726 research outputs found
Variable stars and stellar populations in Andromeda XXI: II. Another merged galaxy satellite of M31?
B and V time-series photometry of the M31 dwarf spheroidal satellite
Andromeda XXI (And XXI) was obtained with the Large Binocular Cameras at the
Large Binocular Telescope. We have identified 50 variables in And XXI, of which
41 are RR Lyrae stars (37 fundamental-mode RRab, and 4 first-overtone RRc,
pulsators) and 9 are Anomalous Cepheids (ACs). The average period of the RRab
stars ( = 0.64 days) and the period-amplitude diagram place And~XXI in the
class of Oosterhoff II - Oosterhoff-Intermediate objects. From the average
luminosity of the RR Lyrae stars we derived the galaxy distance modulus of
(m-M)= mag, which is smaller than previous literature
estimates, although still consistent with them within 1 . The galaxy
color-magnitude diagram shows evidence for the presence of three different
stellar generations in And~XXI: 1) an old ( 12 Gyr) and metal poor
([Fe/H]=1.7 dex) component traced by the RR Lyrae stars; 2) a slightly
younger (10-6 Gyr) and more metal rich ([Fe/H]=1.5 dex) component populating
the red horizontal branch, and 3) a young age ( 1 Gyr) component with
same metallicity, that produced the ACs. Finally, we provide hints that And~XXI
could be the result of a minor merging event between two dwarf galaxies.Comment: accepted for publications in Ap
Low-noise design issues for analog front-end electronics in 130 nm and 90 nm CMOS technologies
Deep sub-micron CMOS technologies provide wellestablished solutions to the implementation of low-noise front-end electronics in various detector applications. The IC designers’ effort is presently shifting to 130 nm CMOS technologies, or even to the next technology node, to implement readout integrated circuits for silicon strip and pixel detectors, in view of future HEP applications. In this work the results of noise measurements carried out on CMOS devices in 130 nm and 90 nm commercial processes are presented. The behavior of the 1/f and white noise terms is studied as a function of the device polarity and of the gate length and width. The study is focused on low current density applications where devices are biased in weak or moderate inversion. Data obtained from the measurements provide a powerful tool to establish design criteria in nanoscale CMOS processes for detector front-ends in LHC upgrades
A bag of tricks: Using proper motions of Galactic stars to identify the Hercules ultra-faint dwarf galaxy members
Hercules is the prototype of the ultra-faint dwarf (UFD) galaxies. To date,
there are still no firm constraints on its total luminosity, due to the
difficulty of disentangling Hercules bona-fide stars from the severe Galactic
field contamination. In order to better constrain Hercules properties we aim at
removing foreground and background contaminants in the galaxy field using the
proper motions of the Milky Way stars and the colour-colour diagram. We have
obtained images of Hercules in the rSloan, BBessel and Uspec bands with the
Large Binocular Telescope (LBT) and LBC-BIN mode capabilities. The rSloan new
data-set combined with data from the LBT archive span a time baseline of about
5 yr, allowing us to measure for the first time proper motions of stars in the
Hercules direction. The Uspec data along with existing LBT photometry allowed
us to use colour-colour diagram to further remove the field contamination.
Thanks to a highly-accurate procedure to derive the rSloan-filter geometric
distortion solution for the LBC-red, we were able to measure stellar relative
proper motions to a precision of better than 5 mas yr^-1 down to rSloan=22 mag
and disentangle a significant fraction (\>90\%) of Milky Way contaminants. We
ended up with a sample of 528 sources distributed over a large portion of the
galaxy body (0.12 deg^2). Of these sources, 171 turned out to be background
galaxies and additional foreground stars, from the analysis of the Uspec -
BBessel vs. BBessel - rSloan colour-colour diagram. This leaves us with a
sample of 357 likely members of the Hercules UFD. We compared the cleaned
colour-magnitude diagram (CMD) with evolutionary models and synthetic CMDs,
confirming the presence in Hercules of an old population (t=12\pm 2 Gyr), with
a wide spread in metallicity (-3.3\<[Fe/H]\<-1.8).Comment: 16 pages, 15 figures, 3 tables, accepted for publication in A&
Deep R-band counts of z~3 Lyman break galaxy candidates with the LBT
Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different
fields, Q0933, Q1623, and COSMOS, for a total area of ~1500arcmin^2. The data
were obtained with the Large Binocular Camera on the Large Binocular Telescope.
Methods. To select our Lyman break galaxy (LBG) candidates, we adopted the well
established and widely used color-selection criterion (U-G vs. G-R). One of the
main advantages of our survey is that it has a wider dynamic color range for
U-dropout selection than in previous studies. This allows us to fully exploit
the depth of our R-band images, obtaining a robust sample with few interlopers.
