Related papers: EUCLIA - Exploring the UV/optical continuum lag in…

We examine whether the spectral energy distribution of UV continuum emission of active galactic nuclei changes during flux variation. We used multi-epoch photometric data of QSOs in the Stripe 82 observed by the SDSS Legacy Survey and…

We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM-Newton. The analysis of X-ray lags (up to the…

The characteristic timescale ($\tau$) of continuum variability of the accretion disk in active galactic nuclei (AGNs) is known to be related to the thermal timescale, which is predicted to scale with AGN luminosity ($L$) and restframe…

It is generally thought that AGN optical variability is produced, at least in part, by reprocessing of central X-rays by a surrounding accretion disc, resulting in wavelength-dependent lags between bands. Any good model of AGN optical…

Measuring time lags between time-series or lighcurves at different wavelengths from a variable or transient source in astronomy is an essential probe of physical mechanisms causing multiwavelength variability. Time-lags are typically…

We examine simultaneous X-ray and UV light curves from multi-epoch 8 day XMM Newton observations of the narrow line Seyfert 1 galaxy 1H 0707-495. The simultaneous observations reveal that both X-ray and UV emission are variable and that the…

The ``UV upturn'' is a sharp rise in spectra of elliptical galaxies shortward of rest-frame 2500 A. It is a ubiquitous phenomenon in nearby giant elliptical galaxies, and is thought to arise primarily from low-mass evolved stars on the…

We present results from intensive (x3 daily), three-month-long X-ray, UV and optical monitoring of the bright Seyfert active galactic nucleus (AGN) MCG+08-11-11 with Swift, supported by optical-infrared ground-based monitoring. The 12…

The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in five bands from the near UV to the I-band, combining new Wide Field…

Temporal analysis of X-ray binaries and Active Galactic Nuclei have shown that hard X-rays react to variation of soft ones after a time delay. The opposite trend, or soft lag, has only been seen in a few rare Quasi-periodic Oscillations in…

Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled $\sim$200-350 times in 0.3-10 keV X-ray and six UV/optical bands. Uniform reduction and cross-correlation analysis of these datasets yields three…

We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to…

We present new results for a sample of 33 narrow-lined UV-selected active galactic nuclei (AGNs), identified in the course of a spectroscopic survey for star-forming galaxies at z ~ 2-3. The rest-frame UV composite spectrum for our AGN…

Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib). It has…

We use GALEX/optical photometry to construct color-color relationships for early-type galaxies sorted by morphological type. We have matched objects in the GALEX GR1 public release and the first IR1.1 internal release, with the RC3…

Using GALEX, UVOT and optical photometry, we explore the prevalence and strength of the UV-upturn in the spectra of quiescent early type galaxies in several nearby clusters. Even for galaxies with completely passive optical colours, there…

X-rays illuminating the accretion disc in active galactic nuclei give rise to an iron K line and its associated reflection spectrum which are lagged behind the continuum variability by the light-travel time from the source to the disc. The…

During 1998 April 13-16, NGC 3516 was monitored almost continuously with HST for 10.3 hr in the UV and 2.8 d in the optical, and simultaneous RXTE and ASCA monitoring covered the same period. The X-rays were strongly variable with the soft…

We present the GALEX far FUV and near NUV ultraviolet imaging of three nearby shell galaxies, namely NGC 2865, NGC 5018 and NGC 7135. The system of shells and fine structures visible in the optical is detected in the NUV image of NGC 2865…

We test the "reprocessing paradigm" of the optical -- UV AGN variability by detailed modeling of the correlated X-ray -- optical (3590 and 5510 Angstrem) variability of the recent multiwavelength campaign of NGC 3516. We produce model…