Cosmological Applications of Gravitational Lensing

The last decade has seen an enormous increase of activity in the field of gravitational lensing, mainly driven by improvements of observational capabilities. I will review the basics of gravitational lens theory, just enough to understand the rest of this contribution, and will then concentrate on several of the main applications in cosmology. Cluster lensing, and weak lensing, will constitute the main part of this review.Comment: 26 pages, including 2 figures (a third figure can be obtained from the author by request) gziped and uuencoded postscript file; to be published in Proceedings of the Laredo Advanced Summer School, Sept. 9

Bright Opportunities for Atmospheric Characterization of Small Planets: Masses and Radii of K2-3 b, c, and d and GJ3470 b from Radial Velocity Measurements and Spitzer Transits

We report improved masses, radii, and densities for four planets in two bright M-dwarf systems, K2-3 and GJ3470, derived from a combination of new radial velocity and transit observations. Supplementing K2 photometry with follow-up Spitzer transit observations refined the transit ephemerides of K2-3 b, c, and d by over a factor of 10. We analyze ground-based photometry from the Evryscope and Fairborn Observatory to determine the characteristic stellar activity timescales for our Gaussian Process fit, including the stellar rotation period and activity region decay timescale. The stellar rotation signals for both stars are evident in the radial velocity data and is included in our fit using a Gaussian process trained on the photometry. We find the masses of K2-3 b, K2-3 c, and GJ3470 b to be 6.48, 2.14, and 12.58 M ⊕, respectively. K2-3 d was not significantly detected and has a 3σ upper limit of 2.80 M ⊕ . These two systems are training cases for future TESS systems; due to the low planet densities (ρ < 3.7 g cm -3 ) and bright host stars (K < 9 mag), they are among the best candidates for transmission spectroscopy in order to characterize the atmospheric compositions of small planets

Powering the Broad H alpha Line in BL Lacertae

Original paper can be found at: http://www.astrosociety.org/pubs/cs/070-112.html--Copyright Astronomical Society of the Pacifi

A Seyfert Nucleus in BL Lacertae

Original paper can be found at: http://161.58.115.79/pubs/cs/156-194.html--Copyright Astronomical Society of the PacificWe have obtained spectroscopic observations of the broad Ha line in BL Lacertae over a period of 30 months. These data show that the line equivalent width is anti-correlated with the continuum flux implying that the broad line emission is not powered primarily by synchrotron emission from the relativistic jet. The most probable explanation is that the broad line region in BL Lacertae is photoionized by continuum emission from an accretion disk which at optical wavelengths is dominated by the Doppler beamed synchroton continuum

Monitoring the Ha Line in BL Lacertae - Evidence for an Accretion Disk

Original paper can be found at: http://161.58.115.79/pubs/cs/156-194.html--Copyright Astronomical Society of the PacificWe present new spectroscopic observations of the recently discovered broad Ha line in BL Lacertae. These data, obtained over a period of 30 months, indicate that the line equivalent width is anti-correlated with the continuum flux, implying that the broad line emission is not powered primarily by synchroton emission from the relativistic jet. The most probable explanation is that the broad line region in BL Lacertae is photoionized by continuum emission from an accretion disk which at optical wavelengths is dominated by the Doppler beamed synchroton continuum

Optical Spectropolarimetry of Broad Line Active Galaxies

Original paper can be found at: http://161.58.115.79/pubs/cs/156-194.html--Copyright Astronomical Society of the PacificWe present new optical spectropolarimetry of two bright type 1 AGNs. The observations are part of a project on broad line active galaxies in which, through data analysis and modelling, we aim to identify the polarization mechanism and to probe both the BLR and scattering region geometry and kinematics

The profiles of polarized broad Hα lines in radio galaxies

Original article can be found at: www3.interscience.wiley.com Copyright Blackwell Publishing / Royal Astronomical Society. DOI: 10.1046/j.1365-8711.1998.01420.x [Full text of this article is not available in the UHRA]We present spectropolarimetric observations of seven broad-line radio galaxies. We find significantly polarized broad Hα emission in four objects including two, Arp 102B and 3C 390.3, which have double-peaked line profiles. In these objects the prominent redshifted and blueshifted peaks of the broad Hα line have no clear counterparts in polarized flux. This conflicts with theoretical predictions for a relativistic line-emitting disc with an electron scattering atmosphere, one of the leading models advanced to account for the double-peaked lines. The shapes and widths of the polarized line profiles can be explained if, as expected in unified schemes, the scattering occurs near the poles of an obscuring torus. However, the observed polarization position angles favour geometries in which the scattering plane is perpendicular to the radio jet. A configuration in which Hα photons emitted by a biconical flow are scattered off the inner wall of the torus has this property, and would also produce a single-peaked scattered line profile. With the exception of 3C 227, the sample as a whole conforms to the general trend in powerful radio galaxies for the optical polarization to be aligned with the radio source axis, favouring toroidal rather than polar scattering.Peer reviewe