Research Showcase

As well as imaging, the FT team is involved in research and is pleased to involve as many FT users as possible. One extremely successful project that we have been running since 2006 is a project involving the optical monitoring of ~35 Low-Mass X-ray Binaries (LMXBs). This project was set up by Dr David Russell (New York University Abu Dhabi), Professor Rob Fender (Oxford), Dr Paul Roche (FT) and Dr Fraser Lewis (FT).  We are hugely grateful for all the help we have received.

Our XRB project is here


R. M. Plotkin, J. Bright, J. C. A. Miller-Jones, A. W. Shaw, J. A. Tomsick, T. D. Russell, G.-B.Zhang, D. M. Russell, R. P. Fender, J. Homan, P. Atri, F. Bernardini, J. D. Gelfand, F. Lewis, T. M. Cantwell, S. H. Carey, K. J. B. Grainge, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, A. M. M. Scaife, P. F. Scott, D. J. Titterington

The candidate black hole X-ray binary Swift J1753.5-0127 faded to quiescence in 2016 November, after a prolonged outburst that was discovered in 2005. Nearly three months later the system displayed renewed activity that lasted through 2017 July. Here, we present radio and X-ray monitoring over ~3 months of the renewed activity to study the coupling between the jet and the inner regions of the disk/jet system. Our observations cover low X-ray luminosities that have not historically been well-sampled (Lx~2e33 - 1e36 erg/s; 1-10 keV), including time periods when the system was both brightening and fading. At these low luminosities Swift J1753.5-0127 occupies a parameter space in the radio/X-ray luminosity plane that is comparable to "canonical" systems (e.g., GX 339-4), regardless of whether the system was brightening or fading, even though during its >11-year outburst Swift J1753.5-0127 emitted less radio emission from its jet than expected. We discuss implications for the existence of a single radio/X-ray luminosity correlation for black hole X-ray binaries at the lowest luminosities (Lx < 1e35 erg/s), and we compare to supermassive black holes. Our campaign includes the lowest luminosity quasi-simultaneous radio/X-ray detection to date for a black hole X-ray binary during its rise out of quiescence, thanks to early notification from optical monitoring combined with fast responses from sensitive multiwavelength facilities.

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Disk-jet coupling in low-luminosity accreting neutron stars 

V. Tudor, J. C. A. Miller-Jones, A. Patruno, C. R. D'Angelo, P. G. Jonker, D. M. Russell, T. D. Russell, F. Bernardini, F. Lewis, A. T. Deller, J. W. T. Hessels, S. Migliari, R. M. Plotkin, R. Soria, R. Wijnands

In outburst, neutron star X-ray binaries produce less powerful jets than black holes at a given X-ray luminosity. This has made them more difficult to study as they fade towards quiescence. To explore whether neutron stars power jets at low accretion rates (LX≲1036 erg/s), we investigate the radio and X-ray properties of three accreting millisecond X-ray pulsars (IGR J17511-3057, SAX J1808.4-3658 and IGR J00291+5934) during their outbursts in 2015, and of the non-pulsing neutron star Cen X-4 in quiescence (2015) and in outburst (1979).

We did not detect the radio counterpart of IGR J17511-3057 in outburst or of Cen X-4 in quiescence, but did detect IGR J00291+5934 and SAX J1808.4-3658, showing that at least some neutron stars launch jets at low accretion rates. While the radio and X-ray emission in IGR J00291+5934 seem to be tightly correlated, the relationship in SAX J1808.4-3658 is more complicated. We find that SAX J1808.4-3658 produces jets during the reflaring tail, and we explore a toy model to ascertain whether the radio emission could be attributed to the onset of a strong propeller. The lack of a universal radio/X-ray correlation, with different behaviours in different neutron star systems (with various radio/X-ray correlations; some being radio faint and others not), points at distinct disk-jet interactions in individual sources, while always being fainter in the radio band than black holes at the same X-ray luminosity. 

Read the preprint here 

Multiwavelength monitoring of a very active dwarf nova AX J1549.8−5416 with an unusually high duty cycle 

Guobao Zhang, Joseph D. Gelfand, David M. Russell (NYUAD), Fraser Lewis (FT/LJMU), Nicola Masetti (INAF Bologna/Universidad Andres Bello, Santiago, Chile), Federico Bernardini (NYUAD), Ileana Andruchow, L. Zibecchi (Universidad Nacional de La Plata Argentina/Instituto de Astrofısica La PlataArgentina)

We present the results of our analysis of new optical, ultraviolet (UV) and X-ray observations of a highly variable source − AX J1549.8−5416. Both the detection of several fast rise, exponential decay outbursts in the optical light curve and the lack of He II emission lines in the optical spectra suggest AX J1549.8−5416 is a cataclysmic variable of the dwarf nova (DN) type. The multiwavelength analysis of three mini-outbursts and one normal outburst represent one of the most complete multiwavelength studies of a DN and help to refine the relationship between the X-ray, UV and optical emission in this system. We find that the UV emission is delayed with respect to the optical by 1.0−5.4 days during the rising phase of the outburst. The X-ray emission is suppressed during the peak of the optical outburst and recovers during the end of the outburst. From our analysis of archival Swift, Chandra and XMM-Newton observations of AX J1549.8−5416, we estimate this DN has a high duty cycle (∼50%), suggesting a quiescent X-ray luminosity larger than 10^32 erg/s. We also find the X-ray and UV flux are roughly anti-correlated. Furthermore, we find that, at low X-ray fluxes, the X-ray spectrum is well described by a single temperature thermal plasma model, while at high X-ray fluxes, an isobaric cooling flow model also works. We find that the maximum temperature of the plasma in quiescence is significantly higher than that in outburst. 

Read the preprint here

Polarized synchrotron emission in quiescent black hole X-ray transients 

D.M. Russell (NYUAD), T. Shahbaz (IAC, Spain), Fraser Lewis (FT/LMU), E. Gallo (Michigan)

We present near-infrared polarimetric observations of the black hole X-ray binaries Swift J1357.2-0933 and A0620-00. In both sources, recent studies have demonstrated the presence of variable infrared synchrotron emission in quiescence, most likely from weak compact jets. For Swift J1357.2-0933 we find that the synchrotron emission is polarized at a level of 8.0 +- 2.5 per cent (a 3.2 sigma detection of intrinsic polarization). The mean magnitude and rms variability of the flux (fractional rms of 19-24 per cent in Ks-band) agree with previous observations. These properties imply a continuously launched (stable on long timescales), highly variable (on short timescales) jet in the Swift J1357.2-0933 system in quiescence, which has a moderately tangled magnetic field close to the base of the jet. We find that for A0620-00, there are likely to be three components to the optical-infrared polarization; interstellar dust along the line of sight, scattering within the system, and an additional source that changes the polarization position angle in the reddest (H and Ks) wave-bands. We interpret this as a stronger contribution of synchrotron emission, and by subtracting the line-of-sight polarization, we measure an excess of ~ 1.25 +- 0.28 per cent polarization and a position angle of the magnetic field vector that is consistent with being parallel with the axis of the resolved radio jet. These results imply that weak jets in low luminosity accreting systems have magnetic fields which possess similarly tangled fields compared to the more luminous, hard state jets in X-ray binaries. 

Read the preprint here 

A "high-hard" outburst of the black hole X-ray binary GS 1354-64 

K. I. I. Koljonen, D. M. Russell (NYUAD), J. M. Corral-Santana (Pontificia Universidad Catholica de Chile), M. Armas Padilla, T. Muñoz-Darias (IAC), F. Lewis (FT/LJMU), M. Coriat (Toulouse), F. E. Bauer (Pontificia Universidad Catholica de Chile, Millennium Institute of Astrophysics, Space Science Institute)

We study in detail the evolution of the 2015 outburst of GS 1354-64 (BW Cir) at optical, UV and X-ray wavelengths using Faulkes Telescope South, SMARTS and Swift. The outburst was found to stay in the hard X-ray state, albeit being anomalously luminous with a peak luminosity of LX> 0.15 LEdd, which could be the most luminous hard state observed in a black hole X-ray binary. We found that the optical/UV emission is tightly correlated with the X-ray emission, consistent with accretion disc irradiation and/or a jet producing the optical emission. The X-ray spectra can be fitted well with a Comptonisation model, and show softening towards the end of the outburst. In addition, we detect a QPO in the X-ray lightcurves with increasing centroid frequency during the peak and decay periods of the outburst. The long-term optical lightcurves during quiescence show a statistically significant, slow rise of the source brightness over the 7 years prior to the 2015 outburst. This behaviour as well as the outburst evolution at all wavelengths studied can be explained by the disc instability model with irradiation and disc evaporation/condensation.

