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1.
We present photometric measurements of the eclipsing dwarf nova and X-ray source GY Cnc. The observations were collected during
outbursts and in quiescence. The investigation of plates from the Sonneberg archive showed that the mean outburst interval
is about 210–270 days, that the outburst is very fast, and lasts for about 5 days. 相似文献
2.
U. Mukherjee S. Bapna H. Raichur B. Paul S. N. A. Jaaffrey 《Journal of Astrophysics and Astronomy》2006,27(1):25-35
We have investigated the Quasi Periodic Oscillation (QPO) properties of the transient accreting X-ray pulsar XTE J1858 + 034
during the second outburst of this source in April–May 2004. We have used observations made with the Proportional Counter
Array (PCA) of the Rossi X-ray Timing Explorer (RXTE) during May 14–18, 2004, in the declining phase of the outburst. We detected
the presence of low frequency QPOs in the frequency range of 140–185 mHz in all the RXTE-PCA observations. We report evolution
of the QPO parameters with the time, X-ray flux, and X-ray photon energy. Though a correlation between the QPO centroid frequency
and the instantaneous X-ray flux is not very clear from the data, we point out that the QPO frequency and the one day averaged
X-ray flux decreased with time during these observations. We have obtained a clear energy dependence of the RMS variation
in the QPOs, increasing from about 3% at 3 keV to 6% at 25 keV. The X-ray pulse profile is a single peaked sinusoidal, with
pulse fraction increasing from 20% at 3 keV to 45% at 30keV. We found that, similar to the previous outburst, the energy spectrum
is well fitted with a model consisting of a cut-off power law along with an iron emission line. 相似文献
3.
S. Naik P. C. Agrawal B. Paul A. R. Rao S. Seetha K. Kasturirangan 《Journal of Astrophysics and Astronomy》2000,21(1-2):29-38
The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following
the outburst, X-ray observations of the source were made in the 2–18 keV energy band with the Pointed Proportional Counters
of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian satellite IRS-P3 during 1998 June 2nd–10th. The X-ray
flux of the source in the main outburst decreased exponentially during the period of observation. No large amplitude short-term
variability in the intensity is detected from the source. The power density spectrum obtained from the timing analysis of
the data shows no indication of any quasi-periodic oscillations in 0.002–0.5 Hz band. The hardness ratio i.e. the ratio of
counts in 6–18 keV to 2–6 keV band, indicates that the X-ray spectrum is soft with spectral index >2. From the similarities
of the X-ray properties with those of other black hole transients, we conclude that the X-ray transient XTE J2012+381 is likely
to be a black hole. 相似文献
4.
We report the observation of an outburst of comet Hale–Bopp (C/1995 O1) happened on September 10–11, 1996, carried by the
1.56 m telescope of Shanghai Astronomical Observatory. Two ejecta were found in CCD images during the outburst. According
to the positions of ejecta, we discuss the motion of the ejecta considering dust particles are subjected to the gravity and
the Solar radiation pressure, and conclude that the mean radii of dust grains in the ejecta were about submicron-sized. So
the observed X-ray emission are most likely produced by small size particles scattering the Solar X-ray.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
K. Byckling J. P. Osborne P. J. Wheatley G. A. Wynn A. Beardmore V. Braito K. Mukai R. G. West 《Monthly notices of the Royal Astronomical Society》2009,399(3):1576-1586
The second known outburst of the WZ Sge type dwarf nova GW Lib was observed in 2007 April. We have obtained unique multiwavelength data of this outburst which lasted ∼26 days. The American Association of Variable Star Observers ( AAVSO ) recorded the outburst in the optical, which was also monitored by Wide Angle Search for Planets , with a peak V magnitude of ∼8. The outburst was followed in the ultraviolet and X-ray wavelengths by the Swift ultraviolet/optical and X-ray telescopes. The X-ray flux at optical maximum was found to be three orders of magnitude above the pre-outburst quiescent level, whereas X-rays are normally suppressed during dwarf nova outbursts. A distinct supersoft X-ray component was also detected at optical maximum, which probably arises from an optically thick boundary layer. Follow-up Swift observations taken 1 and 2 years after the outburst show that the post-outburst quiescent X-ray flux remains an order of magnitude higher than the pre-outburst flux. The long interoutburst time-scale of GW Lib with no observed normal outbursts support the idea that the inner disc in GW Lib is evacuated or the disc viscosity is very low. 相似文献
6.
Jin Zhang 《中国天文和天体物理学报》2009,9(7)
W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions (SEDs) which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron + synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ～25 and δ～20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is～14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 0 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future. 相似文献
7.
