47,388 research outputs found
Obscured Binary Quasar Cores in SDSS J104807.74+005543.5?
We report the discovery of a possible close binary system of quasars in SDSS
J1048+0055. The [OIII]4959,5007 emission lines are clearly double-peaked, and
two discrete radio sources with a projected physical separation of ~20 pc are
found in the VLBA milliarcsec resolution image at 8.4 GHz. Each of the [O
III]4959,5007 doublets and Hbeta can be well modelled by two Gaussians and the
line ratio, [O III]5007/Hbeta ~7, is typical of Seyfert 2 galaxies. No broad
component of Hbeta was detected and its [O III]5007 luminosity, L_[OIII] ~ 9.2
times 10^42 erg s^-1, is comparable to luminous quasars and is a few ten times
more luminous than typical Seyfert galaxies. One natural interpretation is that
SDSS J1048+0055 contains two close quasar-like nuclei and the BLR around them
are obscured. Other possible models are also discussed. We suggest that
double-peaked narrow emission line profile may be an effective way of selecting
candidates of binary black holes with intermediate separation
Integer colorings with forbidden rainbow sums
For a set of positive integers , an -coloring of is
rainbow sum-free if it contains no rainbow Schur triple. In this paper we
initiate the study of the rainbow Erd\H{o}s-Rothchild problem in the context of
sum-free sets, which asks for the subsets of with the maximum number of
rainbow sum-free -colorings. We show that for , the interval is
optimal, while for , the set is optimal. We
also prove a stability theorem for . The proofs rely on the hypergraph
container method, and some ad-hoc stability analysis.Comment: 20 page
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