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Gamma-ray emission of young stellar objects and discovery of superorbital variability at high energies
Get PDFSe puede dividir mi tesis en tres partes: 1. Estudios de la emisi.n gamma de los sistemas binarios LS I +61 303 y LS 5039 a altas energ.as con el Fermi Large Area Telescope (LAT) y el primer descubrimiento de variabilidad superorbital a altas energ.as de la fuente LS I +61 303 Los sistemas binarios de rayos gamma son sistemas estelares cuyo espectro tiene su máximo a altas energías (sin tener en cuenta su emisión térmica). Ha sido detectada desde radio hasta rayos gamma (TeV), el sistema binario LS I +61 303 es muy variable en todas las frecuencias. Una característica de la variabilidad de este sistema es la modulación de su emisión a 26.496 días que coincide con su período orbital. En esta tesis mostramos por primera vez que la emisión gamma de LS I +61 303 presenta también una variabilidad superorbital con un período de 1667 días. Esta modulación es más presente en fases orbitales alrededor de apastro, aunque no introduce un cambio visible cerca de periastro. Además, se observa una aparición y desaparición de la variabilidad orbital en el espectro de potencias de los datos. Este comportamiento se puede explicar por una evolución cuasi-°©‐cíclica del disco ecuatorial de la estrella acompañante (estrella Be) cuyas características influyen en las condiciones para generar rayos gamma. Estos descubrimientos abren por primera vez la posibilidad de usar observaciones de rayos gamma para estudiar los discos de estrellas masivas en sistemas binarios excéntricos. 2. Estudios de la emisi.n gamma de magnetares a altas y muy altas energ.as con el LAT y con los telescopios Cherenkov MAGIC Los magnetares son una clase particular de estrellas de neutrones que muestran emisión desde radio hasta unos centenares de keV. Se pueden caracterizar por sus explosiones de rayos X y por sus perdidas de energía, las cuales son demasiado pequeñas para justificar su luminosidad en rayos X. Por esta razón, la teoría más aceptada es que la emisión X de la estrella de neutrones está suministrada por el decaimiento y las inestabilidades de sus altos campos magnéticos. En esta tesis, estos objetos han sido estudiados por primera vez a altas y a muy altas energías con el LAT y con los telescopios MAGIC. Hemos impuesto las primeras cotas a la posible emisión gamma de estos objetos. Además, este fuerte diagnóstico observacional fuerza una revisión del espacio de parámetros aplicable a la visibilidad del modelo de “outer gap” de Cheng & Zhang (2001) and Zhang & Cheng (2002) para cada magnetar. 3. Predicciones para la astronom.a Cherenkov con los telescopios CTA La siguiente generación de telescopios Cherenkov será CTA. Este experimento está ahora en la fase de diseño. En esta tesis, evaluamos las capacidades de CTA para estudiar la física no-°©‐térmica de sistemas binarios de rayos gamma. Eso requiere la observación de fenómenos a altas energías a tiempos y a escalas espaciales diferentes. Para hacer eso, hemos estudiado los sistemas binarios de rayos gamma en el contexto de la física conocida o esperada de estas fuentes. CTA será capaz de demostrar los procesos físicos detrás de la emisión gamma en sistemas binarios con una resolución espectral, temporal y espacial alta. Además crecerá el número de fuentes detectadas significativamente. Hemos observado que la sensibilidad de CTA conseguirá un muestreo de curvas de luz y espectros a escalas de tiempo muy cortas de alta calidad. Además, se podrá monitorear fuentes a tiempo largo usando una parte de los telescopios que todavía alcanzará una sensibilidad 2 o 3 veces mayor que cualquier instrumento actual operando a muy altas energías. En particular, es notable que CTA reducirá la indeterminación de los flujos e índices espectrales en unos cuantos factores.My
thesis
can
be
divided
into
three
parts:
1. Study
of
the
gamma-ray
emission
of
the
binary
systems
LS
I
+61
303
and
LS
5039
at
high
energies
with
the
Fermi
Large
Area
Telescope
(LAT)
and
the
first
discovery
of
superorbital
variability
at
high
energies
from
the
source
LS
I
+61
303.
