2,587 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
Evaluation of fiber-optic phase-gradient meta-tips for sensing applications
Recently, within the emerging framework of "lab-on-fiber" technologies, we successfully demonstrated the integration of phase-gradient plasmonic metasurfaces on the tip of an optical fiber. The res..
Near-Infrared Observations of RR Lyrae Variables in Galactic Globular Clusters. I. The Case of M92
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
Optical Spectral Variability of the Very-High-Energy Gamma-Ray Blazar 1ES 1011+496
We present results of five years of optical (UBVRI) observations of the
very-high-energy gamma-ray blazar 1ES 1011+496 at the MDM Observatory. We
calibrated UBVRI magnitudes of five comparison stars in the field of the
object. Most of our observations were done during moderately faint states of
1ES 1011+496 with R > 15.0. The light curves exhibit moderate, closely
correlated variability in all optical wavebands on time scales of a few days. A
cross-correlation analysis between optical bands does not show significant
evidence for time lags. We find a positive correlation (Pearson's r = 0.57;
probability of non-correlation P(>r) ~ 4e-8) between the R-band magnitude and
the B - R color index, indicating a bluer-when-brighter trend. Snap-shot
optical spectral energy distributions (SEDs) exhibit a peak within the optical
regime, typically between the V and B bands. We find a strong (r = 0.78;
probability of non-correlation P (>r) ~ 1e-15) positive correlation between the
peak flux and the peak frequency, best fit by a relation with k = 2.05 +/- 0.17. Such a correlation is
consistent with the optical (synchrotron) variability of 1ES 1011+496 being
primarily driven by changes in the magnetic field.Comment: Accepted for publication in ApJ. 16 pages, including 7 figure
Effect of s-triazine ring substitution on the synthesis of organic resorcinol-formaldehyde xerogels
Resorcinol (R) and formaldehyde (F) gel synthesis has been well-studied along with alternative reagents. We present the synthesis of formaldehyde-based xerogels using chemically similar s-triazine precursors, with comparison to traditional analogues. The substitution ranges from tri-hydroxyl to tri-amine, with an intermediate species, allowing changing chemistry to be investigated. Each molecule (X) offers different acid/base properties, known to influence gel formation, as well as differences in crosslinking potential. Varying X/F ratios were selected to recreate the stoichiometry used in RF systems, where one represented higher F to match the increased reaction sites of the additives. X/C ratios were selected to probe different catalyst (C) ratios, while working within the range likely to produce viable gels. Results obtained show little impact for ammeline as an additive due to its similarity to resorcinol (activation sites and pKa); while melamine and cyanuric acid show differing behavior depending on the level of addition. Low concentrations show melamine to have the most impact due to increased activation and competition for formaldehyde; while at high concentrations, cyanuric acid is shown to have the greatest impact as it creates a more acidic environment, which diminishes textural character, possibly attributable to larger clusters and/or weaker cross-linking of the system
A Chemical Map of the Outbursting V883 Ori system: Vertical and Radial Structures
We present the first results of a pilot program to conduct an Atacama Large
Millimeter/submillimeter Array (ALMA) Band 6 (211-275 GHz) spectral line study
of young stellar objects (YSO) that are undergoing rapid accretion episodes,
i.e. FU Ori objects (FUors). Here, we report on molecular emission line
observations of the FUor system, V883 Ori. In order to image the FUor object
with full coverage from ~0.5 arcsec to the map size of ~30 arcsec, i.e. from
disc to outflow scales, we combine the ALMA main array (the 12-m array) with
the Atacama Compact Array (7-m array) and the total power (TP) array. We detect
HCN, HCO, CHOH, SO, DCN, and HCO emissions with most of these
lines displaying complex kinematics. From PV diagrams, the detected molecules
HCN, HCO, CHOH, DCN, SO, and HCO probe a Keplerian rotating
disc in a direction perpendicular to the large-scale outflow detected
previously with the CO and CO lines. Additionally, HCN and
HCO reveal kinematic signatures of infall motion. The north outflow is
seen in HCO, HCO, and SO emissions. Interestingly, HCO
emission reveals a pronounced inner depression or "hole" with a size comparable
to the radial extension estimated for the CHOH and 230 GHz continuum. The
inner depression in the integrated HCO intensity distribution of V883 Ori
is most likely the result of optical depth effects, wherein the optically thick
nature of the HCO and continuum emission towards the innermost parts of
V883 Ori can result in a continuum subtraction artifact in the final HCO
flux level
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