1,676 research outputs found
Simulated Galactic methanol maser distribution to constrain Milky Way parameters
Using trigonometric parallaxes and proper motions of masers associated with
massive young stars, the Bar and Spiral Structure Legacy (BeSSeL) survey has
reported the most accurate values of the Galactic parameters so far. The
determination of these parameters with high accuracy has a widespread impact on
Galactic and extragalactic measurements. This research is aimed at establishing
the confidence with which such parameters can be determined. This is relevant
for the data published in the context of the BeSSeL survey collaboration, but
also for future observations, in particular from the Southern Hemisphere. In
addition, some astrophysical properties of the masers can be constrained,
notably the luminosity function. We have simulated the population of
maser-bearing young stars associated with Galactic spiral structure, generating
several samples and comparing them with the observed samples used in the BeSSeL
survey. Consequently, we checked the determination of Galactic parameters for
observational biases introduced by the sample selection. Galactic parameters
obtained by the BeSSeL survey do not seem to be biased by the sample selection
used. In fact, the published error estimates appear to be conservative for most
of the parameters. We show that future BeSSeL data and future observations with
Southern arrays will improve the Galactic parameters estimates and smoothly
reduce their mutual correlation. Moreover, by modeling future parallax data
with larger distance and, thus, greater relative uncertainties for a larger
numbers of sources, we found that parallax-distance biasing is an important
issue. Hence, using fractional parallax uncertainty in the weighting of the
motion data is imperative. Finally, the luminosity function for 6.7 GHz
methanol masers was determined, allowing us to estimate the number of Galactic
methanol masers.Comment: Accepted for publication in A&A. Language edition include
Finding evolved stars in the inner Galactic disk with Gaia
The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey will provide
positions and line-of-sight velocities of ~20,000 evolved, maser bearing stars
in the Galactic plane. Although this Galactic region is affected by optical
extinction, BAaDE targets may have Gaia cross-matches, eventually providing
additional stellar information. In an initial attempt to cross-match BAaDE
targets with Gaia, we have found more than 5,000 candidates. Of these, we may
expect half to show SiO emission, which will allow us to obtain velocity
information. The cross-match is being refined to avoid false positives using
different criteria based on distance analysis, flux variability, and color
assessment in the mid- and near-IR. Once the cross-matches can be confirmed, we
will have a unique sample to characterize the stellar population of evolved
stars in the Galactic bulge, which can be considered fossils of the Milky Way
formation.Comment: To appear in the Proceedings of the IAU Symposium No. 330:
"Astrometry and Astrophysics in the Gaia sky
Eclipsing high-mass binaries I. Light curves and system parameters for CPD-518946, PISMIS24-1 and HD319702
We present first results of a comprehensive photometric O-star survey
performed with a robotic twin refractor at the Universit\"atssternwarte Bochum
located near Cerro Armazones in Chile. For three high-mass stars, namely
Pismis24-1, CPD-518946 and HD319702, we determined the period through the
Lafler-Kinman algorithm and model the light curves within the framework of the
Roche geometry. For Pismis24-1, a previously known eclipsing binary, we provide
first light curves and determined a photometric period of 2.36 days together
with an orbital inclination of 61.8 degrees. The best-fitting model solution to
the light curves suggest a detached configuration. With a primary temperature
of T1 = 42520K we obtain the temperature of the secondary component as T2 =
41500K. CPD-518946 is another known eclipsing binary for which we present a
revised photometric period of 1.96 days with an orbital inclination of 58.4
degrees. The system has likely a semi-detached configuration and a mass ratio q
= M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34550K we obtain T2 =
21500K for the secondary component. HD319702 is a newly discovered eclipsing
binary member of the young open cluster NGC6334. The system shows well-defined
eclipses favouring a detached configuration with a period of 2.0 days and an
orbital inclination of 67.5 degrees. Combining our photometric result with the
