jupiter-size objects, experience an irradiance below the threshold level
for a runaway greenhouse on an Earth-like planet and are thus in a "habitable
zone".Comment: MNRAS, in press. Tables 1, 3, and 4 are available in electronic form
in the "anc" director
The Spitzer c2d survey of Large, Nearby, Interstellar Clouds. V. Chamaeleon II Observed with IRAC
We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the
Chamaeleon II molecular cloud. The observed area covers about 1 square degree
defined by . Analysis of the data in the 2005 c2d catalogs reveals a
small number of sources (40) with properties similar to those of young
stellaror substellar objects (YSOs). The surface density of these YSO
candidates is low, and contamination by background galaxies appears to be
substantial, especially for sources classified as Class I or flat SED. We
discuss this problem in some detail and conclude that very few of the candidate
YSOs in early evolutionary stages are actually in the Cha II cloud. Using a
refined set of criteria, we define a smaller, but more reliable, set of 24 YSO
candidates.Comment: 19 pages, 10 figures, in press Ap
Dust Evolution in Protoplanetary Disks
(abridged) In the core accretion scenario for the formation of planetary
rocky cores, the first step toward planet formation is the growth of dust
grains into larger and larger aggregates and eventually planetesimals. Although
dust grains are thought to grow from the submicron sizes typical of
interstellar dust to micron size particles in the dense regions of molecular
clouds and cores, the growth from micron size particles to pebbles and
kilometre size bodies must occur in protoplanetary disks. This step in the
formation of planetary systems is the last stage of solids evolution that can
be observed directly in young extrasolar systems.
In this chapter we review the constraints on the physics of grain-grain
collisions as they have emerged from laboratory experiments and numerical
computations. We then review the current theoretical understanding of the
global processes governing the evolution of solids in protoplanetary disks,
including dust settling, growth, and radial transport. The predicted
observational signatures are summarized.
We discuss recent developments in the study of grain growth in molecular
cloud cores and in collapsing envelopes of protostars as these provide the
initial conditions for the dust in disks. We discuss the observational evidence
for the growth of grains in young disks from mm surveys, as well as the recent
evidence of radial variations of the dust properties in disks. We include a
brief discussion of the constraints on the small end of the grain size
distribution and on dust settling as derived from optical and IR observations.
The observations are discussed in the context of global dust evolution models,
in particular we focus on the emerging evidence for a very efficient early
growth of grains and the radial distribution of grain sizes in disks. We also
highlight the limits of current models, including the need to slow the radial
drift of grains.Comment: Accepted for publication as a chapter in Protostars and Planets VI,
University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C.
Dullemond, Th. Hennin
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