Optical observations of the X-ray Transient XTE J1118+480

ATel #402; C. Zurita (IAC), P. Rodríguez-Gil (IAC), J. Casares (IAC), T. Muñoz-Darias (IAC), M. A. P. Torres (CfA), T. Shahbaz (IAC)
on 28 Jan 2005; 18:36 UT
Credential Certification: P. Rodriguez-Gil (prguez@ll.iac.es)

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Time resolved (40-sec resolution, ~6-hours per night), R-band photometry of the outbursting black hole candidate XTE J1118+480 (ATEL #383) was obtained with the European Space Agency, 1-m OGS telescope at the Spanish Observatorio del Teide (Tenerife) from 2005 Jan 21.01 to Jan 26.30. The average R-band magnitude displays a linear decay with a rate of ~0.06 mag/day. Mean magnitudes are: Jan 21.3, 13.54+-0.01; Jan 22.07, 13.61+-0.01; Jan 23.14, 13.65+-0.01; Jan 24.15, 13.70+-0.01; Jan 25.15, 13.77+-0.01; Jan 26.12, 13.84+-0.01. On Jan 20 and Jan 22, we found a 0.02-mag amplitude modulation consistent with the 0.170-day superhump period observed during the 2000 outburst (IAUC # 7394 , # 7407 ), and with the periodic humps reported in 2005 (ATEL #399). However, no orbital variation was apparent in the remaining nights, although substantial scatter was present.