143 research outputs found
Spectral variability studies in Active Galactic Nuclei: Exploring continuum and emission line regions in the age of LSST and JWST
The investigation of emission line regions within active galaxies (AGNs) has
a rich and extensive history, now extending to the use of AGNs and quasars as
"standardizable" cosmological indicators, shedding light on the evolution of
our universe. As we enter the era of advanced observatories, such as the
successful launch of JWST and the forthcoming Vera C. Rubin Observatory's
Legacy Survey of Space and Time (LSST), the landscape of AGN exploration across
cosmic epochs is poised for exciting advancements. In this work, we delve into
recent developments in AGN variability research, anticipating the substantial
influx of data facilitated by LSST. The article highlights recent strides made
by the AGN Polish Consortium in their contributions to LSST. The piece
emphasizes the role of quasars in cosmology, dissecting the intricacies of
their calibration as standard candles. The primary focus centers on the
relationship between the broad-line region size and luminosity, showcasing
recent breakthroughs that enhance our comprehension of this correlation. These
breakthroughs encompass a range of perspectives, including spectroscopic
analyses, photoionization modeling, and collaborative investigations with other
cosmological tools. The study further touches on select studies, underlining
how the synergy of theoretical insights and advancements in observational
capabilities has yielded deeper insights into these captivating cosmic
entities.Comment: 34 pages, 5 figures, accepted for publication as a review in
MDPI/Univers
Broad-line region structure and line profile variations in the changing look AGN HE1136-2304
A strong X-ray outburst was detected in HE1136-2304 in 2014. Accompanying
optical spectra revealed that the spectral type has changed from a nearly
Seyfert 2 type (1.95), classified by spectra taken 10 and 20 years ago, to a
Seyfert 1.5 in our most recent observations. We seek to investigate a detailed
spectroscopic campaign on the spectroscopic properties and spectral variability
behavior of this changing look AGN and compare this to other variable Seyfert
galaxies. We carried out a detailed spectroscopic variability campaign of
HE1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014
December and 2015 July. The broad-line region (BLR) of HE1136-2304 is
stratified with respect to the distance of the line-emitting regions. The
integrated emission line intensities of Halpha, Hbeta, HeI 5876, and HeII 4686
originate at distances of 15.0 (+4.2,-3.8), 7.5 (+4.6,-5.7), 7.3 (+2.8,-4.4),
and 3.0 (+5.3,-3.7) light days with respect to the optical continuum at 4570AA.
The variability amplitudes of the integrated emission lines are a function of
distance to the ionizing continuum source as well. We derived a central black
hole mass of 3.8 (+-3.1) 10exp(7) M_solar based on the line widths and
distances of the BLR. The outer line wings of all BLR lines respond much faster
to continuum variations indicating a Keplerian disk component for the BLR. The
response in the outer wings is about two light days shorter than the response
of the adjacent continuum flux with respect to the ionizing continuum flux. The
vertical BLR structure in HE1136-2304 confirms a general trend that the
emission lines of narrow line active galactic nuclei (AGNs) originate at larger
distances from the midplane in comparison to AGNs showing broader emission
lines. Otherwise, the variability behavior of this changing look AGN is similar
to that of other AGN.Comment: 21 pages, 33 figure
Comportamiento emprendedor de alumnos que cursan cuarto ano de ensenanza media en la comuna de Curico.
60 p.La investigación consistió en la medición de la Capacidad Emprendedora en jóvenes que cursan cuarto año de enseñanza media en la comuna de Curicó. La medición se realizó a través de aplicación del test de tendencia emprendedora construido en la Universidad de Durham. El instrumento fue aplicado a una muestra de 419 alumnos, provenientes de once establecimientos, de los cuales 243 alumnos pertenecen a establecimientos que imparten una educación científico humanista y los 176 alumnos restantes pertenecen a la educación técnico profesional. Previamente a la aplicación del test a través de la construcción del marco teórico se definieron seis factores que supuestamente influyen sobre la Capacidad emprendedora, siendo estas: sexo de los encuestados, tipo de establecimiento, tipo de educación, trabajo de los padres, educación de los padres y rendimiento escolar. Con estos factores previamente definidos se construyo un cuestionario semiestructurado que fue anexado al test, obteniéndose la información adicional requerida Con el uso de herramientas estadísticas en el análisis de la información se puede concluir que:
• los promedios obtenidos se encuentran bajo los promedios estándares que establece el test, por lo que se podría decir que estos jóvenes no son emprendedores.
