Abstract. The ISO galactic survey provides images of the inner disk in two broad filters (around 7 and 15 µm) over some 15 square degrees, away from the brightest star forming regions. A multiresolution analysis of the images leads to a catalogue of infrared dark clouds, most of which are condensed cores of large molecular clouds, several kpc away from the Sun, seen in absorption in front of the diffuse galactic emission. The longitude distributions of the background emission and of the dark clouds correlate with known tracers of young population components. We analyse the morphology of the dark clouds and the intensity fluctuations within the cloud boundaries at the two wavelengths. The 7 to 15 µm contrast ratio is 0.75 ± 0.15 for the clouds located away from the Galactic Centre (|l| > 1• ) and 1.05 ± 0.15 for the clouds closest to the Galactic Centre (|l| < 1Using a simple absorption model, we derive a 7 to 15 µm opacity ratio equal to 0.7 ± 0.1 for the clouds located away from the Galactic Centre and estimate the opacity, τ , of a few objects at 15 µm in the range 1 to 4. Several explanations for the variation of the contrast ratio, including absorption along the line of sight and local variations of the extinction curve are discussed.

OJ287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in a binary black hole model. The model predicted a major optical outburst in 2015 December. We found that the outburst did occur within the expected time range, peaking on 2015 December 5 at magnitude 12.9 in the optical R-band. Based on Swift/XRT satellite measurements and optical polarization data, we find that it included a major thermal component. Its timing provides an accurate estimate for the spin of the primary black hole, 0.313 0.01 c =  . The present outburst also confirms the established general relativistic properties of the system such as the loss of orbital energy to gravitational radiation at the 2% accuracy level, and it opens up the possibility of testing the black hole no-hair theorem with 10% accuracy during the present decade.

Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole (BBH) central engine of blazar OJ287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ287. We develop an approach that incorporates this effect into the BBH model for OJ287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ287ʼs central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole "no-hair theorem" at the 10% level.

Aims. We derive a new map of the interstellar extinction near the Galactic Centre (GC), extending to much higher values of A V than previously available, and use the results obtained to better characterise the long-period variable star population of the region. Methods. We take the Spitzer IRAC catalogue of GC point sources (Ramírez et al. 2008, ApJS, 175, 147) and combine it with new isochrones (Marigo et al. 2008, A&A, 482, 883) to derive extinctions based on the photometry of red giants and asymptotic giant branch (AGB) stars. We apply it to deredden the LPVs found by Glass et al. (2001) near the GC (Glass-LPVs). We make periodmagnitude diagrams and compare them to those from other regions of different metallicity. Results. Our new extinction map of the GC region covers 2.0• × 1.4• (280 × 200 pc at a distance of 8 kpc). The Glass-LPVs follow well-defined period-luminosity relations (PL) in the IRAC filter bands at 3.6, 4.5, 5.8, and 8.0 μm. The period-luminosity relations are similar to those in the Large Magellanic Cloud, suggesting that the PL relation in the IRAC bands is universal. We use ISOGAL data to derive mass-loss rates and find for the Glass-LPV sample some correlation between mass loss and pulsation period, as expected theoretically. Theoretical isochrones for a grid of different metallicities and ages are able to reproduce this relation. The GC has an excess of high-luminosity and long-period LPVs compared to the bulge, which supports previous suggestions that it contains a younger stellar population.

Abstract. We present version 1.0 of the ISOGAL-DENIS Point Source Catalogue (PSC), containing more than 100 000 point sources detected at 7 and/or 15 µm in the ISOGAL survey of the inner Galaxy with the ISOCAM instrument on board the Infrared Space Observatory (ISO). These sources are cross-identified, wherever possible, with near-infrared (0.8-2.2 µm) data from the DENIS survey. The overall surface covered by the ISOGAL survey is about 16 square degrees, mostly (95%) distributed near the Galactic plane (|b| < ∼ 1• ), where the source extraction can become confusion limited and perturbed by the high background emission. Therefore, special care has been taken aimed at limiting the photometric error to ∼0.2 mag down to a sensitivity limit of typically 10 mJy. The present paper gives a complete description of the entries and the information which can be found in this catalogue, as well as a detailed discussion of the data processing and the quality checks which have been completed. The catalogue is available at the Centre de Données Astronomiques de Strasbourg (via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/403/955) and also via the server at the Institut d'Astrophysique de Paris (http://www-isogal.iap.fr/). A more complete version of this paper, including a detailed description of the data processing, is available in electronic form through the ADS service and at http://www.edpsciences.org.