Browsing by Subject "x-ray binaries"
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Item Hydrostatic Gas Constraints On Supermassive Black Hole Masses: Implications For Hydrostatic Equilibrium And Dynamical Modeling In A Sample Of Early-Type Galaxies(2009-10) Humphrey, Phillip J.; Buote, David A.; Brighenti, Fabrizio; Gebhardt, Karl; Mathews, William G.; Gebhardt, KarlWe present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M(BH)) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGC4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with MBH measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than similar to 10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M(bondi)), finding that the two galaxies with the highest M(bondi) exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.Item The impact of x-rays on primordial minihalos(2014-05) Oliveri, Anthony; Bromm, VolkerOne of the current problems in cosmology is to understand how the first gravitationally- bound objects, or dark matter minihalos, evolved to form chemically rich, star-forming galaxies. The first stars to exist are believed to have formed in the center of minihalos that have cooled and collapsed enough to fragment into stellar-sized gas clouds. However, to reach such low temperatures, minihalos needed a more effective coolant than atomic hydrogen, namely molecular hydrogen (H2). The formation of H2 could be catalyzed by an x-ray background, which is expected to originate primarily from high-mass x-ray binaries (HMXBs). By simulating the collapse of a minihalo in the presence of x-ray backgrounds of varying strengths, we ascertain the resulting properties of a minihalo and compare to the case of no x-ray background. For sufficiently weak backgrounds (energy density uXR < 10−16J/m3), a minihalo can cool to lower temperatures than without an x- ray background, leading to the formation of lower mass stars. The mass of these primitive stars affected the abundance of heavy chemical elements that formed during their deaths as supernovae, which in turn influenced how the earliest galaxies formed.Item Multiwavelength Observations Of A0620-00 In Quiescence(2011-12) Froning, Cynthia S.; Cantrell, Andrew G.; Maccarone, Thomas J.; France, Kevin; Khargharia, Juthika; Winter, Lisa M.; Robinson, Edward L.; Hynes, Robert I.; Broderick, Jess W.; Markoff, Sera; Torres, Manuel A. P.; Garcia, Michael; Bailyn, Charles D.; Prochaska, J. Xavier; Werk, Jessica; Thom, Chris; Beland, Stephane; Danforth, Charles W.; Keeney, Brian; Green, James C.; Robinson, Edward L.We present contemporaneous X-ray, ultraviolet, optical, near-infrared, and radio observations of the black hole binary system, A0620-00, acquired in 2010 March. Using the Cosmic Origins Spectrograph on the Hubble Space Telescope, we have obtained the first FUV spectrum of A0620-00 as well as NUV observations with the Space Telescope Imaging Spectrograph. The observed spectrum is flat in the FUV and very faint (with continuum fluxes similar or equal to 1e -17 erg cm(-2) s(-1) angstrom(-1)). The UV spectra also show strong, broad (FWHM similar to 2000 km s(-1)) emission lines of Si IV, CIV, HeII, FeII, and MgII. The Civ doublet is anomalously weak compared to the other lines, which is consistent with the low carbon abundance seen in NIR spectra of the source. Comparison of these observations with previous NUV spectra of A0620-00 shows that the UV flux has varied by factors of 2-8 over several years. We compiled the dereddened, broadband spectral energy distribution (SED) of A0620-00 and compared it to previous SEDs as well as theoretical models. The SEDs show that the source varies at all wavelengths for which we have multiple samples. Contrary to previous observations, the optical-UV spectrum does not continue to drop to shorter wavelengths, but instead shows a recovery and an increasingly blue spectrum in the FUV. We created an optical-UV spectrum of A0620-00 with the donor star contribution removed. The non-stellar spectrum peaks at similar or equal to 3000 angstrom. The peak can be fit with a T = 10,000 K blackbody with a small emitting area, probably originating in the hot spot where the accretion stream impacts the outer disk. However, one or more components in addition to the blackbody are needed to fit the FUV upturn and the red optical fluxes in the optical-UV spectrum. By comparing the mass accretion rate determined from the hot spot luminosity to the mean accretion rate inferred from the outburst history, we find that the latter is an order of magnitude smaller than the former, indicating that similar to 90% of the accreted mass must be lost from the system if the predictions of the disk instability model and the estimated interoutburst interval are correct. The mass accretion rate at the hot spot is 10(5) the accretion rate at the black hole inferred from the X-ray luminosity. To reconcile these requires that outflows carry away virtually all of the accreted mass, a very low rate of mass transfer from the outer cold disk into the inner hot region, and/or radiatively inefficient accretion. We compared our broadband SED to two models of A0620-00 in quiescence: the advection-dominated accretion flow model and the maximally jet-dominated model. The comparison suggests that strong outflows may be present in the system, indicated by the discrepancies in accretion rates and the FUV upturn in flux in the SED.Item Multiwavelength Observations Of Swift J1753.5-0127(2014-01) Froning, Cynthia S.; Maccarone, Thomas J.; France, Kevin; Winter, Lisa; Robinson, Edward L.; Hynes, Robert I.; Lewis, Fraser; Robinson, Edward L.We present contemporaneous X-ray, ultraviolet (UV), optical, and near-infrared observations of the black hole binary system Swift J1753.5-0127 acquired in 2012 October. The UV observations, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, are the first UV spectra of this system. The dereddened UV spectrum is characterized by a smooth, blue continuum and broad emission lines of C IV and He II. The system was stable in the UV to <10% during our observations. We estimated the interstellar reddening by fitting the 2175 angstrom absorption feature and fit the interstellar absorption profile of Ly alpha to directly measure the neutral hydrogen column density along the line of sight. By comparing the UV continuum flux to steady-Statethin accretion disk models, we determined upper limits on the distance to the system as a function of black hole mass. The continuum is well fit with disk models dominated by viscous heating rather than irradiation. The broadband spectral energy distribution shows the system has declined at all wavelengths since previous broadband observations in 2005 and 2007. If we assume that the UV emission is dominated by the accretion disk, the inner radius of the disk must be truncated at radii above the innermost stable circular orbit to be consistent with the X-ray flux, requiring significant mass loss from outflows and/or energy loss via advection into the black hole to maintain energy balance.Item The Structure Of The Accretion Disk In The ADC Source 4U 1822-371(2010-07) Bayless, A. J.; Robinson, E. L.; Hynes, R. I.; Ashcraft, T. A.; Cornell, M. E.; Bayless, A. J.; Robinson, E. L.The low-mass X-ray binary (LMXB) 4U 1822-371 has an accretion disk corona (ADC) that scatters X-ray photons from the inner disk and neutron star out of the line of sight. It has a high orbital inclination and the secondary star eclipses the disk and ADC. We have obtained new time-resolved UV spectrograms and V- and I-band photometry of 4U 1822-371. The large quadratic term in our new optical eclipse ephemeris confirms that the system has an extremely high rate of mass transfer and mass accretion. The C IV lambda lambda = 1548 - 1550 angstrom emission line has a half width of similar to 4400 km/s, indicating a strong, high velocity wind is being driven off the accretion disk. Near the disk the wind is optically thick in UV, V, and J and the eclipse analysis shows that in V and J the optically thick wind extends nearly to the outer edge of the disk. The ADC must also extend vertically to a height equal to approximately half the disk radius.