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ESO-VLT discovery of the variable nIR counterpart to the AXP 1E1547.0-5408

ATEL # 1909; G.L. Israel (INAF-OAR), N. Rea, E. Rol (U. of Amsterdam), R. Mignani (MSSL), V. Testa, L. Stella (INAF-OAR), P. Esposito, S. Mereghetti, A. Tiengo (INAF-IASF, MI), G. Marconi (ESO), M. Burgay, A. Possenti (INAF-AOC), S. Zane (MSSL), on behalf of a larger collaboration
on 26 Jan 2009; 21:54 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Nanda Rea (

Subjects: Infra-Red, Request for Observations, Neutron Stars, Pulsars, Soft Gamma-ray Repeaters, Transients

On 2009 January 22nd, Swift-BAT, INTEGRAL-ACS, Fermi-GBM, and other satellites triggered on several short and long bursts from the direction of the Anomalous X-ray Pulsar (AXP) 1E1547.0-5408 (GCNs #8833, #8835, #8837, #8838, #8841, #8845, #8848), a transient AXP which showed a few weaker outbursts in the past two years (Gelfand & Gaensler 2007; Halpern et al. 2008; GCN #8312; #8313; #8321) and radio pulsations (Camilo et al. 2007).

Prompted by the AXP reactivation, we triggered our ToO program at ESO-VLT, and observed on January 22nd, 24th and 25th, in the Ks-band, the field of 1E1547.0-5408 with the NAOS -CONICA (NACO) instrument mounted on UT4-Yepun.

A nIR source, not present in our first epoch, has been detected in the second and third epochs within the 1 sigma radio error circle of the AXP (~0.2"; Camilo et al. 2007). The source has a magnitude of about Ks=18.5+/-0.3 (w.r.t. the 2MASS star at RA=237.72328, Dec= -54.30807) both during the second and third observation.

This AXP has been searched in the past for nIR emission without a conclusive detection (Mignani et al. 2008, arXiV:0901.3576; ATel #1758; ATel #1904).  Note that this new transient source was not present in our past nIR observations of this AXP (upper limit of about Ks=21 inferred on July 2007).

Further observations from VLT are planned for the next few days. We acknowledge excellent support from the observing staff at ESO-Paranal.

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R. E. Rutledge , Editor
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