Publications by Katherine Blundell


The X-ray luminous cluster underlying the z = 1.04 quasar PKS1229-021

Monthly Notices of the Royal Astronomical Society 422 (2012) 590-599

HR Russell, AC Fabian, GB Taylor, JS Sanders, KM Blundell, CS Crawford, RM Johnstone, E Belsole

We present a 100ks Chandra observation studying the extended X-ray emission around the powerful z= 1.04 quasar PKS1229-021. The diffuse cluster X-ray emission can be traced out to ∼15arcsec (∼120kpc) radius and there is a drop in the calculated hardness ratio inside the central 5arcsec consistent with the presence of a cool core. Radio observations of the quasar show a strong core and a bright, one-sided jet leading to the south-west hotspot and a second hotspot visible on the counter-jet side. Although the wings of the quasar point spread function (PSF) provided a significant contribution to the total X-ray flux at all radii where the extended cluster emission was detected, we were able to accurately subtract the PSF emission using Chandra Ray Tracer and marx simulations. The resulting steep cluster surface brightness profile for PKS1229-021 appears similar to the profile for the FR II (Fanaroff-Riley class II) radio galaxy 3C444, which has a similarly rapid surface brightness drop caused by a powerful shock surrounding the radio lobes. Using a model surface brightness profile based on 3C444, we estimated the total cluster luminosity for PKS1229-021 to be. We discuss the difficulty of detecting cool-core clusters, which host bright X-ray sources, in high redshift surveys. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Concepts in Thermal Physics 2nd Edition

, 2012

SJ Blundell, KM Blundell


Steve Rawlings 1961-2012

ASTRONOMY & GEOPHYSICS 53 (2012) 45-45

K Blundell


Probing the history of SS433's jet kinematics via decade-resolution radio observations of W50

Monthly Notices of the Royal Astronomical Society 414 (2011) 2828-2837

PT Goodall, KM Blundell, SJ Bell Burnell

We present the results of a kinematical study of the W50 nebula using high-resolution radio observations from the Very Large Array spanning a 12-yr period, sampled in 1984, 1993 and 1996. We conduct a careful analysis of the proper motions of the radio filaments across the W50 nebula at each epoch and detect no significant motion for them during this period. The apparent lack of movement in the radio filaments mandates either (i) a high degree of deceleration of SS433's jet ejecta in the W50 nebula; or (ii) that the lobes of W50 formed a long time ago in SS433's history, during a jet outburst with appreciably different characteristics from the well-known precessing jet state observed in SS433 at the present day. We discuss the possible scenarios which could explain this result, with relevance to the nature of SS433's current jet activity. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


When microquasar jets and supernova collide: Hydrodynamically simulating the SS433-W50 interaction

Monthly Notices of the Royal Astronomical Society 414 (2011) 2838-2859

PT Goodall, F Alouani-Bibi, KM Blundell

We present investigations of the interaction between the relativistic, precessing jets of the microquasar SS433 and the surrounding, expanding supernova remnant (SNR) shell, W50, and the consequent evolution in the inhomogeneous interstellar medium (ISM). We model their evolution using the hydrodynamic flash code, which uses adaptive mesh refinement. We show that the peculiar morphology of the entire nebula can be reproduced to a good approximation, due to the combined effects of (i) the evolution of the SNR shell from the free-expansion phase through the Sedov blast wave in an exponential density profile from the Milky Way disc, and (ii) the subsequent interaction of the relativistic, precessing jets of SS433. Our simulations reveal: (1) Independent measurement of the Galaxy scaleheight and density local to SS433 (as n 0= 0.2cm -3,Z d= 40pc), with this scaleheight being in excellent agreement with the work of Dehnen & Binney. (2) A new mechanism for hydrodynamic refocusing of conical jets. (3) The current jet precession characteristics do not simply extrapolate back to produce the lobes of W50, but a history of episodic jet activity having at least three different outbursts with different precession characteristics would be sufficient to produce the W50 nebula. A history of intermittent episodes of jet activity from SS433 is also suggested in a kinematic study of W50 detailed in a companion paper. (4) An estimate of the age of W50, and equivalently the age of SS433's black hole created during the supernova explosion, in the range of 17000-21000yr. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


The inverse-Compton ghost HDF130 and the giant radio galaxy 6C0905+3955: Matching an analytic model for double-lobed radio source evolution

