VLT observations of the magnetar CXO J164710.2-455216 and the detection of a candidate infrared counterpart

Abstract

We present deep observations of the field of the magnetar CXOJ164710.2-455216 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 {\em Chandra} position of the magnetar, of magnitudes $\mathrm{J}=23.5\pm 0.2$, $\mathrm{H}=21.0\pm 0.1$, and ${\mathrm{K}}_{\mathrm{S}}=20.4\pm 0.1$. The K${}_{\mathrm{S}}$-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 2 $\sigma$ level), consistent with the fact that the observations were taken when CXOJ164710.2-455216 was in quiescence. At the same time, we also present colour--magnitude and colour--colour diagrams in the J, H, and K${}_{\mathrm{S}}$ 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 CXOJ164710.2-455216. Future near-infrared observations of the field, following-up a source outburst, would be crucial to confirm the association from the detection of near-infrared variability and colour evolution.

arXiv comment5 pages, 3 figures, accepted for publication in MNRAS

References in corpus (19)

• A statistical study of 233 pulsar proper motions
• The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)
• Magnetars
• A Debris Disk Around An Isolated Young Neutron Star
• A Neutron Star with a Massive Progenitor in Westerlund 1
• Instantaneous starburst of the massive clusters Westerlund 1 and NGC 3603 YC
• The Post-Burst Awakening of the Anomalous X-ray Pulsar in Westerlund 1
• Optical, ultraviolet, and infrared observations of isolated neutron stars
• A VLT/FLAMES survey for massive binaries in Westerlund 1. IV. Wd1-5 - binary product and a pre-supernova companion for the magnetar CXOU J1647-45?
• Correlated Infrared and X-ray Flux Changes Following the 2002 June Outburst of the Anomalous X-ray Pulsar 1E 2259+586
• Multi-wavelength variability of the magnetar 4U 0142+61
• The most massive progenitors of neutron stars: CXO J164710.2-455216
• Spectral and timing properties of the magnetar CXOU~J164710.2-455216
• Adaptive optics near-infrared observations of magnetars
• Pulse Phase-coherent Timing and Spectroscopy of CXOU J164710.2-45521 Outbursts
• VLT/NACO observations of the High-Magnetic field radio pulsar PSR J1119-6127
• The 2006 Outburst of the Magnetar CXOU J164710.2-455216
• Near-infrared observations of Rotating Radio Transients
• Suzaku Observation of the Anomalous X-ray Pulsar CXOU J164710.2--455216

Cited by in corpus (3)

• Where are the magnetar binary companions? Candidates from a comparison with binary population synthesis predictions
• New candidates for magnetar counterparts from a deep search with the Hubble Space Telescope
• The infrared counterpart and proper motion of magnetar SGR0501+4516