Institut f Astronomie u Astrophysik Tbingen work on

Institut f. Astronomie u. Astrophysik Tübingen work on Swift J 0243. 6+6124. Victor Doroshenko, Ji Long, Andrea Santangelo The second Joint workshop on Insight-HXMT calibration and science, Beijing 11 -13. 04. 2018

Swift J 0243. 6+6124 • The transient X-ray source Swift J 0243. 6+6124 was first detected by Swift/BAT on Oct 3, 2017 (Kennea et al. 2017). • Pulsations with period ∼ 9. 86 s detected by Swift/XRT and Fermi/GBM (Jenke & Wilson-Hodge 2017), • together with the transient behavior and tentative optical counterpart classification (Kouroubatzakis et al. 2017) suggest that it is a new Galactic Be X-ray transient. Doroshenko et al. 2017

Spin evolution and orbital parameter Intrinsic spin frequency derivative best-fit with the Ghosh & Lamb (1979) model. High accretion rate a distance in excess of about 5 kpc and strong field in excess of ∼ 1013 G.

Orbital Parameters But: Photometric/spectroscopic observations of the counterpart at 6 m BTA and 1. 5 Rus/Turkish telescopes (ATEL #10968) He. I/II lines, Bowen blend -> early B spectral class Teff~30000 K, Mbol~-6. 45 mag E(B-V) from optical spectra ~1 -1. 5, ~2 from X-ray absorption D~2. 5 kpc is estimated as a result Tension!

Distance to the source (spin-up rate)

Outburst light curve Swift (BAT+XRT) Nu. STAR (5 obs)

Transition of regime? Morphology changes in the pulse profiles.

HXMT? • Focus on timing analysis of HE for now (best statistics, calibration not an issue) • Pulse period evolution is well measured and consistent with GBM • We believe it is possible to improve orbital solution significantly over the GBM result (have not started such analysis yet) • Spin-up/down of the pulsar might also be studied in greater detail • Coordination with IHEP needed! Can we work on the data?

HMT Swift J 0243. 6+6124: Pulse profile evolution peak tail • Pulse profile exhibit strong evolution with time/flux • Tracing “smooth” evolution following the outburst (i. e. with time) • Pulse profiles at the same flux level are the same in rising/declining parts • Two characteristic changes in pulse profile are observed, at about 2. 5 e-8, and 7. 5 e-8, both can be interpreted as transition through “critical” luminosity (onset of the accretion column) for 4 kpc distance, analysis/calculations still ongoing

Swift J 0243. 6+6124: Power spectra Additional noise Power Peak of the outburst Break frequency vs flux in 1 A 0535+262 intermediate fx low fx Frequency • • (Doroshenko et al, 2014) Independent diagnostic of inner disc radius Was found to be correlated with flux Idea is to repeat analysis for the source Analysis ongoing (no correlation so-far due to difficulties in subtraction of the pulsations/power spectra fitting)

Thank you. Contact: Andrea Santangelo Abteilung Hochenergieastrophysik Sand 1, 72076 Tübingen · Germany Phone: +49 7071 29 -76128 Andrea. Santangelo@uni-tuebingen. de