共查询到20条相似文献,搜索用时 46 毫秒
1.
U. Mukherjee H. Raichur B. Paul S. Naik N. Bhatt 《Journal of Astrophysics and Astronomy》2006,27(4):411-423
We report here results from detailed timing and spectral studies of the high mass X-ray binary pulsar 4U 1538-52 over several
binary periods using observations made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX satellites. Pulse timing analysis
with the 2003 RXTE data over two binary orbits confirms an eccentric orbit of the system. Combining the orbitial parameters
determined from this observation with the earlier measurements we did not find any evidence of orbital decay in this X-ray
binary. We have carried out orbital phase resolved spectroscopy to measure changes in the spectral parameters with orbital
phase, particularly the absorption column density and the iron line flux. The RXTE-PCA spectra in the 3–20 keV energy range
were fitted ∼6.4 keV, whereas the BeppoSAX spectra needed only a power law and Gaussian emission line at ∼6.4 keV in the restricted
energy range of 0.3–10.0 keV. An absorption along the line of sight was included for both the RXTE and BeppoSAX data. The
variation of the free spectral parameters over the binary orbit was investigated and we found that the variation of the column
density of absorbing material in the line of sight with orbital phase is in reasonable agreement with a simple model of a
spherically symmetric stellar wind from the companion star. 相似文献
2.
N. I. Shakura N. A. Ketsaris M. E. Prokhorov & K. A. Postnov 《Monthly notices of the Royal Astronomical Society》1998,300(4):992-998
An analysis of the publicly available Rossi X-ray Timing Explorer ( RXTE ) archive on Her X-1, including data on 23 34.85-d cycles, is performed. The turn-on times for these cycles are determined. The number of cycles with a duration of 20.5 orbits has been found to be much larger than the number of shorter (20 orbits) or longer (21 orbits) cycles. A correlation between the duration of a cycle and its mean X-ray flux is noted. The mean X-ray light curve shows a very distinct short on-state. The anomalous X-ray absorption dip is found during the first orbit, after the turn-on in the main on-state for the cycles starting near the binary phase 0.25, and is present during two successive orbits in the low on-state. The post-eclipse recovery feature has not been found in the main on-state but appears at least for two orbits during the low on-state. The pre-eclipse dips are present in both main and low on-states and demonstrate a behaviour like that of early observations. The comparison of durations of the main and short on-states enables us to constrain the accretion disc semithickness and its inclination to the orbital plane. 相似文献
3.
Magnus Axelsson Stefan Larsson Linnea Hjalmarsdotter 《Monthly notices of the Royal Astronomical Society》2009,394(3):1544-1550
We study the soft X-ray variability of Cygnus X-3. By combining data from the All-Sky Monitor and Proportional Counter Array instruments on the RXTE satellite with EXOSAT /Medium Energy (ME) detector observations, we are able to analyse the power density spectrum (PDS) of the source from 10−9 to 0.1 Hz, thus covering time-scales from seconds to years. As the data on the longer time-scales are unevenly sampled, we combine traditional power spectral techniques with simulations to analyse the variability in this range. The PDS at higher frequencies (≳10−3 Hz) are for the first time compared for all states of this source. We find that it is for all states well described by a power law, with index ∼−2 in the soft states and a tendency for a less steep power law in the hard state. At longer time-scales, we study the effect of the state transitions on the PDS, and find that the variability below ∼10−7 Hz is dominated by the transitions. Furthermore, we find no correlation between the length of a high/soft-state episode and the time since the previous high/soft state. On intermediate time-scales, we find evidence for a break in the PDS at time-scales of the order of the orbital period. This may be interpreted as evidence for the existence of a tidal resonance in the accretion disc around the compact object, and constraining the mass ratio to M 2 / M 1 ≲ 0.3 . 相似文献
4.
