Volume 525, January 2011
|Number of page(s)||7|
|Section||Stellar structure and evolution|
|Published online||06 December 2010|
HST and VLT observations of the neutron star 1E 1207.4–5209⋆
Istituto Universitario di Studi Superiori,
Viale Lungo Ticino Sforza 56,
2 INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, via Bassini 15, 20133 Milano, Italy
3 Istituto Nazionale di Fisica Nucleare, Sez. di Pavia, via Bassi 6, 27100 Pavia, Italy
4 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
5 Università degli Studi di Pavia, Dipartimento di Fisica Nucleare e Teorica, via Bassi 6, 27100 Pavia, Italy
6 European Southern Observatory, Karl Schwarzschild-Str. 2, 85748 Garching, Germany
Accepted: 20 June 2010
The peculiar central compact object 1E 1207.4−5209 in the G296.5+10.0 supernova remnant has been proposed to be an “anti-magnetar” – a young neutron star born with a weak dipole field. Accretion, possibly of supernova fallback material, has also been invoked to explain a large surface temperature anisotropy as well as the generation of peculiar cyclotron absorption features superimposed on its thermal spectrum. Interestingly enough, a faint optical/infrared source was proposed as a possible counterpart to 1E 1207.4−5209, but later questioned, based on coarse positional coincidence. On the basis of the large offset of 1E 1207.4−5209 with respect to the center of its host supernova remnant, the source should move at ~70 mas yr-1. Thus, we tested the association by measuring the proper motion of the proposed optical counterpart. Using Hubble Space Telescope (HST) observations spanning 3.75 years, we computed a 3σ upper limit of 7 mas yr-1. Absolute astrometry on the same HST data set also places the optical source significantly off the 99% confidence Chandra position. This allows us to safely rule out the association. Using the HST data set, coupled to ground-based observations collected at the ESO/Very Large Telescope (VLT), we set the deepest limits ever obtained on the optical/infrared emission from 1E 1207.4−5209. By combining these limits with the constraints derived from X-ray timing, we rule out accretion as the source of the thermal anisotropy of the neutron star.
Key words: stars: neutron / pulsars: individual: 1E 1207.4−5209
© ESO, 2010
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