505 research outputs found
Safety shield for vacuum/pressure chamber viewing port
Observers are protected from flying debris resulting from a failure of a vacuum or pressure chamber viewing port following an implosion or explosion by an optically clear shatter resistant safety shield which spaced apart from the viewing port on the outer surface of the chamber
Modeling and Analysis of a Spectrum of the Globular Cluster NGC 2419
NGC 2419 is the most distant massive globular cluster in the outer Galactic
halo. It is unusual also due to the chemical peculiarities found in its red
giant stars in recent years. We study the stellar population of this unusual
object using spectra obtained at the 1.93-m telescope of the Haute-Provence
Observatory. At variance with commonly used methods of high-resolution
spectroscopy applicable only to bright stars, we employ spectroscopic
information on the integrated light of the cluster. We carry out population
synthesis modeling of medium-resolution spectra using synthetic stellar
atmosphere models based on a theoretical isochrone corresponding accurately to
the observed color-magnitude diagram. We study the influence of non-Local
Thermodynamic Equilibrium for some chemical elements on our results. The
derived age (12.6 Gyr), [Fe/H]=-2.25 dex, helium content Y=0.25, and abundances
of 12 other chemical elements are in a good qualitative agreement with
published high-resolution spectroscopy estimates for red giant members in the
cluster. On the other hand, the derived element abundance, [alpha/Fe]=0.13 dex
(the mean of [O/Fe], [Mg/Fe] and [Ca/Fe]), differs from the published one
([alpha/Fe] =0.4 dex) for selected red giants in the cluster and may be
explained by a large dispersion in the alpha-element abundances recently
discovered in NGC2419. We suggest that studies of the {\it integrated} light in
the cluster using high-resolution spectrographs in different wavelength regions
will help to understand the nature of these chemical anomalies.Comment: 19 pages, 6 figures, accepted for publication in the journal
"Astronomy Reports". This work was presented in a poster at IAU General
Assembly XXVIII, Beijing 2012 (Special Session 1 "Origin and Complexity of
Massive Star Clusters"). Four sentences were added thanks comments of Th. H.
Puzi
Review of \u3cem\u3eQueer Excursions: Retheorizing Binaries in Language, Gender and Sexuality\u3c/em\u3e. Lal Zimman, Jenny Davis and Joshua Raclaw (Eds.). Reviewed by Sherri Shimansky
Lal Zimman, Jenny Davis, and Joshua Raclaw (Eds.), Queer Excursions: Retheorizing Binaries in Language, Gender and Sexuality. Oxford University Press (2014), 231 pages, $23.70 (paperback)
Gemini spectroscopy of the outer disk star cluster BH176
BH176 is an old metal-rich star cluster. It is spatially and kinematically
consistent with belonging to the Monoceros Ring. It is larger in size and more
distant from the Galactic plane than typical open clusters, and it does not
belong to the Galactic bulge. Our aim is to determine the origin of this unique
object by accurately determining its distance, metallicity, and age. The best
way to reach this goal is to combine spectroscopic and photometric methods. We
present medium-resolution observations of red clump and red giant branch stars
in BH176 obtained with the Gemini South Multi-Object Spectrograph.We derive
radial velocities, metallicities, effective temperatures, and surface gravities
of the observed stars and use these parameters to distinguish member stars from
field objects. We determine the following parameters for BH176:
km/s, , age Gyr, , distance
kpc, -element abundance dex (the
mean of [Mg/Fe], and [Ca/Fe]). BH176 is a member of old Galactic open clusters
that presumably belong to the thick disk. It may have originated as a massive
star cluster after the encounter of the forming thin disk with a high-velocity
gas cloud or as a satellite dwarf galaxy.Comment: 15 pages, 7 fufures, Accepted for publication in Astronomy &
Astrophysic
On the influence of multiple stellar populations in globular clusters on their medium-resolution integrated-light spectra
We take a closer look at our published results of determination of ages,
metallicities, helium mass fractions and abundances of chemical elements in
Galactic globular clusters in order to find possible signatures of the
phenomenon of multiple stellar populations in these data. Our analysis reveals
that carbon abundances in the atmospheres of stars in the studied clusters
change gradually during their evolution. The changes of the helium mass
fraction and C, O, Mg and Na abundance anomalies caused by the effect of
multiple stellar populations on the analyzed integrated-light spectra are
detected through the comparison of our results with models of chemical
evolution and literature data for Galactic field stars.Comment: 4 pages, 2 tables, to be published in the proceedings of the
conference 'Ground-Based Astronomy in Russia. 21st Century', Nizhnii Arkhyz,
Russia, 21-25 Sep 202
1RXS J180834.7+101041 is a new cataclysmic variable with non-uniform disc
Results of photometric and spectroscopic investigations of the recently
discovered disc cataclysmic variable star 1RXS J180834.7+101041 are presented.
Emission spectra of the system show broad double peaked hydrogen and helium
emission lines. Doppler maps for the hydrogen lines demonstrate strongly
non-uniform emissivity distribution in the disc, similar to that found in IP
Peg. It means that the system is a new cataclysmic variable with a spiral
density wave in the disc. Masses of the components (M_WD = 0.8 +/- 0.22 M_sun
and M_RD = 0.14 +/- 0.02 M_sun), and the orbit inclination (i = 78 +/- 1.5 deg)
were estimated using the various well-known relations for cataclysmic
variables.Comment: 4 pages, 3 figures, conference "European White Dwarf Workshop, 2010",
Tuebingen, German
- …