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The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical

Hulleman, F. and van Kerkwijk, M. H. and Kulkarni, S. R. (2004) The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical. Astronomy & Astrophysics, 416 (3). pp. 1037-1045. ISSN 0004-6361. doi:10.1051/0004-6361:20031756.

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We present new optical and infrared observations of the counterpart to the Anomalous X-ray Pulsar (AXP) 4U 0142+61 taken with the Keck I telescope. The counterpart is found to be variable in the infrared. This contrasts with our optical observations, which do not show any evidence for variability. Apart from the variability the AXP shows a remarkable spectral energy distribution. In particular, we find a sudden drop in flux going from V to B, presumably due to a spectral feature. We compare our results to those obtained for the two other securely identified AXP counterparts, to 1E 2259+586 and 1E 1048.1-5937. 4U 0142+61 is very similar to the former source in its X-ray timing and spectral properties, and we find that this similarity extends to the quiescent infrared to X-ray flux ratio. For 1E 1048.1-5937, which has different X-ray properties, the situation is less clear: in one observation, the infrared to X-ray flux ratio was much larger, but another observation gave an upper limit which is consistent with that observed for 4U 0142+61. Assuming the quiescent ratios are all similar, we estimate the optical and infrared brightnesses for the three AXPs that remain to be identified as well as for the four Soft Gamma-ray Repeaters. We also discuss briefly how the observed optical and infrared emission might arise, in particular in the context of the magnetar model.

Item Type:Article
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Kulkarni, S. R.0000-0001-5390-8563
Additional Information:© 2004 ESO. Received: 10 January 2003. Accepted: 2 December 2003. We thank David Kaplan and Brian Jacoby for obtaining the 2000 July and November Palomar 60 inch data, and David Kaplan and George Djorgovski for obtaining the September and December Keck LRIS data. Part of this work was done while the authors were visiting the Institute for Theoretical Physics at UCSB, which is supported by NSF grant PHY 99-07949. F.H. thanks the Netherlands Organization for Scientific Research (NWO) and the Leids Kerkhoven Bosscha Fund for their grants, which made this visit possible. M.H.v.K. acknowledges support from a fellowship of the Royal Netherlands Academy of Arts and Sciences.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
NSFPHY 99-07949
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Leids Kerkhoven Bosscha FundUNSPECIFIED
Koninklijke Nederlandse Akademie van Wetenschappen (KNAW)UNSPECIFIED
Subject Keywords:pulsars: individual: 4U 0142+61 - stars: neutron - stars: magnetic fields - X-rays: general
Issue or Number:3
Record Number:CaltechAUTHORS:20180208-080358736
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Official Citation:The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical F. Hulleman, M. H. van Kerkwijk and S. R. Kulkarni A&A, 416 3 (2004) 1037-1045 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84735
Deposited By: Ruth Sustaita
Deposited On:08 Feb 2018 16:18
Last Modified:15 Nov 2021 20:22

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