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oai:figshare.com:article/33820654 2026-09-15T19:56:58Z portal_1197 item_type_3 month_year_09_2026

ULTRACAM Observations of PSR J2039-5617 Colin J. Clark (24954280) Guillaume Voisin (24954283) Bruce Allen (24954286) Carsten Aulbert (24954289) Oliver Behnke (24954292) Rene P. Breton (24870028) Cristophe Choquet (24954295) Alessandro Corongiu (24954298) Vik S. Dhillon (24800845) Heinz-Bernd Eggenstein (24954301) Henning Fehrmann (24954304) Lucas Guillemot (24954307) Alice K. Harding (24954310) Mark R. Kennedy (15008846) Bernd Machenschalk (24954313) Tom Marsh (4488163) Daniel Mata Sánchez (24954316) Roberto P. Mignani (24929392) James Stringer (24954319) Zorawar Wadiasingh (24954322) Jason Wu (360804) Neutron stars Pulsars Gamma rays Double stars Migrated from ePrints The Fermi Large Area Telescope gamma-ray source 3FGL J2039.6–5618 contains a periodic optical and X-ray source that was predicted to be a ‘redback’ millisecond pulsar (MSP) binary system. However, the conclusive identification required the detection of pulsations from the putative MSP. To better constrain the orbital parameters for a directed search for gamma-ray pulsations, we obtained new optical light curves in 2017 and 2018, which revealed long-term variability from the companion star. The resulting orbital parameter constraints were used to perform a targeted gamma-ray pulsation search using the Einstein@Home-distributed volunteer computing system. This search discovered pulsations with a period of 2.65 ms, confirming the source as a binary MSP now known as PSR J2039–5617. Optical light-curve modelling is complicated, and likely biased, by asymmetric heating on the companion star and long-term variability, but we find an inclination i ≳ 60°, for a low pulsar mass between 1.1M⊙<br>Data record consists of 16 raw data files in dat, par and gz format. Optical observations of PSR J2039-5617 taken by the high-speed triple-beam CCD camera ULTRACAM on ESO's New Technology Telescope. Observations were taken on 2017 June 18, 2018 June 02 and 2019 July 07. Files with names like _fluxes_.dat contain the reduced light curves in ASCII format. Columns are: 1) MJD time (barycentered TDB), 2) orbital phase (in rotations, with phase = 0 corresponding to pulsar's ascending node), 3) flux density (in erg cm-2 s-1 Hz-1) 4) flux density uncertainty (in erg cm-2 s-1 Hz-1) "ultracam_rawdata.tar.gz" contains all of the raw ULTRACAM data (bias frames, flat frames, calibration observations of standard stars and science frames) from which the reduced light curves were produced. These files are in the ULTRACAM data pipeline format. "J2039-5617.par" is an ephemeris file that is compatible with a recent version of tempo2 in which the "ORBIFUNC" parameters describing an interpolating function for the orbital phase variations have been implemented. 2026-09-15T19:56:58Z Dataset Dataset 10.82444/warw.33820654.v1 https://figshare.com/articles/dataset/ULTRACAM_Observations_of_PSR_J2039-5617/33820654 CC BY 4.0