1,619 research outputs found
A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
We present new Near-Infrared (J,K) magnitudes for 114 RR Lyrae stars in the
globular cluster Omega Cen (NGC 5139) which we combine with data from the
literature to construct a sample of 180 RR Lyrae stars with J and K mean
magnitudes on a common photometric system. This is presently the largest such
sample in any stellar system. We also present updated predictions for J,K-band
Period-Luminosity relations for both fundamental and first-overtone RR Lyrae
stars, based on synthetic horizontal branch models with metal abundance ranging
from Z=0.0001 to Z=0.004. By adopting for the Omega Cen variables with measured
metal abundances an alpha-element enhancement of a factor of 3 (about 0.5 dex)
with respect to iron we find a true distance modulus of 13.70 (with a random
error of 0.06 and a systematic error of 0.06), corresponding to a distance
d=5.5 Kpc (with both random and systematic errors equal to 0.03 Kpc). Our
estimate is in excellent agreement with the distance inferred for the eclipsing
binary OGLEGC-17, but differ significantly from the recent distance estimates
based on cluster dynamics and on high amplitude Delta Scuti stars.Comment: 24 pages, 7 figures, accepted for publication on The Astrophysical
Journa
Immunotherapy as a turning point in the treatment of acute myeloid leukemia
Acute myeloid leukemia (AML) is a malignant disease of hematopoietic precursors at
the earliest stage of maturation, resulting in a clonalproliferation of myoblasts replacing normal
hematopoiesis. AML represents one of the most common types of leukemia, mostly affecting elderly
patients. To date, standard chemotherapy protocols are only effective in patients at low risk of relapse
and therapy-related mortality. The average 5-year overall survival (OS) is approximately 28%. Allogeneic hematopoietic stem cell transplantation (HSCT) improves prognosis but is limited by donor
availability, a relatively young age of patients, and absence of significant comorbidities. Moreover, it
is associated with significant morbidity and mortality. However, increasing understanding of AML
immunobiology is leading to the development of innovative therapeutic strategies. Immunotherapy
is considered an attractive strategy for controlling and eliminating the disease. It can be a real
breakthrough in the treatment of leukemia, especially in patients who are not eligible forintensive
chemotherapy. In this review, we focused on the progress of immunotherapy in the field of AML by
discussing monoclonal antibodies (mAbs), immune checkpoint inhibitors, chimeric antigen receptor
T cells (CAR-T cells), and vaccine therapeutic choices
When Viruses Meet Fungi: Tackling the Enemies in Hematology
The association of invasive fungal infections (IFI) and viral infections has been described in patients with hematologic malignancies (HM), in particular in hematopoietic stem cell transplant recipients. Regrettably, the diagnosis is often challenging, making the treatment inappropriate in some circumstances. The present review takes into consideration the viral infections commonly associated with IFI. Clinical presentation of IFI and viral infections, risk factors, and impact on the outcome of HM patients are discussed throughout the paper
Hubble Space Telescope Observations of an Outer Field in Omega Centauri: A Definitive Helium Abundance
We revisit the problem of the split main sequence (MS) of the globular
cluster omega Centauri, and report the results of two-epoch Hubble Space
Telescope observations of an outer field, for which proper motions give us a
pure sample of cluster members, and an improved separation of the two branches
of the main sequence. Using a new set of stellar models covering a grid of
values of helium and metallicity, we find that the best possible estimate of
the helium abundance of the bluer branch of the MS is Y = 0.39 +/- 0.02. For
the cluster center we apply new techniques to old observations: we use indices
of photometric quality to select a high-quality sample of stars, which we also
correct for differential reddening. We then superpose the color-magnitude
diagram of the outer field on that of the cluster center, and suggest a
connection of the bluer branch of the MS with one of the more prominent among
the many sequences in the subgiant region. We also report a group of undoubted
cluster members that are well to the red of the lower MS.Comment: 26 pages, 10 figures (4 in low resolution. AJ accepted on March 21,
201
B, V, I photometry of the complete sample of 23 Cepheids in the field of NGC 1866
We present the result of BVI photometry, obtained by using FORS@VLT, of the
Cepheids present in the field of the Large Magellanic Cloud cluster NGC 1866.
We found the 22 known variables plus an additional new Cepheid located about
10' from the cluster center. The accuracy of the photometry allowed us to
derive B, V and I mean magnitudes with an uncertainty lower than 0.02 mag for
22 out of the 23 objects, with the exception of only one Cepheid (WS9) which
presents a noisy light curve due to the probable occurrence of image blending.
As a result, we provide accurate observational data for a substantial sample of
variables all lying at the same distance and with a common original
composition. The resulting period-luminosity relations are presented and
briefly discussed.Comment: 4 pages, 6 figure, to appear in the proceedings of the Workshop
"Stellar pulsation and evolution", 2005. Monte Porzio Catone, Italy. Eds.: A.
