62 research outputs found
H-alpha observations of the gamma-ray-emitting Be/X-ray binary LSI+61303: orbital modulation, disk truncation, and long-term variability
We report 138 spectral observations of the H-alpha emission line of the
radio- and gamma-ray-emitting Be/X-ray binary LSI+61303 obtained during the
period of September 1998 -- January 2013. From measuring various H-alpha
parameters, we found that the orbital modulation of the H-alpha is best visible
in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue
hump, and in the radial velocity of the central dip. The periodogram analysis
confirmed that the H-alpha emission is modulated with the orbital and
superorbital periods. For the past 20 years the radius of the circumstellar
disk is similar to the Roche lobe size at the periastron. It is probably
truncated by a 6:1 resonance. The orbital maximum of the equivalent width of
H-alpha emission peaks after the periastron and coincides on average with the
X-ray and gamma-ray maxima. All the spectra are available upon request from the
authors and through the CDS.Comment: 11 pages, accepted for publication in A&
Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql
We performed high-resolution optical spectroscopy and X-ray observations of
the recently identified Mira-type symbiotic star EF Aql. Based on
high-resolution optical spectroscopy obtained with SALT, we determine the
temperature (55 000 K) and the luminosity ( 5.3 ) of the
hot component in the system. The heliocentric radial velocities of the emission
lines in the spectra reveal possible stratification of the chemical elements.
We also estimate the mass-loss rate of the Mira donor star. Our Swift
observation did not detect EF Aql in X-rays. The upper limit of the X-ray
observations is 10 erg cm s, which means that EF Aql is
consistent with the faintest X-ray systems detected so far. Otherwise we
detected it with the UVOT instrument with an average UVM2 magnitude of 14.05.
During the exposure, EF Aql became approximately 0.2 UVM2 magnitudes fainter.
The periodogram analysis of the V-band data reveals an improved period of
320.40.3 d caused by the pulsations of the Mira-type donor star. The
spectra are available upon request from the authors.Comment: Accepted for publication in MNRA
Pre-outburst signal in the light curves of the recurrent novae RS Oph and T CrB
Pre-outburst signal (a decrease of the optical brightness) just before the
outburst is clearly detected in the observations of the T CrB obtained before
and during the 1946 outburst. A similar decrease is also visible in the light
curve of RS Oph during the 2021 outburst. We suppose that this is due to
formation of a thick, dense envelope around the white dwarf, and we estimate
its size (1000 - 2000 km), mass (5.10 - 6.10 M) and
average density (5 - 16 g cm).Comment: preliminary versio
- …