Read the preprint here

Events leading up to the June 2015 outburst of V404 Cyg 

F. Bernardini, D.M. Russell (New York University Abu Dhabi), A.W. Shaw (Southampton), F. Lewis (FT, LJMU), P.A. Charles (Southampton), K.I.I. Koljonen (New York University Abu Dhabi), J.P. Lasota (Institut d’Astrophysique de Paris, Nicolaus Copernicus Astronomical Center, Warsaw), J. Casares (IAC, Tenerife, La Laguna, Oxford)

On 2015 June 15 the burst alert telescope (BAT) on board Swift detected an X-ray outburst from the black hole transient V404 Cyg. We monitored V404 Cyg for the last 10 years with the 2-m Faulkes Telescope North in three optical bands (V, R, and i′). We found that, one week prior to this outburst, the optical flux was 0.1–0.3 mag brighter than the quiescent orbital modulation, implying an optical precursor to the X-ray outburst. There is also a hint of a gradual optical decay (years) followed by a rise lasting two months prior to the outburst. We fortuitously obtained an optical spectrum of V404 Cyg 13 hours before the BAT trigger. This too was brighter (~ 1 mag) than quiescence, and showed spectral lines typical of an accretion disk, with characteristic absorption features of the donor being much weaker. No He II emission was detected, which would have been expected had the X-ray flux been substantially brightening. This, combined with the presence of intense Hα emission, about 7 times the quiescent level, suggests that the disk entered the hot, outburst state before the X-ray outburst began. We propose that the outburst is produced by a viscous-thermal instability triggered close to the inner edge of a truncated disk. An X-ray delay of a week is consistent with the time needed to refill the inner region and hence move the inner edge of the disk inwards, allowing matter to reach the central BH, finally turning on the X-ray emission. 

Read the preprint here

Properties and evolution of the redback millisecond pulsar binary PSR J2129−0429 

Eric C. Bellm (Caltech), David L. Kaplan (Wisconsin-Milwaukee), Rene P. Breton (Jodrell Bank, Southampton), E. Sterl Phinney (Caltech), Varun B. Bhalerao (IUCAA, India), Fernando Camilo (Columbia), Sumit Dahal (New York University Abu Dhabi), S. G. Djorgovski, Andrew J. Drake (Caltech), J. W. T. Hessels (ASTRON, Amsterdam), Russ R. Laher (IPAC, Caltech), David B.
Levitan (Caltech), Fraser Lewis (FT, LJMU), Ashish A. Mahabal (Caltech), Eran O. Ofek (Weizmann Institute of Science, Israel), Thomas A. Prince (Caltech), Scott M. Ransom (NRAO, Virginia), Mallory S. E. Roberts, David M. Russell (New York University Abu Dhabi), Branimir Sesar (MPIA, Germany), Jason A. Surace (IPAC, Caltech), Sumin Tang (Caltech)

PSR J2129−0429 is a “redback” eclipsing millisecond pulsar binary with an unusually long 15.2 hour orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean mR = 16.6 mag), allowing us to construct the longest baseline photometric dataset available for such a system. We present ten years of archival and new photometry of the companion from LINEAR, CRTS, PTF, the Palomar 60-inch, and LCOGT. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200- inch indicates that the pulsar is massive: 1.74 ± 0.18 solar masses. The G-type pulsar companion has mass 0.44 ± 0.04 solar masses , one of the heaviest known redback companions. It is currently 95±1% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr−1 secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical lightcurve shape. This behavior may indicate that the companion is cooling. Binary evolution calculations indicate that PSR J2129−0429 has an orbital period almost exactly at the bifurcation period between systems that converge into tighter orbits as black widows and redbacks and those that diverge into wider pulsar–white dwarf binaries. Its eventual fate may depend on whether it undergoes future episodes of mass transfer and increased irradiation. 

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A long-period Cepheid variable in the starburst cluster VdBH222

J. S. Clark (Open University), I.Negueruela (Alicante), M. E. Lohr (Open University), R. Dorda (Alicante), C.Gonzalez-Fernandez (Cambridge), F. Lewis (FT, LJMU) and P. Roche (FT)

Context Galactic starburst clusters play a twin role in astrophysics, serving as laboratories for the study of stellar physics and also delineating the structure and recent star formation history of the Milky Way.

Aims In order to exploit these opportunities we have undertaken a spectroscopic survey of the red supergiant dominated young massive clusters thought to be present at both near and far ends of the Galactic Bar.

Methods Specifically, multi-epoch observations were employed to identify and investigate stellar variability and its potential role in initiating mass loss amongst the cool super-/hypergiant populations of these aggregates.

Results Significant spectroscopic variability suggestive of radial pulsations was found for the yellow supergiant VdBH222 #505. Follow-up photometric investigations revealed modulation with a period of ~ 23.325 d; both timescale and pulsational profile are consistent with a Cepheid classification.

Conclusions #505 is one of the longest period Galactic cluster Cepheids identified to date and hence of considerable use in constraining the bright end of the period/luminosity relation at solar metallicities. In conjunction with extant photometry we infer a distance of ~ 6kpc for VdBH222 and an age of ~ 20Myr. This results in a moderate reduction in both the integrated cluster mass (2 × 10^4 solar masses) and the initial masses of the evolved cluster members (~ 10 solar masses). As such VdBH222 becomes an excellent test-bed for studying the properties of some of the lowest mass stars observed to undergo type-II supernovae. Moreover, the distance is in tension with a location of VdBH222 at the far end of the Galactic Bar. Instead a birthsite in the near 3kpc arm is suggested; providing compelling evidence of extensive recent star formation in a region of the inner Milky Way which has hitherto been thought to be devoid of such activity. 

Read the pre-print here


HERschel Observations of Edge-on Spirals (HEROES) II. Tilted-ring modelling of the atomic gas disks 

F. Allaert (Gent), G. Gentile (Gent, Brussels), M. Baes, G. De Geyter (Gent), T.M. Hughes (Gent, Valparaiso), F. Lewis (FT, LJMU), S. Bianchi (INAF Firenze), I. De Looze (Gent, Cambridge), J. Fritz (UNAM Mexico), B. W. Holwerda (Leiden), J. Verstappen (Groningen), and S. Viaene (Gent)

Context. Edge-on galaxies can offer important insights in galaxy evolution as they are the only systems where the distribution of the different components can be studied both radially and vertically. The HEROES project was designed to investigate the interplay between the gas, dust, stars and dark matter (DM) in a sample of 7 massive edge-on spiral galaxies. 

Aims. In this second HEROES paper we present an analysis of the atomic gas content of 6 out of 7 galaxies in our sample. The remaining galaxy was recently analysed according to the same strategy. The primary aim of this work is to constrain the surface density distribution, the rotation curve and the geometry of the gas disks in a homogeneous way. In addition we identify peculiar features and signs of recent interactions. 

Methods. We construct detailed tilted-ring models of the atomic gas disks based on new GMRT 21-cm observations of NGC 973 and UGC 4277 and re-reduced archival HI data of NGC 5907, NGC 5529, IC 2531 and NGC 4217. Potential degeneracies between different models are resolved by requiring a good agreement with the data in various representations of the data cubes. 

Results. From our modelling we find that all but one galaxy are warped along the major axis. In addition, we identify warps along the line of sight in three galaxies. A flaring gas layer is required to reproduce the data only for one galaxy, but (moderate) flares cannot be ruled for the other galaxies either. A coplanar ring-like structure is detected outside the main disk of NGC 4217, which we suggest could be the remnant of a recent minor merger event. We also find evidence for a radial inflow of 15 +- 5 km/s in the disk of NGC 5529, which might be related to the ongoing interaction with two nearby companions. 

