312 research outputs found
HST/WFPC2 imaging of the circumnuclear structure of LLAGNs. I Data and nuclear morphology
To advance our knowledge of the nature of the central source in LLAGNs and
its relation with stellar clusters, we are carrying out several imaging
projects with HST at near-UV, optical and near-IR wavelengths. In this paper,
we present the first results obtained with observations of the central regions
of 57 LLAGNs imaged with the WFPC2 through any of the V (F555W, F547M, F614W)
and I (F791W, F814W) filters that are available in the HST archive. The sample
contains 34% of the LINERs and 36% of the TOs in the Palomar sample. The mean
spatial resolution of these images is 10 pc. With these data we have built an
atlas that includes structural maps for all the galaxies, useful to identify
compact nuclear sources and, additionally, to characterize the circumnuclear
environment of LLAGNs, determining the frequency of dust and its morphology.
The main results obtained are: 1) We have not found any correlation between the
presence of nuclear compact sources and emission-line type. Thus, nucleated
LINERs are as frequent as nucleated TOs. 2) The nuclei of "Young-TOs" are
brighter than the nuclei of "Old-TOs" and LINERs. These results confirm our
previous results that Young-TOs are separated from other LLAGNs classes in
terms of their central stellar population properties and brightness. 3)
Circumnuclear dust is detected in 88% of the LLAGNs, being almost ubiquitous in
TOs. 4) The dust morphology is complex and varied, from nuclear spiral lanes to
chaotic filaments and nuclear disk-like structures. Chaotic filaments are as
frequent as dust spirals; but nuclear disks are mainly seen in LINERs. These
results suggest an evolutionary sequence of the dust in LLAGNs, LINERs being
the more evolved systems and Young-TOs the youngest. The full collection of
figures are at http://www.iaa.es/~rosa/research/LLAGNs2007/LLAGNs-HSTIma1.htmlComment: Paper accepted in AJ, pdf file and the full collection of figures are
at the ULR: http://www.iaa.es/~rosa/research/LLAGNs2007/LLAGNs-HSTIma1.htm
A Tale of Two Type Ia Supernovae: The Fast-declining Siblings SNe 2015bo and 1997cn
We thank the anonymous referee for their comments. W.B.H. acknowledges support from the Research Experience for Undergraduates program at the Institute for Astronomy, University of Hawaii-Manoa, funded through NSF grant #2050710. L.G. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MCIN) under the 2019 Ramon y Cajal program RYC2019-027683 and from the Spanish MCIN project HOSTFLOWS PID2020-115253GA-I00. M.G.M., R.G.D., and S.M.T. were funded by the European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant agreement No. 839090. Based on observations collected at the European Southern Observatory under ESO program 106.2104. The work of the CSP-II has been generously supported by the National Science Foundation under grant Nos. AST-1008343, AST-1613426, AST-1613455, and AST-1613472. The CSP-II was also supported in part by the Danish Agency for Science and Technology and Innovation through a Sapere Aude Level 2 grant. E.B. was partially supported by NASA grant No. 80NSSC20K0538 J.D.L. acknowledges support from a UK Research and Innovation Fellowship (MR/T020784/1). C.R.B. acknowledges support from NSF grant Nos. AST-1008384, AST-1613426, AST-1613455, and AST-1613472. M.S and S.H. are supported by grants from the VILLUM FONDEN (grant No. 28021) and the Independent Research Fund Denmark (IRFD; 8021-00170B).We present optical and near-infrared photometric and spectroscopic observations of the fast-declining Type Ia
supernova (SN) 2015bo. SN 2015bo is underluminous (MB=−17.50 ± 0.15 mag) and has a fast-evolving light
curve (Δm15(B)=1.91 ± 0.01 mag and sBV=0.48 ± 0.01). It has a unique morphology in the observed V −r
color curve, where it is bluer than all other supernovae (SNe) in the comparison sample. A 56Ni mass of
0.17±0.03Me was derived from the peak bolometric luminosity, which is consistent with its location on the
luminosity–width relation. Spectroscopically, SN 2015bo is a cool SN in the Branch classification scheme. The
velocity evolution measured from spectral features is consistent with 1991bg-like SNe. SN 2015bo has a SN twin
(similar spectra) and sibling (same host galaxy), SN 1997cn. Distance moduli of μ=34.33±0.01 (stat)±
0.11 (sys) mag and μ=34.34±0.04 (stat)±0.12 (sys) mag are derived for SN 2015bo and SN 1997cn, respectively.