We present the optical light curve of EG Cancri during its outburst in 1996–1997. It displayed some brightness fluctuations
in the phase of decline. Mini-outbursts were detected. Optical spectra obtained during the decline showed it to be a dwarf
nova on account of its broad absorption lines superimposed on a blue continuum. Optical spectra near minimum brightness revealed
doubled Balmer lines in emission, over broad absorptions, but no HeII4686. An additional heating presented in the last stage
of decline. CCD time-resolved photometry showed a possible orbital period 0.0575(26) day. Superhumps was observed during outburst
byMatsumoto(1996). EG Cancri is a short-period CV which has a large-amplitude outburst(∼ 7 mag), a slow decline from outburst,
and a long interval between outburst. From the above properties, a classification as a WZ Sge type DN is plausible.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
9.
C. Brocksopp P. G. Jonker R. P. Fender P. J. Groot M. van der Klis S. J. Tingay 《Monthly notices of the Royal Astronomical Society》2001,323(2):517-528
We present observations of the 1997 outburst of the X-ray transient GS 1354−64 (BW Cir) at X-ray, optical and, for the first time, radio wavelengths; our results include upper limits to the linear and circular polarization for the radio data. The X-ray outburst was unusual in that the source remained in the low/hard X-ray state throughout; the X-ray peak was also preceded by at least one optical outburst, suggesting that it was an 'outside-in' outburst – similar to those observed in dwarf novae systems, although possibly taking place on a viscous time-scale in this case. It therefore indicates that the optical emission was not dominated by the reprocessing of X-rays, but that instead we see the instability directly. While the radio source was too faint to detect any extended structure, spectral analysis of the radio data and a comparison with other similar systems suggest that mass ejections, probably in the form of a jet, took place and that the emitted synchrotron spectrum may have extended as far as infrared wavelengths. Finally, we compare this 1997 outburst of GS 1354−64 with possible previous outbursts and also with other hard-state objects, both transient and persistent. It appears that a set of characteristics – such as a weak, flat-spectrum radio jet, a mHz QPO increasing in frequency, a surprisingly high optical/X-ray luminosity ratio, and the observed optical peak preceding the X-ray peak – may be common to all hard-state X-ray transients. 相似文献
10.
T. Shahbaz R. M. Bandyopadhyay P. A. Charles R. M. Wagner P. Muhli P. Hakala J. Casares & J. Greenhill 《Monthly notices of the Royal Astronomical Society》1998,300(4):1035-1040
We present optical spectroscopy and optical and infrared photometry of the neutron star soft X-ray transient Aql X–1 during its X-ray outburst of 1997 August. By modelling the X-ray, optical and IR light curves, we find a 3-d delay between the IR and X-ray rise times, analogous to the UV–optical delay seen in dwarf novae outbursts and black hole X-ray transients. We interpret this delay as the signature of an 'outside-in' outburst, in which a thermal instability in the outer disc propagates inward. This outburst is the first of this type definitively identified in a neutron star X-ray transient. 相似文献
11.
L. Homer P.A. Charles D. Chakrabarty L. van Zyl 《Monthly notices of the Royal Astronomical Society》2001,325(4):1471-1476
We report the first extensive set of optical photometric observations of the counterpart to SAX J1808.4−3658 (V4580 Sagittarii) in quiescence. The source was detected at V ∼21 , 5 mag fainter than at the peak of its 1998 outburst. However, a comparable ∼6 per cent semi-amplitude 2-h modulation of its flux is revealed. This has the same phasing and approximately sinusoidal modulation as seen during outburst, and with photometric minimum when the pulsar is behind the companion. The lack of a double-humped morphology rules out an ellipsoidal origin, implying that the bulk of the optical flux does not arise from the companion. Moreover, applying crude modelling to the disc and X-ray irradiated face of the donor shows that the internal energy release of a remnant disc (with mass transfer driven by gravitational radiation) is sufficient to explain most of the optical emission, and with the modulation because of the varying contribution of the heated face of the star. We note that this model is also consistent with the much lower X-ray to optical flux ratio in quiescence versus outburst, and with the phasing of the optical modulation. 相似文献
12.
