Peer-Reviewed Journal Details
Mandatory Fields
Garcia, MR,Callanan, PJ,McCarthy, J,Eriksen, K,Hjellming, RM
Astrophysical Journal
Aquila X-1 in outburst and quiescence
Optional Fields
binaries : close stars : individual (Aquila X-1) stars : neutron X-rays : stars X-RAY SOURCES CENTAURUS X-4 NEUTRON-STARS TRANSIENT BINARIES DWARF MASS EMISSION PERIOD CURVE
We present photometry and spectroscopy of the soft X-ray transient Aq1 X-1. Optical photometry during an active state shows a strong (0.6 mag peak-to-peak) modulation at a period of 19 hr. Infrared (K' band) photometry during a quiescent state limits any ellipsoidal variations to less than 0.07 mag (peak-to-peak), which implies an inclination i < 31 degrees (90% limit). Spectroscopy in a quiescent state shows at most very small radial velocity variations, which implies a very low inclination of i < 12 degrees (90% limit). The low inclination is rather unexpected given the large photometric modulation seen in the active state. The upper limit to the equivalent width of the anomalous Li 6707 Angstrom line is less than 0.3 Angstrom, which is similar to the measured strength of this line in several other X-ray transients.
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