2009A&A...495L...1C -
Astronomy and Astrophysics, volume 495, L1-4 (2009/2-3)
Phase-resolved spectroscopy of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during the 2008 outburst.
CORNELISSE R., D'AVANZO P., MUNOZ-DARIAS T., CAMPANA S., CASARES J., CHARLES P.A., STEEGHS D., ISRAEL G. and STELLA L.
Abstract (from CDS):
We obtained phase-resolved spectroscopy of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during its outburst in 2008 to find a signature of the donor star, constrain its radial velocity semi-amplitude (K2), and derive estimates for the pulsar mass. Using Doppler images of the Bowen region, we find a significant (≥8σ) compact spot at a position where the donor star is expected. If this is a signature of the donor star, we measure Kem=248±20km/s (1σ confidence), which represents a strict lower limit to K2. Also, the Doppler map of HeII λ4686 shows the characteristic signature of the accretion disc, and there is a hint of enhanced emission that may be a result of tidal distortions in the accretion disc that are expected in very low mass-ratio interacting binaries. The lower limit on K2 leads to a lower limit on the mass function of f(M1)≥0.10M☉. Applying the maximum K-correction gives 228<K2<322 km/s and a mass ratio of 0.051<q<0.072. Despite the limited S/N of the data, we were able to detect a signature of the donor star in SAXJ1808.4-3658, although future observations during a new outburst are still needed to confirm this. If the derived Kem is correct, the largest uncertainty in determining of the mass of the neutron star in SAXJ1808.4-3658 using dynamical studies lies with the poorly known inclination.
Abstract Copyright:
∼
Journal keyword(s):
accretion, accretion disks - X-rays: binaries - stars: individual: SAXJ1808.4-3658
Simbad objects:
3
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2009A&A...495L...1C and select 'bookmark this link' or equivalent in the popup menu