10 research outputs found
Investigation of Non-Stable Processes in Close Binary Ry Scuti
We present results of reanalysis of old electrophotometric data of early type
close binary system RY Scuti obtained at the Abastumani Astrophysical
Observatory, Georgia, during 1972-1990 years and at the Maidanak Observatory,
Uzbekistan, during 1979-1991 years. It is revealed non-stable processes in RY
Sct from period to period, from month to month and from year to year. This
variation consists from the hundredths up to the tenths of a magnitude.
Furthermore, periodical changes in the system's light are displayed near the
first maximum on timescales of a few years. That is of great interest with
regard to some similar variations seen in luminous blue variable (LBV) stars.
This also could be closely related to the question of why RY Sct ejected its
nebula.Comment: 11 pages, 6 figures, 2 table
Results of UBV Photoelectric Observations of the Early-Type Eclipsing Binary System XZ Cep
Results of the three-colour photoelectric observation of the close binary
system XZ Cep, obtained at the Abastumani Astrophysical observatory, are
presented.Comment: 23 pages, 3 figures, 1 tebl
Episodic mass loss in binary evolution to the Wolf-Rayet phase: Keck and HST proper motions of RY Scuti's nebula
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for
producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to
account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a
massive binary star caught in this brief but important phase. Its toroidal
nebula indicates equatorial mass loss during RLOF, while the mass-gaining star
is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula
has two components: an inner ionised double-ring system, and an outer dust
torus that is twice the size of the ionised rings. We present two epochs of
Lband Keck NGS-AO images of the dust torus, plus three epochs of HST images of
the ionised gas rings. Proper motions show that the inner ionised rings and the
outer dust torus came from two separate ejection events roughly 130 and 250 yr
ago. This suggests that RLOF in massive contact binaries can be accompanied by
eruptive and episodic burst of mass loss, reminiscent of LBVs. We speculate
that the repeating outbursts may arise in the mass gainer from instabilities
associated with a high accretion rate. If discrete mass-loss episodes in other
RLOF binaries are accompanied by luminous outbursts, they might contribute to
the population of extragalactic optical transients. When RLOF ends for RY
Scuti, the overluminous mass gainer, currently surrounded by an accretion disk,
will probably become a B[e] supergiant and may outshine the hotter mass-donor
star that should die as a Type Ib/c supernova.Comment: 15 pages, 7 figures, submitted to MNRA
COMET Phase-I Technical Design Report
International audienceThe Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminum nucleus (â ||â|| conversion, ||â ); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is ||â , or 90% upper limit of a branching ratio of ||â , which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the ||â|| conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described