27 research outputs found
Identification of the Mass Donor Star's Spectrum in SS 433
We present spectroscopy of the microquasar SS 433 obtained near primary
eclipse and disk precessional phase Psi = 0.0, when the accretion disk is
expected to be most ``face-on''. The likelihood of observing the spectrum of
the mass donor is maximized at this combination of orbital and precessional
phases since the donor is in the foreground and above the extended disk
believed to be present in the system. The spectra were obtained over four
different runs centered on these special phases. The blue spectra show clear
evidence of absorption features consistent with a classification of A3-7 I. The
behavior of the observed lines indicates an origin in the mass donor. The
observed radial velocity variations are in anti-phase to the disk, the
absorption lines strengthen at mid-eclipse when the donor star is expected to
contribute its maximum percentage of the total flux, and the line widths are
consistent with lines created in an A supergiant photosphere. We discuss and
cast doubt on the possibility that these lines represent a shell spectrum
rather than the mass donor itself. We re-evaluate the mass ratio of the system
and derive masses of 10.9 +/- 3.1 Msun and 2.9 +/- 0.7 Msun for the mass donor
and compact object plus disk, respectively. We suggest that the compact object
is a low mass black hole.
In addition, we review the behavior of the observed emission lines from both
the disk/wind and high velocity jets.Comment: submitted to ApJ, 24 pages, 7 figure
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Photometric observations of the radio bright B[e]/X-ray binary CI Cam
We present multiwavelength (optical, IR, radio) observations of CI Cam, the optical counterpart to the transient X-ray source XTE J0421+560. Pre-outburst quiescent observations reveal the presence of a dusty envelope around the system. Pronounced short term variability is observed at all wavebands from U-K, but no indication of prior flaring of a similar magnitude to the 1998 April outburst is found in these data.
Data obtained during the 1998 April X-ray flare reveal pronounced optical-radio flaring. The optical flux was observed to quickly return to quiescent levels, while the radio flare was of much longer duration. The optical component is likely to result from a combination of free-free/free-bound emission, emission line and thermal dust emission, caused by re-radiation of the X-ray flux, while the behaviour of the multiwavelength radio data is consistent with emission from expanding ejecta emitting via the synchrotron mechanism.
Post-outburst (1998 August-1999 March) U-M broadband photometric observations reveal that while the optical (UBV) flux remains at pre-outburst quiescent levels, near IR (JHKLM) fluxes exceed the pre-outburst fluxes by ~0.5 magnitudes. Modelling the pre- and post-outburst spectral energy distribution of CI Cam reveals that the structure and/or composition of the dusty component of the circumstellar envelope appears to have changed. Due to a lack of information on the precise chemical composition of the dust within the system several explanations for this behaviour are possible, such as the production of new dust at the inner edge of the envelope, or modification of the composition of the dust due to X-ray irradiation
Fast optical variability of SS 433
We study the optical variability of the peculiar Galactic source SS 433 using
the observations made with the Russian Turkish 1.5-m telescope (RTT150). A
simple technique which allows to obtain high-quality photometric measurements
with 0.3-1 s time resolution using ordinary CCD is described in detail. Using
the test observations of nonvariable stars, we show that the atmospheric
turbulence introduces no significant distortions into the measured light
curves. Therefore, the data obtained in this way are well suited for studying
the aperiodic variability of various objects.
The large amount of SS 433 optical light curve measurements obtained in this
way allowed us to obtain the power spectra of its flux variability with a
record sensitivity up to frequencies of ~0.5 Hz and to detect its break at
frequency =~2.4e-3 Hz. We suggest that this break in the power spectrum results
from the smoothing of the optical flux variability due to a finite size of the
emitting region. Based on our measurement of the break frequency in the power
spectrum, we estimated the size of the accretion-disk photosphere as 2e12 cm.
We show that the amplitude of the variability in SS 433 decreases sharply
during accretion-disk eclipses, but it does not disappear completely. This
suggests that the size of the variable optical emission source is comparable to
that of the normal star whose size is therefore R_O \approx 2e12 cm \approx 30
R_sun. The decrease in flux variability amplitude during eclipses suggests the
presence of a nonvariable optical emission component with a magnitude
m_R=~13.2.Comment: 12 pages, 11 figures. Accepted for publication in Astronomy Letters.
