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2012-01-01

Altamirano, Diego, Keek, L., Cumming, A., Sivakoff, Gregory Robert, Heinke, Craig O., Wijnands, Rudy, Degenaar, Nathalie, Homan, Jeroen, Pooley, David

We report on Chandra, Rossi X-ray Timing Explorer (RXTE), Swift/Burst Alert Telescope (BAT) and MAXI observations of an X-ray flare of ∼1 d and subsequent outburst of a transient X-ray source observed in 2011 October–November in the globular cluster Terzan 5. We show that the source is the same...

2018-01-01

Sanna, Andrea, Bahramian, Arash, Bozzo, E., Heinke, Craig O., Wijnands, Rudy, Degenaar, Nathalie, Maccarone, T., Riggio, Alessandro, Di Salvo, Tiziana, Iaria, Rosario, Burgay, M., Possenti, Andrea, Ferrigno, C., Papitto, A., Sivakoff, Gregory Robert, D'Amico, Nicolo, Burderi, Luciano, Altamirano, Diego

We report the discovery of X-ray pulsations at 105.2 Hz (9.5 ms) from the transient X-ray binary IGR J16597–3704 using NuSTAR and Swift. The source was discovered by INTEGRAL in the globular cluster NGC 6256 at a distance of 9.1 kpc. The X-ray pulsations show a clear Doppler modulation that...

2018-01-01

Tudor, Vlad, Miller-Jones, James C. A., Knigge, C., Maccarone, Thomas J., Tauris, T. M., Bahramian, Arash, Chomiuk, Laura, Heinke, Craig O., Sivakoff, Gregory Robert, Strader, Jay, Plotkin, Richard M., Soria, Roberto, Albrow, M. D., Anderson, G. E., van den Berg, Maureen, Bernardini, Federico, Bogdanov, Slavko, Britt, Christopher. T., Russell, D. M., Zurek, David R.

To confirm the nature of the donor star in the ultracompact X-ray binary candidate 47 Tuc X9, we obtained optical spectra (3000–10 000 Å) with the Hubble Space Telescope / Space Telescope Imaging Spectrograph. We find no strong emission or absorption features in the spectrum of X9. In particular,...

2018-01-01

Shaw, A. W., Heinke, Craig O., Mukai, K., Sivakoff, Gregory Robert, Tomsick, John A., Rana, Vikram

The X-ray spectra of intermediate polars can be modelled to give a direct measurement of white dwarf mass. Here, we fit accretion column models to NuSTAR spectra of three intermediate polars; V709 Cas, NY Lup, and V1223 Sgr in order to determine their masses. From fits to 3–78 keV spectra, we...

2017-01-01

Bahramian, Arash, Heinke, Craig O., Tudor, Vlad, Miller-Jones, James. C. A., Bogdanov, Slavko, Maccarone, Thomas J., Knigge, C., Sivakoff, Gregory Robert, Chomiuk, Laura, Strader, Jay, Garcia, Javier A., Kallman, Timothy

47 Tuc X9 is a low-mass X-ray binary (LMXB) in the globular cluster 47 Tucanae, and was previously thought to be a cataclysmic variable. However, Miller-Jones et al. recently identified a radio counterpart to X9 (inferring a radio/X-ray luminosity ratio consistent with black hole LMXBs), and...

2018-01-01

Sivakoff, Gregory Robert, Tetarenko, Bailey E., Dubus, G., Lasota, Jean-Pierre, Heinke, Craig O.

The X-ray light curves of the recurring outbursts observed in low-mass X-ray binaries provide strong test beds for constraining (still) poorly understood disc-accretion processes. These light curves act as a powerful diagnostic to probe the physics behind the mechanisms driving mass inflow and...