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Multiwavelength observations of the black hole transient Swift J1745-26 during the outburst decay

Emrah Kalemci (Sabanci, Turkey), Mehtap Ozbey Arabaci (Ankara, Turkey), Tolga Guver (Istanbul, Turkey), David M. Russell (New York Abu Dhabi), John Tomsick (Berkeley), Joern Wilms (Erlangen-Nurnberg), Georg Weidenspointner (Hamburg, MPI Garching), Erik Kuulkers (ESAC Madrid), Maurizio Falanga (Bern), Tolga Dincer (Sabanci, Turkey), Sebastian Drave (Southampton), Tomaso Belloni (Brera), Mickael Coriat (Cape Town), Fraser Lewis (FT), Teo Munoz-Darias (Oxford)

We characterized the broad-band X-ray spectra of Swift J1745-26 during the decay of the 2013 outburst using INTEGRAL ISGRI, JEM-X and Swift XRT. The X-ray evolution is compared to the evolution in optical and radio. We fit the X- ray spectra with phenomenological and Comptonization models. We discuss possible scenarios for the physical origin of a ~50 day flare observed both in optical and X- rays ~170 days after the peak of the outburst. We conclude that it is a result of enhanced mass accretion in response to an earlier heating event. We characterized the evolution in the hard X-ray band and showed that for the joint ISGRI-XRT fits, the e-folding energy decreased from 350 keV to 130 keV, while the energy where the exponential cut-off starts increased from 75 keV to 112 keV as the decay progressed.We investigated the claim that high energy cut-offs disappear with the compact jet turning on during outburst decays, and showed that spectra taken with HEXTE on RXTE provide insufficient quality to characterize cut-offs during the decay for typical hard X-ray fluxes. Long INTEGRAL monitoring observations are required to understand the relation between the compact jet formation and hard X-ray behavior. We found that for the entire decay (including the flare), the X-ray spectra are consistent with thermal Comptonization, but a jet synchrotron origin cannot be ruled out. 

Paper here

Multiwavelength Observations of Swift J1753.5-0127

Froning, C. S. (Colorado), Maccarone, T. J. (Texas Tech), France, K. (Colarado), Winter, L. (Colorado), Robinson, E. L. (Texas Tech) , Hynes, R. I.(Louisiana State), Lewis, F. (FT, USW, LJMU)

We present contemporaneous X-ray, ultraviolet, optical and near-infrared observations of the black hole binary system, Swift J1753.5-0127, acquired in 2012 October. The UV observations, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, are the first UV spectra of this system. The dereddened UV spectrum is characterized by a smooth, blue continuum and broad emission lines of CIV and HeII. The system was stable in the UV to <10% during our observations. We estimated the interstellar reddening by fitting the 2175 Angstrom absorption feature and fit the interstellar absorption profile of Lyman alpha to directly measure the neutral hydrogen column density along the line of sight. By comparing the UV continuum flux to steady-state thin accretion disk models, we determined upper limits on the distance to the system as a function of black hole mass. The continuum is well fit with disk models dominated by viscous heating rather than irradiation. The broadband spectral energy distribution shows the system has declined at all wavelengths since previous broadband observations in 2005 and 2007. If we assume that the UV emission is dominated by the accretion disk the inner radius of the disk must be truncated at radii above the ISCO to be consistent with the X-ray flux, requiring significant mass loss from outflows and/or energy loss via advection into the black hole to maintain energy balance. 

Paper here 

An evolving compact jet in the black hole X-ray binary MAXI J1836-194 

D. M. Russell (IAC), T. D. Russell (Curtin), J. C. A. Miller-Jones (Curtin), K. O’Brien (Oxford), R. Soria (Curtin), G. R. Sivakoff (Alberta), T. Slaven-Blair (Curtin), F. Lewis (FT), S. Markoff (Amsterdam), J. Homan (MIT), D. Altamirano (Amsterdam), P. A. Curran (Curtin), M. P. Rupen (NRAO), T. M. Belloni (Brera), M. Cadolle Bel (ESAC), P. Casella (INAF), S. Corbel (CEA), V. Dhawan (NRAO), R. P. Fender (Southampton), E. Gallo (Michigan), P. Gandhi (JAXA, Durham), S. Heinz (Wisconsin-Madison), E. G. Kording (Nijmegen), H. A. Krimm (NASA GSFC, USRA), D. Maitra (Michigan), S. Migliari (Barcelona), R.A. Remillard (MIT), C. L. Sarazin(Virginia) , T. Shahbaz (IAC), V. Tudose (ASTRON)

We report striking changes in the broadband spectrum of the compact jet of the black hole transient MAXI J1836–194 over state transitions during its discovery outburst in 2011. A fading of the optical–infrared (IR) flux occurred as the source entered the hard–intermediate state, followed by a brightening as it returned to the hard state. The optical–IR spectrum was consistent with a power law from optically thin synchrotron emission, except when the X-ray spectrum was softest. By fitting the radio to optical spectra with a broken power law we constrain the frequency and flux of the optically thick/thin break in the jet synchrotron spectrum. The break gradually shifted to higher frequencies as the source hardened at X-ray energies, from 1011 to  4×1013 Hz. The radiative jet luminosity integrated over the spectrum appeared to be greatest when the source entered the hard state during the outburst decay (although this is dependent on the high energy cooling break, which is not seen directly), even though the radio flux was fading at the time. The physical process responsible for suppressing and reactivating the jet (neither of which are instantaneous but occur on timescales of weeks) is uncertain, but could arise from the varying inner accretion disk radius regulating the fraction of accreting matter that is channeled into the jet This provides an unprecedented insight into the connection between inflow and outflow, and has implications for the conditions required for jets to be produced and hence their launching process.

Paper here

The optical counterpart of the bright X-ray transient Swift J1745-26 

T. Muñoz-Darias (Southampton), A. de Ugarte Postigo (Andalucia, Copenhagen), D. M. Russell (IAC, La Laguna), S. Guziy (Nicolaev, Andalucia), J. Gorosabel (Andalucia, Pais Basco, Bilbao), J. Casares (IAC, La Laguna), M. Armas Padilla (Amsterdam), P. A. Charles (Southampton, Cape Town), R. P. Fender (Southampton), T. M. Belloni (Brera), F. Lewis (FT), S. Motta (ESAC), A. Castro-Tirado (Andalucia), C. G. Mundell (Liverpool JMU), R. Sánchez-Ramírez, C. C. Thöne (Andalucia)

We present a 30-day monitoring campaign of the optical counterpart of the bright X-ray transient Swift J1745-26, starting only 19 minutes after the discovery of the source. We observe the system peaking at i' ~17.6 on day 6 (MJD 56192) to then decay at a rate of ~0.04 mag/day. We show that the optical peak occurs at least 3 days later than the hard X-ray (15-50 keV) flux peak. Our measurements result in an outburst amplitude greater than 4.3 magnitudes, which favours an orbital period < 21 h and a companion star with a spectral type later than ~ A0. Spectroscopic observations taken with the GTC-10.4 m telescope reveal a broad (FWHM ~ 1100 km/s), double-peaked H alpha emission line from which we constrain the radial velocity semi-amplitude of the donor to be K2 > 250 km/s. The breadth of the line and the observed optical and X-ray fluxes suggest that Swift J1745-26 is a new black hole candidate located closer than ~7 kpc.

Paper here 

A 420 day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127

Shaw, A.W. (Southampton), Charles, P.A. (Southampton, Cape Town), Bird, A.J. (Southampton), Cornelisse, R., Casares, J. (IAC, La Laguna), Lewis, F. (FT), Muñoz-Darias, T. (Southampton), Russell, D.M., Zurita, C. (IAC, La Laguna)

We have discovered a 420d modulation, with associated X-ray dips, in RXTE-ASM/MAXI/Swift-BAT archival light-curves of the short-period (3.2h) black-hole X-ray transient, Swift J1753.5-0127. This modulation only appeared at the end of a gradual rebrightening, approximately 3 years after the initial X-ray outburst in mid-2005. The same periodicity is present in both the 2-20 keV and 15-50 keV bands, but with a 0.1 phase offset 40d). Contemporaneous photometry in the optical and near-IR reveals a weaker modulation, but consistent with the X-ray period. There are two substantial X-ray dips (very strong in the 15-50 keV band, weaker at lower energies) that are separated by an interval equal to the X-ray period. This likely indicates two physically separated emitting regions for the hard X-ray and lower energy emission. We interpret this periodicity as a property of the accretion disc, most likely a long-term precession, where the disc edge structure and X-ray irradiation is responsible for the hard X-ray dips and modulation, although we discuss other possible explanations, including Lense-Thirring precession in the inner disc region and spectral state variations. Such precession indicates a very high mass ratio LMXB, which even for a 10 solar mass BH requires a brown dwarf donor (~0.02 solar masses), making Swift J1753.5-0127 a possible analogue of millisecond X-ray pulsars.We compare the properties of Swift J1753.5-0127 with other recently discovered short-period transients, which are now forming a separate population of high latitude BH transients located in the galactic halo. 