Gamma-‐ray
binaries
are
stellar
systems
for
which
the
spectral
energy
distribution
(discounting
the
thermal
stellar
emission)
peaks
at
high
energies.
Detected
from
radio
to
TeV
gamma
rays,
the
gamma-‐ray
binary
LS
I
+61
303
is
highly
variable
across
all
frequencies.
One
aspect
of
this
system's
variability
is
the
modulation
of
its
emission
with
the
timescale
set
by
the
26.496-‐day
orbital
period.
In
this
thesis
we
show
for
the
first
time
that
the
gamma-‐ray
emission
of
LS
I
+61
303
also
presents
a
sinusoidal
variability
at
the
known
superorbital
period
of
1667
days.
This
modulation
is
more
prominently
seen
at
orbital
phases
around
apastron,
whereas
it
does
not
introduce
a
visible
change
close
to
periastron.
It
is
also
found
in
the
appearance
and
disappearance
of
variability
at
the
orbital
period
in
the
power
spectrum
of
the
data.
This
behavior
could
be
explained
by
a
quasi-‐cyclical
evolution
of
the
equatorial
outflow
of
the
Be
companion
star,
whose
features
influence
the
conditions
for
generating
gamma
rays.
These
findings
open
for
the
first
time
the
possibility
to
use
gamma-‐ray
observations
to
study
the
outflows
of
massive
stars
in
eccentric
binary
systems.
2. Study
of
the
gamma-ray
emission
of
magnetars
at
high
and
very
high
energies
with
the
LAT
and
the
MAGIC
Cherenkov
telescopes.
Magnetars
are
a
peculiar
class
of
neutron
stars
showing
emission
from
radio
up
to
some
hundreds
of
keV.
They
can
be
characterized
through
their
bursting
behavior
and
through
an
energy
loss
rate,
which
is
too
small
to
power
their
X-‐ray
luminosity.
Therefore,
it
is
believed
that
the
X-‐ray
emission
of
the
neutron
star
is
powered
by
the
decay
and
the
instabilities
of
their
strong
magnetic
field.
In
this
thesis,
these
objects
are
studied
for
the
first
time
at
high
and
very
high
energies
with
the
LAT
and
the
MAGIC
telescopes.
We
put
the
first
constraints
on
their
emission
in
this
high
energy
regime.
Furthermore,
this
strong
observational
diagnostic
forces
a
revision
of
the
parameter
space
applicable
for
the
viability
of
the
outer
gap
model
of
Cheng
&
Zhang
(2001)
and
Zhang
&
Cheng
(2002)
to
each
magnetar.
3. Prospects
for
the
Cherenkov
astronomy
with
the
future
Cherenkov
Telescope
Array
(CTA).
The
next
generation
of
Imaging
Air
Cherenkov
Telescopes
will
be
CTA.
This
experiment
is
nowadays
in
the
design
phase.
In
this
thesis
we
evaluate
the
potentialities
of
CTA
to
study
the
non-‐thermal
physics
of
gamma-‐ray
binaries,
which
requires
the
observation
of
high-‐energy
phenomena
at
different
time
and
spatial
scales.
To
do
so
we
study
gamma-‐ray
binaries
in
the
context
of
the
known
or
expected
physics
of
these
sources.
CTA
will
be
able
to
probe
with
high
spectral,
temporal
and
spatial
resolution
the
physical
processes
behind
the
gamma-‐ray
emission
in
binaries,
significantly
increasing
as
well
the
number
of
known
sources.
We
found
that
the
sensitivity
of
CTA
will
lead
to
a
very
good
sampling
of
light
curves
and
spectra
on
very
short
timescales.
It
will
allow
as
well
long
source
monitoring
using
subarrays,
still
with
a
sensitivity
2–3
times
better
than
any
previous
instrument
operating
at
VHE
energies.
In
particular,
it
is
noteworthy
that
CTA
will
reduce
by
a
factor
of
a
few
the
errors
in
the
determination
of
fluxes
and
spectral
indexes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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