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Register a new userTime Evolution and the Nature of the Near-Infrared Jets in GRS1915+105
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Added by
Stephen S. Eikenberry
Publication date
1996
fields
Physics
and research's language is
English
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We observed the galactic microquasar GRS1915+105 in the K ($2.2 mu$m) band on October 16 and 17, 1995 UTC using the COB infrared (IR) imager on the Kitt Peak National Observatory 2.1-m telescope with a 0.2-arcsec/pixel plate scale and under good ($sim 0.7$-arcsec) seeing conditions. Using a neighboring star in the image frames to determine the point spread function (PSF), we PSF-subtract the images of GRS1915+105. We find no evidence of extended emission such as the apparent near-IR jets seen by Sams et al. (1996) in July, 1995. Simple modelling of the star + jet structure allows us to place an upper limit on any similar emission at that position of $K>16.4$ at the 95% confidence level, as compared to $K=13.9$ as seen by Sams et al. (1996). This lack of extended IR flux during continued hard X-ray flaring activity confirms the hypothesis that the extended IR emission arises from the superluminal radio-emitting jets rather than reprocessing of the X-ray emission on other structures around the compact central object. Given the large apparent velocity of the radio-emitting jets, by the time of our observations the Sams et al. feature would have moved $>1$ arcsec from GRS1915+105, and we can place a limit of $K>17.7$ (95% confidence level) on any infrared emission in this region. We can thus place an upper limit on the radiative timescale of the feature of $tau < 25$ days, which is consistent with synchrotron jet emission.
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There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than were subsequently found from higher-resolution observations made with the Very Long Baseline Array and the Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign to use all three arrays to attempt to track the motion of the jet knots from the 2006 February outburst of the source, giving us unprecedented simultaneous coverage of all angular scales, from milliarcsecond scales out to arcsecond scales. The derived proper motion, which was dominated by the VLA measurements, was found to be 17.0 mas per day, demonstrating that there has been no significant permanent change in the properties of the jets since 1994. We find no conclusive evidence for deceleration of the jet knots, unless this occurs within 70 mas of the core. We discuss possible causes for the varying proper motions recorded in the literature.
GRS 1915+105 is a prominent black hole system exhibiting variability over a wide range of time scales and its observed light curves have been classified into 12 temporal states. Here we undertake a complete analysis of these light curves from all the states using various quantifiers from nonlinear time series analysis, such as, the correlation dimension (D_2), the correlation entropy (K_2), singular value decomposition (SVD) and the multifractal spectrum ($f(alpha)$ spectrum). An important aspect of our analysis is that, for estimating these quantifiers, we use algorithmic schemes which we have proposed recently and tested successfully on synthetic as well as practical time series from various fields. Though the schemes are based on the conventional delay embedding technique, they are automated so that the above quantitative measures can be computed using conditions prescribed by the algorithm and without any intermediate subjective analysis. We show that nearly half of the 12 temporal states exhibit deviation from randomness and their complex temporal behavior could be approximated by a few (3 or 4) coupled ordinary nonlinear differential equations. These results could be important for a better understanding of the processes that generate the light curves and hence for modelling the temporal behavior of such complex systems. To our knowledge, this is the first complete analysis of an astrophysical object (let alone a black hole system) using various techniques from nonlinear dynamics.
We present a new dynamical study of the black hole X-ray transient GRS1915+105 making use of near-infrared spectroscopy obtained with X-shooter at the VLT. We detect a large number of donor star absorption features across a wide range of wavelengths spanning the H and K bands. Our 24 epochs covering a baseline of over 1 year permit us to determine a new binary ephemeris including a refined orbital period of P=33.85 +/- 0.16 d. The donor star radial velocity curves deliver a significantly improved determination of the donor semi-amplitude which is both accurate (K_2=126 +/- 1 km/s) and robust against choice of donor star template and spectral features used. We furthermore constrain the donor stars rotational broadening to vsini=21 +/-4 km/s, delivering a binary mass ratio of q=0.042 +/- 0.024. If we combine these new constraints with distance and inclination estimates derived from modelling the radio emission, a black hole mass of M_BH=10.1 +/- 0.6 M_sun is inferred, paired with an evolved mass donor of M_2=0.47 +/- 0.27 M_sun. Our analysis suggests a more typical black hole mass for GRS1915+105 rather than the unusually high values derived in the pioneering dynamical study by Greiner et al. (2001). Our data demonstrate that high-resolution infrared spectroscopy of obscured accreting binaries can deliver dynamical mass determinations with a precision on par with optical studies.
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We present predictions for the evolution of radio emission from Active Galactic Nuclei (AGNs). We use a model that follows the evolution of Supermassive Black Hole (SMBH) masses and spins, within the latest version of the GALFORM semi-analytic model of galaxy formation. We use a Blandford-Znajek type model to calculate the power of the relativistic jets produced by black hole accretion discs, and a scaling model to calculate radio luminosities. First, we present the predicted evolution of the jet power distribution, finding that this is dominated by objects fuelled by hot halo accretion and an ADAF accretion state for jet powers above $10^{32}mathrm{W}$ at $z=0$, with the contribution from objects fuelled by starbursts and in a thin disc accretion state being more important for lower jet powers at $z=0$ and at all jet powers at high redshifts ($zgeq3$). We then present the evolution of the jet power density from the model. The model is consistent with current observational estimates of jet powers from radio luminosities, once we allow for the significant uncertainties in these observational estimates. Next, we calibrate the model for radio emission to a range of observational estimates of the $z=0$ radio luminosity function. We compare the evolution of the model radio luminosity function to observational estimates for $0<z<6$, finding that the predicted evolution is similar to that observed. Finally, we explore recalibrating the model to reproduce luminosity functions of core radio emission, finding that the model is in approximate agreement with the observations.
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