Monthly Notices of the Royal Astronomical Society 417 (2011) 1576-1583

P Mocz, AC Fabian, KM Blundell, PT Goodall, SC Chapman, DJ Saikia

We present new Giant Metre-wave Radio Telescope (GMRT) observations of Hubble Deep Field (HDF)130, an inverse-Compton (IC) ghost of a giant radio source that is no longer being powered by jets. We compare the properties of HDF130 with the new and important constraint of the upper limit of the radio flux density at 240 MHz to an analytic model. We learn what values of physical parameters in the model for the dynamics and evolution of the radio luminosity and X-ray luminosity [due to IC scattering of the cosmic microwave background (CMB)] of a Fanaroff-Riley type II (FR II) source are able to describe a source with features (lobe length, axial ratio, X-ray luminosity, photon index and upper limit of radio luminosity) similar to those of the observations. HDF130 is found to agree with the interpretation that it is an IC ghost of a powerful double-lobed radio source, and we are observing it at least a few Myr after jet activity (which lasted 5-100 Myr) has ceased. The minimum Lorentz factor of injected particles into the lobes from the hotspot is preferred to be γ~ 103 for the model to describe the observed quantities well, assuming that the magnetic energy density, electron energy density and lobe pressure at time of injection into the lobe are linked by constant factors according to a minimum energy argument, so that the minimum Lorentz factor is constrained by the lobe pressure. We also apply the model to match the features of 6C0905+3955, a classical double FR II galaxy thought to have a low-energy cut-off of γ~ 104 in the hotspot due to a lack of hotspot IC X-ray emission. The models suggest that the low-energy cut-off in the hotspots of 6C0905+3955 is γ≳ 103, just slightly above the particles required for X-ray emission. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.


The inverse-Compton ghost HDF130 and the giant radio galaxy 6C0905+3955: Matching an analytic model for double-lobed radio source evolution

Monthly Notices of the Royal Astronomical Society (2011)

P Mocz, AC Fabian, KM Blundell, PT Goodall, SC Chapman, DJ Saikia


Probing the history of SS433's jet kinematics via decade-resolution radio observations of W50

Monthly Notices of the Royal Astronomical Society (2011)

PT Goodall, KM Blundell, SJ Bell Burnell


SS433's accretion disc, wind and jets: before, during and after a major flare

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 417 (2011) 2401-2410

KM Blundell, L Schmidtobreick, S Trushkin


The dynamics and stability of circumbinary orbits

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 418 (2011) 2656-2668

S Doolin, KM Blundell


When microquasar jets and supernova collide: Hydrodynamically simulating the SS433-W50 interaction

Monthly Notices of the Royal Astronomical Society (2011)

PT Goodall, F Alouani-Bibi, KM Blundell

We present investigations of the interaction between the relativistic, precessing jets of the microquasar SS433 and the surrounding, expanding supernova remnant (SNR) shell, W50, and the consequent evolution in the inhomogeneous interstellar medium (ISM). We model their evolution using the hydrodynamic flash code, which uses adaptive mesh refinement. We show that the peculiar morphology of the entire nebula can be reproduced to a good approximation, due to the combined effects of (i) the evolution of the SNR shell from the free-expansion phase through the Sedov blast wave in an exponential density profile from the Milky Way disc, and (ii) the subsequent interaction of the relativistic, precessing jets of SS433. Our simulations reveal: (1) Independent measurement of the Galaxy scaleheight and density local to SS433 (as n 0 = 0.2cm -3 ,Z d = 40pc), with this scaleheight being in excellent agreement with the work of Dehnen and Binney. (2) A new mechanism for hydrodynamic refocusing of conical jets. (3) The current jet precession characteristics do not simply extrapolate back to produce the lobes of W50, but a history of episodic jet activity having at least three different outbursts with different precession characteristics would be sufficient to produce the W50 nebula. A history of intermittent episodes of jet activity from SS433 is also suggested in a kinematic study of W50 detailed in a companion paper. (4) An estimate of the age of W50, and equivalently the age of SS433's black hole created during the supernova explosion, in the range of 17000-21000yr. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.


The Dynamics and Stability of Circumbinary Orbits

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 418 (2011) 2656-2668

S Doolin, KM Blundell

We numerically investigate the dynamics of orbits in 3D circumbinary phase-space as a function of binary eccentricity and mass fraction. We find that inclined circumbinary orbits in the elliptically-restricted three-body problem display a nodal libration mechanism in the longitude of the ascending node and in the inclination to the plane of the binary. We (i) analyse and quantify the behaviour of these orbits with reference to analytical work performed by Farago & Laskar (2010) and (ii) investigate the stability of these orbits over time. This work is the first dynamically aware analysis of the stability of circumbinary orbits across both binary mass fraction and binary eccentricity. This work also has implications for exoplanetary astronomy in the existence and determination of stable orbits around binary systems.


How Much Light Has Been Produced since the Universe Was Born? Finally, a Way to Measure It.

