Search Publications
The CMB neutrino mass/vacuum energy degeneracy: a simple derivation of the degeneracy slopes
Sutherland, Will
It is well known that estimating cosmological parameters from cosmic microwave background (CMB) data alone results in a significant degeneracy between the total neutrino mass and several other cosmological parameters, especially the Hubble constant H0 and the matter density parameter Ωm. Adding low-redshift measurements such …
Measuring the black hole mass in ultraluminous X-ray sources with the X-ray scaling method
Titarchuk, L.; Satyapal, S.; Gliozzi, M. +1 more
In our recent work, we demonstrated that a novel X-ray scaling method, originally introduced for Galactic black holes (BH), could be reliably extended to estimate the mass of supermassive black holes accreting at moderate to high level. Here, we apply this X-ray scaling method to ultraluminous X-ray sources (ULXs) to constrain their MBH…
The changing source of X-ray reflection in the radio-intermediate Seyfert 1 galaxy III Zw 2
Gallo, L. C.; Gonzalez, A. G.; Waddell, S. G. H.
We report on X-ray observations of the radio-intermediate, X-ray bright Seyfert 1 galaxy, III Zw 2, obtained with XMM-Newton, Suzaku, and Swift over the past 17 yr. The source brightness varies significantly over yearly time-scales, but more modestly over periods of days. Pointed observations with XMM-Newton in 2000 and Suzaku in 2011 show spectra…
X-ray limits on the progenitor system of the Type Ia supernova 2017ejb
Kilpatrick, Charles D.; Coulter, David A.; Foley, Ryan J. +6 more
We present deep X-ray limits on the presence of a pre-explosion counterpart to the low-luminosity Type Ia supernova (SN Ia) 2017ejb. SN 2017ejb was discovered in NGC 4696, a well-studied elliptical galaxy in the Centaurus cluster with 894 ks of Chandra imaging between 14 and 3 yr before SN 2017ejb was discovered. Using post-explosion photometry an…
Correcting the extended-source calibration for the Herschel-SPIRE Fourier-transform spectrometer
Valtchanov, I.; Spencer, L. D.; Wu, R. +20 more
We describe an update to the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier-transform spectrometer (FTS) calibration for extended sources, which incorporates a correction for the frequency-dependent far-field feedhorn efficiency, ηff. This significant correction affects all FTS extended-source calibrated spectra in s…
Detection of low-metallicity warm plasma in a galaxy overdensity environment at z ∼ 0.2
Savage, Blair D.; Wakker, Bart P.; Narayanan, Anand +3 more
We present results from the analysis of a multiphase O VI-broad Ly α (BLA) absorber at z = 0.19236 in the HubbleSpaceTelescope/Cosmic Origins Spectrograph spectrum of PG 1121 + 422. The low and intermediate ionization metal lines in this absorber have a single narrow component, whereas the Ly α has a possible broad component with b({H {I}}) ∼ 71 k…
On the high energy cut-off of accreting sources: Is general relativity relevant?
Tamborra, Francesco; Papadakis, Iossif; Dovčiak, Michal +1 more
The hard X-ray emission observed in accreting compact sources is believed to be produced by inverse Compton scattering of soft photons arising from the accretion disc by energetic electrons thermally distributed above the disc, the so-called X-ray corona. Many independent observations suggest that such coronae should be compact and located very cl…
Variable blurred reflection in the narrow-line Seyfert 1 galaxy Mrk 493
Fabian, A. C.; Gallo, L. C.; Wilkins, D. R. +1 more
We examine a 200 ks XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 493. The active galaxy was half as bright as in a previous 2003 snapshot observation and the current lower flux enables a study of the putative reflection component in detail. We determine the characteristics of the 2015 X-ray continuum by first analysing the short-…
The ultrafast outflow of WKK 4438: Suzaku and NuSTAR X-ray spectral analysis
Fabian, Andrew C.; Walton, Dominic J.; Jiang, Jiachen +1 more
Previous X-ray spectral analysis has revealed an increasing number of active galactic nuclei (AGNs) with high accretion rates where an outflow with a mildly relativistic velocity originates from the inner accretion disc. Here we report the detection of a new ultrafast outflow (UFO) with a velocity of v_out=0.319^{+0.005}_{-0.008}c in addition to a…
Hubble Space Telescope FUV observations of M31's globular clusters suggest a spatially homogeneous helium-enriched subpopulation
Kundu, Arunav; Strader, Jay; Zepf, Stephen E. +4 more
We present high spatial resolution, far ultraviolet (FUV) F140LP observations of 12 massive globular clusters in M 31 obtained using the ACS/SBC on the Hubble Space Telescope (HST). These observations resolve the cluster profiles to scales similar to their core radii and enable the study of the spatial distribution of blue and extreme horizontal b…