Owens Alan Oosterbroek T. Orr A. Parmar A. N. Schulz R. Tozzi G.P. 《Earth, Moon, and Planets》1997,77(3):293-298
We report the detection of soft X-rays from comet C/1995 O1 (Hale-Bopp) by the Low Energy Concentrator Spectrometer (LECS)
on-board the X-ray satellite, BeppoSAX. The observations took place on 1996 September 10–11 approximately 1 day after a large
dust outburst (Schulz et al., 1997–1999). After correcting for the comets motion, a 7σ enhancement was found centered (2.1
± 1.3) x 105 km from the position of the nucleus, in the general solar direction. The total X-ray luminosity in the 0.1–2.0 keV energy
band is 5 x 1016 erg s−1 which is at least a factor of ∼ 3 greater than measured by the Extreme Ultraviolet Explorer (EUVE)4 days later and suggests
that the bulk of the emission measured by the LECS is related to the dust outburst. The extracted LECS spectrum is well fit
by a thermal bremsstrahlung-like distribution of temperature of 0.29 ± 0.06 keV - consistent with that observed in other comets.
We find no evidence for fluorescent carbon or oxygen emission and place 95% confidence limits of 1.0 x 1015 and 7.8 x 1015 erg s−1 to narrow line emission at 0.28 and 0.53 keV, respectively. We calculate that if such lines are present, they constitute
at most 18% of the 0.1–2.0 keV continuum luminosity.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Details of the discovery of a new X-ray source, IGR J18462-0223, on October 12, 2007, during a short (several hours), intense
(∼35 mCrab at the peak) outburst of hard radiation by the IBIS/ISGRI gamma-ray telescope onboard the INTEGRAL observatory
are given. The detection of another earlier outburst from this source occurred on April 28, 2006, in the archival data of
the telescope is reported. We present the results of the source’s localization and our spectral/timing analysis of the observational
data. The source may turn out to be yet another representative of the continuously growing population of fast X-ray transients,
which are the focus of attention because of the identification of their optical counterparts with early-type supergiants. 相似文献
14.
We report on VLA observations of HST-1 in M87 at 8 GHz from 2003–2007, during which a long major outburst occurs from radio to X-ray wave bands. At the VLA resolution, the flux density of HST-1 rises rapidly from 2003, peaks at the end of 2004, and then falls slowly in subsequent stages, which is similar to that in optical and X-ray wave bands. It appears that HST-1 moves with an apparent speed of 1.23c±0.91c, and the fractional polarization keeps rising through the whole major outburst. The persistent increase in polarization level may mainly be attributed to the formation of a couple of new ‘subcomponents’ of relatively high degree of polarization within HST-1, and the weakening depolarization due to Faraday rotation and/or opacity through the whole major outburst. 相似文献
15.
A. E. Rosenbush 《Astrophysics》1999,42(3):270-274
A review of light curves of known x-ray novae made it possible to identify criteria by which x-ray nova candidates were selected
among old novae: amplitude of optical outburst 7–10
m, shape of light curve during the outburst with a temporary fading by 2–3m lasting up to four days and an abrupt final fading from the 6m level (relative to the quiet state). We identified LS And, AL Com, V592 Her, and HV Vir as x-ray nova candidates. Recurrent
outbursts should be expected for the first and third stars. Less reliable candidates are V341 Nor, V787 Sgr, and V719 Sco.
A possible recurrent nova candidate may be V1330 Cyg.
Translated from Astrofizika, Vol. 42, No. 3, pp. 359–364, July–September, 1999. 相似文献
16.
The results of study of the classical symbiotic star Z And during the recent activity period that began in 2000 are presented.
Up to now series of six outbursts took place. Comparison of observational data with the results of gasdynamic modeling allow
us to suggest the possible scenario for activity in this system describing all stages of an outburst development—from the
mechanism of transition to the outburst and outburst development to the behavior of the system during all the activity period.
Particularly, the proposed scenario explains the principal difference between outbursts—the presence of high-velocity bipolar
collimated optical outflows in strong recurring outbursts. We have not found contradictions with the available data for previous
outbursts of Z And. We assume that the proposed scenario could be also typical for other classic symbiotic stars. In order
to check and improve our model additional observations are highly desirable and the UV spectral range could provide us with
very useful data. 相似文献
17.
P. A. Evans A. P. Beardmore J. P. Osborne G. A. Wynn 《Monthly notices of the Royal Astronomical Society》2009,399(3):1167-1174
The 2006 outburst of GK Persei differed significantly at optical and ultraviolet (UV) wavelengths from typical outbursts of this object. We present multiwavelength (X-ray, UV and optical) Swift and AAVSO data, giving unprecedented broad-band coverage of the outburst, allowing us to follow the evolution of the longer-than-normal 2006 outburst across these wavelengths. In the optical and UV we see a triple-peaked morphology with maximum brightness ∼1.5 mag lower than in previous years. In contrast, the peak hard X-ray flux is the same as in previous outbursts. We resolve this dichotomy by demonstrating that the hard X-ray flux only accounts for a small fraction of the total energy liberated during accretion, and interpret the optical/UV outburst profile as arising from a series of heating and cooling waves traversing the disc, caused by its variable density profile. 相似文献
18.
