136 research outputs found
The photometric and spectral investigation of CI Camelopardalis, an X-ray transient and B[e] star
We combined the results of UBVR photometry of CI Cam taken at Sternberg
Astronomical Institute in 1998--2001, and moderate resolution spectroscopy
taken at Special Astrophysical Observatory during the same time period.
Photometry as well as fluxes of Balmer emissions and of some Fe II emission
lines of CI Cam in quiet state reveal a cyclic variation with the period of
. The variation like this may be due to an orbital motion in a
wide pair with a giant star companion that exhibits the reflection effect on
its side faced to a compact companion.
The V-band photometry also confirms the pre-outburst 11.7 day period found by
Miroshnichenko earlier, but with a lower amplitude of 3 per cent. The
possibility of identity of this photometric period with the period of jet's
rotation in the VLA radio map of the object CI Cam was investigated. The radio
map modelling reveals the inclination of the jet rotation axis to the line of
sight, , the angle between the rotation axis and the direction of
ejection of the jet, , and jet's spatial velocity of
0.23--0.26c.
Equivalent widths and fluxes of various spectral lines show different
amplitudes of changes during the outburst, and essentially distinct behaviour
in quiescence. Five types of such behaviour were revealed, that indicates the
strong stratification of a gas and dust envelope round the system . The time
lag of strengthening of 50--250 in the forbidden line of nitrogen [N II]
was found relatively to the X-ray outburst maximum.Comment: 15 pages, 8 figures, 3 tables, Astron. Zh., 2002, (in press), vol.79,
number
In-the-Gap SU UMa-Type Dwarf Nova, Var73 Dra with a Supercycle of about 60 Days
An intensive photometric-observation campaign of the recently discovered SU
UMa-type dwarf nova, Var73 Dra was conducted from 2002 August to 2003 February.
We caught three superoutbursts in 2002 October, December and 2003 February. The
recurrence cycle of the superoutburst (supercycle) is indicated to be 60
d, the shortest among the values known so far in SU UMa stars and close to
those of ER UMa stars. The superhump periods measured during the first two
superoutbursts were 0.104885(93) d, and 0.10623(16) d, respectively. A
0.10424(3)-d periodicity was detected in quiescence. The change rate of the
superhump period during the second superoutburst was , which
is an order of magnitude larger than the largest value ever known. Outburst
activity has changed from a phase of frequent normal outbursts and infrequent
superoutbursts in 2001 to a phase of infrequent normal outbursts and frequent
superoutbursts in 2002. Our observations are negative to an idea that this star
is an related object to ER UMa stars in terms of the duty cycle of the
superoutburst and the recurrence cycle of the normal outburst. However, to
trace the superhump evolution throughout a superoutburst, and from quiescence
more effectively, may give a fruitful result on this matter.Comment: 9 pages, 8 figures, submitted to A&
High-Dispersion Spectroscopy of the X-Ray Transient RXTE J0421+560 (= CI Cam) during Outburst
We obtained high dispersion spectra of CI Cam, the optical counterpart of XTE
J0421+560, two weeks after the peak of its short outburst in 1998 April. The
optical counterpart is a supergiant B[e] star emitting a two-component wind.
The cool wind (the source of narrow emission lines of neutral and ionized
metals) has a velocity of 32 km/s and a temperature near 8000 K. Dense and
roughly spherical, it fills the space around the sgB[e] star, and, based on the
size of an infrared-emitting dust shell around the system, extends to a radius
between 13 - 50 AU. It carries away mass at a high rate, Mdot > 10^(-6) solar
masses per year. The hot wind has a velocity in excess of 2500 km/s and a
temperature of 1.7 +/-0.3 x 10^4 K. From UV spectra of CI Cam obtained in 2000
March with Hubble Space Telescope, we derive a differential extinction E(B-V) =
0.85 +/- 0.05. We derive a distance to CI Cam > 5 kpc. Based on this revised
distance, the X-ray luminosity at the peak of the outburst was L(2-25 keV) >
3.0 x 10^38 erg/s, making CI Cam one of the most luminous X-ray transients. The
ratio of quiescent to peak luminosity in the 2 - 25 keV band is < 1.7 x
10^(-6). The compact star in CI Cam is immersed in the dense circumstellar wind
from the sgB[e] star and burrows through the wind producing little X-ray
emission except for rare transient outbursts. This picture (a compact star
traveling in a wide orbit through the dense circumstellar envelope of a sgB[e]
star, occasionally producing transient X-ray outbursts) makes CI Cam unique
among the known X-ray binaries. Strong circumstantial evidence suggests that
the compact object is a black hole, not a neutron star. We speculate that the
X-ray outburst was short because the accretion disk around the compact star is
fed from a stellar wind and is smaller than disks fed by Roche-lobe overflow.Comment: 20 pages incl. 3 tables + 10 figures; accepted for publication in
Feb. 2002 Astrophysical Journal; full resolution figures available at
http://pisces.as.utexas.edu/robinson/Papers/papers00-04.htm
Effect of the reverse shock on the parameters of the observed X-Ray emission during the 1998 outburst of CI Cam
Based on the model of interaction between spherically symmetrical expanding
matter and the external medium, we have estimated the parameters of the matter
heated by the shock that was produced in the envelope ejected by the explosion
of a classical nova during its interaction with the stellar wind from the
optical companion. Using this model, we have shown that the matter ejected
during the outburst in the system CI Cam had no steep velocity gradients and
that the reverse shock could heat the ejected matter only to a temperature of
