1,546 research outputs found
The SMC X-ray transient XTE J0111.2-7317 : a Be/X-ray binary in a SNR?
We report observations which confirm the identity of the optical/IR
counterpart to the Rossi X-ray Timing Explorer transient source XTE
J0111.2-7317. The counterpart is suggested to be a B0-B2 star (luminosity class
III--V) showing an IR excess and strong Balmer emission lines. The distance
derived from reddening and systemic velocity measurements puts the source in
the SMC. Unusually, the source exhibits an extended asymetric H alpha
structure.Comment: 5 pages, 3 figs, accepted by MNRA
Solar Irradiance Variability and Climate
The brightness of the Sun varies on all time scales on which it has been
observed, and there is increasing evidence that it has an influence on climate.
The amplitudes of such variations depend on the wavelength and possibly on the
time scale. Although many aspects of this variability are well established, the
exact magnitude of secular variations (going beyond a solar cycle) and the
spectral dependence of variations are under discussion. The main drivers of
solar variability are thought to be magnetic features at the solar surface. The
climate reponse can be, on a global scale, largely accounted for by simple
energetic considerations, but understanding the regional climate effects is
more difficult. Promising mechanisms for such a driving have been identified,
including through the influence of UV irradiance on the stratosphere and
dynamical coupling to the surface. Here we provide an overview of the current
state of our knowledge, as well as of the main open questions
Optical studies of two LMC X-ray transients : RX J0544.1-7100 and RX J0520.5-6932
We report observations which confirm the identities of the optical
counterpart to the transient sources RX J0544.1-7100 and RX J0520.5-6932. The
counterparts are suggested to be a B-type stars. Optical data from the
observations carried out at ESO and SAAO, together with results from the OGLE
data base, are presented. In addition, X-ray data from the RXTE all-sky monitor
are investigated for long term periodicities. A strong suggestion for a binary
period of 24.4d is seen in RX J0520.5-6932 from the OGLE data.Comment: 6 pages, 7 figure
Disc loss and renewal in A0535+26
This paper presents observations of the Be/X-ray binary system A0535+26
revealing the first observed loss of its circumstellar disc, demonstrated by
the loss of its JHK infrared excess and optical/IR line emission. However
optical/IR spectroscopy reveals the formation of a new inner disc with
significant density and emission strength at small radii; the disc has proven
to be stable over 5 months in this intermediate state.Comment: 4 pages, 4 figures, accepted by MNRAS, uses mn.st
What children know about the source of their knowledge without reporting it as the source
We argue that, amongst 3- to 5- year-olds, failure to report the source of knowledge recently acquired in answer to âHow do you knowâŠ?â is due to a specific failure to make a causal inference, in line with source monitoring theory but not fuzzy trace theory. In three Experiments, children (N = 37; 30; 59) identified a hidden toy by seeing, feeling, or by being told, having had two modes of access on each trial, one informative (e.g. seeing a toy identified by colour) and the other uninformative (e.g. being told the toyâs colour by the Experimenter who had only felt it). Children who answered the know question wrongly nevertheless reported accurately who saw and who felt the toy, and what the well-informed player had said. They also realised when
the Experimenterâs uninformative access implied their own knowledge was unreliable, suggesting precocious working understanding of knowledge sources
Cyclical behaviour and disc truncation in the Be/X-ray binary A0535+26
A0535+26 is shown to display quantised IR excess flux states, which are
interpreted as the first observational verification of the resonant truncation
scheme proposed by Okazaki and Negueruela (2001) for BeXRBs. The simultaneity
of X-ray activity with transitions between these states strongly suggests a
broad mechanism for outbursts, in which material lost from the disc during the
reduction of truncation radius is accreted by the NS. Furthermore changes
between states are shown to be governed by a 1500 day period, probably due to
precession of the Be disc, which profoundly dictates the global behaviour of
the system. Such a framework appears to be applicable to BeXRBs in general.Comment: 10 pages, 11 figs, submitted to MNRA
Structure of Be probed via secondary beam reactions
The low-lying level structure of the unbound neutron-rich nucleus Be
has been investigated via breakup on a carbon target of secondary beams of
B at 35 MeV/nucleon. The coincident detection of the beam velocity
Be fragments and neutrons permitted the invariant mass of the
Be+ and Be++ systems to be reconstructed. In the case of
the breakup of B, a very narrow structure at threshold was observed in
the Be+ channel. Contrary to earlier stable beam fragmentation
studies which identified this as a strongly interacting -wave virtual state
in Be, analysis here of the Be++ events demonstrated that
this was an artifact resulting from the sequential-decay of the
Be(2) state. Single-proton removal from B was found to
populate a broad low-lying structure some 0.70 MeV above the neutron-decay
threshold in addition to a less prominent feature at around 2.4 MeV. Based on
the selectivity of the reaction and a comparison with (0-3)
shell-model calculations, the low-lying structure is concluded to most probably
arise from closely spaced J=1/2 and 5/2 resonances
(E=0.400.03 and 0.85 MeV), whilst the broad
higher-lying feature is a second 5/2 level (E=2.350.14 MeV). Taken
in conjunction with earlier studies, it would appear that the lowest 1/2
and 1/2 levels lie relatively close together below 1 MeV.Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical
Review
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