SUMMARY OF PROPOSAL 63012
UNIVERSITY OF OXFORD
NUCLEAR PHYICS LABORATORY, KEBLE ROAD
OXFORD
OXFORDSHIRE UK OX1 3RH
Tel: 44-1865 273374 Fax: 44-1865 273390
Medium: CD ROM
Subject: X-RAY BINARIES
GS1826-24: THE FIRST 2HR PERIOD LMXB?
ABSTRACT
GS1826-24 was first discovered by Ginga in 1988 and originally suggested to be a soft X-ray transient black-hole candidate. However, bursts have recently been detected in X-rays by SAX and in the optical counterpart by us, thereby confirming a neutron star primary. More importantly, our fast optical photometry reveals a 2hr modulation, plus irregular variability that is reminiscent of X1636-536 and X1735-444. If confirmed as the orbital period, this places GS1826-24 in a unique evolutionary position amongst LMXBs. We propose here to use ASCA to undertake the first detailed X-ray spectral study, in particular (a) to search for soft X-ray spectral features, (b) to undertake a spectral analysis of the bursts, (c) to investigate the structure of the short-term optical variations.
CO-INVESTIGATORS
| CO-I NAME | INSTITUTE | COUNTRY |
|---|
| LEE HOMER | UNIVERSITY OF OXFORD | UK |
| ERIK KUULKERS | UNIVERSITY OF OXFORD | UK |
| DARRAGH O'DONOGHUE | SA ASTR. OBSERVATORY | S AFRICA |
TARGETS
| TARGET NAME | PRI | RA | DEC | TIME | TC | OFF | GIS | SIS CNT | OBS |
|---|
| 1)GS1826-24 | 1 | 277.3675 | -23.7970 | 20 ks | N | N | P | 400.00000 | 1 |
TARGET 1
NOTE THAT WE SHALL ENDEAVOUR TO ARRANGE FOR SIMULTNEOUS OPTICAL OBSERVATIONS FROM SAAO ONCE THE ASCA SCHEDULING IS KNOWN.