J. N. Reeves P. T. O'Brien S. Vaughan D. Law-Green M. Ward C. Simpson K. A. Pounds R. Edelson 《Monthly notices of the Royal Astronomical Society》2000,312(2):L17-L21
We present quasi-simultaneous ASCA and RXTE observations of the most luminous known active galactic nucleus in the local ( z <0.3) Universe, the recently discovered quasar PDS 456. Multiwavelength observations have been conducted that show that PDS 456 has a bolometric luminosity of ∼1047 erg s−1 peaking in the ultraviolet part of the spectrum. In the X-ray band the 2–10 keV (rest-frame) luminosity is 1045 erg s−1 . The broad-band X-ray spectrum obtained with ASCA and RXTE contains considerable complexity. The most striking feature observed is a very deep, ionized iron K edge, observed at 8.7 keV in the quasar rest-frame. We find that these features are consistent with reprocessing from highly ionized matter, probably the inner accretion disc. PDS 456 appeared to show a strong (factor of ∼2.1) outburst in just ∼17 ks, although non-intrinsic sources cannot be completely ruled out. If confirmed, this would be an unusual event for such a high-luminosity source, with a light-crossing-time corresponding to ∼2 R S . The implication would be that flaring occurs within the very central regions, or else that PDS 456 is a 'super-Eddington' or relativistically beamed system. Overall we conclude on the basis of the extreme blue/UV luminosity, the rapid X-ray variability and from the imprint of highly ionized material on the X-ray spectrum, that PDS 456 is a quasar with an unusually high accretion rate. 相似文献
5.
6.
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
7.
Altan Baykal Tod Strohmayer Jean Swank M. Ali Alpar Michael J. Stark 《Monthly notices of the Royal Astronomical Society》2000,319(1):205-208
We analysed the Rossi X-ray Timing Explorer ( RXTE ) archival data of 1E 1048.1−5937 covering a time-span of more than one year. The spin-down rate of this source decreases by ∼30 per cent during the observation. We could not resolve the X-ray flux variations because of contamination by eta Carinae. We find that the level of pulse frequency fluctuations of 1E 1048.1−5937 is consistent with typical noise levels of accretion-powered pulsars . Recent RXTE observations of 1E 2259+586 have shown a constant spin-down with a very low upper limit on timing noise. We used the RXTE archival X-ray observations of 1E 2259+586 to show that the intrinsic X-ray luminosity times-series is also stable, with an rms fractional variation of less than 15 per cent. The source could have been in a quiet phase of accretion with a constant X-ray luminosity and spin-down rate. 相似文献
8.
Ya-Juan Lei Li-Ming Song Jin-Lu Qu Cheng-Min Zhang 《Astrophysics and Space Science》2007,310(3-4):307-315
The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries
(XRBs) and active galactic nuclei (AGN). The rms–flux relation with Rossi X-ray Timing Explorer (RXTE) data for the dips and nondip of black hole Cyg X-1 has been investigated in this paper. Our results show that there exist
the linear rms–flux relations in the frequency range 0.1–10 Hz for the dipping light curve. Moreover, this linear relation
still remains during the nondip regime, but with the steeper slope than that of the dipping case in the low energy band. For
the high energy band, the slopes of the dipping and nondipping cases are hardly constant within errors. The explanations of
the results have been made by means of the “Propagating Perturbation” model of Lyubarskii (Lyubarskii, Y.E., Mon. Not. Roy.
Astron. Soc. 292, 679–685 (1997)). 相似文献
9.
Gavin Ramsay S. B. Potter David A. H. Buckley Peter J. Wheatley 《Monthly notices of the Royal Astronomical Society》1999,306(4):809-814
CP Tuc (AX J2315–592) shows a dip in X-rays which lasts for approximately half the binary orbit and is deeper in soft X-rays compared with hard X-rays. It has been proposed that this dip is due to the accretion stream obscuring the accretion region from view. If CP Tuc were a polar, as has been suggested, then the length of such a dip would make it unique amongst polars since in those polars in which a dip is seen in hard X-rays the dip lasts for only 0.1 of the orbit. We present optical polarimetry and RXTE observations of CP Tuc which show circular polarization levels of ∼10 per cent and find evidence for only one photometric period. These data confirm CP Tuc as a polar. Our modelling of the polarization data implies that the X-ray dip is due to the bulk of the primary accretion region being self-eclipsed by the white dwarf. The energy dependence of the dip is due to a combination of this self-eclipse and also the presence of an X-ray temperature gradient over the primary accretion region. 相似文献
10.