• que los seis factores definidos no resultan ser determinantes en el comportamiento emprendedor de los jóvenes.
• y que aún cuando el test puede estar validado universalmente, puede no ser el más adecuado para esta población con características tan singulares
Expectations for time-delay measurements in active galactic nuclei with the Vera Rubin Observatory
The Vera Rubin Observatory will provide an unprecedented set of
time-dependent observations of the sky. The planned Legacy Survey of Space and
Time (LSST) operating for 10 years will provide dense lightcurves for thousands
of active galactic nuclei (AGN) in Deep Drilling Fields (DDFs) and less dense
lightcurves for millions of AGN. We model the prospects for measuring time
delays for emission lines with respect to the continuum, using these data. We
model the artificial lightcurves using Timmer-Koenig algorithm, we use the
exemplary cadence to sample them, we supplement lightcurves with the expected
contamination by the strong emission lines (Hbeta, Mg II and CIV as well as
with Fe II pseudo-continuum and the starlight). We choose the suitable
photometric bands appropriate for the redshift and compare the assumed line
time delay with the recovered time delay for 100 statistical realizations of
the light curves. We show that time delays for emission lines can be well
measured from the Main Survey for the bright tail of the quasar distribution
(about 15% of all sources) with the accuracy within 1 sigma error, for DDFs
results for fainter quasars are also reliable when all 10 years of data are
used. There are also some prospects to measure the time delays for the faintest
quasars at the smallest redshifts from the first two years of data, and
eventually even from the first season. The entire quasar population will allow
obtaining results of apparently high accuracy but in our simulations, we see a
systematic offset between the assumed and recovered time delay depending on the
redshift and source luminosity which will not disappear even in the case of
large statistics. Such a problem might affect the slope of the
radius-luminosity relation and cosmological applications of quasars if
simulations correcting for such effects are not performed.Comment: Submitted to Astronomy & Astrophysics, comments wellcom
739 observed NEAs and new 2-4m survey statistics within the EURONEAR network
We report follow-up observations of 477 program Near-Earth Asteroids (NEAs)
using nine telescopes of the EURONEAR network having apertures between 0.3 and
4.2 m. Adding these NEAs to our previous results we now count 739 program NEAs
followed-up by the EURONEAR network since 2006. The targets were selected using
EURONEAR planning tools focusing on high priority objects. Analyzing the
resulting orbital improvements suggests astrometric follow-up is most important
days to weeks after discovery, with recovery at a new opposition also valuable.
Additionally we observed 40 survey fields spanning three nights covering 11 sq.
