2149 20160706150028.0 DOI 10.1051/0004-6361/201322940 ASTROimport-306 Aleman, I. 2014 Aims: We report the first detections of OH+ emission in planetary nebulae (PNe). Methods: As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed a line survey in these PNe over the entire spectral range between 51µm and 672µm to look for new detections. Results: The rotational emission lines of OH+ at 152.99, 290.20, 308.48, and 329.77µm were detected in the spectra of three planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures and column densities derived from these lines are in the range of 27-47 K and 2 × 1010-4 × 1011 cm-2, respectively. Conclusions: In PNe, the OH+ rotational line emission appears to be produced in the photodissociation region (PDR) in these objects. The emission of OH+ is observed only in PNe with hot central stars (Teff> 100 000 K), suggesting that high-energy photons may play a role in OH+ formation and its line excitation in these objects, as seems to be the case for ultraluminous galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Herschel Planetary Nebula Survey (HerPlaNS). First detection of OH+ in planetary nebulae Ueta, T. Ladjal, D. Exter, K. M. Kastner, J. H. Montez, R. Tielens, A. G. G. M. Chu, Y.-H. Izumiura, H. McDonald, I. Sahai, R. Siódmiak, N. Szczerba, R. van Hoof, P. A. M. Villaver, E. Vlemmings, W. Wittkowski, M. Zijlstra, A. A. A79 Astronomy and Astrophysics 566 2014 http://esoads.eso.org/abs/2014A%26A...566A..79A published in REFERD