321 research outputs found
Profile of idursulfase for the treatment of Hunter syndrome
Simona Sestito, Ferdinando Ceravolo, Michele Grisolia, Elisa Pascale, Licia Pensabene, Daniela Concolino Department of Pediatrics, University Magna Graecia of Catanzaro, Catanzaro, Italy Abstract: Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is a rare X-linked lysosomal storage disorder caused by deficiency of the enzyme iduronate-2-sulfatase (IDS). Enzyme replacement therapy (ERT) with recombinant human IDS, available since 2005, is currently the most appropriate treatment for this progressive, multisystemic, chronic, and life-threatening disease. Efficacy and safety of therapy with idursulfase have been assessed in several clinical trials, and confirmed in many clinical reports. Long-term follow-up of patients receiving ERT has demonstrated the importance of an early onset of treatment with idursulfase, before irreversible pathological changes occur. Intravenously administered idursulfase is not able to cross the blood–brain barrier, so neurological signs and symptoms cannot benefit from ERT, still remaining a major challenge in the treatment of MPS II. Keywords: MPS II, glycosaminoglycans, enzyme replacement therapy, ER
Open clusters towards the Galactic center: chemistry and dynamics. A VLT spectroscopic study of NGC6192, NGC6404, NGC6583
In the framework of the study of the Galactic metallicity gradient and its
time evolution, we present new high-resolution spectroscopic observations
obtained with FLAMES and the fiber link to UVES at VLT of three open clusters
(OCs) located within 7~kpc from the Galactic Center (GC): NGC~6192,
NGC~6404, NGC~6583. We also present new orbit determination for all OCs with
Galactocentric distances (R8~kpc and metallicity from
high-resolution spectroscopy. We aim to investigate the slope of the inner disk
metallicity gradient as traced by OCs and at discussing its implication on the
chemical evolution of our Galaxy. We have derived memberships of a group of
evolved stars for each clusters, obtaining a sample of 4, 4, and 2 member stars
in NGC~6192, NGC~6404, and NGC~6583, respectively. Using standard LTE analysis
we derived stellar parameters and abundance ratios for the iron-peak elements
Fe, Ni, Cr, and for the -elements Al, Mg, Si, Ti, Ca. We calculated the
orbits of the OCs currently located within 8~kpc from the GC, and discuss their
implication on the present-time radial location. {The average metallicities of
the three clusters are all oversolar: [Fe/H]= (NGC~6192),
(NGC 6404), (NGC 6583). They are in qualitative
agreement with their Galactocentric distances, being all internal OCs, and thus
expected to be metal richer than the solar neighborhood. The abundance ratios
of the other elements over iron [X/Fe] are consistent with solar values. The
clusters we have analysed, together with other OC and Cepheid data, confirm a
steep gradient in the inner disk, a signature of an evolutionary rate different
than in the outer disk.Comment: 17 pages, 13 figures, A&A accepted for publicatio
Enhanced lithium depletion in Sun-like stars with orbiting planets
The surface abundance of lithium on the Sun is 140 times less than
protosolar, yet the temperature at the base of the surface convective zone is
not hot enough to burn Li. A large range of Li abundances in solar type stars
of the same age, mass and metallicity is observed, but theoretically difficult
to understand. An earlier suggestion that Li is more depleted in stars with
planets was weakened by the lack of a proper comparison sample of stars without
detected planets. Here we report Li abundances for an unbiased sample of
solar-analogue stars with and without detected planets. We find that the
planet-bearing stars have less than 1 per cent of the primordial Li abundance,
while about 50 per cent of the solar analogues without detected planets have on
average 10 times more Li. The presence of planets may increase the amount of
mixing and deepen the convective zone to such an extent that the Li can be
burned.Comment: 13 pages, 2 figure
Pre-Main Sequence stars in the star forming complex Sh 2-284
Located at the galactic anticenter, Sh 2-284 is a HII region which harbors
several young open clusters; Dolidze 25, a rare metal poor (Z~0.004) young
cluster, is one of these. Given its association with Sh 2-284, it is reasonable
to assume the low metallicity for the whole HII region. Sh~2-284 is expected to
host a significant population of Pre-Main Sequence (PMS) stars of both low and
intermediate mass stars (Herbig Ae stars). We aim at characterizing these stars
by means of a spectroscopic and photometric survey conducted with VIMOS@VLT and
complemented with additional optical and infrared observations. In this survey
we selected and characterized 23 PMS objects. We derived the effective
temperature, the spectral energy distribution and luminosity of these objects;
using theoretical PMS evolutionary tracks, with the appropriate metallicity, we
estimated the mass and the age of the studied objects. We also estimated a
distance of 4 Kpc for Sh 2-284 by using spectroscopic parallax of 3 OB stars.
From the age determination we concluded that triggered star formation is in act
in this region. Our results show that a significant fraction of the young
stellar objects (YSOs) may have preserved their disk/envelopes, in contrast
with what is found in other recent studies of low-metallicity star forming
regions in the Galaxy. Finally, among the 23 bona fide PMS stars, we identified
8 stars which are good candidates to pulsators of the delta Scuti type.Comment: accepted for publication in MNRA
VLT multi-epoch radial velocity survey toward NGC 6253. Analysis of three transiting planetary candidates
We measured the radial velocity of 139 stars in the region of NGC 6253,
discussing cluster's membership and binarity in this sample, complementing our
analysis with photometric, proper motion, and radial velocity data available
from previous studies of this cluster, and analyzing three planetary transiting
candidates we found in the field of NGC 6253. Spectra were obtained with the
UVES and GIRAFFE spectrographs at the VLT, during three epochs in August 2008.