degrees near opposition, using the Wide Field Camera on the 2.5m Isaac Newton
Telescope (INT), resulting in 104 discovered main belt asteroids (MBAs) and
another 626 unknown one-night objects. These fields, plus program NEA fields
from the INT and from the wide field MOSAIC II camera on the Blanco 4m
telescope, generated around 12,000 observations of 2,000 minor planets (mostly
MBAs) observed in 34 square degrees. We identify Near Earth Object (NEO)
candidates among the unknown (single night) objects using three selection
criteria. Testing these criteria on the (known) program NEAs shows the best
selection methods are our epsilon-miu model which checks solar elongation and
sky motion and the MPC's NEO rating tool. Our new data show that on average 0.5
NEO candidates per square degree should be observable in a 2m-class survey (in
agreement with past results), while an average of 2.7 NEO candidates per square
degree should be observable in a 4m-class survey (although our Blanco
statistics were affected by clouds). At opposition just over 100 MBAs (1.6
unknown to every 1 known) per square degree are detectable to R=22 in a 2m
survey based on the INT data, while our two best ecliptic Blanco fields away
from opposition lead to 135 MBAs (2 unknown to every 1 known) to R=23.Comment: Published in Planetary and Space Sciences (Sep 2013
Firefly Luciferase and Rluc8 Exhibit Differential Sensitivity to Oxidative Stress in Apoptotic Cells
Over the past decade, firefly Luciferase (fLuc) has been used in a wide range of biological assays, providing insight into gene regulation, protein-protein interactions, cell proliferation, and cell migration. However, it has also been well established that fLuc activity can be highly sensitive to its surrounding environment. In this study, we found that when various cancer cell lines (HeLa, MCF-7, and 293T) stably expressing fLuc were treated with staurosporine (STS), there was a rapid loss in bioluminescence. In contrast, a stable variant of Renilla luciferase (RLuc), RLuc8, exhibited significantly prolonged functionality under the same conditions. To identify the specific underlying mechanism(s) responsible for the disparate sensitivity of RLuc8 and fLuc to cellular stress, we conducted a series of inhibition studies that targeted known intracellular protein degradation/modification pathways associated with cell death. Interestingly, these studies suggested that reactive oxygen species, particularly hydrogen peroxide (H2O2), was responsible for the diminution of fLuc activity. Consistent with these findings, the direct application of H2O2 to HeLa cells also led to a reduction in fLuc bioluminescence, while H2O2 scavengers stabilized fLuc activity. Comparatively, RLuc8 was far less sensitive to ROS. These observations suggest that fLuc activity can be substantially altered in studies where ROS levels become elevated and can potentially lead to ambiguous or misleading findings
Comparison of seven prognostic tools to identify low-risk pulmonary embolism in patients aged <50 years
publishersversionPeer reviewe
Rate and duration of hospitalisation for acute pulmonary embolism in the real-world clinical practice of different countries : Analysis from the RIETE registry
publishersversionPeer reviewe
Pulsations in main sequence OBAF-type stars
CONTEXT: The third Gaia data release provides photometric time series covering 34 months for about 10 million stars. For many of those stars, a characterisation in Fourier space and their variability classification are also provided. This paper focuses on intermediate- to high-mass (IHM) main sequence pulsators (M ≥ 1.3 M⊙) of spectral types O, B, A, or F, known as β Cep, slowly pulsating B (SPB), δ Sct, and γ Dor stars. These stars are often multi-periodic and display low amplitudes, making them challenging targets to analyse with sparse time series. AIMS: We investigate the extent to which the sparse Gaia DR3 data can be used to detect OBAF-type pulsators and discriminate them from other types of variables. We aim to probe the empirical instability strips and compare them with theoretical predictions. The most populated variability class is that of the δ Sct variables. For these stars, we aim to confirm their empirical period-luminosity (PL) relation, and verify the relation between their oscillation amplitude and rotation. METHODS: All datasets used in this analysis are part of the Gaia DR3 data release. The photometric time series were used to perform a Fourier analysis, while the global astrophysical parameters necessary for the empirical instability strips were taken from the Gaia DR3 gspphot tables, and the v sin i data were taken from the Gaia DR3 esphs tables. The δ Sct PL relation was derived using the same photometric parallax method as the one recently used to establish the PL relation for classical Cepheids using Gaia data. RESULTS: We show that for nearby OBAF-type pulsators, the Gaia DR3 data are precise and accurate enough to pinpoint them in the Hertzsprung-Russell (HR) diagram. We find empirical instability strips covering broader regions than theoretically predicted. In particular, our study reveals the presence of fast rotating gravity-mode pulsators outside the strips, as well as the co-existence of rotationally modulated variables inside the strips as reported before in the literature. We derive an extensive period–luminosity relation for δ Sct stars and provide evidence that the relation features different regimes depending on the oscillation period. We demonstrate how stellar rotation attenuates the amplitude of the dominant oscillation mode of δ Sct stars. CONCLUSIONS: The Gaia DR3 time-series photometry already allows for the detection of the dominant (non-)radial oscillation mode in about 100 000 intermediate- and high-mass dwarfs across the entire sky. This detection capability will increase as the time series becomes longer, allowing the additional delivery of frequencies and amplitudes of secondary pulsation modes
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