ISO observations of the radio-loud BALQSO 1556+3517

Abstract

To date, the quasar 1556+3517 is the only radio loud Broad Absorption Line QSO (BALQSO; Becker et al. 1997). This prompted narrow band filter imaging observations in the range 4-15 mu with the ISO satellite. The source is clearly detected in all filters and appears point-like and isolated at the resolution of ISO. The overall Spectral Energy Distribution (SED) in erg s(-1) peaks at a rest wavelength >= 6 mu and is reddened by 1.6 visual magnitudes. Correction for reddening brings 1556+3517 within 1.3 sigma from the log R=1 dividing line between radio-loud and radio-quiet sources. The mid-IR luminosity integrated over the 1.8-6 mu rest wavelength range is ~ 210(46ergs({-1})) (H_{0=75kms(-1}Mpc({-1)) , q₀=0}), which requires at least 4M_⊙ of dust and 800M_⊙ of associated gas. It is unlikely that such a large mass stems from the BAL wind itself. Based on observations with ISO, an ESA project with Instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) with the participation of ISAS and NASA