We present a detailed NIR/optical/UV study of the transient low mass X-ray binary 1RXS J180408.9-342058 performed during its 2015 outburst, aimed at determining the nature of its companion star. We obtained three optical spectra at the 2.1 m San Pedro Martir Observatory telescope (Mexico). We performed optical and NIR photometric observations with both the REM telescope and the New Technology Telescope (NTT) in La Silla. We obtained optical and UV observations from the Swift archive. Finally, we performed optical polarimetry of the source by using the EFOSC2 instrument mounted on the NTT. The optical spectrum of the source is almost featureless since the hydrogen and He I emissions lines, typically observed in LMXBs, are not detected. Similarly, carbon and oxygen lines are neither observed. We marginally detect the He II 4686 AA emission line, suggesting the presence of helium in the accretion disc. No significant optical polarisation level was observed. The lack of hydrogen and He I emission lines in the spectrum implies that the companion is likely not a main sequence star. Driven by the tentative detection of the He II 4686 AA emission line, we suggest that the system could harbour a helium white dwarf. If this is the case, 1RXS J180408.9-342058 would be an ultra-compact X-ray binary. By combining an estimate of the mass accretion rate together with evolutionary tracks for a He white dwarf, we obtain a tentative orbital period of ~ 40 min. On the other hand, we also built the NIR-optical-UV spectral energy distribution (S...
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Climate change Research Articles published between Jun 20, 2022 to Jun 26, 2022
Jun 27, 2022
Articles Included: 2
One eighth of the bird species in the world is considered globally threatened; the avifauna of Iraq comprises 409 species and is considered as the maj...Read More