Publications



Refereed

7) Suzaku broadband spectroscopy of Swift J1753.5-0127 in the Low-Hard State
Mark Reynolds, Jon Miller, Jeroen Homan, Giovanni Miniutti, arXiv:0911.3642 (ApJ accepted)

We present Suzaku observations of the Galactic black hole candidate Swift J1753.5-0127 in the low-hard state. The broadband coverage of Suzaku enables us to detect the source over the energy range 0.6 -- 250 keV. The broadband spectrum (2 -- 250 keV) is found to be consistent with a simple power-law (gamma \sim 1.63). In agreement with previous observations of this system, a significant excess of soft X-ray flux is detected consistent with the presence of a cool accretion disc. Estimates of the disc inner radius infer a value consistent with the ISCO (R_{in} \lesssim 6 R_g, for certain values of, e.g. N_H, i), although we cannot conclusively rule out the presence of an accretion disc truncated at larger radii (R_{in} \sim 10 - 50 R_g). A weak, relativistically-broadened iron line is also detected, in addition to disc reflection at higher energy. However, the iron-K line profile favours an inner radius larger than the ISCO (R _{in} \sim 10 - 20 R_g). The implications of these observations for models of the accretion flow in the low-hard state are discussed.
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6) A photometric study of the field around the candidate recoiling/binary black hole SDSS J092712.65+294344.0
Roberto Decarli, Mark Reynolds, Massimo Dotti, 2009, MNRAS, 397, 458

We present a photometric FUV to Ks-band study of the field around quasar SDSS J092712.65+294344.0. The SDSS spectrum of this object shows various emission lines with two distinct redshifts, at z=0.699 and z=0.712. Because of this peculiar spectroscopic feature this source has been proposed as a candidate recoiling or binary black hole. A third alternative model involves two galaxies moving in the centre of a rich galaxy cluster. Here we present a study addressing the possible presence of such a rich cluster of galaxies in the SDSS J092712.65+294344.0 field. We observed the 3.6x2.6 square arcmin field in the Ks-band and matched the NIR data with the FUV and NUV images in the GALEX archive and the ugriz observations in the SDSS. From various colour-colour diagrams we were able to classify the nature of 32 sources, only 6-11 of which have colours consistent with galaxies at z~0.7. We compare these numbers with the surface density of galaxies, stars & quasars, and the expectations for typical galaxy clusters both at low and high redshift. Our study shows that the galaxy cluster scenario is in clear disagreement with the new observations.
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5) Broad Relativistic Iron Line Emission Observed in SAX J1808.4-3658
Edward Cackett, Diego Altamirano, Alessandro Patruno, Jon Miller, Mark Reynolds, Manuel Linares, Rudy Wijnands, 2009, ApJ, 694, 21

During the September-October 2008 outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe K-alpha emission line which is present in both data-sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 +/- 2.5 GM/c^2. The inner disk radius measured from the Fe K line suggests that the accretion disk is not very receded in the island state. If the inner disk (as measured by the Fe line) is truncated at the magnetospheric radius this implies a magnetic field strength of ~3E8 G at the magnetic poles, consistent with other independent estimates.
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4) Optical Spectroscopy and Photometry of SAX J1808.4-3658 in Outburst
Patrick Elebert, Mark Reynolds, Paul Callanan, Dan Hurley, Gavin Ramsay, Fraser Lewis, Dave Russell, Brian Nord, Stephen Kane, D. LePoy, Pasi Hakala, 2009, MNRAS, 395, 884

