Astrophys. J., 837, 3-3 (2017/March-1)
Central engine and host galaxy of RXJ 1301.9+2747: a multiwavelength view of a low-mass black hole active galactic nuclei with ultra-soft X-ray emission.
SHU X.W., WANG T.G., JIANG N., WANG J.X., SUN L.M. and ZHOU H.Y.
Abstract (from CDS):
RXJ 1301.9+2747 is an optically identified very-low-mass AGN candidate with MBH∼1×106 M☉, which shows extremely soft X-ray emission and unusual X-ray variability in the form of short-lived flares. We present an analysis of multiwavelength observations of RXJ 1301.9+2747 in order to study the properties of the active nucleus and its host galaxy. The UV-to-X-ray spectrum in the quiescent state can be well and self-consistently described by a thermal and a Comptonized emission from the accretion disk, with the black body dominating ∼70% of the X-rays in the 0.2-2 keV. The same model can describe the X-ray spectrum in the flare state, but the Comptonized component becomes dominant (∼80%). The best fit implies an Eddington ratio of ∼0.14 and a black-hole mass of (1.7-2.8)×106M☉, in agreement with the estimation from the optical data within errors. However, the best-fitting model under predicts the optical flux for the HST point source by a factor of ∼2. The excess of nuclear optical emission could be attributed to a nuclear stellar cluster, which is frequently seen in low-mass AGNs. The X-ray to optical spectral slope (αox) is lower than in most other active galaxies, which may be attributed to intrinsically X-ray weakness due to very little hot and optically thin coronal emission. We performed a pilot search for weak or hidden broad emission lines using optical spectropolarimetry observations, but no polarized broad lines are detected. The host galaxy appears to be a disk galaxy with a boxy pseudobulge or nuclear bar accounting for ∼15% of the total starlight, which is consistent with the general characteristics of the host of low-mass AGNs.
© 2017. The American Astronomical Society. All rights reserved.
galaxies: active - galaxies: individual: RXJ 1301.9+2747 - galaxies: nuclei - X-rays: galaxies - X-rays: galaxies
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