Paper here 

Quiescent X-Ray/Optical Counterparts of the Black Hole Transient H 1705-250

Yi-Jung Yang (Amsterdam), Albert K. H. Kong (Taiwan), David M. Russell (IAC), Fraser Lewis (FT), Rudy Wijnands (Amsterdam)

We report the result of a new Chandra observation of the black hole X-ray transient H 1705-250 in quiescence. H 1705-250 was barely detected in the new 50 ks Chandra observation. With 5 detected counts, we estimate the source quiescent luminosity to be Lx~9.1 x 1030 erg/s in the 0.5-10 keV band (adopting a distance of 8.6 kpc). This value is in line with the quiescent luminosities
found among other black hole X-ray binaries with similar orbital periods. By using images taken with the Faulkes Telescope North, we derive a refined position of H 1705-250. We also present the long-term lightcurve of the optical counterpart from 2006 to 2012, and show evidence for variability in quiescence.

Paper here

Photometry and imaging of comet 103P/Hartley in the 2010-2011 apparition

Giannantonio Milani, Erik Bryssinck, Martino Nicolini, Herman Mikuž, Giovanni Sostero, Paolo Bacci, Walter Borghini, Dario Castellano, Mauro Facchini, Giancarlo Favero, Gianni Galli, Ernesto Guido, Bernhard Hausler, Kamil Hornoch, Nick Howes, Rolando Ligustri, Carmen Perrella, Enrico Prosperi, Jure Skvarč, Jiří Srba, Roberto Trabatti, Carlo Vinante, Gyula Szabó

The results of a CARA (Cometary Archive for Afρ) campaign on comet 103P/Hartley 2 are presented. The main goal was to monitor extensively the comet during the apparition with CCD R and I imaging and photometry, as a support of Epoxi Mission.

Paper here

Overview of an Extensive Multi-wavelength Study of GX 339-4 during the 2010 Outburst

M. Cadolle Bel (ESAC Madrid), J. Rodriguez (Universite Paris Diderot), P. D'Avanzo (Brera, Italy), D. M. Russell (Amsterdam), J. Tomsick (UC Berkeley), S. Corbel (Universite Paris Diderot), F. Lewis (FT), F. Rahoui (Harvard), M. Buxton (Yale), P. Goldoni (Universite Paris Diderot), E. Kuulkers (ESAC Madrid)

The microquasar GX 339-4 experienced a new outburst in 2010: it was observed simultaneously at various wavelengths from radio up to soft gamma-rays. We focused on observations that are quasi-simultaneous with those made with the INTEGRAL and RXTE satellites: these were collected in 2010 March-April during our INTEGRAL Target of Opportunity program, and during some of the other INTEGRAL observing programs with GX 339-4 in the field-of-view. X-ray transients are extreme systems that often harbour a black hole, and are known to emit throughout the whole electromagnetic spectrum when in outburst. The goals of our program are to understand the evolution of the physical processes close to the black hole and to study the connections between the accretion and ejection. We analysed radio, NIR, optical, UV, X-ray and soft gamma-ray observations. We studied the source evolution in detail by producing light curves, hardness-intensity diagrams and spectra. We fitted the broadband data with phenomenological, then physical, models to study the emission coming from the distinct components. Based on the energy spectra, the source evolved from the canonical hard state to the canonical soft state. The source showed X-ray spectral variations that were correlated with changes in radio, NIR and optical emission. The bolometric flux increased from 0.8 to 2.9 x 108 erg / cm/ s while the relative flux and contribution of the hot medium globally decreased. Reprocessing in the disc was likely to be strong at the end of our observations. The source showed a behaviour similar to that of previous outbursts, with some small deviations in the hard X-rays parameters' evolution. The radio, NIR and optical emission from jets was detected, and seen to fade as the source softened. The results are discussed within the context of disc and jet models. 

Paper here

A variable mid-infrared synchrotron break associated with the compact jet in GX 339-4 

P. Gandhi (JAXA, Japan), A.W. Blain (Leicester), D.M. Russell (Amsterdam), P. Casella (Southampton), J. Malzac (Toulouse), S. Corbel (Universite Paris Diderot), P. D'Avanzo (Brera, Italy), F.W. Lewis (FT), S. Markoff (Amsterdam), M. Cadolle Bel (ESAC Madrid), P. Goldoni (CEA Saclay), S. Wachter (Caltech), D. Khangulyan (JAXA, Japan), A. Mainzer (JPL)

Many X-ray binaries remain undetected in the mid-infrared, a regime where emission from their compact jets is likely to dominate. Here, we report the detection of the black hole binary GX 339-4 with the Wide-field Infrared Survey Explorer (WISE) during a very bright, hard accretion state in 2010. Combined with a rich contemporaneous multiwavelength dataset, clear spectral curvature is found in the infrared, associated with the peak flux density expected from the compact jet. An optically-thin slope of ~-0.7 and a jet radiative power of > 6 x 1035 erg/s (d/8 kpc)2 are measured. A ~24 h WISE light curve shows dramatic variations in mid-infrared spectral slope on timescales at least as short as the satellite orbital period ~95 mins. There is also significant change during one pair of observations spaced by only 11 s. These variations imply that the spectral break associated with the transition from self-absorbed to optically-thin jet synchrotron radiation must be varying across the full wavelength range of ~3-22 microns that WISE is sensitive to, and more. Based on four-band simultaneous mid-infrared detections, the break lies at ~5 x1013 Hz in at least two epochs of observation, consistent with a magnetic field B~1.5 x 104 G assuming a single-zone synchrotron emission region. The observed variability implies that either B, or the size of the acceleration zone above the jet base, are being modulated by factors of ~10 on relatively-short timescales. 

Paper here

A late jet rebrightening revealed from multi-wavelength monitoring of the black hole candidate XTE J1752-223 

D.M. Russell (Amsterdam), P.A. Curran (CEA Saclay), T. Muñoz-Darias (Brera, Italy), F. Lewis (FT), S. Motta, H. Stiele, T. Belloni (Brera, Italy), J.C.A. Miller-Jones (Curtin University, Australia), P.G. Jonker (SRON, Harvard, Nijmegen), K. O'Brien (UC Santa Barbara), J. Homan (MIT), P. Casella (Southampton), P. Gandhi (JAXA, Japan), P. Soleri (Groningen), S. Markoff (Amsterdam), D. Maitra, E. Gallo (Michigan), M. Cadolle Bel (ESAC, Madrid) 

We present optical monitoring of the black hole candidate XTE J1752-223 during its 2009 - 2010 outburst and decay to quiescence. The optical light curve can be described by an exponential decay followed by a plateau, then a more rapid fade towards quiescence. The plateau appears to be due to an extra component of optical emission that brightens and then fades over ~ 40 days. We show evidence for the origin of this optical 'flare' to be the synchrotron jet during the decaying hard state, and we identify and isolate both disc and jet components in the spectral energy distributions. The optical flare has the same morphology and amplitude as a contemporaneous X-ray rebrightening. This suggests a common origin, but no firm conclusions can be made favouring or disfavouring the jet producing the X-ray flare. The quiescent optical magnitudes are B > 20.6, V > 21.1, R > 19.5, i' > 19.2. From the optical outburst amplitude we estimate a likely orbital period of < 22 h. We also present near-infrared (NIR) photometry and polarimetry and rare mid-infrared imaging (8 - 12 microns) when the source is nearing quiescence. The fading jet component, and possibly the companion star may contribute to the NIR flux. We derive deep mid-IR flux upper limits and NIR linear polarization upper limits. With the inclusion of radio data, we measure an almost flat jet spectral index between radio and optical; Fnu ~ nu(~0.05). The data favour the jet break to optically thin emission to reside in the infrared, but may shift to frequencies as high as the optical or UV during the peak of the flare. 

