SWIFT-BAT HARD X-RAY SKY MONITORING UNVEILS THE ORBITAL PERIOD OF THE HMXB IGR J18219–1347
- INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via U. La Malfa 153, I-90146 Palermo (Italy)
- Dipartimento di Fisica e Chimica, Università di Palermo, via Archirafi 36, I-90123 Palermo (Italy)
- INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129 Bologna (Italy)
IGR J18219–1347 is a hard X-ray source discovered by INTEGRAL in 2010. We have analyzed the X-ray emission of this source exploiting the Burst Alert Telescope (BAT) survey data up to 2012 March and the X-Ray Telescope (XRT) data that include also an observing campaign performed in early 2012. The source is detected at a significance level of ∼13 standard deviations in the 88 month BAT survey data, and shows a strong variability along the survey monitoring, going from high intensity to quiescent states. A timing analysis on the BAT data revealed an intensity modulation with a period of P {sub 0} = 72.44 ± 0.3 days. The significance of this modulation is about seven standard deviations in Gaussian statistics. We interpret it as the orbital period of the binary system. The light curve folded at P {sub 0} shows a sharp peak covering ∼30% of the period, superimposed to a flat level roughly consistent with zero. In the soft X-rays the source is detected only in 5 out of 12 XRT observations, with the highest recorded count rate corresponding to a phase close to the BAT folded light-curve peak. The long orbital period and the evidence that the source emits only during a small fraction of the orbit suggests that the IGR J18219–1347 binary system hosts a Be star. The broadband XRT+BAT spectrum is well modeled with a flat absorbed power law with a high-energy exponential cutoff at ∼11 keV.
- OSTI ID:
- 22224071
- Journal Information:
- Astrophysical Journal Letters, Vol. 775, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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