Search Publications
Interstellar Extinction and Polarization of Stars in the Open Cluster NGC 6709
Topasna, G. A.; Kaltcheva, N. T.; Gibson, S. D.
We present BVRI polarimetric measurements of 23 stars in the direction of the open cluster NGC 6709. Fifteen stars display wavelength-dependence of polarization which is typically due to selective extinction in the interstellar medium and could be fitted to the Serkwoski equation. Based on these stars, we obtained an average maximum degree of pola…
The neutron-capture and α-elements abundance ratios scatter in old stellar populations: cosmological simulations of the stellar halo
Chiappini, Cristina; Cescutti, Gabriele; Scannapieco, Cecilia
We investigate the origin of the abundance ratios and scatter of the neutron-capture elements Sr, Ba, and Eu in the stellar halo of a Milky Way-mass galaxy formed in a hydrodynamical cosmological simulation, and compare them with those of α elements. For this, we implement a novel treatment for chemical enrichment of Type II supernovae that consid…
Understanding High-Energy (UV and X-ray) Emission from AGB Stars—Episodic Accretion in Binary Systems
Sanz-Forcada, Jorge; Sahai, Raghvendra; Ortiz, Roberto +2 more
X-ray surveys of UV-emitting AGB stars show that ∼40% of objects with FUV emission and GALEX FUV/NUV flux ratio Rfuv/nuv ∼> 0.2 (fuvAGB stars) have variable X-ray emission characterized by very high temperatures (Tx∼35–160 MK) and luminosities (Lx∼0.002–0.2 L⊙), indicating the presence of accretion associated with a close binary companion. Howe…
Massive Molecular Gas Reservoir in a Luminous Submillimeter Galaxy during Cosmic Noon
Cooray, A.; Marchetti, L.; Nayyeri, H. +11 more
We present multiband observations of an extremely dusty star-forming lensed galaxy (HERS1) at z = 2.553. High-resolution maps of HST/WFC3, SMA, and ALMA show a partial Einstein ring with a radius of ~3″. The deeper HST observations also show the presence of a lensing arc feature associated with a second lens source, identified to be at the same re…
Multi-passband Observations of a Solar Flare over the He I 10830 Å line
Polito, Vanessa; Xu, Yan; Cao, Wenda +5 more
This study presents a C3.0 flare observed by the Big Bear Solar Observatory/Goode Solar Telescope (GST) and Interface Region Imaging Spectrograph (IRIS) on 2018 May 28 around 17:10 UT. The Near-Infrared Imaging Spectropolarimeter of GST was set to spectral imaging mode to scan five spectral positions at ±0.8, ±0.4 Å and line center of He I 10830 Å…
Evolution of a dark vortex on Neptune with transient secondary features
de Pater, Imke; Wong, Michael H.; Irwin, Patrick G. J. +8 more
Dark spots on Neptune observed by Voyager and the Hubble Space Telescope are thought to be anticyclones with lifetimes of a few years, in contrast with very long-lived anticyclones in Jupiter and Saturn. The full life cycle of any Neptune dark spot has not been captured due to limited temporal coverage, but our Hubble observations of a recent feat…
The recent star formation history of NGC 628 on resolved scales
Saintonge, Amélie; De Looze, Ilse; Decleir, Marjorie +1 more
Star formation histories (SFHs) are integral to our understanding of galaxy evolution. We can study recent SFHs by comparing the star formation rate (SFR) calculated using different tracers, as each probes a different time-scale. We aim to calibrate a proxy for the present-day rate of change in SFR, dSFR/dt, which does not require full spectral en…
Properties of IR-selected active galactic nuclei
García Lambas, D.; Alonso, M. V.; Bornancini, C. G. +1 more
Context. Active galactic nuclei (AGNs) of galaxies play an important role in the life and evolution of galaxies through the impact they exert on certain properties and on the evolutionary path of galaxies. It is well known that infrared (IR) emission is useful for selecting galaxies with AGNs, although it has been observed that there is contaminat…
The Cluster Ages Experiment (CASE) - IX. Analysis of four detached eclipsing binaries in the globular cluster NGC 3201
Marshall, J. L.; Thompson, I. B.; Morrell, N. +14 more
We use photometric and spectroscopic observations of four detached eclipsing binaries in the globular cluster NGC 3201 to derive masses, radii, and luminosities of the component stars. Spanning across almost three magnitudes in the colour-magnitude diagram, the components offer a unique possibility to test the theory of stellar evolution. Their ma…
Detached eclipsing binaries from the Kepler field: radii and photometric masses of components in short-period systems
Diaz, Marcos P.; Cruz, Patricia; Aguilar, John F. +2 more
The characterization of detached eclipsing binaries with low-mass components has become important when verifying the role of convection in stellar evolutionary models, which requires model-independent measurements of stellar parameters with great precision. However, spectroscopic characterization depends on single-target radial velocity observatio…