Paper here

Testing the jet quenching paradigm with an ultradeep observation of a steadily soft state black hole

D. M. Russell (Amsterdam), J. C. A. Miller-Jones (ICRAR - Curtin), T. J. Maccarone, Y. J. Yang, R. P. Fender (Southampton), F. Lewis (Faulkes Telescope Project, Univ. of Glamorgan, Open University)

We present ultradeep radio observations with the Expanded Very Large Array of 4U 1957+11, a Galactic black hole candidate X-ray binary known to exist in a persistent soft X-ray state. We derive a stringent upper limit of 11.4 micro-Jy / beam (3 sigma) at 5-7 GHz, which provides the most rigorous upper limit to date on the presence of jets in a soft state black hole X-ray binary. X-ray, UV and optical fluxes obtained within a few weeks of the radio data can be explained by thermal emission from the disk. At this X-ray luminosity, a hard state black hole X-ray binary that follows the established empirical radio--X-ray correlation would be at least 330-810 times brighter at radio frequencies, depending on the distance to 4U 1957+11. This jet quenching of > 2.5 orders of magnitude is greater than some models predict, and implies the jets are prevented from being launched altogether in the soft state. 4U 1957+11 is also more than one order of magnitude fainter than the faintest of the 'radio-quiet' population of hard state black holes. In addition, we show that on average, soft state stellar-mass BHs probably have fainter jets than most active galactic nuclei in a state equivalent to the soft state. These results have implications for the conditions required for powerful, relativistic jets to form, and provide a new empirical constraint for time- and accretion mode-dependent jet models, furthering our understanding of jet production and accretion onto BHs.

Rapid variations of polarization in low-mass X-ray binaries

D.M. Russell (Amsterdam), P.G. Casella, R.P. Fender (Southampton), P. Soleri (Groningen), M.L. Pretorius (ESO, Santiago), F. Lewis (FT), M. van der Klis (Amsterdam)

Time-resolved optical and infrared polarimetric observations of black hole and neutron star lowmass X-ray binaries are presented. Data were acquired with the VLT, UKIRT and HIPPO on the AAO 1.9-m. We find that for some sources in outburst, a rapidly variable component of polarization is evident that is stronger in the redder wavebands. We attribute this to the polarimetric signature of synchrotron emission from jets in these systems, the emission of which is known to dominate these redder bands. Such synchrotron emission from jets launched close to black holes and neutron stars can be highly linearly polarized, depending on the configuration of the magnetic field. The variability of the polarization is suggestive of a tangled and turbulent magnetic field at the location of the compact jet. For some sources the position angle of polarization is consistent with a magnetic field that is parallel to the observed radio jet. These are some of the first observational constraints of the geometry and magnetic structure at the inner regions of the outflow. We also present the first ever simultaneous optical polarization and X-ray campaign of an X-ray binary, using data taken simultaneously with HIPPO and RXTE with sub-second time resolution.

Paper here

A dwarf nova in the globular cluster M13

M. Servillat (Harvard), N.A. Webb (Toulouse), F. Lewis (FT), C. Knigge (Southampton), M. van den Berg (Utrecht/Harvard), A. Dieball (Southampton) and J. Grindlay (Harvard)

Dwarf novae in globular clusters seem to be rare with only 12 detections in the 157 known Galactic globular clusters. We report the identification of a new dwarf nova in M13, the 13th dwarf nova identified in a globular cluster to date. Using the 2m Faulkes Telescope North, we conducted a search for stars in M13 that show variability over a year (2005–2006) on timescales of days and months. This led to the detection of one dwarf nova showing several outbursts. A Chandra X-ray source is coincident with this dwarf nova and shows both a spectrum and variability consistent with that expected from a dwarf nova, thus supporting the identification. We searched for a counterpart in Hubble Space Telescope ACS/WFC archived images and found at least 11 candidates, of which we could characterize only the 7 brightest, including one with a 3 sigma H-alpha excess and a faint blue star. The detection of one dwarf nova when more could have been expected likely indicates that our knowledge of the global Galactic population of cataclysmic variables is too limited. The proportion of dwarf novae may be lower than found in catalogs, or they may have a much smaller duty cycle in general as proposed by some population synthesis models and recent observations in the field.

Paper here

The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system

W. D. Taylor, C. J. Evans, H. Sana, N. R. Walborn, S. E. de Mink, V. E. Stroud, A. Alvarez-Candal, R. H. Barb, J. M. Bestenlehner, A. Z. Bonanos, I. Brott, P. A. Crowther A. de Koter, K. Friedrich, G. Grafener, V. H´enault-Brunet, A. Herrero, L. Kaper, N. Langer, D. J. Lennon, J. Maız Apellaniz, N. Markova, N. Morrell, L. Monaco, and J. S. Vink

We report the discovery that R139 in 30 Doradus is a massive spectroscopic binary system. Multi-epoch optical spectroscopy of R139 was obtained as part of the VLT-FLAMES Tarantula Survey, revealing a double-lined system. The two components are of similar spectral types; the primary exhibits strong C III 4650 emission and is classified as an O6.5 Iafc supergiant, while the secondary is an O6 Iaf supergiant. The radial-velocity variations indicate a highly eccentric orbit with a period of 153.9 days. Photometry obtained with the Faulkes Telescope South shows no evidence for significant variability within an 18 month period. The orbital solution yields lower mass limits for the components of M1 sin3 i = 78 +/- 8 M and M2 sin3 i = 66 +/-7 M . As R139 appears to be the most massive binary system known to contain two evolved Of supergiants, it will provide an excellent test for atmospheric and evolutionary models.

paper here

Isolating the jet in broadband spectra of XBs

D. M. Russell (Amsterdam), F. Lewis (FT), D. Maitra (Michigan), R.J.H. Dunn (Munich), S. Markoff (Amsterdam), P.G. Jonker (SRON, Harvard, Nijmegen), M. Linares (MIT), V. Tudose (Netherlands Institute for Radio Astronomy)

Most accretion-powered relativistic jet sources in our Galaxy are transient X-ray binaries (XBs). Efforts to coordinate multiwavelength observations of these objects have improved dramatically over the last decade. Now the challenge is to interpret broadband spectral energy distributions (SEDs) of XBs that are well sampled in both wavelength and time. Here we focus on the evolution of the jet in their broadband spectra. Some of the most densely sampled broadband SEDs of a neutron star transient (IGR J00291+5934) are used to constrain the optically thick–thin break in the jet spectrum. For the black hole transient XTE J1550-564, infrared – X-ray correlations, evolution of broadband spectra and timing signatures indicate that synchrotron emission from the jet likely dominates the X-ray power law at low luminosities  during the hard state outburst decline.

Paper here

Observational detection of eclipses of J5 Amalthea by the Galilean satellites

A.A. Christou (Armagh), F. Lewis, P. Roche (FT), M.G. Hidas, T.M. Brown (LCOGT, Santa Barbara)

Aims. We carried out observations of the small jovian satellite Amalthea (J5) as it was being eclipsed by the Galilean satellites near the 2009 equinox of Jupiter in order to apply the technique of mutual event photometry to the astrometric determination of this satellite’s position.

Methods. The observations were carried out during the period 06/2009−09/2009 from the island of Maui, Hawaii and Siding Spring, Australia with the 2m Faulkes Telescopes North and South respectively. We observed in the near-infrared part of the spectrum using a PanStarrs-Z filter with Jupiter near the edge of the field in order to mitigate against the glare from the planet. Frames were acquired at rates > 1/min during eclipse times predicted using recent JPL ephemerides for the satellites. Following subtraction of the sky background from these frames, differential aperture photometry was carried out on Amalthea and a nearby field star.

Results. We have obtained three lightcurves which show a clear drop in the flux from Amalthea, indicating that an eclipse took place as predicted. These were model-fitted to yield best estimates of the time of maximum flux drop and the impact parameter. These are consistent with Amalthea’s ephemeris but indicate that Amalthea is slightly ahead of, and closer to Jupiter than, its predicted position by approximately half the ephemeris uncertainty in these directions. We argue that a ground-based campaign of higher-cadence photometry accurate at the 5% level or better during the next season of eclipses in 2014-15 should yield positions to within 0.̣05" and affect a corresponding improvement in Amalthea’s ephemeris.