~0.1 keV. Therefore, this matter did not contribute to the mean temperature and
luminosity of the system observed in the energy range 3-20 keV.Comment: 7 pages, 5 figure
ВЛИЯНИЕ НУКЛЕОСПЕРМАТА НАТРИЯ НА ХАРАКТЕР ИНТЕГРАЛЬНЫХ РЕАКЦИЙ ОРГАНИЗМА ПРИ КОМБИНИРОВАННОМ ЛЕЧЕНИИ ЗЛОКАЧЕСТВЕННЫХ ОПУХОЛЕЙ ОРГАНОВ ГОЛОВЫ И ШЕИ
The development of adaptation responses to sodium nucleospermate during postoperative chemotherapy was studied in 20 patients with stage III–IV head and neck cancer. Unidirectional transition of different background reactions to acute and chronic stress with leucocytosis level of 14,0×109 /L was observed after injecting the agent. This effect was short-term and reversible. On day 6, the development of anti-stress reactions of training and activation with increase in the level of lymphocytes and upper normal limits of leukocyte count was registered, thus showing positive biological and clinical effect.Проведено изучение развития общих адаптационных реакций у 20 больных с опухолями органов головы и шеи III–IV стадий в ответ на воздействие нуклеоспермата натрия при проведении послеоперационной химиотерапии. После введения препарата наблюдался однонаправленный переход спектра различных фоновых реакций в стрессорный тип острой и хронической формы с уровнем лейкоцитоза 14,0×109 /л. Этот эффект имел краткосрочный и обратимый характер. На 6-е сут регистрировали развитие антистрессорных реакций тренировки и активации с повышением уровня лимфоцитов и содержанием лейкоцитов на верхних границах нормы, что имело позитивный биологический и клинический смысл
Open and Hidden Charm Production in 920 GeV Proton-Nucleus Collisions
The HERA-B collaboration has studied the production of charmonium and open
charm states in collisions of 920 GeV protons with wire targets of different
materials. The acceptance of the HERA-B spectrometer covers negative values of
xF up to xF=-0.3 and a broad range in transverse momentum from 0.0 to 4.8
GeV/c. The studies presented in this paper include J/psi differential
distributions and the suppression of J/psi production in nuclear media.
Furthermore, production cross sections and cross section ratios for open charm
mesons are discussed.Comment: 5 pages, 9 figures, to be published in the proceedings of the 6th
International Conference on Hyperons, Charm & Beauty Hadrons (BEACH04),
Chicago, IL, June 27 - July 3, 200
Search for the Flavor-Changing Neutral Current Decay with the HERA-B Detector
We report on a search for the flavor-changing neutral current decay using events recorded with a dimuon trigger in
interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find
no evidence for such decays and set a 90% confidence level upper limit on the
branching fraction .Comment: 17 pages, 4 figures (of which 1 double), paper to be submitted to
Physics Letters
Measurement of the J/Psi Production Cross Section in 920 GeV/c Fixed-Target Proton-Nucleus Interactions
The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production
cross sections of J/Psi mesons are measured in proton-nucleus interactions.
Data collected by the HERA-B experiment in interactions of 920 GeV/c protons
with carbon, titanium and tungsten targets are used for this analysis. The
J/Psi mesons are reconstructed by their decay into lepton pairs. The total
production cross section obtained is sigma_(pN)(J/Psi) = 663 +- 74 +- 46
nb/nucleon. In addition, our result is compared with previous measurements
Interacting supernovae and supernova impostors. LSQ13zm: an outburst heralds the death of a massive star
We report photometric and spectroscopic observations of the optical transient LSQ13zm. Historical data reveal the presence of an eruptive episode (that we label as ‘2013a’) followed by a much brighter outburst (‘2013b’) three weeks later, that we argue to be the genuine supernova explosion. This sequence of events closely resemble those observed for SN 2010mc and (in 2012) SN 2009ip. The absolute magnitude reached by LSQ13zm during 2013a (MR = ?14.87 ± 0.25?mag) is comparable with those of supernova impostors, while that of the 2013b event (MR = ?18.46 ± 0.21?mag) is consistent with those of interacting supernovae. Our spectra reveal the presence of a dense and structured circumstellar medium, probably produced through numerous pre-supernova mass-loss events. In addition, we find evidence for high-velocity ejecta, with a fraction of gas expelled at more than 20 000?km s?1. The spectra of LSQ13zm show remarkable similarity with those of well-studied core-collapse supernovae. From the analysis of the available photometric and spectroscopic data, we conclude that we first observed the last event of an eruptive sequence from a massive star, likely a Luminous Blue Variable, which a short time later exploded as a core-collapse supernova. The detailed analysis of archival images suggest that the host galaxy is a star-forming Blue Dwarf Compact Galaxy
Inclusive Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions
Inclusive differential cross sections and
for the production of \kzeros, \lambdazero, and
\antilambda particles are measured at HERA in proton-induced reactions on C,
Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to
GeV in the proton-nucleon system. The ratios of differential
cross sections \rklpa and \rllpa are measured to be and , respectively, for \xf . No significant dependence upon the
target material is observed. Within errors, the slopes of the transverse
momentum distributions also show no significant
dependence upon the target material. The dependence of the extrapolated total
cross sections on the atomic mass of the target material is
discussed, and the deduced cross sections per nucleon are
compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table
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