These distances are consistent at the 0.06σ level with each other, and they are also consistent with distances derived
using surface-brightness fluctuations and redshift-corrected cosmology. This suggests that fast-declining SNe could
be accurate distance indicators, which should not be excluded from future cosmological analyses.Research Experience for Undergraduates program at the Institute for Astronomy, University of Hawaii-ManoaNational Science Foundation (NSF) AST-1008384
AST-1613426
AST-1613455
AST-1613472Spanish Ministry of Science, Innovation and Universities (MCIN) RYC2019-027683Spanish MCIN project HOSTFLOWS PID2020-115253GA-I00European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie 839090
106.2104National Science Foundation (NSF) AST-1613426
AST-1613455
AST-1613472
AST-1008343Danish Agency for Science and Technology and Innovation through a Sapere Aude Level 2 grantNational Aeronautics & Space Administration (NASA) 80NSSC20K0538UK Research and Innovation Fellowship MR/T020784/1Villum Fonden 28021Independent Research Fund Denmark 8021-00170
The Large Magellanic Cloud stellar content with SMASH I. Assessing the stability of the Magellanic spiral arms
The Large Magellanic Cloud (LMC) is the closest and most studied example of an irregular galaxy. Among its principal defining
morphological features, its off-centred bar and single spiral arm stand out, defining a whole family of galaxies known as the Magellanic
spirals (Sm). These structures are thought to be triggered by tidal interactions and possibly maintained via gas accretion. However, it
is still unknown whether they are long-lived stable structures. In this work, by combining photometry that reaches down to the oldest
main sequence turn-off in the colour-magnitude diagrams (CMD, up to a distance of ∼4.4 kpc from the LMC centre) from the SMASH
survey and CMD fitting techniques, we find compelling evidence supporting the long-term stability of the LMC spiral arm, dating
the origin of this structure to more than 2 Gyr ago. The evidence suggests that the close encounter between the LMC and the Small
Magellanic Cloud (SMC) that produced the gaseous Magellanic Stream and its Leading Arm also triggered the formation of the LMC’s
spiral arm. Given the mass difference between the Clouds and the notable consequences of this interaction, we can speculate that this
should have been one of their closest encounters. These results set important constraints on the timing of LMC-SMC collisions, as
well as on the physics behind star formation induced by tidal encounters.AEI/FEDER, UE
AYA201789076-P
AYA2016-77237-C3-1-P
AYA2015-63810-PMinisterio de Ciencia, Innovacion y Universidades (MCIU), through Juan de la Cierva - Formacion grant
FJCI-2016-30342Consejeria de Economia, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community, through Regional BudgetSpanish Public State Employment Service (SEPE)National Science Foundation (NSF)
AST 1655677
AST-1909497Premiale INAF "MITIC"Ministry of Economy and Competitiveness of Spain
AYA201342781PINFN (Iniziativa specifica TAsP)European Research Council (ERC)
682115"Centre of Excellence Severo Ochoa" award
SEV-2017-0709Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT FONDECYT
1181797Max Planck Society through a Partner Group grantComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT PIA/BASAL
AFB-170002Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT FONDECYT
1170364AYA2016-81065-C2-2PGC2018-095049-B-C2
Geometric Approach to Pontryagin's Maximum Principle
Since the second half of the 20th century, Pontryagin's Maximum Principle has
been widely discussed and used as a method to solve optimal control problems in
medicine, robotics, finance, engineering, astronomy. Here, we focus on the
proof and on the understanding of this Principle, using as much geometric ideas
and geometric tools as possible. This approach provides a better and clearer
understanding of the Principle and, in particular, of the role of the abnormal
extremals. These extremals are interesting because they do not depend on the
cost function, but only on the control system. Moreover, they were discarded as
solutions until the nineties, when examples of strict abnormal optimal curves
were found. In order to give a detailed exposition of the proof, the paper is
mostly self\textendash{}contained, which forces us to consider different areas