We present phase resolved optical spectroscopy and photometry of V4580 Sagittarii, the optical counterpart to the accretion powered millisecond pulsar SAX J1808.4-3658, obtained during the 2008 September/October outburst. Doppler tomography of the N III 4640.64 Bowen blend emission line reveals a focused spot of emission at a location consistent with the secondary star. The velocity of this emission occurs at 324 +/- 15 km/s; applying a "K-correction", we find the velocity of the secondary star projected onto the line of sight to be 370 +/- 40 km/s. Based on existing pulse timing measurements, this constrains the mass ratio of the system to be 0.044^{+0.005}_{-0.004}, and the mass function for the pulsar to be 0.44^{+0.16}_{-0.13} Msun. Combining this mass function with various inclination estimates from other authors, we find no evidence to suggest that the neutron star in SAX J1808.4-3658 is more massive than the canonical value of 1.4 Msun. Our optical light curves exhibit a possible superhump modulation, expected for a system with such a low mass ratio. The equivalent width of the Ca II H and K interstellar absorption lines suggest that the distance to the source is ~2.5 kpc. This is consistent with previous distance estimates based on type-I X-ray bursts which assume cosmic abundances of hydrogen, but lower than more recent estimates which assume helium-rich bursts.
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3) IR Contamination in Galactic XRNe
Mark Reynolds, Paul Callanan, Edward Robinson, Cynthia Froning, 2008, MNRAS, 387, 788

The most widely used means of measuring the mass of black holes in Galactic binaries - specifically the X-ray novae - involves both radial velocity measurements of the secondary star, and photometric measurements of its ellipsoidal variability. The latter is important in constraining the inclination and mass ratio, and requires as direct a measure of the flux of the secondary as possible. Up to now, such measurements have been preferentially carried out in the NIR (1 -- 2.5$\mu m$), where the flux from the cooler secondary is expected to dominate over that from the accretion disc. However, here we present evidence of a significant non-stellar contribution to the NIR flux in many of those quiescent X-ray novae that are thought to contain a black hole primary. We discuss origins of this excess and the effect of such contamination on Galactic black hole mass measurements.
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2) The Light Curve of the Companion to PSR B1957+20
Mark Reynolds, Paul Callanan, Andy Fruchter, Manuel Torres, Martin Beer, Rachel Gibbons, 2007, MNRAS, 379, 1117

We present a new analysis of the light curve for the secondary star in the eclipsing binary millisecond pulsar system PSR B1957+20. Combining previous data and new data points at minimum from the Hubble Space Telescope, we have 100% coverage in the R-band. We also have a number of new K_s-band data points, which we use to constrain the infrared magnitude of the system. We model this with the Eclipsing Light Curve code (ELC). From the modelling with the ELC code we obtain colour information about the secondary at minimum light in BVRI and K. For our best fit model we are able to constrain the system inclination to 65 +/- 2 degrees for pulsar masses ranging from 1.3 -- 1.9 M_sun. The pulsar mass is unconstrained. We also find that the secondary star is not filling its Roche lobe. The temperature of the un-irradiated side of the companion is in agreement with previous estimates and we find that the observed temperature gradient across the secondary star is physically sustainable.
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1) Keck K-band Observations of GRO J0422+32
Mark Reynolds, Paul Callanan, Alex Filippenko, 2007, MNRAS, 374, 657

We present Keck K-band photometry and low-resolution H & K-band spectroscopy of the X-ray nova GRO J0422+32 obtained while the system was in the quiescent state. No clear ellipsoidal modulation is present in the light curve, which is instead dominated by a strong flickering component. In the K-band we observe strong Br_gamma emission, with an equivalent width of 38 +/- 5 Angstroms. From this we conclude that the accretion disc is the most likely source of the observed photometric contamination, and that previous infrared-based attempts to constrain the mass of the putative black hole in this system are prone to considerable uncertainty. We finally proceed to show how it is possible to place meaningful constraints on some of the binary parameters of this system, even in the presence of a relatively high level of contamination from the disc.
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Conference Proceedings

Suzaku Broadband Spectroscopy Of The Black Hole Candidate Swift J1753.5-0127
Mark Reynolds, Jon Miller, Jeroen Homan
2009, 213th meeting of the American Astronomical Society, Long Beach, California, 4-8 January