The mean radial velocity of the cluster is -29.11+/-0.85 km/s. Using both
radial velocities and proper motions we found 35 cluster's members, among which
12 are likely cluster's close binary systems. One star may have a sub-stellar
companion, requiring a more intensive follow-up. Our results are in good
agreement with past radial velocity and photometric measurements. Furthermore,
using our photometry, astrometry and spectroscopy we identified a new sub-giant
branch eclipsing binary system, member of the cluster. The cluster's close
binary frequency at 29% +/- 9% (34% +/-10% once including long period
binaries), appears higher than the field binary frequency equal to (22% +/- 5%,
though these estimates are still consistent within the uncertainties. Among the
three transiting planetary candidates the brightest one (V=15.26) is worth to
be more intensively investigated with higher percision spectroscopy. We
discussed the possibility to detect sub-stellar companions (brown dwarfs and
planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS)
around turn-off stars of old open clusters [abridged].Comment: 25 pages, 18 figures, 8 tables. Accepted for publication in A&
Ages for exoplanet host stars
Age is an important characteristic of a planetary system, but also one that
is difficult to determine. Assuming that the host star and the planets are
formed at the same time, the challenge is to determine the stellar age.
Asteroseismology provides precise age determination, but in many cases the
required detailed pulsation observations are not available. Here we concentrate
on other techniques, which may have broader applicability but also serious
limitations. Further development of this area requires improvements in our
understanding of the evolution of stars and their age-dependent
characteristics, combined with observations that allow reliable calibration of
the various techniques.Comment: To appear in "Handbook of Exoplanets", eds. Deeg, H.J. & Belmonte,
J.A, Springer (2018
A new L-dwarf member of the moderately metal-poor triple system HD 221356
We report on the discovery of a fourth component in the HD 221356 star
system, previously known to be formed by an F8V, slightly metal-poor primary
([Fe/H]=-0.26), and a distant M8V+L3V pair. In our ongoing common proper motion
search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have
detected a faint (J=13.76+/-0.04 mag) co-moving companion of the F8 star
located at angular separation of 12.13+/-0.18 arcsec (position angle of
221.8+/-1.7), corresponding to a projected distance of ~312 AU at 26 pc.
Near-infrared spectroscopy of the new companion, covering the 1.5-2.4 micron
wavelength range with a resolving power of R~600, indicates an L1+/-1 spectral
type. Using evolutionary models the mass of the new companion is estimated at
~0.08 solar masses, which places the object close to the stellar-substellar
borderline. This multiple system provides an interesting example of objects
with masses slightly above and below the hydrogen burning mass limit. The low
mass companions of HD 221356 have slightly bluer colours than field dwarfs with
similar spectral type, which is likely a consequence of the sub-solar
metallicity of the system.Comment: 7 pages, 4 figures, accepted for publication in MNRA
WASP-44b, WASP-45b and WASP-46b: three short-period, transiting extrasolar planets
We report the discovery of three extrasolar planets that transit their
moderately bright (Vmag = 12-13) host stars. WASP-44b is a 0.89-MJup planet in
a 2.42-day orbit around a G8V star. WASP-45b is a 1.03-MJup planet which passes
in front of the limb of its K2V host star every 3.13 days. Weak Ca II H+K
emission seen in the spectra of WASP-45 suggests the star is chromospherically
active. WASP-46b is a 2.10-MJup planet in a 1.43-day orbit around a G6V star.
Rotational modulation of the light curves of WASP-46 and weak Ca II H+K
emission in its spectra show the star to be photospherically and
chromospherically active.
We imposed circular orbits in our analyses as the radial velocity data are
consistent with (near-)circular orbits, as could be expected from both
empirical and tidal-theory perspectives for such short-period, Jupiter-mass
planets. We discuss the impact of fitting for eccentric orbits for such planets
when not supported by the data. The derived planetary and stellar radii depend
on the fitted eccentricity and these parameters inform intense theoretical
efforts concerning tidal circularisation and heating, bulk planetary
composition and the observed systematic errors in planetary and stellar radii.
As such, we recommend exercising caution in fitting the orbits of short period,
Jupiter-mass planets with an eccentric model when there is no evidence of
non-circularity.Comment: 12 pages, 8 figures, 6 tables. As accepted for publication in MNRA
RACE-OC Project: Rotation and variability in the epsilon Chamaeleontis, Octans, and Argus stellar associations
We aim at determining the rotational and magnetic-related activity properties
of stars at different stages of evolution. We focus our attention primarily on
members of young stellar associations of known ages. Specifically, we extend
our previous analysis in Paper I (Messina et al. 2010, A&A 520, A15) to 3
additional young stellar associations beyond 100 pc and with ages in the range
6-40 Myr: epsilon Chamaeleontis (~6 Myr), Octans (~20 Myr), and Argus (~40
Myr). Additional rotational data of eta Chamaeleontis and IC2391 clusters are
also considered. Rotational periods were determined from photometric
time-series data obtained by the All Sky Automated Survey (ASAS) and the Wide
Angle Search for Planets (SuperWASP) archives. With the present study we have
completed the analysis of the rotational properties of the late-type members of
all known young loose associations in the solar neighborhood. Considering also
the results of Paper I, we have derived the rotation periods of 241 targets:
171 confirmed, 44 likely, 26 uncertain. The period of the remaining 50 stars
known to be part of loose associations still remains unknown. This rotation
period catalogue, and specifically the new information presented in this paper
at ~6, 20, and 40 Myr, contributes significantly to a better observational
description of the angular momentum evolution of young stars.Comment: Accepted by Astronomy & Astrophysics. Onlines figures will be
available at CD
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