A large fraction of active galactic nuclei (AGN) are 'invisible' in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared (IR)-bright AGN is predicted by models of galaxy-supermassive black hole coevolution and is required to explain the observed X-ray and IR backgrounds. Recently, IR colour cuts with Wide-field Infrared Survey Explorer have identified a portion of this missing population. However, as the host galaxy brightness relative to that of the AGN increases, it becomes increasingly difficult to differentiate between IR emission originating from the AGN and from its host galaxy. As a solution, we have developed a new method to select obscured AGN using their 20-cm continuum emission to identify the objects as AGN. We created the resulting invisible AGN catalogue by selecting objects that are detected in AllWISE (mid-IR) and FIRST (20 cm), but are not detected in SDSS (optical) or 2MASS (near-IR), producing a final catalogue of 46 258 objects. 30 per cent of the objects are selected by existing selection methods, while the remaining 70 per cent represent a potential previously unidentified population of candidate AGN that are missed by mid-IR colour cuts. Additionally, by relying on a radio continuum detection, this technique is efficient at detecting radio-loud AGN at z>=0.29, regardless of their level of dust obscuration or their host galaxy's relative brightness.
UBV profile fitting photometry is presented for 1469 stars within 90arcsec of the center of the ionizing cluster of 30 Doradus (NGC 2070). A value of 0.82+/-0.03 is found for the extinction parameter S=E(U-B)/E(B-V), constant over almost the whole area covered by this research, with some evidence for local variations. Two reddening components can be identified: a smooth and moderate one that increases towards R136, and a clumpy one varying widely across the face of the cluster. The total-to-selective extinction parameter, R_V_= A_V_/E(B-V), is found to be in the range of 3.0 to 3.7, consistent with previous determinations. A new visualization tool, the colour-magnitude stereogram, is introduced and used to argue that: (1) the observations imply mass segregation in a dust filled cluster; (2) that there has been continuous dust formation near the cluster core up to the present; and (3) that an insidious systematic error has plagued previous determinations of IMF slopes. A method to obtain an unbiased estimate of the slope is discussed.
We present Interplanetary Network localization information for 343 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE) between the end of the 4th BATSE catalog and the end of the Compton Gamma-Ray Observatory (CGRO) mission, obtained by analyzing the arrival times of these bursts at the Ulysses, Near Earth Asteroid Rendezvous (NEAR), and CGRO spacecraft. For any given burst observed by CGRO and one other spacecraft, arrival time analysis (or "triangulation") results in an annulus of possible arrival directions whose half-width varies between 11 arcsec and 21{deg}, depending on the intensity, time history, and arrival direction of the burst, as well as the distance between the spacecraft. This annulus generally intersects the BATSE error circle, resulting in an average reduction of the area of a factor of 20. When all three spacecraft observe a burst, the result is an error box whose area varies between 1 and 48000arcmin^2^, resulting in an average reduction of the BATSE error circle area of a factor of 87.
Between 2000 November and 2006 May, one or more spacecraft of the interplanetary network (IPN) detected 226 cosmic gamma-ray bursts that were also detected by the French Gamma-Ray Telescope experiment on board the High Energy Transient Experiment 2 spacecraft. During this period, the IPN consisted of up to nine spacecraft, and using triangulation, the localizations of 157 bursts were obtained. We present the IPN localization data on these events.
To complement the study of transient phenomena and to assist subsequent observations in the mid-infrared, we extract point source photometry from archival mosaics of nearby galaxies with high star formation rates within 4 Mpc. Point spread function photometry was performed on sources detected in both Spitzer IRAC 3.6um and 4.5um bands at greater than 3{sigma} above background. These data were then supplemented by aperture photometry in the IRAC 5.8um and 8.0um bands conducted at the positions of the shorter wavelength sources. For sources with no detected object in the longer wavelengths, we estimated magnitude limits based on the local sky background.
