Line Emission from an Accretion Disk around a Rotating Black Hole: Toward a Measurement of Frame Dragging

Line emission from an accretion disk and a corotating hot spot about a rotating black hole are considered for possible signatures of the frame-dragging effect. We explicitly compare integrated line profiles from a geometrically thin disk about a Schwarzschild and an extreme Kerr black hole, and show that the line profile differences are small if the inner radius of the disk is near or above the Schwarzschild stable-orbit limit of radius 6GM/c^2. However, if the inner disk radius extends below this limit, as is possible in the extreme Kerr spacetime, then differences can become significant, especially if the disk emissivity is stronger near the inner regions. We demonstrate that the first three moments of a line profile define a three-dimensional space in which the presence of material at small radii becomes quantitatively evident in broad classes of disk models. In the context of the simple, thin disk paradigm, this moment-mapping scheme suggests formally that the iron line detected by the Advanced Satellite for Cosmology and Astrophysics mission from MCG-6-30-15 (Tanaka et al. 1995) is 3 times more likely to originate from a disk about a rotating black hole than from a Schwarzschild system. A statistically significant detection of black hole rotation in this way may be achieved after only modest improvements in the quality of data. We also consider light curves and frequency shifts in line emission as a function of time for corotating hot spots in extreme Kerr and Schwarzschild geometries. Both the frequency-shift profile and the light curve from a hot spot are valuable measures of orbital parameters and might possibly be used to detect frame dragging even at radii approaching 6GM/c^2 if the inclination angle of the orbital plane is large.Comment: 15 pages (LaTex), 7 postscript figures; color plot (Figure 1) available at http://cfata2.harvard.edu/bromley/nu_nofun.html (This version contains a new subsection as well as minor corrections.

Region of magnetic dominance near a rotating black hole

This is a brief contribution in which a simplified criterion of the relevance of the test-particle approximation describing motion of material near a magnetized black hole is discussed. Application to processes of the dissipative collimation of astronomical jets (as proposed by de Felice and Curir, 1992) is mentioned.Comment: 11 pages, to appear in General Relativity and Gravitation, also available (with additional illustrations) at http://otokar.troja.mff.cuni.cz/user/karas/au_www/karas/papers.ht

Cardiovascular roles of estrogen receptors: insights gained from knockout models

The effects of estrogen are mediated through two functionally distinct receptors, estrogen receptor α (ER- α ), and estrogen receptor β (ER- β ), both of which are expressed in the cardiovascular system. The etiology of cardiovascular disease is believed to result in part from the loss of endogenous estrogen, indicating that estrogen and its receptors may play important roles in the prevention of cardiovascular disease in women

The role of SRC-3 in estrogen-dependent vasoprotection during vascular wall remodeling postinjury

Estrogen receptors are hormone-inducible transcription factors requiring coactivators such as members of the SRC/p160 family to modulate the transcription of their target genes. This perspective will examine the interplay between estrogen receptors and their coactivators in vasoprotection during vascular wall remodeling

An evolving hot spot orbiting around Sgr A*

Here we report on recent near-infrared observations of the Sgr A* counterpart associated with the super-massive ~ 4x10^6 M_sun black hole at the Galactic Center. We find that the May 2007 flare shows the highest sub-flare contrast observed until now, as well as evidence for variations in the profile of consecutive sub-flares. We modeled the flare profile variations according to the elongation and change of the shape of a spot due to differential rotation within the accretion disk.Comment: 7 pages, 5 figures, contribution for the conference "The Universe under the Microscope" (AHAR 2008), to be published in Journal of Physics: Conference Series by Institute of Physics Publishin

Coordinated mm/sub-mm observations of Sagittarius A* in May 2007

At the center of the Milky Way, with a distance of ~8 kpc, the compact source Sagittarius A* (SgrA*) can be associated with a super massive black hole of ~4x10^6 solar masses. SgrA* shows strong variability from the radio to the X-ray wavelength domains. Here we report on simultaneous NIR/sub-millimeter/X-ray observations from May 2007 that involved the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope, the Australian Telescope Compact Array (ATCA), the US mm-array CARMA, the IRAM 30m mm-telescope, and other telescopes. We concentrate on the time series of mm/sub-mm data from CARMA, ATCA, and the MAMBO bolometer at the IRAM 30m telescope.Comment: 7 pages, 3 figures, contribution for the conference "The Universe under the Microscope" (AHAR 2008), to be published in Journal of Physics: Conference Series by Institute of Physics Publishin