K. E. McGowan P. A. Charles D. O'Donoghue A. P. Smale 《Monthly notices of the Royal Astronomical Society》2003,345(3):1039-1048
We have obtained high time resolution (seconds) photometry of LMC X-2 in 1997 December, simultaneously with the Rossi X-ray Timing Explorer ( RXTE ), in order to search for correlated X-ray and optical variability on time-scales from seconds to hours. We find that the optical and X-ray data are correlated only when the source is in a high, active X-ray state. Our analysis shows evidence for the X-ray emission leading the optical with a mean delay of <20 s. The time-scale for the lag can be reconciled with disc reprocessing, driven by the higher-energy X-rays, only by considering the lower limit for the delay. The results are compared with a similar analysis of archival data of Sco X-1. 相似文献
11.
V. T. Doroshenko S. G. Sergeev E. Yu. Vovk Yu. S. Efimov S. A. Klimanov S. V. Nazarov 《Astronomy Letters》2010,36(9):611-633
Based on our UBV RI observations and X-ray data from the RXTE satellite, we have investigated the variability of the galaxy NGC 7469 over the
period 1995–2009. In 1995–2000, the optical brightness of the galactic nucleus changed almost by 1
m
in the U band. In 2000–2009, the amplitude of the optical variations was considerably lower. Regular X-ray observations began only
in 2003. The X-ray fractional variability amplitude is higher than the optical one. The optical variability amplitude decreases
with increasing wavelength. The full width at half maximum of the X-ray and B-band autocorrelation functions is about 8 and 62 days, respectively. The structure functions (SF) in the X-ray range on time scales up to 7 days and in the optical range on time scales up to 100 days have the form of a
power law SF(τ) ∼ τ
b
, where τ is the time shift. On time scales of more than a day, where both structure functions have been determined rather reliably,
their slopes differ markedly: b = 1.34 ± 0.06 and b = 0.25 ± 0.05 for the optical and X-ray ranges, respectively. The X-ray and B-band structure functions begin to flatten, respectively, near 6–8 days and on time scales of about 90 days. The observed
structure functions can be described by the model of a superposition of independent Gaussian flares whose number changes with
duration ω as n(ω) ∼ ω
α and whose amplitudes depend on duration as A(ω) ∼ ω
β. The flux distribution and the flux-amplitude relation are consistent with the model of a light curve in the form of a superposition
of random flares. Once the fast intensity variations have been filtered out on long time scales, the X-ray light curve correlates
well with the optical one. No lag of the X-ray variations relative to those in the B band is detected. The light variations in the R and I bands lag behind those in the B band calculated from the centroid of the cross-correlation function by 2.6 and 3.5 days, respectively, at a 3σ confidence level. 相似文献
12.
We report the discovery of a decay in the superorbital period of the binary X-ray pulsar LMC X-4. Combining archival data
and published long term X-ray light curves, we have found a decay in the third period in this system (P ∼ 30.3 day, P ∼ −2 × 10−5 s s−1). Along with this result, a comparison of the superorbital intensity variations in LMC X-4, Her X-1 and SMC X-1 is also presented. 相似文献
13.
D. K. Ojha A. Omont S. Ganesh G. Simon M. Schultheis 《Journal of Astrophysics and Astronomy》2000,21(1-2):77-90
ISOGAL is a survey at 7 and 15 μm with ISOCAM of the inner galactic disk and bulge of our Galaxy. The survey covers ∼ 22 deg2 in selected areas of the centrall = ±30 degree of the inner Galaxy. In this paper, we report the study of a small ISOGAL field in the inner galactic bulge
(l = 0°,b = −1°, area = 0.033deg2). Using the multicolor nearinfrared data (IJKs) of DENIS (DEep Near Infrared Southern Sky Survey) and mid-infrared ISOGAL data, we discuss the nature of the ISOGAL sources.
