Discovery of a transient X-ray source in the compact stellar nucleus of NGC 2403

作者：Yukita Mihoko^*; Swartz Douglas A; Soria Roberto; Tennant Allyn F

来源：Astrophysical Journal, 2007, 664(1): 277-283.

DOI：10.1086/518237

• galaxies : evolution
• galaxies : individual (NGC 2403)
• galaxies : nuclei
• galaxies : star clusters
• X-rays : binaries
• X-rays : galaxies

We report the discovery of an X- ray source coincident with the nuclear star cluster at the dynamical center of the nearby late-type spiral galaxy NGC 2403. The X-ray luminosity of this source varies from below detection levels, similar to 1035 erg s(-1) in the 0.5-8.0 keV band to 7 x 10(38) erg s(-1) on timescales between observations of <2 months. The X-ray spectrum is well fit by an accretion disk model consisting of multiple blackbody components and corresponding physically to a compact object mass of greater than or similar to 5 M-circle dot. No pulsations nor aperiodic behavior is evident in its X- ray light curve on the short timescales of the individual observations. The X-ray properties of the source are more similar to those of the nuclear source X-8 in M33, believed to be a low-mass X-ray binary, then to those of the low-luminosity active galactic nucleus (AGN) in NGC 4395. The brightness of the nuclear star cluster, M-I similar to - 11: 8 mag, is typical of clusters in late-type spirals but its effective radius, r(e) similar to 12 pc, is several times larger than average indicating a relatively relaxed cluster and a low probability of a central massive object. Estimating from its observed colors and brightness, the cluster has a mass of greater than or similar to 10(6.5) M-circle dot and an age of similar to 1.4 Gyr.

• 出版日期2007-7-20