Proposal Details - 0720012
Hercules X-1 -- the detailed study of cyclotron lines, magnetic field and accretion (Shakura)

Proposal Abstract

We propose to observe Her~X-1 during \textsl{INTEGRAL's} AO-7 for a total observing time of \textbf{~600\,ksec}: covering one ``Main-On'' with three INTEGRAL orbits, the first near the early maximum and the next two during the decay of the ``Main-On.'' Our prime objectives are to systematically measure the centroid \textbf{energy of the fundamental cyclotron line} $E_{cyc}$ as a function of \textbf{time, X-ray flux, 35\,day phase and 1.24\,s phase}. Such a dedicated systematic study will yield information about \textbf{fundamental physics} in this accreting binary pulsar with respect to: the structure of the \textbf{magnetic field} at the polar caps, the physics of \textbf{sub-Eddington accretion}, the generation of\textbf{pulse profiles} and variation of $E_{cyc}$ with pulse phase.

Observation Strategy (Recommended by TAC)

Total of 600 ks split into three observations of 200 ks each in the standard 5x5 mode centred on RA, Dec = 254.458, 35.342 (l, b = 58.149, 37.523). The observations will take place a specific times, (not yet defined since Main-Ons appear with a somewhat irregular clock), to cover distinct pulse phases: one "Main-On" with three INTEGRAL orbits: the first near the early maximum (phases 0.02 to 0.10 of the 35-day cycle) and the next two during the decay of the same "Main-On" period (phases 0.20 to 0.25 of the 35-day cycle). The timing of the observations will be predicted on the basis of RXTE/ASM and SWIFT/BAT observations (with a confidence of +/-1 day two months before), and more reliable one month before the actual INTEGRAL observation.

Proposal grade: A

Data Rights (Recommended by TAC)

The TAC has allocated the PI all the data rights on Her X-1.

Consult the Data Rights policy for more information on Russian Federation proposals.

Exposure Map

The exposure maps are in galactic coordinates and units of ksec, and the colour scale is indicated at the bottom. The green lines provide the 100 ksec contour.