The original version in Russian is available at
http://hea.iki.rssi.ru/rtt150/ru/ss433_pazh10/pss433_fast.pd
Optical Multicolor WBVR-Observations of the X-Ray Star V1341 Cyg = Cyg X-2 in 1986-1992
We present the results of observations of the low-mass X-ray binary
V1341 X--2. Our observations include a total of
2375 individual measurements in four bands on 478 nights in 1986-1992. We tied
the comparison and check stars used for the binary to the catalog using
their magnitudes. The uncertainty of this procedure was 3 in the
and bands and 8%-10% for the and bands. In quiescence, the
amplitude of the periodic component in the binary's brightness variations
is within ( in ); this is due
to the ellipsoidal shape of the optical component, which is distorted with
gravitational forces from the X-ray component. Some of the system's active
states (long flares) may be due to instabilities in the accretion disk, and
possibly to instabilities of gas flows and other accretion structures. The
binary possesses a low-luminosity accretion disk. The light curves reveal no
indications of an eclipse near the phases of the upper and lower conjunctions
in quiescence or in active states during the observed intervals. We conclude
that the optical star in the close binary V1341
X-2 is a red giant rather than a blue straggler. We studied the long-term
variability of the binary during the seven years covered by our observations.
The optical observations presented in this study are compared to X-ray data
from the Ginga observatory for the same time intervals.Comment: 35 pages, 8 figure
Spectral Components of SS 433
We present results from new optical and UV spectroscopy of the unusual binary
system SS 433, and we discuss the relationship of the particular spectral
components we observe to the properties of the binary. (1) The continuum
spectrum which we associate with flux from the super-Eddington accretion disk
and the dense part of its wind. (2) H-alpha moving components which are formed
far from the binary orbital plane in the relativistic jets. (3) H-alpha and He
I "stationary" emission lines which we suggest are formed in the disk wind in a
volume larger than the dimensions of the binary. (4) A weak "stationary"
emission feature we identify as a C II 7231,7236 blend that attains maximum
radial velocity at the orbital quadrature of disk recession. (5) Absorption and
emission features from outflowing clumps in the disk wind (seen most clearly in
an episode of blue-shifted Na I emission). (6) We found no clear evidence of
the absorption line spectrum of the optical star, although we point out the
presence of He I absorption features (blended with the stationary emission)
with the expected radial velocity trend at the orbital and precessional phases
when the star might best be seen. (7) A rich interstellar absorption spectrum
of diffuse interstellar bands. The results suggest that the binary is embedded
in an expanding thick disk (detected in recent radio observations) which is fed
by the wind from the super-Eddington accretion disk.Comment: Submitted to Ap
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
A Luminous Red Nova in M31 and its Progenitor System
We present observations of M31LRN 2015 (MASTER OT J004207.99+405501.1), discovered in M31 in January 2015, and identified as a rare and enigmatic luminous red nova (LRN). Spectroscopic and photometric observations obtained by the Liverpool Telescope showed the LRN becoming extremely red as it faded from its M(V) = -9.4 +/- 0.2 peak. Early spectra showed strong Halpha emission that weakened over time as a number of absorption features appeared, including Na I D and Ba II. At later times strong TiO absorption bands were also seen. A search of archival Hubble Space Telescope data revealed a luminous red source to be the likely progenitor system, with pre-outburst Halpha emission also detected in ground-based data. The outburst of M31LRN 2015 shows many similarities, both spectroscopically and photometrically, with that of V838 Mon, the best studied LRN. We finally discuss the possible progenitor scenarios
The first spectroscopically confirmed Mira star in M33
We present photometry and moderate-resolution spectroscopy of the luminous
red variable [HBS2006] 40671 originally detected as a possible nova in the
galaxy M33. We found that the star is a pulsating Mira-type variable with a
long period of 665 days and an amplitude exceeding 7 mag in the R band.
[HBS2006] 40671 is the first confirmed Mira-type star in M33. It is one of the
most luminous Mira-type variables. In the K band its mean absolute magnitude is
M_K = -9.5, its bolometric magnitude measured in the maximum light is also
extreme, M_bol = -7.4. The spectral type of the star in the maximum is M2e -
M3e. The heliocentric radial velocity of the star is -475 km/s. There is a big
negative excess (-210~km/s) in radial velocity of [HBS2006] 40671 relative to
the average radial velocity of stars in its neighborhood pointing at an
exceptional peculiar motion of the star. All the extreme properties of the new
Mira star make it important for further studies.Comment: 7 pages, 4 figures, accepted by MNRA