A New Near-Ultraviolet Source in the M87 Jet

ATel #4267; Juan P. Madrid (Swinburne University, Australia)
on 20 Jul 2012; 04:26 UT
Credential Certification: Juan Madrid (jmadrid@astro.swin.edu.au)

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A new source has appeared along the plasma jet emerging from the supermassive black hole of Messier 87 (M87), the central galaxy of the Virgo Cluster. Hubble Space Telescope (HST) data reveal the presence of this new Near-Ultraviolet source located along the axis of the jet between knots D and E.

The Space Telescope Imaging Spectrograph data became publicly available on 2012 July 11, a year after the observation taken on 2011 July 11. The detector in use was the Near-Ultraviolet MAMA detector with a crystal quartz filter centered at a wavelength of 2364 Angstroms. The data were retrieved from the Multimission Archive at Space Telescope and reduced with the Pyraf task Multidrizzle following standard procedures. The observations consist of four different exposures that are combined into a single frame. The bright new source is present in all four exposures.

The section of the jet where the new source occurs has very faint emission in the NUV. That is, the new source is not coincident with a knot previously catalogued in the standard nomenclature of the M87 jet.

The new NUV source is located along the jet axis 4.6 arcseconds (or 354 parsecs, projected) from the nucleus of the galaxy. The HST image yields the following coordinates RA 12:30:49.09 and DEC +12:23:29.31. Preliminary photometric measurements yield a magnitude of m(STSMAG)=22.51 mag in the STMAG system.

Likely physical origins for this new source are: (i) a nova in M87 or (ii) activity associated with the jet. Evidence for both phenomena exist in the literature. Novae in M87 have been reported even back at the time of Edwin Hubble (Bowen 1952). Observations of M87 with HST have revealed several transient sources in that galaxy (Madrid et al. 2007) but none so far which could be associated with the jet.

The spatial coincidence, at least in projection, with the M87 synchrotron jet leaves open the possibility of a section of the jet changing in brightness or experiencing an outburst. The first documented outburst from a section of an AGN jet comes precisely from the M87 jet and its knot HST-1 (Harris et al. 2003, Madrid 2009). Observers of M87 are encouraged to examine their data for additional information on this source and its light curve.