in mathematics such as algebra, analysis, geometry.Comment: Final version. Minors changes have been made. 56 page
Measurement of the Crab Nebula spectrum over three decades in energy with the MAGIC telescopes
The MAGIC stereoscopic system collected 69 hours of Crab Nebula data between
October 2009 and April 2011. Analysis of this data sample using the latest
improvements in the MAGIC stereoscopic software provided an unprecedented
precision of spectral and night-by-night light curve determination at gamma
rays. We derived a differential spectrum with a single instrument from 50 GeV
up to almost 30 TeV with 5 bins per energy decade. At low energies, MAGIC
results, combined with Fermi-LAT data, show a flat and broad Inverse Compton
peak. The overall fit to the data between 1 GeV and 30 TeV is not well
described by a log-parabola function. We find that a modified log-parabola
function with an exponent of 2.5 instead of 2 provides a good description of
the data (). Using systematic uncertainties of red the MAGIC and
Fermi-LAT measurements we determine the position of the Inverse Compton peak to
be at (53 3stat + 31syst -13syst) GeV, which is the most precise
estimation up to date and is dominated by the systematic effects. There is no
hint of the integral flux variability on daily scales at energies above 300 GeV
when systematic uncertainties are included in the flux measurement. We consider
three state- of-the-art theoretical models to describe the overall spectral
energy distribution of the Crab Nebula. The constant B-field model cannot
satisfactorily reproduce the VHE spectral measurements presented in this work,
having particular difficulty reproducing the broadness of the observed IC peak.
Most probably this implies that the assumption of the homogeneity of the
magnetic field inside the nebula is incorrect. On the other hand, the
time-dependent 1D spectral model provides a good fit of the new VHE results
when considering a 80 {\mu}G magnetic field. However, it fails to match the
data when including the morphology of the nebula at lower wavelengths.Comment: accepted by JHEAp, 9 pages, 6 figure
MAGIC observations of MWC 656, the only known Be/BH system
Context: MWC 656 has recently been established as the first observationally
detected high-mass X-ray binary system containing a Be star and a black hole
(BH). The system has been associated with a gamma-ray flaring event detected by
the AGILE satellite in July 2010. Aims: Our aim is to evaluate if the MWC 656
gamma-ray emission extends to very high energy (VHE > 100 GeV) gamma rays.
Methods. We have observed MWC 656 with the MAGIC telescopes for 23 hours
during two observation periods: between May and June 2012 and June 2013. During
the last period, observations were performed contemporaneously with X-ray
(XMM-Newton) and optical (STELLA) instruments. Results: We have not detected
the MWC 656 binary system at TeV energies with the MAGIC Telescopes in either
of the two campaigns carried out. Upper limits (ULs) to the integral flux above
300 GeV have been set, as well as differential ULs at a level of 5% of
the Crab Nebula flux. The results obtained from the MAGIC observations do not
support persistent emission of very high energy gamma rays from this system at
a level of 2.4% the Crab flux.Comment: Accepted for publication in A&A. 5 pages, 2 figures, 2 table
Insulinoma de páncreas que imita epilepsia
El insulinoma es una neoplasia endocrina funcional rara, que provoca un estado hiperinsulÃnico hipoglucémico derivado de la ausencia de regulación endocrina de la secreción de insulina. Su incidencia es de 1 a 5 caso por millón de personas al año a nivel mundial. Es la sintomatologÃa más comúnmente manifestada por sÃntomas neuroglucopénicos y simpaticoadrenales. El diagnóstico se establece por la trÃada de Whipple, los niveles elevados de insulina, el péptido C, la proinsulina y los niveles disminuidos de betahidroxibutirato, además de descartar el uso de sulfonilureas. El manejo de elección es la resección quirúrgica, dado su alto nivel de benignidad y curación total. Se presenta el caso de un hombre en manejo anticonvulsivante por epilepsia con refractariedad de sÃntomas, quien debutó con cuadro de hipoglucemia grave necesaria para el diagnóstico de insulinoma, con manejo quirúrgico y resolución del cuadro de base
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