Gravitational Waves from Chaotic Dynamical System

To investigate how chaos affects gravitational waves, we study the gravitational waves from a spinning test particle moving around a Kerr black hole, which is a typical chaotic system. To compare the result with those in non-chaotic dynamical system, we also analyze a spinless test particle, which orbit can be complicated in the Kerr back ground although the system is integrable. We estimate the emitted gravitational waves by the multipole expansion of a gravitational field. We find a striking difference in the energy spectra of the gravitational waves. The spectrum for a chaotic orbit of a spinning particle, contains various frequencies, while some characteristic frequencies appear in the case of a spinless particle.Comment: 8 pages, 13 figures. submitted to PR

Policy implications of technologies for cognitive enhancement

The Advanced Concepts Group at Sandia National Laboratory and the Consortium for Science, Policy and Outcomes at Arizona State University convened a workshop in May 2006 to explore the potential policy implications of technologies that might enhance human cognitive abilities. The group's deliberations sought to identify core values and concerns raised by the prospect of cognitive enhancement. The workshop focused on the policy implications of various prospective cognitive enhancements and on the technologies/nanotechnology, biotechnology, information technology, and cognitive science--that enable them. The prospect of rapidly emerging technological capabilities to enhance human cognition makes urgent a daunting array of questions, tensions, ambitions, and concerns. The workshop elicited dilemmas and concerns in ten overlapping areas: science and democracy; equity and justice; freedom and control; intergenerational issues; ethics and competition; individual and community rights; speed and deliberations; ethical uncertainty; humanness; and sociocultural risk. We identified four different perspectives to encompass the diverse issues related to emergence of cognitive enhancement technologies: (1) Laissez-faire--emphasizes freedom of individuals to seek and employ enhancement technologies based on their own judgment; (2) Managed technological optimism--believes that while these technologies promise great benefits, such benefits cannot emerge without an active government role; (3) Managed technological skepticism--views that the quality of life arises more out of society's institutions than its technologies; and (4) Human Essentialism--starts with the notion of a human essence (whether God-given or evolutionary in origin) that should not be modified. While the perspectives differ significantly about both human nature and the role of government, each encompasses a belief in the value of transparency and reliable information that can allow public discussion and decisions about cognitive enhancement. The practical question is how to foster productive discussions in a society whose attention is notably fragmented and priorities notably diverse. The question of what to talk about remains central, as each of the four perspectives is concerned about different things. Perhaps the key issue for initial clarification as a condition for productive democratic discussion has to do with the intended goals of cognitive enhancement, and the mechanisms for allowing productive deliberation about these goals

Coordinated multi-wavelength observations of Sgr A*

We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the ~4x10^6 solar masses super-massive black hole (SMBH) at the Galactic Center. The goal of these coordinated multi-wavelength observations is to investigate the variable emission from Sgr A* in order to obtain a better understanding of the underlying physical processes in the accretion flow/outflow. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope (July 2005, May 2007) and the ACIS-I instrument aboard the Chandra X-ray Observatory (July 2005). We report on a polarized NIR flare synchronous to a 8x1033 erg/s X-ray flare in July 2005, and a further flare in May 2007 that shows the highest sub-flare to flare contrast observed until now. The observations can be interpreted in the framework of a model involving a temporary disk with a short jet. In the disk component flux density variations can be explained due to hot spots on relativistic orbits around the central SMBH. The variations of the sub-structures of the May 2007 flare are interpreted as a variation of the hot spot structure due to differential rotation within the disk.Comment: 15 pages, 7 figures, contribution for the conference "The Universe under the Microscope" (AHAR 2008), to be published in Journal of Physics: Conference Series by Institute of Physics Publishin