Astronomy and Astrophysics, volume 326, 489-492 (1997/10-2)
Two X-ray clusters close to line of sight of the luminous QSO HS 1700+6416.
REIMERS D., TOUSSAINT F., HAGEN H.-J., HIPPELEIN H. and MEISENHEIMER K.
Abstract (from CDS):
We report the serendipitous discovery with ROSAT of two X-ray clusters close to the line of sight of the QSO HS 1700+6416 (z=2.72) which is itself one of the most luminous QSOs known. Cluster A (1'40" northwest of the QSO) is Abell 2246, while cluster B (3' northeast) is a hitherto unknown distant cluster. We have determined the redshifts of clusters A and B as z=0.25 and z=0.44 respectively. Although both clusters appear barely resolved by ROSAT, the X-ray surface brightness distribution can be represented well by β-models I(θ)=Io(1+(θ/θc)2)–3β+0.5 where θc is the cluster core radius (cf. Henry et al. 1993) if the detector point spread function is taken into account. Assuming β=2/3 we find core radii θc(A)=14"±2" and θc(B)=18"±2". Gas temperatures are T(A)=6±3x107K and T(B)=3±1.5x107K, X-ray luminosities are Lx(0.4-2keV rest frame)=4.1x1043erg/s and 8.45x1043erg/s respectively (H0=50, q0=1/2). Cluster B shows a giant luminous arc located approximately 15'' (≃1 core radius) NW of the cluster center. We show that magnification of HS 1700+6416 by cluster lensing by the two X ray clusters can be excluded as reason for the high apparent luminosity of the QSO.
galaxies: clusters: individual: A 2246, HS 1700 B - quasars: individual: HS 1700+6416 - cosmology: gravitational lensing