EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 371/1 Article
Free access article

Issue A&A
Volume 371, Number 1, May III 2001
Page(s) 198 - 204
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010340



A&A 371, 198-204 (2001)
DOI: 10.1051/0004-6361:20010340

A search for the optical counterpart to PSR B1821-24 in M 28

A. Golden, R. F. Butler and A. Shearer

National University of Ireland, Galway, Ireland

(Received 18 September 2000 / Accepted 7 March 2001)

Abstract
We have analysed archival HST/WFPC2 images in both the F555W & F814W bands of the core field of the globular cluster M 28 in an attempt to identify the optical counterpart of the magnetospherically active millisecond pulsar PSR B1821-24. Examination of the radio derived error circle yielded several potential candidates, down to a magnitude of V ~ 24.5 (V0 ~ 23.0). Each were further investigated, both in the context of the CMD of M 28, and also with regard to phenomenological models of pulsar magnetospheric emission. The latter was based on both luminosity-spindown correlations and known spectral flux density behaviour in this regime from the small population of optical pulsars observed to date. None of the potential candidates exhibited emission expected from a magnetospherically active pulsar. The fact that the magnetic field & spin coupling for PSR B1821-24 is of a similar magnitude to that of the Crab pulsar in the vicinity of the light cylinder has suggested that the millisecond pulsar may well be an efficient nonthermal emitter. ASCA's detection of a strong synchrotron-dominated X-ray pulse fraction encourages such a viewpoint. We argue that only future dedicated 2-d high speed photometry observations of the radio error-circle can finally resolve this matter.


Key words: pulsars: general -- pulsars: individual PSR B1821-24 -- globular clusters: general -- globular clusters: individual M 28/NGC 6626 -- Techniques: image processing -- Astrometry

Offprint request: A. Golden, agolden@itc.nuigalway.ie

SIMBAD Objects



© ESO 2001


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.