R. Walker and G. Bon
On the distance and reddening of the starburst galaxy IC10
We present deep and accurate optical photometry of the Local Group starburst
galaxy IC10. The photometry is based on two sets of images collected with the
Advanced Camera for Surveys and with the Wide Field Planetary Camera 2 on board
the Hubble Space Telescope. We provide new estimates of the Red Giant Branch
tip (TRGB) magnitude, m_{F814W}^{TRGB}=21.90+-0.03, and of the reddening,
E(B-V)=0.78+-0.06, using field stars in the Small Magellanic Cloud (SMC) as a
reference. Adopting the SMC and two globulars, Omega Centauri and 47 Tucanae,
as references we estimate the distance modulus to IC10: independent
calibrations give weighted average distances of mu=24.51+-0.08 (TRGB) and
mu=24.56+-0.08 (RR Lyrae). We also provide a new theoretical calibration for
the TRGB luminosity, and using these predictions we find a very similar
distance to IC10 (mu~24.60+-0.15). These results suggest that IC10 is a likely
member of the M31 subgroup.Comment: 4 pages, 4 figures, ApJ Letters accepte
Relative distances of Omega Centauri and 47 Tucanae
We present precise optical and near-infrared ground-based photometry of two
Globular Clusters (GCs): Omega Cen and 47 Tuc. These photometric catalogs are
unbiased in the Red Giant Branch (RGB) region close to the tip. We provide new
estimates of the RGB tip (TRGB) magnitudes--m_I(TRGB)=9.84+/-0.05, Omega Cen;
m_I(TRGB)=9.46+/-0.06, 47 Tuc--and use these to determine the relative
distances of the two GCs. We find that distance ratios based on different
calibrations of the TRGB, the RR Lyrae stars and kinematic distances agree with
each other within one sigma. Absolute TRGB and RR Lyrae distance moduli agree
within 0.10--0.15 mag, while absolute kinematic distance moduli are 0.2--0.3
mag smaller. Absolute distances to 47 Tuc based on the
Zero-Age-Horizontal-Branch and on the white dwarf fitting agree within 0.1 mag,
but they are 0.1--0.3 mag smaller than TRGB and RR Lyrae distances.Comment: 5 pages, 4 figures, accepted for publication by ApJ
Star Counts in the Globular Cluster Omega Centauri. I. Bright Stellar Components
We present an extensive photometry on HB, RGB, and MSTO stars in Omega Cen.
The central regions of the cluster were covered with a mosaic of F435W, F625W,
and F658N-band data collected with ACS/HST. The outer reaches were covered with
a large set of U,B,V,I-band data collected with the [email protected] ESO/MPI telescope.
The final catalogue includes ~1.7 million stars. We identified ~3,200 likely HB
stars and ~12,500 stars brighter than the subgiant branch and fainter than the
RGB bumps. The HB morphology changes with the radial distance. The relative
number of extreme HB stars decreases from ~30% to ~21% when moving from the
center toward the outer regions of the cluster, while the fraction of less hot
HB stars increases from ~62% to ~72%. We performed a detailed comparison
between observed ratios of different stellar tracers and predictions based on
canonical evolutionary models with a primordial helium (Y=0.23) content and
metal abundances (Z=0.0002,0.001) that bracket the observed spread in
metallicity of Omega Cen stars. We found that the empirical star counts of HB
stars are on average larger (30%-40%) than predicted. Moreover, the rate of HB
stars is 43% larger than the MSTO rate. The discrepancy between the rate of HB
compared with the rate of RG and MSTO stars supports the evidence that we are
facing a true excess of HB stars. The same comparison was performed by assuming
a mix of stellar populations made with 70% of canonical stars and 30% of
He-enhanced stars. The discrepancy between theory and observations decreases by
a factor of two when compared with rates predicted by canonical He content
models, but still 15%-25% (Y=0.42) and 15%-20% (Y=0.33) higher than observed.
Furthermore, the ratio between HB and MSTO star counts are ~24% (Y=0.42) and
30% (Y=0.33) larger than predicted lifetime ratios.Comment: 54 pages, 17 figures,to be published in ApJ, see link at
http://stellari.wiki.zoho.co
On the anomalous red giant branch of the globular cluster Omega Cen
We present three different optical and near-infrared (NIR) data sets for
evolved stars in the Galactic Globular Cluster Omega Cen The comparison between
observations and homogeneous sets of stellar isochrones and Zero-Age Horizontal
Branches provides two reasonable fits. Both of them suggest that the so-called
anomalous branch has a metal-intermediate chemical composition (-1.1 < [Fe/H] <
-0.8) and is located ~500 pc beyond the bulk of Omega Cen stars. These findings
are mainly supported by the shape of the subgiant branch in four different
color-magnitude diagrams (CMDs). The most plausible fit requires a higher
reddening, E(B-V)=0.155 vs. 0.12, and suggests that the anomalous branch is
coeval, within empirical and theoretical uncertainties, to the bulk of Omega
Cen stellar populations. This result is supported by the identification of a
sample of faint horizontal branch stars that might be connected with the
anomalous branch. Circumstantial empirical evidence seems to suggest that the
stars in this branch form a clump of stars located beyond the cluster.Comment: Accepted for publication on ApJ. High resolution figures can be
downloaded from ftp://ftp.mporzio.astro.it/dist/monelli2
Near-IR period-luminosity relations for pulsating stars in Centauri (NGC 5139)
Centauri (NGC 5139) hosts hundreds of pulsating variable stars of
different types, thus representing a treasure trove for studies of their
corresponding period-luminosity (PL) relations. Our goal in this study is to
obtain the PL relations for RR Lyrae, and SX Phoenicis stars in the field of
the cluster, based on high-quality, well-sampled light curves in the
near-infrared (IR). Centauri was observed using VIRCAM mounted on
VISTA. A total of 42 epochs in and 100 epochs in were obtained,
spanning 352 days. Point-spread function photometry was performed using DoPhot
and DAOPHOT in the outer and inner regions of the cluster, respectively. Based
on the comprehensive catalogue of near-IR light curves thus secured, PL
relations were obtained for the different types of pulsators in the cluster,
both in the and bands. This includes the first PL relations in
the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and
periods of Type II Cepheids and RR Lyrae stars were used to derive an updated
true distance modulus to the cluster, with a resulting value of mag, where the error bars correspond to the adopted
statistical and systematic errors, respectively. Adding the errors in
quadrature, this is equivalent to a heliocentric distance of
kpc.Comment: 10 pages, 8 figures, accepted for publication in A&
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