A 0.35x0.29{deg} field centered at l=-18.63{deg}, b=0.35{deg} was observed during the ISOGAL survey by ISOCAM imaging at 7{mu}m and 15{mu}m. 648 objects were detected and their brightness are measured. By combining with the DENIS data in the near-infrared J and Ks bands, one derives the extinction at 7{mu}m through A_Ks_-A_7_=0.35(A_J_-A_Ks_) which yields A_7_/Av~0.03 from the near-IR extinction values of van de Hulst-Glass (Glass, 1999MNRAS.308..127G). The extinction structure along the line of sight is then determined from the values of J-Ks or Ks-[7] of the ISOGAL sources identified as RGB or early AGB stars with mild mass-loss. The distribution of Av ranges from 0 to ~45 and it reflects the concentration of the extinction in the spiral arms. Based on their locations in color-magnitude diagrams and a few cross-identifications with IRAS and MSX sources, the nature of objects is discussed in comparison with the case of a low extinction field in Baade's Window. Most of the objects are either AGB stars with moderate mass loss rate or luminous RGB stars. Some of them may be AGB stars with high mass loss rate. In addition, a few young stellar objects (YSOs) are present.
The ISOGAL survey is one of the largest imaging programme performed by the ISO satellite. About 16deg^2^ mainly distributed in the inner Galactic disk were mapped at 7 and/or 15 micron ({mu}m). Because of highly structured background and high source density, a special point source extraction algorithm was used and resulted in a 100000 point source catalogue. The mid-infrared data have been associated with near-infrared DENIS sources, providing an up to five wavelength photometric catalogue with a typical astrometric accuracy better than 1 arcsecond. The point source catalogue contains the positional and photometric parameters of all ISOGAL sources, together with various quality flags aimed at giving an estimate of the reliability of the detections and of the associations between the different bands (see the paper for a complete description).
We present an atlas of near-infrared spectra (2.36{mu}m-4.1{mu}m) of ~300 stars at moderate resolution ({lambda}/{delta}{lambda}~1500-2000). The spectra were recorded using the Short-Wavelength Spectrometer aboard the Infrared Space Observatory (ISO-SWS). The bulk of the observations were performed during a dedicated observation campaign after the liquid helium depletion of the ISO satellite, the so-called post-helium programme. This programme was aimed at extending the MK-classification to the near-infrared.
This paper describes the first data release of the Kepler-INT Survey (KIS) that covers a 116deg^2^ region of the Cygnus and Lyra constellations. The Kepler field is the target of the most intensive search for transiting planets to date. Despite the fact that the Kepler mission provides superior time-series photometry, with an enormous impact on all areas of stellar variability, its field lacks optical photometry complete to the confusion limit of the Kepler instrument necessary for selecting various classes of targets. For this reason, we follow the observing strategy and data reduction method used in the IPHAS and UVEX galactic plane surveys in order to produce a deep optical survey of the Kepler field. This initial release concerns data taken between 2011 May and August, using the Isaac Newton Telescope on the island of La Palma. Four broadband filters were used, U, g, r, i, as well as one narrowband one, H{alpha}, reaching down to a 10{sigma} limit of ~20th mag in the Vega system. Observations covering ~5 deg^2^, thus about half of the field, passed our quality control thresholds and constitute this first data release. We derive a global photometric calibration by placing the KIS magnitudes as close as possible to the Kepler Input Catalog (KIC) photometry. The initial data release catalog containing around 6 million sources from all the good photometric fields is available for download from the KIS Web site (www.astro.warwick.ac.uk/research/kis/) as well as via MAST (KIS magnitudes can be retrieved using the MAST enhanced target search page http://archive.stsci.edu/kepler/kepler_fov/search.php and also via Casjobs at MAST Web site http://mastweb.stsci.edu/kplrcasjobs/).
Variability-induced motion (VIM) is an observable effect in simultaneous astrometric and photometric measurements caused by brightness variation in one of the components of a double source or blended image, which manifests itself as a strongly correlated shift of the optical photocenter. We have processed the entire collection of Kepler long-cadence light curve data, looking for correlated signals in astrometry and photometry on the time basis of a quarter-year. Limiting the VIM correlation coefficient to 0.3, VIM events are detected for 129525 Kepler stars in at least one quarter. Of 7305 Kepler objects of interest, 4440 are detected as VIM at least once. Known variable stars and resolved double stars have elevated rates of VIM detection. Confident VIM occurrences are found for stars with suggested superflare events, indicating possible signal contamination. We present a complete catalog of all quarterly VIM detections. This catalog should be checked for such astrophysically significant events as transits of exoplanets, new eclipsing stars, and superflares of solar-type stars.
