NGC 3599

NGC 3599 is a lenticular galaxy located in the constellation Leo. It was discovered by William Herschel on March 14, 1784. The galaxy is located at a distance of 20.4 Mpc from the Sun. NGC 3599 is a member of the Leo II group of galaxies in the Virgocentric flow.

The morphological classification of NGC 3599 is SA0:, which indicates this is a lenticular galaxy but with some uncertainty in the classification. There is a weak ring structure $876 km/s$ from the nucleus, and a small bar about $$ in length. The galaxy is inclined at an angle of 28° to the plane of the sky, so it is being viewed from nearly face-on. The nucleus is compact and not associated with any non-thermal activity. Although not optically active, NGC 3599 is classified as a Seyfert 2 or a LINER-type galaxy. The mass of the central black hole is estimated at $0$.

In 2003, a sudden rise in X-ray emission from NGC 3599 was observed by the XMM-Newton space observatory. Follow-up observations showed a rapid decay in flux during the following years. This was originally suggested as a candidate tidal disruption event but it may instead have been caused by thermal instability of the accretion disk orbiting a black hole.