Voyager far UV observations of Markarian 509

Abstract

Voyager far ultraviolet (500–1700 Å) observations of the Seyfert 1 galaxy Markarian 509 are presented. Markarian 509 was observed for 4.2 hours on day 87/014, for 8.8 hours on day 87/016, for 2.6 hours on day 87/019 and for 4.2 hours on day 87/023 with the ultraviolet spectrometer on board the Voyager 2 spacecraft. The average flux at 1050 A during these observations of Markarian 509 was 3.67 × 10⁻¹² ergs cm⁻² sec⁻¹ Å⁻¹. This flux value is approximately ten times higher than the brightest IUE SWP image of Markarian 509. The continuum of both observations is similar and is flat throughout the far UV spectral region and no flux shortward of 912 Å is seen. This result for Markarian 509 implies that either this galaxy was unexpectedly bright during the Voyager observations or that the spectrum measured is instead due to a nearby luminous accretion disk system, such as a cataclysmic variable. However, an optical survey of the region has not produced any potential candidates.