The various color-color and color-magnitude diagrams are discussed in the paper. While most of the detected sources are red
giants (RGB tip stars), a few of them show an excess in J-Ks and Ks-[15] colors with respect to the red giant sequence. Most of them are probably AGB stars with large mass-loss rates. 相似文献
14.
V2213 Cyg was discovered as a variable star by Pavlenko (1999) in 1998. We present our photometry of V2213 Cyg from 1998–2003
based on CCD observations with the K-380 Cassegrain telescope of CrAO and the 60 cm Zeiss telescope of SAI. Observations have
been carried out mostly in R and sometimes in B and V Johnson system. The total amount of data is 2270 points, covering ∼50 nights. We classify this binary as a W UMa-type contact
system. Using all data we determined the orbital period to be 0.350079 ± 0.000007 day. The mean brightness varies between
R = 14.35 and 14.05. The mean 1999–2003 orbital light curve has two humps and a primary minimum (I), which is 0.04 mag brighter
than the deeper secondary one (II). The mean humps have slightly different height. The difference between two individual maxima
varies within 0.1 mag, which may indicate an activity of the components. The highest hump is an asymmetrical one: it has sort
of a shoulder at phases 0.75–0.80, before entering the less deep primary minimum (phase 0.0). The system is rather reddened,
its colour indices are: B−V ∼ 0.8 and V−R ∼ 0.7, and give a spectral class of V2213 Cyg earlier than K. 相似文献
15.
S. Ç. nam . ahiner A. Baykal 《Monthly notices of the Royal Astronomical Society》2009,395(2):1015-1020
We present timing and spectral analysis of RXTE -PCA (Proportional Counter Array) observations of the accretion powered pulsar 4U 1907+09 between 2007 June and 2008 August. 4U 1907+09 had been in a spin-down episode with a spin-down rate of −3.54 × 10−14 Hz s−1 before 1999. From RXTE observations after 2001 March, the source showed a ∼60 per cent decrease in spin-down magnitude, and INTEGRAL observations after 2003 March showed that source started to spin-up. We found that the source recently entered into a new spin-down episode with a spin-down rate of −3.59 × 10−14 Hz s−1 . This spin-down rate is pretty close to the previous long-term spin-down rate of the source measured before 1999. From the spectral analysis, we showed that hydrogen column density varies with the orbital phase. 相似文献
16.
We report on 10 yr of monitoring of the 8.7-s Anomalous X-ray Pulsar 4U 0142+61 using the Rossi X-Ray Timing Explorer (RXTE). This pulsar exhibited stable rotation from 2000 until February 2006: the RMS phase residual for a spin-down model which
includes ν,
, and
is 2.3%. We report a possible phase-coherent timing solution valid over a 10-yr span extending back to March 1996. A glitch
may have occurred between 1998 and 2000, but it is not required by the existing data. We also report that the source’s pulse
profile has been evolving in the past 6 years, such that the dip of emission between its two peaks has been getting shallower
since 2000, almost as if the profile is recovering to its pre-2000 morphology, in which there was no clear distinction between
the peaks. These profile variations are seen in the 2–4 keV band but not in 6–8 keV. Finally, we present the pulsed flux time
series of the source in 2–10 keV. There is evidence of a slow but steady increase in the source’s pulsed flux since 2000.
The pulsed flux variability and the narrow-band pulse profile changes present interesting challenges to aspects of the magnetar
model.
This work was supported by the Natural Sciences and Engineering Research Council (NSERC) PGSD scholarship to R.D. F.P.G. holds
a National Research Council Research Associateship Award at NASA Goddard Space Flight Center. Additional support was provided
by NSERC Discovery Grant Pgpin 228738-03 NSERC Steacie Supplement Smfsu 268264-03, FQRNT, CIAR, and CFI. V.M.K. is a Canada
Research Chair. 相似文献
17.
