SUMMARY OF PROPOSAL 73007
OSSERVATORIO ASTRONOMICO DI ROMA
VIA FRASCATI 33
MONTEPORZIO CATONE
ROMA ITALY I-00040
Tel: +39-6-9449019 Fax: +39-6-9447243
Medium: CD ROM
Subject: X-RAY BINARIES
ASCA TIMING OF THE UNIQUE PULSATING X-RAY BINARY HD49798
ABSTRACT
We have discovered a 13s periodic signal in the X-ray flux emitted by HD49798, an hydrogen depleted subdwarf O6 spectroscopic binary with an orbital period of 1.55d. This revealed that the unseen companion is an accreting degenerate star. It is unclear yet whether this is a white dwarf or a neutron star. In either case HD49798 represents an evolutionary stage that had not been observed before. We propose a single 30ks ASCA observation of this unique source aimed at obtaining an additional accurate period measurement and to look for orbital signatures (dips, smooth flux variation, Doppler shift) expected for such low-mass X-ray binary system.
CO-INVESTIGATORS
| CO-I NAME | INSTITUTE | COUNTRY |
|---|
| LUIGI STELLA | OA ROMA | ITALY |
| LORELLA ANGELINI | NASA-GSFC | USA |
| NICK WHITE | NASA-GSFC | USA |
| ALDO TREVES | UNI COMO | ITALY |
| ARVIND PARMAR | ESA-ESTEC | NETH |
| TIM OOSTERBROEK | ESA-ESTEC | NETH |
| SANDRO MEREGHETTI | CNR MILANO | ITALY |
TARGETS
| TARGET NAME | PRI | RA | DEC | TIME | TC | OFF | GIS | SIS CNT | OBS |
|---|
| 1)HD49798 | A | 101.9988 | -44.3289 | 30 ks | N | N | P | 0.10000 | 1 |