Publications by Katherine Blundell


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.


Hydrodynamic simulations of the SS 433-W50 complex

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

P Goodall, FA Bibi, K Blundell

The compelling evidence for a connection between SS 433 and W50 has provoked much imagination for decades. There are still many unanswered questions: What was the nature of the progenitor of the compact object in SS 433? What causes the evident re-collimation in SS 433's jets? How recent is SS 433's current precession state? What mass and energy contributions from a possible supernova explosion are required to produce W50? Here we comment on two of our 53 models: (i) featuring the SNR evolution alone, and (ii) the SNR combined with a simple jet model. © 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


Radio-loud and radio-quiet quasars: one population, different epochs of observation

ASP Conference Series (2008)

K Blundell

I bring together evidence for the rapidity with which quasars' radio synchrotron lobe emission fades and for the intermittency with which jet plasma is ejected from individual quasars and radio galaxies and affirm the picture presented by Nipoti et al (2005) that the radio-loudness of quasars is a function of the epoch at which they are observed. I briefly illustrate this account with examples of successive episodes of jet activity where the axis along which jet plasma is launched appears to have precessed. A new model for the weak core radio emission from radio-quiet quasars, that is not any kind of jet ejecta, is also briefly described.


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 - art. no. 70145A

GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY II, PTS 1-4 7014 (2008) A145-A145

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


The Nuclear Bulge extinction

AIP CONF PROC 1010 (2008) 168-170

J Andrew, KM Blundell, RM Bandyopadhyay, P Lucas

We present a new, high resolution (5 '' per pixel) near-infrared extinction map of the Nuclear Bulge using data from the UKIDSS-GPS. Using photometry from the J, H and K-bands we show that the extinction law parameter a is also highly variable in this region on similar scales to the absolute extinction. We show that only when this extinction law variation is taken into account can the extinction be measured consistently at different wavelengths.


Extended Inverse-Compton emission from distant, powerful radio galaxies

ESO Astrophysics Symposia 2008 (2008) 212-214

MC Erlund, AC Fabian, KM Blundell, A Celotti, CS Crawford


Energy... Beyond Oil

OUP Oxford, 2007

FA Armstrong, KM Blundell

This book focuses on solutions to the energy problem, and not just the problem itself.


Low-frequency radio observations of Galactic X-ray binary systems

Proceedings of Science 56 (2007)

J Miller-Jones, A Kapińska, K Blundell, B Stappers, R Braun

© 2018 The author(s). With the advent of facilities enabling wide-field monitoring of the dynamic radio sky, new areas of parameter space will be opened up for exploration. Such monitoring will be done primarily at low frequencies, in order to maximise the available field of view. One class of radio sources known to be highly variable at GHz frequencies are the so-called 'microquasars', X-ray binaries with relativistic jets. To date however, their low-frequency behaviour has not been well constrained by observations. I will present some of the first attempts to measure their low-frequency properties, showing wide-field images made from data taken with the 74-MHz system on the Very Large Array (VLA) and also the Low Frequency Front Ends (LFFEs), the new suite of low-frequency (117-175 MHz) receivers on the Westerbork Synthesis Radio Telescope (WSRT). I will show results including the low-frequency spectra of the three X-ray binaries SS 433, GRS 1915+105 and Cygnus X-3, a low-frequency study of the W 50 nebula surrounding SS 433, a search for synchrotron lobes inflated by the jets of GRS 1915+105, and the evolution of the May 2006 outburst of Cygnus X-3 at MHz frequencies.


On the origin of radio core emission in radio-quiet quasars

Astrophysical Journal 668 (2007)

KM Blundell, Z Kuncic

We present a model for the radio emission from radio-quiet quasar nuclei. We show that a thermal origin for the high brightness temperature, flat spectrum point sources (known as radio "cores") is possible provided that the emitting region is hot and optically thin. We hence demonstrate that optically thin bremsstrahlung from a slow, dense disk wind can make a significant contribution to the observed levels of radio core emission. This is a much more satisfactory explanation, particularly for sources where there is no evidence of a jet, than a sequence of self-absorbed synchrotron components that collectively conspire to give a flat spectrum. Furthermore, such core phenomena are already observed directly via milliarcsecond radio imaging of the Galactic microquasar SS 433 and the active galaxy NGC 1068. We contend that radio-emitting disk winds must be operating at some level in radio-loud quasars and radio galaxies as well (although in these cases, observations of the radio cores are frequently contaminated/dominated by synchrotron emission from jet knots). This interpretation of radio core emission mandates mass accretion rates that are substantially higher than Eddington. Moreover, acknowledgment of this mass-loss mechanism as an AGN feedback process has important implications for the input of energy and hot gas into the intergalactic medium (IGM) since it is considerably less directional than that from jets. © 2007. The American Astronomical Society. All rights reserved.


Radio and X-ray study of Cygnus A

Astrophysics and Space Science 310 (2007) 321-325

KC Steenbrugge, KM Blundell

We present a comparative analysis of 5 GHz VLA and 200 ks Chandra ACIS-I image. In the 5 GHz image the familiar jet and much weaker counterjet are seen, which bend as the jet propagates towards the hotspots. Furthermore, where the lobe detected in 5 GHz emission starts to interact with the jet, we see that the jet "threads". In the 0.2-10 keV X-ray image we do not detect the jet, but do detect a relic of the counterjet. © 2007 Springer Science+Business Media B.V.


