Search Publications
Time lags in the ultraluminous X-ray source NGC 5408 X-1: implications for the black hole mass
Belloni, T.; Cappi, M.; Ponti, G. +4 more
We present the analysis of the X-ray variability and spectral timing properties of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the most variable ULXs known so far. The variability properties are used as a diagnostic of the accretion state of the source and to derive estimates of the black hole (BH) mass. The observed high level of fa…
Optical interferometry of early-type stars with PAVO@CHARA - I. Fundamental stellar properties
White, T. R.; Tuthill, P. G.; Huber, D. +8 more
We present interferometric observations of seven main-sequence and three giant stars with spectral types from B2 to F6 using the Precision Astronomical Visible Observations beam combiner at the Center for High Angular Resolution Astronomy array. We have directly determined the angular diameters for these objects with an average precision of 2.3 pe…
Broad iron line in the fast spinning neutron-star system 4U 1636-53
Hiemstra, Beike; Belloni, Tomaso; Méndez, Mariano +3 more
We analysed the X-ray spectra of six observations, simultaneously taken with XMM-Newton and Rossi X-ray Timing Explorer (RXTE), of the neutron-star low-mass X-ray binary 4U 1636-53. The observations cover several states of the source, and therefore a large range of inferred mass accretion rate. These six observations show a broad emission line in …
New Compton-thick AGN in the circumnuclear H2O maser hosts UGC 3789 and NGC 6264
Kadler, M.; Panessa, F.; Henkel, C. +2 more
Large column densities, derived from X-ray studies, are typically measured towards active galactic nuclei (AGN) hosting water masers, especially when the H2O emission is associated with the nuclear accretion disc. In addition, possible correlations between the intrinsic X-ray luminosity and the characteristics of the H2O mase…
The orientation dependence of quasar single-epoch black hole mass scaling relationships
Wills, B. J.; Brotherton, M. S.; Runnoe, Jessie C. +2 more
Black hole masses are estimated for radio-loud quasars using several self-consistent scaling relationships based on emission-line widths and continuum luminosities. The emission lines used, Hβ, Mg ii λ2798 and C iv λ1549, have different dependencies on orientation as estimated by radio core dominance. We compare differences in the log of black hol…
Star formation in luminous quasar host galaxies at z = 1-2
Baum, Stefi A.; O'Dea, Christopher P.; Dunlop, James S. +4 more
We present deep Hubble Space Telescope (HST)/Wide-Field Planetary Camera 2 (WFPC2), rest-frame U images of 17 ∼L⋆ quasars at z ≈ 1 and 2 (V and I bands, respectively), designed to explore the host galaxies. We fit the images with simple axisymmetric galaxy models, including a point source, in order to separate nuclear and host-galaxy em…
The local luminosity function of star-forming galaxies derived from the Planck Early Release Compact Source Catalogue
Bonavera, L.; Clements, D. L.; Delabrouille, J. +18 more
The Planck Early Release Compact Source Catalogue (ERCSC) has offered the first opportunity to accurately determine the luminosity function of dusty galaxies in the very local Universe (i.e. distances ≲100 Mpc), at several (sub-)millimetre wavelengths, using blindly selected samples of low-redshift sources, unaffected by cosmological evolution. Th…
Modelling the interaction of thermonuclear supernova remnants with circumstellar structures: the case of Tycho's supernova remnant
Kaastra, J. S.; Vink, J.; Chiotellis, A. +2 more
The well-established Type Ia remnant of Tycho's supernova (SN 1572) reveals discrepant ambient medium-density estimates based on either the measured dynamics or the X-ray emission properties. This discrepancy can potentially be solved by assuming that the supernova remnant (SNR) shock initially moved through a stellar wind bubble, but is currently…
Characterization of the optical and X-ray properties of the north-western wisps in the Crab nebula
Bucciantini, N.; Weisskopf, M. C.; Idec, W. +4 more
We have studied the wisps to the north-west of the Crab pulsar as part of a multiwavelength campaign in the visible and in X-rays. Optical observations were obtained using the Nordic Optical Telescope in La Palma and X-ray observations were made with the Chandra X-ray Observatory. The observing campaign took place from 2010 October until 2012 Sept…
The ionized absorber and nuclear environment of IRAS 13349+2438: multi-wavelength insights from coordinated Chandra HETGS, HST STIS, HET and Spitzer IRS
Brandt, William N.; Hines, Dean C.; Reynolds, Christopher S. +6 more
We present results from a multi-wavelength infrared (IR)-to-X-ray campaign of the infrared bright (but highly optical-ultraviolet extincted) quasi-stellar object (QSO) IRAS 13349+2438 obtained with the Chandra High Energy Transmission Grating Spectrometer (HETGS), the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS), the Ho…