Paper here

Quiescent limits of GRO J1655-40 & XTE J1550-564

by D. E. Calvelo (Southampton), R. P. Fender (Southampton), D. M. Russell (Amsterdam), E. Gallo (UC Santa Barbara, MIT), S. Corbel (Paris), A. K. Tzioumis (Australia Telescope National Facility), M. E. Bell (Southampton), F. Lewis (FT), T. J. Maccarone (Southampton)

We present the results of radio observations of the black hole binaries GRO J1655-40 and XTE J1550-564 in quiescence, with the upgraded Australia Telescope Compact Array. Neither system was detected. Radio flux density upper limits (3 sigma) of 26 micro Jy (at 5.5 GHz), 47 micro Jy (at 9 GHz) for GRO J1655-40, and 1.4 mJy (at 1.75 GHz), 27 micro Jy (at 5.5 GHz), 47 micro Jy (at 9 GHz) for XTE J1550-564 were measured. In conjunction with quasi-simultaneous Chandra X-ray observations (in the case of GRO J1655-40) and Faulkes Telescope optical observations (XTE J1550-564) we find that these systems provide the first evidence of relatively `radio quiet' black hole binaries at low luminosities; indicating that the scatter observed in the hard state X-ray:radio correlation at higher luminosities may also extend towards quiescent levels.

preprint here

The Double-Peaked 2008 Outburst of the Accreting Milli-Second X-ray Pulsar, IGR J00291+5934

by F.Lewis (FT), D.M.Russell (Amsterdam), P.G.Jonker (SRON, Harvard, Nijmegen), M.Linares (Amsterdam, MIT), V.Tudose (Netherlands Institute for Radio Astronomy), P.Roche (FT), J.S.Clark (Open), M.A.P.Torres (Harvard), D.Maitra (Amsterdam, Michigan), C.G.Bassa (Jodrell Bank), D.Steeghs (Harvard, Warwick), A.Patruno (Amsterdam), S.Migliari (ESAC), R.Wijnands (Amsterdam), G.Nelemans (Nijmegen), L.J.Kewley (Hawaii), V.E.Stroud (FT), M.Modjaz (Hawaii, Berkeley), J.S.Bloom (Berkeley), C.H.Blake (Harvard), D.Starr (Berkeley, LCOGT)

In August 2008, the accreting milli-second X-ray pulsar (AMXP), IGR J00291+5934, underwent an outburst lasting ~ 100 days, the first since its discovery in 2004. We present data from the double-peaked outburst from Faulkes Telescope North, the INT, the Keck Telescope, PAIRITEL, the Westerbork Synthesis Radio Telescope and the Swift, XMM-Newton and RXTE X-ray missions. We study the outburst's evolution at various wavelengths. We study the light curve morphology, presenting the first radio-X-ray Spectral Energy Distributions (SEDs) for this source and the most detailed UV-IR SEDs for any outbursting AMXP. We show simple models that attempt to identify the emission mechanisms responsible. We analyse short-timescale optical variability, and compare a medium resolution optical spectrum with those from 2004. The outburst morphology is unusual for an AMXP, comprising two peaks, the second containing a 'plateau' of ~ 10 days at maximum brightness within 30 days of the initial activity. This has implications on duty cycles of short-period X-ray transients. The X-ray spectrum can be fitted by a single, hard power-law. We detect optical variability of ~ 0.05 magnitudes, on timescales of minutes, but find no periodic modulation. In the optical, the SEDs contain a blue component, indicative of an irradiated disc, and a transient near-infrared (NIR) excess. This excess is consistent with a simple model of an optically thick synchrotron jet (as seen in other outbursting AMXPs). The optical spectrum shows a double-peaked H alpha profile, a diagnostic of an accretion disc, but we do not clearly see other lines (e.g. He I, II) reported in 2004. Optical/IR observations of AMXPs are excellent for studying the evolution of both the outer accretion disc and the inner jet, and may eventually provide us with tight constraints to model disc-jet coupling in accreting neutron stars.

preprint here

A Long-term optical X-ray correlation in 4U 1957+11

by D.M. Russell (Amsterdam), F. Lewis, P. Roche (FT), J.S. Clark (Open University), E. Breedt, R.P. Fender (Southampton)

We present three years of optical monitoring with the Faulkes Telescopes of the Low-Mass X-ray Binary, 4U 1957+11. We see long-term variations which are correlated with X-ray flux as measured by the RXTE satellite's ASM instrument.

preprint here

The VLT-FLAMES Tarantula Survey

by Chris Evans (UK ATC, Royal Observatory, Edinburgh) et al.

The Tarantula Survey is an ambitious ESO Large Programme that has obtained multi-epoch spectroscopy of over 1,000 massive stars in the 30 Doradus region of the Large Magellanic Cloud. Here we introduce the scienti c motivations of the survey and give an overview of the observational sample. Ultimately, quantitative analysis of every star, paying particular attention to the effects of rotational mixing and binarity, will be used to address fundamental questions in both stellar and cluster evolution.

preprint here

CCD BV Photometry of three southern galactic open clusters using Faulkes Telescope South

A paper to be published in the August issue of the British Astronomical Association (BAA) Journal by David Boyd along with staff and students of Kennet School, Thatcham.

Boyd paper

Jupiter - IAU Circular 9055

A. A. Christou, Armagh Observatory, reports that his CCD photometry of Jupiter V (Amalthea), obtained by F. Lewis (Faulkes Telescope Project, Open University) using the 2-m Faulkes Telescope South (+ Pan-STARRS z' filter) reveals an eclipse of this satellite by Jupiter I (Io) on June 23 UT. Twenty-five 5-sec exposures were acquired between June 23.64799 and 23.66425. Amalthea was visible in all these frames with the exception of those starting at June 23.65317 and 23.65379 UT, consistent with a totality between June 23.65292 and 23.65401 predicted by utilizing a generic mutual- eclipse model (Christou 2005, Icarus 178, 171) in combination with the SPICE ephemeris kernel JUP230 for the Galilean satellites and Amalthea. Observations at high cadence (<< 60 s) of further eclipses of Amalthea by Io are encouraged during the current Jovian equinox season. Predictions for July and August 2009 are given here

Robotic Astronomy with the Faulkes Telescopes and Las Cumbres Observatory Global Telescope

by F. Lewis (FT), R. Street (LCOGT), P. Roche, V. Stroud (FT), D.M. Russell (Amsterdam)

submitted to the 'Robotic Astronomy' issue of 'Advances in Astronomy'

We present results from ongoing science projects conducted by members of the Faulkes Telescope (FT) team and Las Cumbres Observatory Global Telescope (LCOGT). Many of these projects incorporate observations carried out and analysed by FT users, comprising amateur astronomers and schools. We also discuss plans for the further development of the LCOGT network.

Malaga proceedings

The Faulkes Telescope Project: Not Just Pretty Pictures

by F. Lewis (FT), P. Roche (FT)

published in ".Astronomy: Networked Astronomy and the New Media", 2009, edited by R.J. Simpson, D. Ward-Thompson

The Faulkes Telescope (FT) Project is an educational and research arm of the Las Cumbres Observatory Global Telescope Network (LCOGTN). As well as producing spectacular images of galaxies, nebulae, supernovae remnants, star clusters, etc., the FT team is involved in several projects pursuing scientific goals. Many of these projects also incorporate data collected and analysed by schools and amateur astronomers.

Available here

Astrometric observations of the Uranian satellites with the Faulkes Telescope North in 2007 September

by M.Y. Khovritchev (Central Astronomical Observatory of Russian Academy of Science)

published in MNRAS, 2009, 393, 1353-1358

Available here

Observational detection of eight mutual eclipses and occultations between the satellites of Uranus

by A. A. Christou (Armagh Observatory), F. Lewis (FT), P. Roche(FT), Y. Hashimoto (SAAO, SALT), D. O’Donoghue (SAAO), H. Worters (SAAO, SALT), D. A. H. Buckley (SAAO, SALT), T. Michalowski (Poznan), D. J. Asher (Armagh), A. Bitsaki (Athens), A. Psalidas (Patras), V. Tsamis (Athens), K. N. Gourgouliatos (Cambridge), A. Liakos (Athens), M. G. Hidas (LCOGT), T. M. Brown (LCOGT)

Published in Astronomy and Astrophysics (A&A)

Available here

Social Networking: An astronomer's field guide

by Gomez, E.L., Gomez H.L., Yardley, J.

published in ".astronomy: Networked Astronomy and the New Media", 2009, edited by R.J. Simpson, D. Ward-Thompson

We present a brief introduction to the phenomenon of "social networking" and its potentially powerful use as an astronomy outreach and educational tool. We briefly discuss the development of applications for websites and Facebook, and the use of web trackers such as Google Analytics to analyze the audience. Finally we discuss how social bookmarking can be used to promote work to unexpected audiences.

