H. Drass

Dust reverberation-mapping of the Seyfert 1 galaxy WPVS48

Using robotic telescopes of the Universitatssternwarte Bochum near Cerro Armazones in Chile, we monitored the z = 0.0377 Seyfert1 galaxy WPVS48 (2MASX J09594263-3112581) in the optical (B and R) and near-infrared (NIR, J and Ks) with a cadence of two days. The light curves show unprecedented variability details. The NIR variation features of WPVS48 are consistent with the corresponding optical variations, but the features appear sharper in the NIR than in the optical, suggesting that the optical photons undergo multiple scatterings. The J and Ks emission, tracing the hot (∼1600 K) dust echo, lags the B and R variations by on average τ = 64 ± 4 days and 71 ± 5 days, respectively (restframe). WPVS48 lies on the known τ − MV relationship. However, the observed lag τ is about three times shorter than expected from the dust sublimation radius rsub inferred from the optical-UV luminosity, and explanations for this common discrepancy are searched for. The sharp NIR echos argue for a face-on torus geometry and allow us to put forward two potential scenarios: 1) as previously proposed, in the equatorial plane of the accretion disk the inner region of the torus is flattened and may come closer to the accretion disk. 2) The dust torus with inner radius rsub is geometrically and optically thick, so that the observer only sees the facing rim of the torus wall, which lies closer to the observer than the torus equatorial plane and therefore leads to an observed foreshortened lag. Both scenarios are able to explain the factor three discrepancy between τ and rsub. Longer-wavelength dust reverberation data might enable one to distinguish between the scenarios.

Eclipsing high-mass binaries - I. Light curves and system parameters for CPD − 51° 8946, PISMIS 24-1, and HD 319702

We present the first results of a comprehensive photometric O-star survey performed with a robotic twin refractor at the Universitatssternwarte Bochum located near Cerro Armazones in Chile. For three high-mass stars, Pismis 24-1, CPD −51 ◦ 8946, and HD 319702, we determined the period through the Lafler-Kinman algorithm and modelled the light curves within the framework of the Roche geometry. For Pismis 24-1, a previously known eclipsing binary, we provide the first light curves and determined a photometric period of 2.36 days together with an orbital inclination of 61.8 ◦ . The best-fitting model solution to the light curves suggests a detached configuration. With a primary temperature of T1 = 42 520 K we obtained the temperature of the secondary component as T2 = 41 500 K. The CPD − 51 ◦ 8946 system is another known eclipsing binary for which we present a revised photometric period of 1.96 days with an orbital inclination of 58.4 ◦ . The system probably has a semi-detached configuration and a mass ratio q = M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34 550 K, we obtain T2 = 21 500 K for the secondary component. The HD 319702 system is a newly discovered eclipsing binary member of the young open cluster NGC 6334. The system shows well-defined eclipses favouring a detached configuration with a period of 2.0 days and an orbital inclination of 67.5 ◦ . Combining our photometric result with the primary spectral type O8 III(f) (T1 = 34 000 K) we derive a temperature of T2 = 25 200 K for the secondary component.

A near-infrared survey of the entire R Coronae Australis cloud

Aims. To understand low- to intermediate-mass star-formation in the nearby R Cr A molecular cloud, we try to identify the stellar content that is accessible with near-infrared observations. Methods. We obtained a JHKs band mosaic of ∼10 � × 60 � covering the entire R CrA molecular cloud with unprecedented sensitivity. We present a catalogue of about 3500 near-infrared sources fainter than the saturation limit Ks ∼ 10 mag, reaching Ks ∼ 18 mag. We analysed the extended sources by inspecting their morphology and point sources by means of colour–colour and colour–magnitude diagrams. Additionally, we compared the extinction inferred from the NIR data with the line-of-sight dust emission at 1.2 mm. Sources towards high dust emission but relatively low H − Ks show a projected mm-excess; these sources are either immediately surrounded by cold circumstellar material or, if too red to be a true foreground object, they are embedded in the front layer of the 1.2 mm emitting dust cloud. In both cases they are most likely associated with the cloud. Results. By means of the projected mm-excess technique we find 33 new faint near-infrared sources deeply embedded in the Coronet cluster around R CrA, for which so far about 20 bright infrared stars have been known. In contrast to the Coronet region, both the northwestern dust ridge and the southeastern cloud condensation “C” appear to be devoid of associated stars detectable with our near-infrared data. Furthermore, about a dozen sources, which are spread over the entire molecular cloud region, exhibit a possible K-band excess, but only with marginal statistical significance (<3σ), so that we do not consider the indicated K-band excess as real. Finally, while the Herbig-Haro-like objects seen on our maps are concentrated around the Coronet, we find four new nebulae also located farther down to the southeast. At the position of IRAS 18595-3712, an X-shaped bipolar nebula is resolved; its exciting star is hidden behind an edge-on disc. Conclusions. The deep near-infrared survey of the entire R CrA molecular cloud strengthens the evidence for the Coronet being the region where most of the young stars are found. Our results are consistent with earlier predictions that the R CrA cloud has fragmented into sub-condensations at different star-forming stages.

ACS (Alma Common Software) operating a set of robotic telescopes

We use the ALMA Common Software (ACS) to establish a unified middleware for robotic observations with the 40cm Optical, 80cm Infrared and 1.5m Hexapod telescopes located at OCA (Observatorio Cerro Armazones) and the ESO 1-m located at La Silla. ACS permits to hide from the observer the technical specifications, like mount-type or camera-model. Furthermore ACS provides a uniform interface to the different telescopes, allowing us to run the same planning program for each telescope. Observations are carried out for long-term monitoring campaigns to study the variability of stars and AGN. We present here the specific implementation to the different telescopes.

Polycyclic aromatic hydrocarbon selected galaxies

Context. This is the fourth in a series of papers based on the ISOCAM Parallel Survey at 6.7 μm. While the first three papers have been devoted to active galactic nuclei (AGN), here we report on emission-line galaxies without AGN signatures in their optical spectra. Aims. Polycyclic aromatic hydrocarbon (PAH) emission has been found in both starbursts and modestly starforming galaxies, but the relation between starforming activity and PAH luminosity is still a matter of debate. The different correlation degrees could be caused by the variety of optical and far-infrared sample selection criteria. In order to obtain a census of the typical properties of PAH emitting galaxies, we here study moderately distant galaxies which have been selected by their PAH emission. Methods. Combining the ISOCAM Parallel Survey at 6.7 μm with 2MASS we have colour-selected a sample of 120 candidates for strong PAH emission. We obtained optical and mid-infrared spectra of 75 and 19 sources, respectively, and analysed IRASADDSCANs and available Spitzer 3.6–160 μm photometry. Results. The Spitzer mid-infrared spectra exhibit clear PAH features and corroborate that our photometric selection criteria trace the PAH emission of galaxies fairly well. The optical spectra show emission lines, at median redshift z ∼ 0.1, as well as Hδ and Ca II absorption, indicating ongoing starformation as well as post-starbursts. The mid- and far-infrared spectral energy distributions (SEDs) provide evidence for a broad range of far-infrared (FIR) luminosities (10 9 L� −2 × 10 12 L� ), but in general the dust is colder (T < 25 K, β = 2) than for starburst galaxies like M 82 (T ≈ 40 K). For most galaxies the monocromatic luminosity (ν · Lν) peaks at about equal height at optical, 6.7 μm (PAH) and FIR wavelengths. In about 15% of the sources the FIR luminosity exceeds the optical and PAH