Elena Pavlenko Kirill Antoniuk Sergei Yu. Shugarov Nataly A. Katysheva Lenie Muzhdabaeva Vyacheslav Mikhajlov 《Astrophysics and Space Science》2005,296(1-4):461-464
We present results of multicolour photometry of the nova-like binary MV Lyr in the years 2002–2003, corresponding to the transition
of the star from its low (V = 17.8) to high (V = 12.3) brightness state. The transition lasted at most 200 days. During the first ∼50 days MV Lyr brightened at the rate
0.06 mag/day, and during the next ∼150 days at the rate 0.01 mag/day. The brightening was accompanied by a blue shift from
0.45 to 0.05 in V−R, interpreted as an increase of the accretion disk contribution to the total light. During the transition MV Lyr displayed
well-known ‘quasi-orbital’ light variations and fast quasi-periodic oscillations with a typical time scale of tens of minutes. 相似文献
18.
Optical spectroscopic data are presented on nova LW Serpentis 1978, obtained during its decline fromV 9.0 to ≃10.2 (compared to a value of ∼ 8.0 at recorded maximum). The spectrum and its evolution compare well with a typical
nova, though the principal absorption (∼ −750 km s−l) was very weak in comparison with the diffuse-enhanced absorption (∼ −1300 km s−1). The principal absorption could be identified only in the lines of O I λλ7774, 8446, and in moderate-resolution observations
of Hα. The salient features of spectral evolution follow: The near-infrared triplet of Ca n continuously weakened. O I λ8446
was always brighter than O I λ 7774, indicating continued importance of Lyman Β fluorescence. The lines due to [O I], [N II]
and N n brightened considerably near the end of our observations (37 days from maximum). The Hα emission line was asymmetric
all through with more emission towards the red. Its emission profile showed considerable structure. Based on the individual
peaks in the Hα line profile, a kinematical model is proposed for the shell of LW Ser. The model consists of an equatorial
ring, and a polar cone on the side away from the earth. The nearer polar cone did not show significant emission of Hα during
our observations. The polar axis of the shell is inclined at a small angle (∼ 15‡) to the line of sight. 相似文献
19.
D.K. Galloway † A.B. Giles ‡ K. Wu J.G. Greenhill 《Monthly notices of the Royal Astronomical Society》2001,325(1):419-425
Sharp dips observed in the pulse profiles of three X-ray pulsars (GX 1+4, RX J0812.4−3114 and A 0535+26) have previously been suggested to arise from partial eclipses of the emission region by the accretion column occurring once each rotation period. We present pulse-phase spectroscopy from Rossi X-ray Timing Explorer satellite observations of GX 1+4 and RX J0812.4−3114, which for the first time confirms this interpretation. The dip phase corresponds to the closest approach of the column axis to the line of sight, and the additional optical depth of photons escaping from the column in this direction gives rise to both the decrease in flux and increase in the fitted optical depth measured at this phase. Analysis of the arrival time of individual dips in GX 1+4 provides the first measurement of azimuthal wandering of a neutron star accretion column. The column longitude varies stochastically with a standard deviation ranging between 2° and 6° depending on the source luminosity. Measurements of the phase width of the dip both from mean pulse profiles and from the individual eclipses demonstrate that the dip width is proportional to the flux. The variation is consistent with that expected if the azimuthal extent of the accretion column depends only upon the Keplerian velocity at the inner disc radius, which varies as a consequence of the accretion rate M˙ . 相似文献
20.
F. Capitanio T. Belloni M. Del Santo P. Ubertini 《Monthly notices of the Royal Astronomical Society》2009,398(3):1194-1200
We report on a campaign of X-ray and soft γ-ray observations of the black hole candidate (BHC) H1743−322 (also named IGR J17464-3213), performed with the RXTE , INTEGRAL and Swift satellites. The source was observed during a short outburst between 2008 October 03 and November 16. The evolution of the hardness–intensity diagram throughout the outburst is peculiar, in that it does not follow the canonical pattern through all the spectral states (the so-called q-track pattern) seen during the outburst of black hole transients. On the contrary, the source only makes a transition from the hard state to the hard–intermediate state. After this transition, the source decreases in luminosity and its spectrum hardens again. This behaviour is confirmed by both spectral and timing analyses. This kind of outburst has been rarely observed before in a transient BHC. 相似文献