Περίληψη:
We present the first polarimetric space very long baseline
interferometry (VLBI) observations of OJ 287, observed with RadioAstron
at 22 GHz during a perigee session on 2014 April 4 and five near-in-time
snapshots, together with contemporaneous ground VLBI observations at 15,
43, and 86 GHz. Ground-space fringes were obtained up to a projected
baseline of 3.9 Earth diameters during the perigee session, and at a
record 15.1 Earth diameters during the snapshot sessions, allowing us to
image the innermost jet at an angular resolution of similar to 50 mu as,
the highest ever achieved at 22 GHz for OJ 287. Comparison with
ground-based VLBI observations reveals a progressive jet bending with
increasing angular resolution that agrees with predictions from a
supermassive binary black hole model, although other models cannot be
ruled out. Spectral analyses suggest that the VLBI core is dominated by
the internal energy of the emitting particles during the onset of a
multiwavelength flare, while the parsec-scale jet is consistent with
being in equipartition between the particles and magnetic field.
Estimated minimum brightness temperatures from the visibility amplitudes
show a continued rising trend with projected baseline length up to
10(13) K, reconciled with the inverse-Compton limit through Doppler
boosting for a jet closely oriented to the line of sight. The observed
electric vector position angle suggests that the innermost jet has a
predominantly toroidal magnetic field, which, together with marginal
evidence of a gradient in rotation measure across the jet width,
indicates that the VLBI core is threaded by a helical magnetic field, in
agreement with jet formation models.
Συγγραφείς:
Gomez, Jose L.
Traianou, Efthalia
Krichbaum, Thomas P. and
Lobanov, Andrei P.
Fuentes, Antonio
Lico, Rocco
Zhao,
Guang-Yao
Bruni, Gabriele
Kovalev, Yuri Y.
Lahteenmaki, Anne
and Voitsik, Petr A.
Lisakov, Mikhail M.
Angelakis, Emmanouil
and Bach, Uwe
Casadio, Carolina
Cho, Ilje
Dey, Lankeswar and
Gopakumar, Achamveedu
Gurvits, I, Leonid
Jorstad, Svetlana and
Kovalev, Yuri A.
Lister, Matthew L.
Marscher, Alan P. and
Myserlis, Ioannis
Pushkarev, Alexander B.
Ros, Eduardo and
Savolainen, Tuomas
Tornikoski, Merja
Valtonen, Mauri J. and
Zensus, Anton
