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Magnitude, color and spectral type of Aql X-1 in quiescence

C. Chevalier·S. A. Ilovaisky·P. Leisy·F. Patat
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Abstract

Direct I and V-band imaging of Aql X-1 in quiescence and during outburst maximum shows that the true optical counterpart is the interloper located 0.48" West of the previously known star. We find for the new counterpart V = 21.6 and V-I = 2.2 in quiescence, when its contribution to the total light was 12% in V and 22% in I. Analysis of this photometry and of low-resolution spectra of the sum of both stars, also taken during quiescence, shows that the likely spectral types for the previously known star and the optical counterpart are late G and late K, respectively, reddened by E(B-V) = 0.5 $\pm$0.1.

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C. Chevalier, S. A. Ilovaisky, P. Leisy, F. Patat. 1999-06-16. Magnitude, color and spectral type of Aql X-1 in quiescence. https://arxiv.org/abs/astro-ph/9906278

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