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Register a new userThe spin measurement of the black hole in 4U 1543-47 constrained with the X-ray reflected emission
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4U 1543-47 is a low mass X-ray binary which harbours a stellar-mass black hole located in our Milky Way galaxy. In this paper, we revisit 7 data sets which were in the Steep Power Law state of the 2002 outburst. The spectra were observed by the Rossi X-ray Timing Explorer. We have carefully modelled the X-ray reflection spectra, and made a joint-fit to these spectra with relxill, for the reflected emission. We found a moderate black hole spin, which is $0.67_{-0.08}^{+0.15}$ at 90% statistical confidence. Negative and low spins (< 0.5) at more than 99% statistical confidence are ruled out. In addition, our results indicate that the model requires a super-solar iron abundance: $5.05_{-0.26}^{+1.21}$, and the inclination angle of the inner disc is $36.3_{-3.4}^{+5.3}$ degrees. This inclination angle is appreciably larger than the binary orbital inclination angle (~21 degrees); this difference is possibly a systematic artefact of the artificially low-density employed in the reflection model for this X-ray binary system.
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We investigate the possible nonlinear variability properties of the black hole X-ray nova 4U1543-47 to complement the temporal studies based on linear techniques, and to search for signs of nonlinearity in Galactic black hole (GBH) light curves. First, we apply the weighted scaling index method (WSIM) to characterize the X-ray variability properties of 4U1543-47 in different spectral states during the 2002 outburst. Second, we use surrogate data to investigate whether the variability is nonlinear in any of the different spectral states. The main findings can be summarized as follows. The mean weighted scaling index appears to be able to parametrize uniquely the temporal variability properties of this GBH: the 3 different spectral states of the 2002 outburst of 4U1543-47 are characterized by different and well constrained values. The search for nonlinearity reveals that the variability is linear in all light curves with the notable exception of the very high state. Our results imply that we can use the WSIM to assign a single number, namely the mean weighted scaling index, to a light curve, and in this way discriminate among the different spectral states of a source. The detection of nonlinearity in the VHS, that is characterized by the presence of most prominent QPOs, suggests that intrinsically linear models which have been proposed to account for the low frequency QPOs in GBHs may be ruled out (abridged).
(shortened) Spectroscopic observations of the soft X-ray transient 4U 1543-47 reveal a radial velocity curve with a period of P=1.123 +/- 0.008 days and a semi-amplitude of K_2 = 124 +/- 4 km/sec. The mass function is f(M) = 0.22 +/- 0.02 solar masses. We derive a distance of d = 9.1 +/-1.1 kpc if the secondary is on the main sequence. The V and I light curves exhibit two waves per orbital cycle with amplitudes of about 0.08 mag. We modeled the light curves as ellipsoidal variations in the secondary star and derive extreme inclination limits of 20 <= i <= 40 deg and formal 3 sigma limits of 24 <= i <= 36 deg for a mass ratio Q = M_1/M_2 > 1. However, there are systematic effects in the data that the model does not account for, so the above constraints should be treated with caution. We argue that the secondary star is still on the main sequence and if the secondary star has a mass near the main sequence values for early A-stars (2.3 <= M_2 <= 2.6 solar masses), then the best fits for the 3 sigma inclination range (24 <= i <= 36 deg) and the 3 sigma mass function range (0.16 <= f(M) <= 0.28 solar masses) imply a primary mass in the range 2.7 <= M_1 <= 7.5 solar masses. Thus the mass of the compact object in 4U 1543-47 is likely to be in excess of approximately 3 solar masses and we conclude 4U 1543-47 most likely contains a black hole.
We present an X-ray spectral and timing analysis of 4U 1543-47 during its 2002 outburst based on 49 pointed observations obtained using the Rossi X-ray Timing Explorer (RXTE). The outburst reached a peak intensity of 4.2 Crab in the 2-12 keV band and declined by a factor of 32 throughout the month-long observation. A 21.9 +- 0.6 mJy radio flare was detected at 1026.75 MHz two days before the X-ray maximum; the radio source was also detected late in the outburst, after the X-ray source entered the low hard state. The X-ray light curve exhibits the classic shape of a rapid rise and an exponential decay. The spectrum is soft and dominated by emission from the accretion disk. The continuum is fit with a multicolor disk blackbody (kT_{max} = 1.04 keV) and a power-law (Gamma ~ 2.7). Midway through the decay phase, a strong low-frequency QPO (nu = 7.3-8.1 Hz) was present for several days. The spectra feature a broad Fe K alpha line that is asymmetric, suggesting that the line is due to relativistic broadening rather than Comptonization. Relativistic Laor models provide much better fits to the line than non-relativistic Gaussian models, particularly near the beginning and end of our observations. The line fits yield estimates for the inner disk radius that are within 6 R_g; this result and additional evidence indicates that this black hole may have a non-zero angular momentum.
We studied a time history of X-ray spectral states of a black-hole candidate, 4U 1630-47, utilizing data from a number of monitoring observations with the Rossi X-Ray Timing Explorer over 1996--2004. These observations covered five outbursts of 4U 1630-47, and most of the data recorded typical features of the high/soft states. We found that the spectra in the high/soft states can be further classified into three states. The first spectral state is explained by a concept of the standard accretion disk picture. The second state appears in the so-called very high state, where a dominant hard component is seen and the disk radius apparently becomes too small. These phenomena are explained by the effect of inverse Compton scattering of disk photons, as shown by Kubota, Makishima, & Ebisawa (2001, ApJ, 560, L147) for GRO J1655-40. The third state is characterized in such a way that the disk luminosity varies in proportion to $T_{rm in}^2$, rather than $T_{rm in}^4$, where $T_{rm in}$ is the inner-disk temperature. This state is suggested to be an optically-thick and advection-dominated slim disk, as suggested by Kubota & Makishima (2004, ApJ, 601, 428) for XTE J1550-564. The second and third states appear, with good reproducibility, when $T_{rm in}$ and the total X-ray luminosity are higher than 1.2 keV and $sim2.5times10^{38}(D/10quad{rm kpc})^2l eft[cos{theta}/(1/sqrt{3})]^{-1}$ erg s$^{-1}$, respectively, where $D$ is the distance to the object and $theta$ is the inclination angle to the disk. The present results suggest that these three spectral states commonly appear among black-hole binaries under high accretion rates.
Recent advancements in the understanding of jet-disc coupling in black hole candidate X-ray binaries (BHXBs) have provided close links between radio jet emission and X-ray spectral and variability behaviour. In soft X-ray states the jets are suppressed, but the current picture lacks an understanding of the X-ray features associated with the quenching or recovering of these jets. Here we show that a brief, ~4 day infrared (IR) brightening during a predominantly soft X-ray state of the BHXB 4U 1543-47 is contemporaneous with a strong X-ray Type B quasi-periodic oscillation (QPO), a slight spectral hardening and an increase in the rms variability, indicating an excursion to the soft-intermediate state (SIMS). This IR flare has a spectral index consistent with optically thin synchrotron emission and most likely originates from the steady, compact jet. This core jet emitting in the IR is usually only associated with the hard state, and its appearance during the SIMS places the jet line between the SIMS and the soft state in the hardness-intensity diagram for this source. IR emission is produced in a small region of the jets close to where they are launched (~ 0.1 light-seconds), and the timescale of the IR flare in 4U 1543-47 is far too long to be caused by a single, discrete ejection. We also present a summary of the evolution of the jet and X-ray spectral/variability properties throughout the whole outburst, constraining the jet contribution to the X-ray flux during the decay.
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