VLT observations of the magnetar CXO J164710.2−455216 and the detection of a candidate infrared counterpart. Issue 3 (3rd October 2017)

• Record Type: Journal Article
• Authors: Testa, V.; Mignani, R. P.; Hummel, W.; Rea, N.; Israel, G. L.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 473:Issue 3(2018)
• Page Start: 3180
• Page End: 3184
• Publication Date: 2017-10-03
• Subjects: stars: neutron -- pulsars: individual: CXOJ164710.2-455216; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx2574
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We present deep observations of the field of the magnetar CXO J164710.2−455216 in the star cluster Westerlund 1, obtained in the near-infrared with the adaptive optics camera NACO@VLT. We detected a possible candidate counterpart at the Chandra position of the magnetar, of magnitudes J = 23.5 ± 0.2, H = 21.0 ± 0.1 and K S = 20.4 ± 0.1. The K S -band measurements available for two epochs (2006 and 2013) do not show significant signs of variability but only a marginal indication that the flux varied (at the 2σ level), consistent with the fact that the observations were taken when CXO J164710.2−455216 was in quiescence. At the same time, we also present colour–magnitude and colour–colour diagrams in the J, H and K S bands from the 2006 epoch only, the only one with observations in all three bands, showing that the candidate counterpart lies in the main bulk of objects describing a relatively well-defined sequence. Therefore, based on its colours and lack of variability, we cannot yet associate the candidate counterpart to CXO J164710.2−455216. Future near-infrared observations of the field, following up a source outburst, would be crucial to confirm the association with the detection of near-infrared variability and colour evolution.