In addition, for 2 of our fields we have spectroscopic redshift information
that is needed to better estimate the completeness of our sample and interloper
fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band
(5\sigma) and 28.6(AB) in the U band (1\sigma). This dataset was used to derive
LBG candidates at z~3. We obtained a catalog with a total of 12264 sources down
to the 50% completeness magnitude limit in the R band for each field. We find a
surface density of ~3 LBG candidates arcmin^2 down to R=25.5, where
completeness is >=95% for all 3 fields. This number is higher than the original
studies, but consistent with more recent samples.Comment: in press by A&A, full LBG candidates' catalog will be available in
electronic form at the CD
MAPS in 130 nm triple well CMOS technology for HEP applications
Deep N-well CMOS monolithic active pixel sensors (DNWMAPS) represent an alternative approach to signal processing in pixellated detectors for high energy physics experiments. Based on different resolution constraints, two prototype MAPS, suitable for applications requiring different detector pitch, have been developed and fabricated in 130 nm triple well CMOS technology. This work presents experimental results from the characterization of some test structures together with TCAD and Monte Carlo simulations intended to study the device properties in terms of charge diffusion and charge sharing among pixels
Large Binocular Telescope view of the atmosphere of GJ1214b
The atmospheric composition and vertical structure of the super-Earth GJ1214b
has been a subject of debate since its discovery in 2009. Recent studies have
indicated that high-altitude clouds might mask the lower layers. However, some
data points that were gathered at different times and facilities do not fit
this picture, probably because of a combination of stellar activity and
systematic errors. We observed two transits of GJ1214b with the Large Binocular
Camera, the dual-channel camera at the Large Binocular Telescope. For the first
time, we simultaneously measured the relative planetary radius
at blue and red optical wavelengths (), thus
constraining the Rayleigh scattering on GJ1214b after correcting for stellar
activity effects. To the same purpose, a long-term photometric follow-up of the
host star was carried out with WiFSIP at STELLA, revealing a rotational period
that is significantly longer than previously reported. Our new unbiased
estimates of yield a flat transmission spectrum extending to shorter
wavelengths, thus confirming the cloudy atmosphere scenario for GJ1214b.Comment: 11 pages, 5 figures, 3 tables. Published in A&A. Minor changes to
reflect the published versio
A long-lasting quiescence phase of the eruptive variable V1118 Ori
V1118 Ori is an eruptive variable belonging to the EXor class of Pre-Main
Sequence stars whose episodic outbursts are attributed to disk accretion
events. Since 2006, V1118 Ori is in the longest quiescence stage ever observed
between two subsequent outbursts of its recent history. We present
near-infrared photometry of V1118 Ori carried out during the last eight years,
along with a complete spectroscopic coverage from 0.35 to 2.5 um. A longterm
sampling of V1118 Ori in quiescence has never been done, hence we can benefit
from the current circumstance to determine the lowest values (i.e. the zeroes)
of the parameters to be used as a reference for evaluating the physical changes
typical of more active phases. A quiescence mass accretion rate between 1--3
10 M_{\sun} yr can be derived and the difference with
previous determinations is discussed. From line emission and IR colors analysis
a visual extinction of 1-2 mag is consistently derived, confirming that V1118
Ori (at least in quiescence) is a low-extinction T Tauri star with a bolometric
luminosity of about 2.1 L_{\sun}. An anti-correlation exists between the
equivalent width of the emission lines and the underlying continuum. We
searched the literature for evaluating whether or not such a behaviour is a
common feature of the whole class. The anti-correlation is clearly recognizable
for all the available EXors in the optical range (H and H
lines), while it is not as much evident in the infrared (Pa and
Br lines). The observed anti-correlation supports the accretion-driven
mechanism as the most likely to account for continuum variations.Comment: 6 figures, 5 tables, accepted on Ap
Real-Time Oil Leakage Detection on Aftermarket Motorcycle Damping System with Convolutional Neural Networks
In this work, we describe in detail how Deep Learning and Computer Vision can help to detect fault events of the AirTender system, an aftermarket motorcycle damping system component. One of the most effective ways to monitor the AirTender functioning is to look for oil stains on its surface. Starting from real-time images, AirTender is first detected in the motorbike suspension system, simulated indoor, and then, a binary classifier determines whether AirTender is spilling oil or not. The detection is made with the help of the Yolo5 architecture, whereas the classification is carried out with the help of a suitably designed Convolutional Neural Network, OilNet40. In order to detect oil leaks more clearly, we dilute the oil in AirTender with a fluorescent dye with an excitation wavelength peak of approximately 390 nm. AirTender is then illuminated with suitable UV LEDs. The whole system is an attempt to design a low-cost detection setup. An on-board device, such as a mini-computer, is placed near the suspension system and connected to a full hd camera framing AirTender. The on-board device, through our Neural Network algorithm, is then able to localize and classify AirTender as normally functioning (non-leak image) or anomaly (leak image)
Characterizing faint galaxies in the reionization epoch: LBT confirms two L<0.2L* sources at z=6.4 behind the CLASH/Frontier Fields cluster MACS0717.5+3745
We report the LBT/MODS1 spectroscopic confirmation of two images of faint
Lyman alpha emitters at behind the Frontier Fields galaxy cluster
MACSJ0717.5+3745. A wide range of lens models suggests that the two images are
highly magnified, with a strong lower limit of mu>5. These are the faintest z>6
candidates spectroscopically confirmed to date. These may be also multiple
images of the same z=6.4 source as supported by their similar intrinsic
properties, but the lens models are inconclusive regarding this interpretation.
To be cautious, we derive the physical properties of each image individually.
Thanks to the high magnification, the observed near-infrared (restframe
ultraviolet) part of the spectral energy distributions and Ly-alpha lines are
well detected with S/N(m_1500)>~10 and S/N(Ly-alpha)~10-15. Adopting mu>5, the
absolute magnitudes, M_1500, and Ly-alpha fluxes, are fainter than -18.7 and
2.8x10^(-18)erg/s/cm2, respectively. We find a very steep ultraviolet spectral
slope beta=-3.0+/-0.5 (F_lambda=lambda^(beta)), implying that these are very
young, dust-free and low metallicity objects, made of standard stellar
populations or even extremely metal poor stars (age<~30Myr, E(B-V)=0 and
metallicity 0.0-0.2 Z/Zsolar). The objects are compact (< 1 kpc^(2)), and with
a stellar mass M* < 10^(8) M_solar. The very steep beta, the presence of the
Ly-alpha line and the intrinsic FWHM (<300 km/s) of these newborn objects do
not exclude a possible leakage of ionizing radiation. We discuss the
possibility that such faint galaxies may resemble those responsible for cosmic
reionization.Comment: Accepted by ApJL; 6 pages, 4 figures, 1 table, emulateapj forma
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