The Optical Counterparts of Binary Millisecond Pulsars in Quiescence
Paul Callanan, Mark Reynolds, Patrick Elebert, Alex Filippenko, Ryan Foley, Peter Garnavich, Glen Mackie
2006, 26th Texas Symposium on Relatavistic Astrophysics, Melbourne University, 11-15 December

On the Reliability of Galactic Black Hole Mass Estimates from Ellipsoidal IR Studies
Mark Reynolds, Paul Callanan
2006, 26th Texas Symposium on Relatavistic Astrophysics, Melbourne University, 11-15 December

IR Observations of Quiescent Black Hole XRNe
Mark Reynolds, Paul Callanan
Black Holes: From Stars to Galaxies - Across the Range of Masses, International Astronomical Union. Symposium no. 238, held 21-25 August, 2006 in Prague, Czech Republic, S238, 149

Optical Observations of Binary Millisecond X-ray Pulsars in Quiescence
Paul Callanan, Mark Reynolds, Alex Filippenko, Peter Garnavich, Ryan Foley
On the Present and Future of Pulsar Astronomy, 26th meeting of the IAU, Joint Discussion 2, 16-17 August, 2006, Prague, Czech Republic, JD02, 58

Keck IR Observation of GRO J0422+32 in Quiescence
Mark Reynolds, Paul Callanan, Alex Filippenko
2005, A Life with stars, A meeting in honour of the 65th birthday of Ed van den Heuvel, eds Kapers, van der Klis, Wijers

Optical Observations of IGR J00291+5934 in the Post Outburst Phase
Mark Reynolds, Patrick Elebert, Paul Callanan, Brian Field, Patrick Tuite, Manuel Torres, Danny Steeghs, Peter Garnavich, Don Terndrup, Alex Filippenko, Ryan Foley, Emilios Harlaftis
Populations of High Energy Sources in Galaxies Proceedings of the 230th Symposium of the International Astronomical Union, Held in Dublin, Ireland 15-19 August 2005, Edited by E. J. A. Meurs; G. Fabbiano. Cambridge: Cambridge University Press, 2006., pp.80-81

The Optical & IR Lightcurve of PSR B1957+20
Mark Reynolds, Paul Callanan, Andrew Fruchter, Manuel Torres, Martin Beer, Rachel Gibbons
Populations of High Energy Sources in Galaxies Proceedings of the 230th Symposi um of the International Astronomical Union, Held in Dublin, Ireland 15-19 August 2005, Edited by E. J. A. Meurs; G. Fabbiano. Cambridge: Cambridge University Press, 2006., pp.55-56

The Light Curve of the Companion to PSR B1957+20
Mark Reynolds, Paul Callanan, Andrew Fruchter, Manuel Torres, Martin Beer, Rachel Gibbons
INTERACTING BINARIES: Accretion, Evolution, and Outcomes. AIP Conference Proceedings, Volume 797, pp. 607-610

Circulars

Astronomer's Telegram #2125 -- NIR Imaging of the Candidate Black Hole Transient XTE J1652-453
Mark Reynolds, Paul Callanan, Takahiro Nagayama

Astronomer's Telegram #1844 -- Broad relativistic iron line observed in SAX J1808.4-3658 by Suzaku
Edward Cackett, Diego Altamirano, Jon Miller, Mark Reynolds, Jennifer Blum, Manuel Linares, Alessandro Patruno, Rudy Wijnands

Astronomer's Telegram #1752 -- ESO VLT spectral observations of SAX J1808.4-3658 in outburst
Gavin Ramsay, Patrick Elebert, Paul Callanan, Mark Reynolds, Pasi Hakala

Astronomer's Telegram #1601 -- Possible near-infrared counterpart to the Galactic transient 1RXH J173523.7-354013
Edward Cackett, Rudy Wijnands, Mark Reynolds

Astronomer's Telegram #1110 -- Optical measurements of HETE J1900.1-2455 with the Large Binocular Telescope
Peter Garnavich, Paul Callanan, Patrick Elebert, Mark Reynolds