ADVANCES IN HELLENIC ASTRONOMY DURING THE IYA09 424 (2010) 344-+

M Georganopoulos, RM Sambruna, D Kazanas, DS Davis, AN Cillis, CC Cheung, ES Perlman, KM Blundell


A New Way to Measure How Much Light Has Been Produced Since the Universe was Born

ACCRETION AND EJECTION IN AGN : A GLOBAL VIEW 427 (2010) 177-+

M Georganopoulos, RM Sambruna, D Kazanas, DS Davis, AN Cillis, CC Cheung, ES Perlman, KM Blundell


Digging the Cosmic Infrared Background out of the lobes of a radio galaxy

AIP Conference Proceedings 1085 (2009) 616-619

M Georganopoulos, RM Sambruna, D Kazanas, AN Cillis, C C.Cheung, ES Perlman, KM Blundell, DS Davis

We describe a new, independent method for breaking the deadlock of measuring the cosmologically very important Cosmic Infrared Background. Our method measures the energy density of the Cosmic Infrared Background at the location of radio galaxies by using Fermi Gamma-ray and multiwavelength observations of their radio lobes. We present an application of our method for the well-studied radio galaxy Fornax A, showing that Fermi observations will provide us with a direct, model independent measurement of the Cosmic Infrared Background. © 2009 American Institute of Physics.


Inflow and outflow from the accretion disc of the microquasar SS433

International Conference Recent Advances in Natural Language Processing, RANLP (2008)

M Sebastian Perez, KM Blundell

A succession of near-IR spectroscopic observations, taken nightly throughout an entire cycle of SS 433's orbit with UKIRT, reveal (i) the persistent signature of SS 433's accretion disc, having a rotation speed of ∼ 500 kms-1and (ii) confirms the presence of the circumbinary disc recently discovered at optical wavelengths by Blundell, Bowler & Schmidtobreick (2008) and (iii) detects a much faster outflow than has previously been measured from the disc wind. Our relatively high spectral resolution at these near-IR wavelengths has enabled us to deconstruct the different components, and their physical origins, that comprise the Brackett-γ line in this binary system. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial- ShareAlike Licence.


SS 433: Observation of the circumbinary disk and extraction of the system mass

ASTROPHYSICAL JOURNAL LETTERS 678 (2008) L47-L50

KM Blundell, MG Bowler, L Schmidtobreick


Counterparts to the Nuclear Bulge X-ray source population

AIP CONF PROC 1010 (2008) 117-121

AJ Gosling, RM Bandyopadhyay, KM Blundell, P Lucas

We present an initial matching of the source positions of the Chandra Nuclear Bulge X-ray sources to the new UKIDSS-GPS near-infrared survey of the Nuclear. Bulge. This task is made difficult by the extremely crowded nature of the region; despite this, we find candidate counterparts to similar to 50% of the X-ray sources. We show that detection in the J-band for a candidate counterpart to an X-ray source preferentially selects those candidate counterparts in the foreground whereas candidate counterparts with only detections in the H and K-bands are more likely to be Nuclear Bulge sources. We discuss the planned follow-up for these candidate counterparts.


The globaljetwatch spectrographs: A fibre-fed spectrograph for small telescopes

Proceedings of SPIE - The International Society for Optical Engineering 7014 (2008)

FJ Clarke, AJ Gosling, S Doolin, P Goodall, S Perez, P Pattinson, R Makin, KM Blundell

The GlobalJetWatch project (www.globaljetwatch.net) will place small (0.5-metre) commerical telescopes in four schools around the world. Each telescope will be equipped with a custom designed spectrograph, currently being built by the Astrophysics sub-department of the University of Oxford. The scientific goal of the project is to provide continual monitoring of a rosetta stone object, the micro-quasar SS433. In addition,the project has a significant out-reach element, aiming to involve school children on four-continents in front-line astronomical research. The spectrograph is a fibre-fed fixed format cross-dispersed echellete design providing R 6000 spectra from 4300-8500Å in a single exposure. The spectrograph is built almost entirely from off-the-shelf components. The four GlobalJetWatch sites (Australia, India, South Africa,Chile) will be commissioned in 2008/09. Here we present the baseline design of the spectrograph, and initial results from the prototype on-sky commissioning in Oxford.


Circumbinary disks

International Conference Recent Advances in Natural Language Processing, RANLP (2008)

S Doolin, K Blundell

We investigate the phenomenon of circumbinary disks: their stability and potentially insightful use as diagnostic tools of outflows. Our fully 3D simulations investigate the behaviour of circumbinary orbits, exploring binary mass fraction - eccentricity parameter space. The work presented also has implications for exoplanetary astronomy in the existence and determination of stable orbits in binary systems. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

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