Radio and X-ray study of cygnus A

ASTROPHYS SPACE SCI 311 (2007) 323-327

KC Steenbrugge, KM Blundell

We present a comparative analysis of 5 GHz VLA and 200 ks Chandra ACIS-I image. In the 5 GHz image the familiar jet and much weaker counterjet are seen, which bend as the jet propagates towards the hotspots. Furthermore, where the lobe detected in 5 GHz emission starts to interact with the jet, we see that the jet "threads". In the 0.2-10 keV X-ray image we do not detect the jet, but do detect a relic of the counterjet.


Determining the nature of the faint X-ray source population near the Galactic Centre

REV MEX AST ASTR 29 (2007) 54-56

RM Bandyopadhyay, AJ Gosling, KM Blundell, SS Eikenberry, VJ Mikles, P Podsiadlowski, JCA Miller-Jones, FE Bauer

We present results of a multi-wavelength program to study the faint discrete X-ray source population discovered by Chandra in the Galactic Centre (GC). From IR imaging obtained with the VLT we identify candidate K-band counterparts to 75% of the X-ray sources in our sample. By combining follow-up VLT K-band spectroscopy of a subset of these candidate counterparts with the magnitude limits of our photometric survey, we suggest that only a small percentage of the sources are HMXBs, while the majority are likely to be canonical LMXBs and CVs at the distance of the GC. In addition, we present our discovery of highly structured small-scale (5-15 '') extinction towards the Galactic Centre. This is the finest-scale extinction study of the Galactic Centre to date.


Radio and X-ray study of Cygnus a

Astrophysics and Space Science 311 (2007) 323-327

KC Steenbrugge, KM Blundell

We present a comparative analysis of 5 GHz VLA and 200 ks Chandra ACIS-I image. In the 5 GHz image the familiar jet and much weaker counterjet are seen, which bend as the jet propagates towards the hotspots. Furthermore, where the lobe detected in 5 GHz emission starts to interact with the jet, we see that the jet "threads". In the 0.2-10 keV X-ray image we do not detect the jet, but do detect a relic of the counterjet. © 2007 Springer Science+Business Media B.V.


Galactic centre X-ray sources

AIP CONF PROC 924 (2007) 893-896

AJ Gosling, RM Bandyopadhyay, KM Blundell

We report on a campaign to identify the counterparts to the population of X-ray sources discovered at the centre of our Galaxy by Wang et al. [7] using Chandra. We have used deep, near infrared images obtained on VLT/ISAAC to identify candidate counterparts as astrometric matches to the X-ray positions. Follow up K-S-band spectroscopic observations of the candidate counterparts are used to search for accretions signatures in the spectrum, namely the Brackett-gamma emission line [1]. From our small initial sample, it appears that only a small percentage, similar to 2-3% of the similar to 1000 X-ray sources are high mass X-ray binaries or wind accreting neutron stars, and that the vast majority will be shown to be canonical low mass X-ray binaries and cataclysmic variables.


Determining the nature of the faint X-ray source population near the galactic centre

International Conference Recent Advances in Natural Language Processing, RANLP (2006)

RM Bandyopadhyay, AJ Gosling, KM Blundell, P Podsiadlowski, SE Eikenberry, VJ Mikles, JCA Miller-Jones, FE Bauer

We present results of a multi-wavelength program to study the faint discrete X-ray source population discovered by Chandra in the Galactic Centre (GC). From IR imaging obtained with the VLT we identify candidate K-band counterparts to 75% of the X-ray sources in our sample. By combining follow-up VLT K-band spectroscopy of a subset of these candidate counterparts with the magnitude limits of our photometric survey, we suggest that only a small percentage of the sources are HMXBs, while the majority are likely to be canonical LMXBs and CVs at the distance of the GC. In addition, we present our discovery of highly structured small-scale (5-15′′) extinction towards the Galactic Centre. This is the finest-scale extinction study of the Galactic Centre to date. Finally, from these VLT observationswe are able to place constraints on the stellar counterpart to the "bursting pulsar" GRO J1744-28.


The emission distribution in SS433

International Conference Recent Advances in Natural Language Processing, RANLP (2006)

L Schmidtobreick, K Blundell

We present the results from a large observing campaign where we obtained 61 medium resolution spectra spread over three months. We thus cover roughly five orbits and about half a precession phase. In this paper we describe the analysis of the so-called "stationary" emission lines, which we use to compute Doppler-maps of the emission distribution in the SS433-system. The radial velocities of the individual line components have been analysed. Periodic variations with the orbital period are confirmed, but also variations on longer timescales are found. These long-term variation might be either either related to the precession phase or to some transient phenomen.


Discovery of the Low-Energy Cutoff in a Powerful Giant Radio Galaxy

Astrophysical Journal Letters 644 (2006) L13-L16

KM Blundell, A.C. Fabian, Carolin S. Crawford, M.C. Erlund


On the binary nature of SS 433

ASTROPHYSICS AND SPACE SCIENCE 304 (2006) 271-274

L Schmidtobreick, K Blundell

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