Aql X-1 in Outburst and Quiescence

Abstract

We present photometry and spectroscopy of the soft x-ray transient Aql X-1. Optical photometry during an active state shows a strong (0.6 mag peak-to-peak) modulation at a period of 19 hours. Infrared (K'-band) photometry during a quiescent state limits any ellipsoidal variations to <0.07 mag (peak-to-peak), which implies an inclination i<31 (90% limit). Spectroscopy in a quiescent state shows at most very small radial velocity variations, which implies a very low inclination of i<12 (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 6707A line is <0.3A, which is similar to the measured strength of this line in several other x-ray transients.

Accepted for publication in ApJ, 12 pages, 5 figures

References in corpus (5)

• Aquila X-1 from outburst to quiescence: the onset of the propeller effect and signs of a turned-on rotation-powered pulsar
• The mass of the neutron star in Cyg X-2 (V1341 Cyg)
• Spectral State Transitions in Aql X-1: Evidence for `Propeller' Effects
• An ``outside-in'' outburst of Aql X--1
• Aquila X--1: a low inclination soft X-ray transient

Cited by in corpus (19)

• Detecting gravitational wave emission from the known accreting neutron stars
• Improved Mass and Radius Constraints for Quiescent Neutron Stars in Omega Cen and NGC 6397
• Variable Thermal Emission from Aql X-1 in Quiescence
• Quiescent Thermal Emission from the Neutron Star in Aql X-1
• The disc-jet coupling in the neutron star X-ray binary Aquila X-1
• The Orbital Light Curve of Aquila X-1
• The evolution of the high energy tail in the quiescent spectrum of the soft X-ray transient Aql X-1
• The donor of Aquila X-1 revealed by high angular resolution near-infrared spectroscopy
• Polarised infrared emission from X-ray binary jets
• Measuring A Truncated Disk in Aquila X-1
• Truncation of the Accretion Disk at One Third of the Eddington Limit in the Neutron Star Low-Mass X-ray Binary Aquila X-1
• An anti-correlation between X-ray luminosity and H-alpha equivalent width in X-ray binaries
• Intermittent dipping in a low-mass X-ray Binary
• A detection of the donor star of Aquila X-1 during its 2004 outburst?
• Serendipitous Discovery of a Cataclysmic Variable in the Globular Cluster NGC 6624
• Lithium enhancement in X-ray binaries due to stellar rotation
• Optical nebular emission following the most luminous outburst of Aquila X-1
• Probing thermonuclear bursts and X-ray reflection features in Aql X-1 during 2024 outburst
• Ubiquitous yet forgotten: broad absorptions in the optical spectra of low-mass X-ray binaries