Background Science

HETE 1900.1-2455 is a bright accreting millisecond pulsar (AMSP) at d ~ 4.5 kpc. It was discovered using HETE II in 2005 and is one of only eight known AMSPs (Vanderspek et al., 2005). The secondary star is estimated to have a mass of ~ 0.085 solar masses, suggesting that it is a brown dwarf.

The brightness of the system is dominated by re-processing of X-rays and the disk suffers eccentric instabilities, becoming both non-axisymmetric and subject to precession (see Figure 1). The CoIs have developed state-of-the-art hydrodynamic simulation code to model the irradiation-driven warping.

Observations are scheduled on June 22-26 using the RC spectrograph on the 4-metre Blanco telescope at the CTIO, La
Serena, Chile.

We need your help in making more observations for the team to explore the contribution of the re-processed emission, in order to refine their simulations.

Observing advice

The system possesses a well-defined orbital period of 83.3 minutes and
has an orbital variability in R band of between 0.1 and 0.3 mags.

Observe for 200s in SDSS i' (not the Bessel I) as many times as you can.

Your account will not be told you have run out of time because everyone is using the same account. Please stop observing when you allotted time is up. Thanks!

Observing schedule