NGC 4725

NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born British astronomer William Herschel on April 6, 1785. The galaxy lies at a distance of approximately 12.3 Mpc from the Milky Way. NGC 4725 is the brightest member of the Coma I Group of the Coma-Sculptor Cloud, although it is relatively isolated from the other members of this group. This galaxy is strongly disturbed and is interacting with neighboring spiral galaxy NGC 4747, with its spiral arms showing indications of warping. The pair have an angular separation of $1,206 km/s$, which corresponds to a projected linear separation of 112 kpc. A tidal plume extends from NGC 4747 toward NGC 4725.

NGC 4725 is a suspected type 2 Seyfert galaxy with a supermassive black hole at the core. The morphological classification of this galaxy is SAB(r)ab pec, indicating a peculiar, weakly-barred spiral galaxy (SAB) with a complete ring surrounding the bar (r) and somewhat tightly-wound spiral arms (ab). It is actually double-barred, a feature found among about a third of all barred spirals. The galactic plane is inclined by approximately 46° to the line of sight from the Earth.

The ring structure of the galaxy is a region of star formation. It is offset from the galactic center and displays non-circular motion. There is a compact radio source positioned approximately 1.9 kpc from the nucleus of NGC 4725. Since there is no optical counterpart at that position, this may be a star forming region that is heavily obscured by dust.

Supernovae
Multiple supernova candidate events have been detected in this galaxy:


 * SN 1940B was detected on a photograph taken May 5, 1940, about $24 arcminute$ northeast of the galactic core. The light curve indicates this was a type II supernova.
 * SN 1969H was discovered on 17 June 1969, with a magnitude of 15.
 * Candidate SN 1987E was detected April 24, 1987 with a magnitude of 15.65. A follow-up study failed to detect this event, so it may have been the result of gravitational lensing.
 * SN 1999gs was detected on December 28, 1999 with a magnitude of 19.3. It was positioned $2.5 arcminute$ west and $3 arcsecond$ south of the nucleus of NGC 4725.
 * On automated images taken July 5, 2016, a magnitude 17.0 transient source was discovered at an angular separation of $105 arcsecond$ from the galactic nucleus. Designated ASASSN-16gu (AT 2016cyu), this was most likely a supernova event. It had an estimated absolute visual magnitude of –13.6.