Available here

Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst

by P. Elebert (Cork), M. T. Reynolds (Michigan), P. J. Callanan (Cork), D. J. Hurley (Cork), G. Ramsay (Armagh), F. Lewis (FT), D. M. Russell (Amsterdam), B. Nord (Michigan), S. R. Kane (Caltech), D. L. DePoy (Texas A&M), P. Hakala (Turku)

published in MNRAS

Available here

An observation of a mutual event between two satellites of Uranus

by M.G. Hidas (LCOGT), A.A. Christou (Armagh), T.M. Brown (LCOGT)

published in MNRAS, 2008, 384, L38-L40

We present observations of the occultation of Umbriel by Oberon on 2007 May 4. We believe this is the first observed mutual event between satellites of Uranus. Fitting a simple geometric model to the light curve, we measure the mid-event time with a precision of 4 s. We assume previously measured values for the albedos of the two satellites, and measure the impact parameter to be 500 +/- 80 km. These measurements are more precise than estimates based on current ephemerides for these satellites. Therefore observations of additional mutual events during the 2007-2008 Uranian equinox will provide improved estimates of their orbital and physical parameters.

Available here

Unifying disc-jet behaviour in X-ray binaries: an optical/IR approach

by D.M. Russell (Amsterdam), D. Maitra (Amsterdam), R.P. Fender (Southampton), F. Lewis (FT)

published in Proceedings of the 7th Microquasar Workshop: Microquasars and Beyond, September 2008, Foca, Turkey

Available here

Continued Monitoring of LMXBs with the Faulkes Telescopes

by F. Lewis (FT) D.M. Russell (Amsterdam), R.P. Fender (Southampton), Paul Roche (FT), J.S. Clark (Open University)

published in Proceedings of the 7th Microquasar Workshop: Microquasars and Beyond, September 2008, Foca, Turkey

Available here

The nature of the close magnetic white dwarf + probable brown dwarf binary SDSS J121209.31+013627.7

by M.R. Burleigh (Leicester), T.R. Marsh (Warwick), B.T. Gänsicke (Warwick), M.R. Goad (Leicester), V.S. Dhillon (Sheffield), S.P. Littlefair (Sheffield), M.Wells (Oundle School), N.P. Bannister, C.P. Hurkett, A. Martindale, P.D. Dobbie, S.L. Casewell, D.E.A. Baker, J. Duke (Leicester), J. Farihi (Gemini Observatory), M.J. Irwin (Cambridge), P.C. Hewett (Cambridge), P. Roche (FT), F. Lewis (FT)

Available here

FT Team members have also been involved in the following Astronomer's Telegrams (ATels) 

10797 David M. Russell (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU), Poshak Gandhi (Southampton)

New outburst of GX 339-4 detected by Faulkes Telescope South 

10682 David M. Russell (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU), Poshak Gandhi (Southampton), Enrico Bozzo (ISDC, Switzerland)

10562  Guobao Zhang, David M. Russell, Federico Bernardini, Joseph D. Gelfand (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)

The black hole candidate Swift J1753.5-0127 is back in quiescence

10341 L. Wyrzykowski, P. Mroz, K. Rybicki (Warsaw) et al. (Gaia microlensing group)

Gaia16aye binary microlensing event is rising for the 5th time

10325 Federico Bernardini, Guobao Zhang, David M. Russell, Joseph D. Gelfand, Ahlam Al Qasim, Aisha AlMannaei (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU), A. W. Shaw (Alberta), J. A. Tomsick (SSL/UC Berkeley), R. M. Plotkin (ICRAR-Curtin) 

The optical flux of Swift J1753.5-0127 strikes back

10288 A. W. Shaw (Alberta), J. A. Tomsick (Berkeley), G. Zhang, D. M. Russell (NYU Abu Dhabi), R. M. Plotkin, J. C.A. Miller-Jones (ICRAR-Curtin), F. Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)

A drop in X-ray/UV/Optical flux from Swift J1753.5-0127 

10097 Guobao Zhang, David M. Russell, Joseph D. Gelfand, Ahlam Al Qasim, Aisha AlMannaei (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)

Swift J1753.5-0127 flux is steady

10075 Ahlam Al Qasim, Aisha AlMannaei, David M. Russell (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU), Guobao Zhang, Joseph D. Gelfand (NYU Abu Dhabi)

Optical brightening of Swift J1753.5-0127 observed with the Faulkes Telescope North 

9708 David M. Russell, Aisha AlMannaei, Ahlam Al Qasim (NYU Abu Dhabi), A. W. Shaw (U. Alberta), P. A. Charles (IAC & U. Southampton), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU) 

Swift J1753.5-0127 is heading to quiescence after an 11-year outburst 

9306 D.M. Russsell, (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU) 

Faulkes Telescope observations of the optical rise of a bright outburst of Aql X-1

8854 D.M. Russsell, S.-M. Udrescu (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

X-ray fading and optical/X-ray flaring in the current faint outburst of MAXI J0556-332 

8517 D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

Optical Faulkes Telescope monitoring of MAXI J0556-332 caught its rise into outburst 

8515 F. Bernardini, D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

V404 Cyg was in optical quiescence from mid October to mid December 2015 

7887  K. I. I. Koljonen, D. M. Russell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU) 

Outburst peak of the black hole transient GS 1354-64 

7837 D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

Optical monitoring of the milli-second X-ray pulsar IGR J00291+5934

7761 F. Bernardini, D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

Faint optical precursor to the 2015 outburst of the black hole binary V404 Cyg

7637  D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

The optical brightening of GS 1354-64

7434  F. Bernardini, D.M. Russsell (NYU Abu Dhabi), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU)

GX 339-4 is still in the soft state 

6705 K. Bognar, D. M. Russell (NYU Abu Dhabi), E. Breedt (University of Warwick), F. Lewis (Faulkes Telescope Project and Astrophysics Research Institute, LJMU), M. J. Mei, S. Dahal, F. Bernardini (NYU Abu Dhabi)

Optical monitoring of the M31 field object iPTF14gnj 

5594 Devraj Pawar (Mumbai), Diego Altamirano (Southampton), Gregory R. Sivakoff (Alberta), James Miller-Jones (Curtin), Tomaso Belloni (INAF-OAB), Dipankar Maitra (Wheaton College, MA and U. Michigan, MI), Michelle Buxton (Yale), Jeroen Homan (MIT), Dave M. Russell (NYU Abu Dhabi), Fraser Lewis (FT Project, Univ. of South Wales and Astrophysics Research Institute, LJMU), John Tomsick (SSL/UCB), Mickael Coriat (University of Cape Town), Teo Munoz-Darias (Oxford) 

Swift X-ray observations indicate that the 2013 outburst of GX 339-4 is probably ending

5252 Devraj Pawar (R. J. College, U. Mumbai), Diego Altamirano (Amsterdam, Southampton), Gregory R. Sivakoff (U. Alberta), James Miller-Jones (ICRAR Curtin), Tomaso Belloni (INAF), Dipankar Maitra (Wheaton College, MA and U. Michigan, MI) Michelle Buxton (Yale Univ.), Jeroen Homan (MIT), Dave Russell (IAC, Tenerife), Fraser Lewis (Faulkes Telescope Project, Univ. of South Wales), John Tomsick (SSL/UC Berkeley), Mickael Coriat (University of Cape Town)

Swift X-ray observations confirm outburst of GX 339-4

5084  D. M. Russell (IAC, Tenerife), F. Lewis (Faulkes Telescope Project, University of South Wales), T. Munoz-Darias (University of Southampton), E. Kalemci (Sabanci University, Turkey)

Optical and X-ray re-brightening in Swift J1745-26

4456 D. M. Russell (IAC, Tenerife), F. Lewis (Univ. of Glamorgan, Faulkes Telescope Project), C. G. Mundell (LJMU), A. Tripp (Faulkes Telescope Project), T. Belloni (INAF-OAB, Italy), P. Curran (ICRAR - Curtin), H. Krimm (NASA-GSFC), D. Maitra (Univ. of Michigan), J. C. A. Miller-Jones (ICRAR - Curtin), G. R. Sivakoff (U. Alberta)

Optical evolution of Swift J174510.8-262411 suggests the compact jet is fading, radio flare imminent? 

4247 T. Maccarone (Southampton), D.M. Russell (IAC), F. Lewis (Univ. of Glamorgan, Faulkes Telescope Project)

The rapid extreme fading of GX 339-4

4162 F. Lewis (Univ. of Glamorgan, Faulkes Telescope Project), D. M. Russell, T. Shahbaz (IAC)

GX 339-4 is rising into outburst, and a deep optical quiescent magnitude observed by Faulkes Telescope South

3622 D. M. Russell (Amsterdam), F. Lewis, (Univ. of Glamorgan, Faulkes Telescope Project, Open Univ.), D. Altamirano (Amsterdam), P. Roche (Univ. of Glamorgan, Faulkes Telescope Project, Open Univ.)

