842 research outputs found
The Solar Neighborhood XXVII: Discovery of New Proper Motion Stars with mu > 0.18 "/yr in the Southern Sky with 16.5 > R_59F > 18.0
Here we present 1584 new southern proper motion systems with mu > 0.18 "/yr
and 16.5 > R_59F > 18.0. This search complements the six previous
SuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky for stars
within the same proper motion range, but with R_59F < 16.5. As in previous
papers, we present distance estimates for these systems and find that three
systems are estimated to be within 25 pc, including one, SCR 1546-5534,
possibly within the RECONS 10 pc horizon at 6.7 pc, making it the second
nearest discovery of the searches. We find 97 white dwarf candidates with
distance estimates between 10 and 120 pc, as well as 557 cool subdwarf
candidates. The subdwarfs found in this paper make up nearly half of the
subdwarf systems reported from our SCR searches, and are significantly redder
than those discovered thus far. The SCR searches have now found 155 red dwarfs
estimated to be within 25 pc, including 10 within 10 pc. In addition, 143 white
dwarf candidates and 1155 cool subdwarf candidates have been discovered. The
1584 systems reported here augment the sample of 4724 systems previously
discovered in our SCR searches, and imply that additional systems fainter than
R_59F = 18.0 are yet to be discovered.Comment: 11 pages of text, seven figure
Spectral time scales for mid-latitude eddies
A few hundred current meter records of roughly one to two years\u27 duration are now available from diverse locations in the world\u27s oceans, primarily the North Atlantic. The shape of the spectrum for low-frequency ocean current fluctuations is shown to have a geographical distribution related to the general circulation. In the offshore segment of the Gulf Stream and Kuroshio Extension systems along with their recirculations, and near the Agulhas Current as well, normalized frequency distributions of eddy kinetic energy tend to be comparatively depth-independent and peaked at the mesoscale. However, in the immediate vicinity of current axes or fronts, spectral shapes may become “red” in the thermocline, as a result of low-frequency meandering of a baroclinic jet across mooring sites. Normalized frequency distributions of eddy kinetic energy from some areas distant from strong currents but perhaps near weaker upper-ocean fronts tend to be baroclinic and not peaked at the mesoscale in the thermocline, rather they are “red” there, although peaked at the mesoscale at abyssal depths. There are also low energy regions where spectral shapes tend to be red and comparatively independent of depth. In some areas, frequency distributions are relatively energetic or peaked at periods of order days, normally at depth near bottom relief
The Solar Neighborhood XXV: Discovery of New Proper Motion Stars with 0.40 "/yr > mu > 0.18 "/yr between Declinations -47 degrees and 00 degrees
We present 2817 new southern proper motion systems with 0.40 "/yr > mu > 0.18
"/yr and declination between -47 degrees and 00 degrees. This is a continuation
of the SuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky. We
use the same photometric relations as previous searches to provide distance
estimates based on the assumption that the objects are single main sequence
stars. We find 79 new red dwarf systems predicted to be within 25 pc, including
a few new components of previously known systems. Two systems - SCR 1731-2452
at 9.5 pc and SCR 1746-3214 at 9.9 pc - are anticipated to be within 10 pc. We
also find 23 new white dwarf candidates with distance estimates of 15-66 pc, as
well as 360 new red subdwarf candidates. With this search, we complete the SCR
sweep of the southern sky for stars with mu > 0.18 "/yr and R_59F < 16.5,
resulting in a total of 5042 objects in 4724 previously unreported proper
motion systems. Here we provide selected comprehensive lists from our SCR
proper motion search to date, including 152 red dwarf systems estimated to be
within 25 pc (nine within 10 pc), 46 white dwarfs (ten within 25 pc), and 598
subdwarf candidates. The results of this search suggest that there are more
nearby systems to be found at fainter magnitudes and lower proper motion limits
than those probed so far.Comment: 47 pages, 16 of text. 7 figure
Naar een hervorming van het Vlaams secundair onderwijs:Evaluatieve bemerkingen ex ante vanuit Nederlands perspectief
Naar een hervorming van het Vlaams secundair onderwijs:Evaluatieve bemerkingen ex ante vanuit Nederlands perspectief
Naar een hervorming van het Vlaams secundair onderwijs:Evaluatieve bemerkingen ex ante vanuit Nederlands perspectief
Chandra Observations of the Dwarf Nova WX Hyi in Quiescence
We report Chandra observations of the dwarf nova WX Hyi in quiescence. The
X-ray spectrum displays strong and narrow emission lines of N, O, Mg, Ne, Si, S
and Fe. The various ionization states implied by the lines suggest that the
emission is produced within a flow spanning a wide temperature range, from T ~
10^6 K to T >~ 10^8 K. Line diagnostics indicate that most of the radiation
originates from a very dense region, with n ~ 10^{13}-10^{14} cm^{-3}. The
Chandra data allow the first tests of specific models proposed in the
literature for the X-ray emission in quiescent dwarf novae. We have computed
the spectra for a set of models ranging from hot boundary layers, to hot
settling flows solutions, to X-ray emitting coronae. WX Hyi differs from other
dwarf novae observed at minimum in having much stronger low temperature lines,
which prove difficult to fit with existing models, and possibly a very strong,
broad O VII line, perhaps produced in a wind moving at a few x 10^3 km/s. The
accretion rate inferred from the X-rays is lower than the value inferred from
the UV. The presence of high-velocity mass ejection could account for this
discrepancy while at the same time explaining the presence of the broad O VII
line. If this interpretation is correct, it would provide the first detection
of a wind from a dwarf nova in quiescence.Comment: accepted to ApJ; 19 pages, 3 figures, 1 tabl
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