We present the results of our optical identification of two X-ray sources from the RXTE and INTEGRAL all-sky surveys: XSS J00564+4548 and IGR J00234+6141. Using optical observations with the 1.5-m Russian-Turkish Telescope
(RTT150) and publicly accessible X-ray data from the SWIFT Orbital Observatory, we show that these sources are most likely intermediate polars, i.e., binary systems with accreting
white dwarfs that possess a moderately strong magnetic field (≲10 MG). We have found periodic optical oscillations with periods
of ≈480 and ≈570 s. These periods most likely correspond to the rotation periods of the white dwarfs in these systems. Further
optical RTT150 observations of these systems will allow their parameters to be studied in more detail.
Published in Russian in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 9, pp. 655–661.
The article was translated by the authors. 相似文献
19.
C. Brocksopp K. E. McGowan H. Krimm O. Godet P. Roming K. O. Mason N. Gehrels M. Still K. Page A. Moretti C. R. Shrader S. Campana J. Kennea 《Monthly notices of the Royal Astronomical Society》2006,365(4):1203-1214
We present Swift observations of the black hole X-ray transient, GRO J1655−40, during the recent outburst. With its multiwavelength capabilities and flexible scheduling, Swift is extremely well suited for monitoring the spectral evolution of such an event. GRO J1655−40 was observed on 20 occasions and data were obtained by all instruments for the majority of epochs. X-ray spectroscopy revealed spectral shapes consistent with the 'canonical' low/hard, high/soft and very high states at various epochs. The soft X-ray source (0.3–10 keV) rose from quiescence and entered the low/hard state, when an iron emission line was detected. The soft X-ray source then softened and decayed, before beginning a slow rebrightening and then spending ∼3 weeks in the very high state. The hard X-rays (14–150 keV) behaved similarly but their peaks preceded those of the soft X-rays by up to a few days; in addition, the average hard X-ray flux remained approximately constant during the slow soft X-ray rebrightening, increasing suddenly as the source entered the very high state. These observations indicate (and confirm previous suggestions) that the low/hard state is key to improving our understanding of the outburst trigger and mechanism. The optical/ultraviolet light curve behaved very differently from that of the X-rays; this might suggest that the soft X-ray light curve is actually a composite of the two known spectral components, one gradually increasing with the optical/ultraviolet emission (accretion disc) and the other following the behaviour of the hard X-rays (jet and/or corona). 相似文献
20.
Peter J. Wheatley Christopher W. Mauche Janet A. Mattei 《Monthly notices of the Royal Astronomical Society》2003,345(1):49-61
We present the most complete multiwavelength coverage of any dwarf nova outburst: simultaneous optical, Extreme Ultraviolet Explorer and Rossi X-ray Timing Explorer observations of SS Cygni throughout a narrow asymmetric outburst. Our data show that the high-energy outburst begins in the X-ray waveband 0.9–1.4 d after the beginning of the optical rise and 0.6 d before the extreme-ultraviolet rise. The X-ray flux drops suddenly, immediately before the extreme-ultraviolet flux rise, supporting the view that both components arise in the boundary layer between the accretion disc and white dwarf surface. The early rise of the X-ray flux shows that the propagation time of the outburst heating wave may have been previously overestimated.
The transitions between X-ray and extreme-ultraviolet dominated emission are accompanied by intense variability in the X-ray flux, with time-scales of minutes. As detailed by Mauche & Robinson, dwarf nova oscillations are detected throughout the extreme-ultraviolet outburst, but we find they are absent from the X-ray light curve.
X-ray and extreme-ultraviolet luminosities imply accretion rates of 3 × 1015 g s−1 in quiescence, 1 × 1016 g s−1 when the boundary layer becomes optically thick, and ∼1018 g s−1 at the peak of the outburst. The quiescent accretion rate is two and a half orders of magnitude higher than predicted by the standard disc instability model, and we suggest this may be because the inner accretion disc in SS Cyg is in a permanent outburst state. 相似文献
The transitions between X-ray and extreme-ultraviolet dominated emission are accompanied by intense variability in the X-ray flux, with time-scales of minutes. As detailed by Mauche & Robinson, dwarf nova oscillations are detected throughout the extreme-ultraviolet outburst, but we find they are absent from the X-ray light curve.
X-ray and extreme-ultraviolet luminosities imply accretion rates of 3 × 10