The optical counterpart of the accreting millisecond X-ray pulsar IGR J17498-2921

3517 D. M. Russell (Amsterdam), F. Lewis, (Univ. of Glamorgan, Faulkes Telescope Project, Open Univ.), L. Schreuder, Y.J. Yang, R. Wijnands, (Amsterdam), A. Tripp (Faulkes Telescope Project)

MAXI J1659-152 fading in optical

3383 D. M. Russell (University of Amsterdam), J. Homan, J. K. Fridriksson (MIT), F. Lewis, P. Roche (Univ. of Glamorgan, Faulkes Telescope Project, Open Univ.), C.
O'Morain (Univ. of Glamorgan)

GX 339-4 is back in a faint state close to quiescence

3359  David M. Russell (Univ. of Amsterdam), Fraser Lewis, Paul Roche (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan) Diego Altimarano (Univ. of Amsterdam)

Candidate optical counterparts of MAXI J1543-564

3191 David M. Russell (Univ. of Amsterdam), Fraser Lewis (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan)

GX 339-4 back in the hard state: optical observations reveal the return of the jet

3116 David M. Russell (Univ. of Amsterdam), Fraser Lewis (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan), Rosa Doran (EU-Hands on Universe), Sarah Roberts (Faulkes Telescope Project, Univ. of Glamorgan)

Optical observations of MAXI J0556-332 and an indication of a probable neutron star primary 

2997 D. M. Russell, Y. J. Yang, N. Degenaar, R. Wijnands, A. Patruno, R. Kaur, M. Armas Padilla (Univ. of Amsterdam), F. Lewis (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan), J. D. Armstrong (Univ. of Hawai'i)

Monitoring of the likely optical counterpart of XTE J1728-295

2884 D. M. Russell (Univ. of Amsterdam), F. Lewis (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan), D. Bersier and Z. Cano (Liverpool JMU), P. Gandhi (ISAS, Japan Aerospace Exploration Agency), A. Patruno, M. Kalamkar, Y. J. Yang, D. Altamirano (Univ. of Amsterdam), P. Casella (Univ. of Southampton), M. Linares (MIT), M. Armas Padilla, Y. Cavecchi, N. Degenaar, R. Kaur, M. van der Klis, A. Watts and R. Wijnands (Univ. of Amsterdam), N. Rea (CSIC-IEEC)

Optical variability in MAXI J1659-152

2871 D. M. Russell (Univ. of Amsterdam), P. Roche, F. Lewis (Faulkes Telescope Project, Open Univ., Univ. of Glamorgan), D. Maitra (Univ. of Michigan)

Aql X-1 in brightest outburst since 2003

2827 D. M. Russell, Y. J. Yang, A. Patruno, N. Degenaar, D. Altamirano, R. Wijnands (University of Amsterdam), F. Lewis (FT)

Candidate optical counterparts of XTE J1728-295 = IGR J17285-2922

2775 Russell, D. (Amsterdam), Munoz-Darias, T. (Brera), Lewis, F. (FT), Soleri, P. (Groningen)

XTE J1752-233 has faded to quiescence; optical and infrared magnitudes 

2722 Armas Padilla, M., Kaur, R., Degenaar, N., Wijnands, R. (Amsterdam), Lewis, F., Russell, D. M.(Amsterdam)

Re-brightening of XMMSL1 J171900.4-353217

2579 Y.J. Yang, D.M. Russell, R. Wijnands, M. van der Klis, D. Altamirano, A. Patruno, A. Watts , M. Armas Padilla, Y. Cavecchi, N. Degenaar, M. Kalamkar, R. Kaur (University of Amsterdam), M. Linares (MIT), P. Casella (Southampton), N. Rea (IEEC-CSIC), P. Soleri (Groningen), F. Lewis (Faulkes Telescope Project, University of Glamorgan) and A.K.H. Kong (NTHU, Taiwan)

SWIFT J1749.4-2807: X-ray decay, refined position and optical observation

2573 M. Cadolle Bel, E. Kuulkers, A. Ibarra, M. Diaz Trigo (ESAC Madrid, Spain), J. Tomsick (SSL/UC Berkeley, USA), J. Rodriguez, L. Prat, S. Corbel (CEA-AIM Saclay, France), D.M. Russell, D. Altamirano (University of Amsterdam), F. Lewis (Faulkes Telescope Project, University of Glamorgan, Open University), E. Bozzo, M. Turler, C. Ferrigno (ISDC, Geneva)

Simultaneous INTEGRAL, RXTE, Swift and FT South observations of the transition of GX 339-4

2547 D.M. Russell (Amsterdam), M. Buxton (Yale), F. Lewis (FT), D. Altamirano (Amsterdam)

Optical/IR flux fading rapidly in GX 339-4: OIR jet quenching

2467 E. Del Monte, R. Campana, I. Donnarumma, Y. Evangelista, M. Feroci (Rome), D. Altamirano, D.M. Russell (Amsterdam), P. Casella (Southampton), E. Kuulkers, C. Sanchez-Fernandez (ESA/ESAC), F. Lewis (FT), J.J.M. in't Zand (SRON, Netherlands)

Spectral transition of 4U 1608-522 during the undergoing 2010 outburst

2459 F. Lewis (FT), D.M. Russell (Amsterdam), M. Cadolle Bel (ESA/ESAC)

Optical Observations of GX 339-4 in Outburst with the Faulkes Telescope South

2288 M. Linares (MIT), J. Miller-Jones (NRAO), D. Altamirano (Amsterdam), G. Sivakoff (Virginia), D. Maitra, D.M. Russell (Amsterdam), F. Lewis (FT), C. Markwardt (U. Maryland & NASA/GSFC), R. Remillard (MIT) and the JACPOT XRB collaboration

Aql X-1 back in outburst: multi-wavelength observations

2270 F. Lewis (FT), D.M. Russell (Amsterdam)

GX 339-4 Approaching Quiescence ?

2072 D.M. Russell (Amsterdam), F. Lewis (FT), P.Roche (FT)

X-ray state change in 4U 1608-52

2000 V. Tudose (Netherlands Institute for Radio Astronomy - ASTRON), Z. Paragi (Joint Institute for Very Long Baseline Interferometry in Europe - JIVE), P. Soleri, D.M. Russell, D. Maitra (Amsterdam), F. Lewis (FT), R.P. Fender (Southampton), M.A. Garrett (ASTRON), R.E. Spencer, A. Rushton (Jodrell Bank)

e-EVN observations of Aql X-1 in outburst

1970 D.M. Russell (Amsterdam), F. Lewis (FT)

Optical and hard X-ray detections of an outburst from Aquila X-1

1962 D.M. Russell (Amsterdam), F. Lewis (FT), P.Casella (Amsterdam), M.L. Pretorius (SAAO), R.P. Fender (Southampton), P. Roche (FT), J.S. Clark (Open University)

Optical photometry and polarimetry of GX 339-4 during its outburst rise

1765 F. Lewis (FT), D.M. Russell (Amsterdam), N. Rea (Amsterdam), P. Roche (FT), J. S. Clark (OU)

Recent optical variability in LSI +61 303

1726 F. Lewis (FT), M. Linares (Amsterdam), D.M. Russell (Amsterdam), R. Wijnands (Amsterdam), P. Roche (FT)

Renewed optical and X-ray activity in IGR J00291+5934

1666 D. M. Russell (Amsterdam), F. Lewis (FT), M. Linares (Amsterdam), P. Roche (FT), D. Maitra (Amsterdam)

Faulkes Telescope monitoring of the current outburst of IGR J00291+5934

1586 D.M. Russell (Amsterdam), D. Altamirano (Amsterdam), F. Lewis (FT), P. Roche (FT), C.B. Markwardt (CRESST/GSFC/UMD), R.P. Fender (Southampton)

Unusual optical and X-ray flaring activity in GX 339-4

1218 D. Maitra (Amsterdam), D.M. Russell (Amsterdam), F. Lewis (FT), C. Bailyn (Yale), R.P Fender (Southampton), P. Roche (FT)

Optical and Near-IR Observations of the Current Outburst of Aql X-1