primary spectral type O8 III(f) (T1 = 34000K) we derive a temperature of T2 =
25200K for the secondary component.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
Astrometric Galactic maser measurements cross-matched with Gaia
Using the VLBA, the BeSSeL survey has provided distances and proper motions
of young massive stars, allowing an accurate measure of the Galactic spiral
structure. By the same technique, we are planning to map the inner Galaxy using
positions and velocities of evolved stars (provided by the BAaDE survey). These
radio astrometric measurements (BeSSeL and BAaDE) will be complementary to Gaia
results and the overlap will provide important clues on the intrinsic
properties and population distribution of the stars in the bulge.Comment: To appear in the Proceedings of the IAU Symposium No. 334:
"Rediscovering our Galaxy
Maser, infrared and optical emission for late-type stars in the Galactic plane
Radio astrometric campaigns using VLBI have provided distances and proper
motions for masers associated with young massive stars (BeSSeL survey). The
ongoing BAaDE project plans to obtain astrometric information of SiO maser
stars located in the inner Galaxy. These stars are associated with evolved,
mass-losing stars. By overlapping optical (Gaia), infrared (2MASS, MSX and
WISE) and radio (BAaDE) sources, we expect to obtain important clues on the
intrinsic properties and population distribution of late-type stars. Moreover,
a comparison of the Galactic parameters obtained with Gaia and VLBI can be done
using radio observations on different targets: young massive stars (BeSSeL) and
evolved stars (BAaDE).Comment: To appear in the Proceedings of the IAU Symposium No. 336:
Astrophysical Masers: Unlocking the Mysteries of the Univers
Dust reverberation-mapping of the Seyfert 1 galaxy WPVS48
Using robotic telescopes of the Universitatssternwarte Bochum near Cerro
Armazones in Chile, we monitored the z=0.0377 Seyfert 1 galaxy WPVS48 (2MASX
J09594263-3112581) in the optical (B and R) and near-infrared (NIR, J and Ks)
with a cadence of two days. The light curves show unprecedented variability
details. The NIR variation features of WPVS48 are consistent with the
corresponding optical variations, but the features appear sharper in the NIR
than in the optical, suggesting that the optical photons undergo multiple
scatterings. The J and Ks emission, tracing the hot (1600 K) dust echo, lags
the B and R variations by on average 64 +/- 4 days and 71 +/- 5 days,
respectively (restframe). WPVS48 lies on the known tau-M_V relationship.
However, the observed lag is about three times shorter than expected from the
dust sublimation radius r_sub inferred from the optical-UV luminosity, and
explanations for this common discrepancy are searched for. The sharp NIR echos
argue for a face-on torus geometry and allow us to put forward two potential
scenarios: 1) as previously proposed, in the equatorial plane of the accretion
disk the inner region of the torus is flattened and may come closer to the
accretion disk. 2) The dust torus with inner radius r_sub is geometrically and
optically thick, so that the observer only sees the facing rim of the torus
wall, which lies closer to the observer than the torus equatorial plane and
therefore leads to an observed foreshortened lag. Both scenarios are able to
explain the factor three discrepancy between tau and r_sub. Longer-wavelength
dust reverberation data might enable one to distinguish between the scenarios.Comment: 4 pages, 6 figures, Published in Astronomy and Astrophysic
CaracterĂsticas anatĂłmicas del huevo de Haematopinus suis (Phthiraptera, Anoplura, Haematopinidae) y su relaciĂłn con la resistencia frente a los factores agresivos del ambiente
Fil: Prieto, Olegario H.. Cátedra de ParasitologĂa y enfermedades parasitarias de la Facultad de Ciencias Veterinarias. UBA; ArgentinaFil: Abrahamovich, Alberto H.. Laboratorio de ApidologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cicchino, Armando Conrado. DivisiĂłn EntomologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Nuñez, Jorge L.. Cátedra de ParasitologĂa y enfermedades parasitarias de la Facultad de Ciencias Veterinarias. UBA; Argentin
DNMT1 and Cancer: An Electrifying Link
Aberrant epigenetic methylation is linked to the onset and progression of cancer. In this issue of Chemistry & Biology, Furst and Barton (2015) describe a sensitive electrochemical assay that can detect hyperactive epigenetic methylation in tumor tissue
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