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SPACE TELESCOPE AND OPTICAL REVERBERATION MAPPING PROJECT.VI. REVERBERATING DISK MODELS FOR NGC 5548
Starkey, D.,Horne, Keith,Fausnaugh, M. M.,Peterson, B. M.,Bentz, M. C.,Kochanek, C. S.,Denney, K. D.,Edelson, R.,Goad, M. R.,Rosa, G. De,Anderson, M. D.,Aré,valo, P.,Barth, A. J.,Bazhaw, C.,Borm American Astronomical Society 2017 The Astrophysical journal Vol.835 No.1
<P>We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves (1158 angstrom to 9157 angstrom) combine simultaneous Hubble Space Telescope, Swift, and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination i = 36 degrees +/- 10 degrees, temperature T-1= (44 +/- 6) x 10(3) K at 1 light day from the black hole, and a temperature-radius slope (T proportional to r(-alpha)) of alpha = 0.99 +/- 0.03. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at L/L-Edd = 0.1.</P>
<i>SPITZER</i>MICROLENS MEASUREMENT OF A MASSIVE REMNANT IN A WELL-SEPARATED BINARY
Shvartzvald, Y.,Udalski, A.,Gould, A.,Han, C.,Bozza, V.,Friedmann, M.,Hundertmark, M.,Beichman, C.,Bryden, G.,Novati, S. Calchi,Carey, S.,Fausnaugh, M.,Gaudi, B. S.,Henderson, C. B.,Kerr, T.,Pogge, R. IOP Publishing 2015 The Astrophysical journal Vol.814 No.2
<P>We report the detection and mass measurement of a binary lens OGLE-2015-BLG-1285La, b, with the more massive component having M-1 > 1.35M(circle dot) (80% probability). A main-sequence star in this mass range is ruled out by limits on blue light, meaning that a primary in this mass range must be a neutron star (NS) or black hole (BH). The system has a projected separation r(perpendicular to) = 6.1 +/- 0.4 AU and lies in the Galactic bulge. These measurements are based on the 'microlens parallax' effect, i.e., comparing the microlensing light curve as seen from Spitzer, which lay at 1.25 AU projected from Earth, to the light curves from four ground-based surveys, three in the optical and one in the near-infrared. Future adaptive optics imaging of the companion by 30 m class telescopes will yield a much more accurate measurement of the primary mass. This discovery both opens the path and defines the challenges to detecting and characterizing BHs and NSs in wide binaries, with either dark or luminous companions. In particular, we discuss lessons that can be applied to future Spitzer and Kepler K2 microlensing parallax observations.</P>
Han, C.,Udalski, A.,Gould, A.,Zhu, Wei,Street, R. A.,Yee, J. C.,Beichman, C.,Bryden, C.,Novati, S. Calchi,Carey, S.,Fausnaugh, M.,Gaudi, B. S.,Henderson, Calen B.,Shvartzvald, Y.,Wibking, B.,Szyma American Astronomical Society 2016 The Astrophysical journal Vol.828 No.1
<P>We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ground and from space exhibit a time offset of similar to 13 days between the caustic spikes, indicating that the relative lens-source positions seen from the two places are displaced by parallax effects. From modeling the light curves, we measure the space-based microlens parallax. Combined with the angular Einstein radius measured by analyzing the caustic crossings, we determine the mass and distance of the lens. We find that the lens is a binary composed of two G-type stars with masses of similar to 1.0 M-circle dot and similar to 0.9 M-circle dot located at a distance. of similar to 3 kpc. In addition, we are able to constrain the complete orbital parameters of the lens thanks to the precise measurement of the microlens parallax derived from the joint analysis. In contrast to the binary event OGLE-2014-BLG-1050, which was also observed by Spitzer, we find that the interpretation of OGLE-2015-BLG-0479 does not suffer from the degeneracy between (+/-, +/-) and (+/-, -/+) solutions, confirming that the four-fold parallax degeneracy in single-lens events collapses into the two-fold degeneracy for the general case of binary-lens events. The location of the blend in the color-magnitude diagram is consistent with the lens properties, suggesting that the blend is the lens itself. The blend is bright enough for spectroscopy and thus this possibility can be checked from future follow-up observations.</P>
Shvartzvald, Y.,Li, Z.,Udalski, A.,Gould, A.,Sumi, T.,Street, R. A.,Novati, S. Calchi,Hundertmark, M.,Bozza, V.,Beichman, C.,Bryden, G.,Carey, S.,Drummond, J.,Fausnaugh, M.,Gaudi, B. S.,Henderson, C. American Astronomical Society 2016 The Astrophysical journal Vol.831 No.2
<P>Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the 'microlens parallax.' We report the discovery of a 30-65M(J) brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of similar to 5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either similar to 0.25 au or similar to 45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events.</P>