3 Remarks on some individual objects

We wish to emphasize here that some sources listed in this catalogue are still uncertain. They need to be regarded with caution in view of the further work necessary. Some sources are tentatively classified as low-mass X-ray binaries due to their X-ray burst feature and/or the similarity of the X-ray properties to other identified systems. No counterpart at other bands has been found.
Finally, we would like to make some remarks on several individual sources. The three luminous supersoft X-ray sources, RX J0527.8-6954, 1E 0543.8-6823 (CAL 83) and 1E 0547.6-7109 (CAL 87), are excluded from the new catalogue. The now generally accepted model for the luminous SSSs is that, with few exceptions, these sources are accreting white dwarfs (WDs) in binaries, which are burning hydrogen in their envelopes in a steady or intermittent way (van den Heuvel et al. 1992; Kahabka & van den Heuvel 1997).
There is a new class of pulsating objects with spin periods in the 6-12 s range, which are different from "normal'' binary X-ray pulsars (Mereghetti & Stella 1995). These objects are referred to as braking X-ray pulsars (BXP) (Mereghetti & Stella 1995) or anomalous X-ray pulsars (van Paradijs et al. 1995). These sources include 4U 0142+61, 1E 2259+586, 1E 1048.1-5937, RX J1838.4-0301 (but see Mereghetti et al. 1997; Song et al. 2000 for RX J1838.4-0301) and the recently discovered sources 1E 1841-045 (Vasisht & Gotthelf 1997), 1RXS J170849.0-400910 (Sugizaki et al. 1997), AX J1845.0-0358 (Torii et al. 1998), and probably RX J0720.4-3125 (Haberl et al. ). 4U 0142+61 and 1E 2259+586 have already been listed in the previous LMXB catalogue, while 1E 1048.1-5937 was listed in the HMXB catalogue. Although it has been suggested that AXPs may consist of neutron stars accreting from a very-low-mass companion (Mereghetti & Stella 1995) or are isolated neutron stars accreting from circumstellar debris (e.g. Corbet et al. 1995; van Paradijs et al. 1995), recently, evidence has been mounting that they are isolated neutron stars with very high magnetic fields, i.e., magnetars related to the soft gamma-ray repeaters (SGRs) (Kouveliotou et al. 1998, 1999; Hurley et al. 1999), as has been suggested by Thompson & Duncan (1996). In view of these developments we have not included the AXPs in this LMXB catalogue, but in an Appendix we present a table of the suspected AXPs.

Acknowledgements

We are grateful to Robert Fender and Michiel van der Klis for carefully reading the manuscript and for useful comments. QZL acknowledges the financial support from KC Wong fellowship of Chinese Academy of Sciences. This work is partially supported by the Netherlands Organization for Scientific Research (NWO) through Spinoza Grant 08-0 to E. P. J. van den Heuvel and by the National Project for Fundamental Research by the Ministry of Science and Technology of China (973 Project) through Grant G1999075405.

Noted added in proof: Rudy Wijnands informed us that we had missed two new sources SAX J1753.5-2349 and SAX J1806.5-2215 (in't Zand et al. 1998, axrs. symp. 228), while the sources SAX J0840.7+2248 (IAUC 6892), SAX J1719.6-4254 (IAUC 7263), XTE J1739-285 (IAUC 7300), XTE J1743-363 (IAUC 7210), and SAX J1818.6-1703 (IAUC 6840) are also likely LMXBs.