An Evaluation of Body-grip Trap Trigger Configurations for Reducing River Otter Take Incidental to Beaver Trapping

River otter (Lontra canadensis) populations in North America have been the focus of significant restoration efforts. Wildlife management agencies, concerned about the unintentional take of river otters incidental to beaver (Castor canadensis) trapping, may recommend techniques to avoid capturing river otters. River otter avoidance techniques that are ineffective or diminish trap performance for beavers are undesirable. We conducted a field evaluation in 2015 and 2016 in Wisconsin to assess how two trigger configurations (offset and center) on body-grip traps would affect the incidental capture rate of river otters during beaver trapping. We also evaluated effects of each configuration on beaver capture rates, body lengths, and anatomical locations of trap-jaw strikes. We used size 330 body-grip traps equipped with identical triggers and alternated between trigger configurations during beaver damage management activities. We captured 8 river otters with each trap trigger configuration. Trap-jaw strikes on beavers differed between trigger configurations, with offset triggers resulting in more abdomen strikes and center triggers causing more cervical vertebrae strikes. We found that an offset trigger configuration did not reduce incidental take of otters and was less effective for trapping beavers

The Nature of Starburst Activity in M82

We present new evolutionary synthesis models of M82 based mainly on observations consisting of near-infrared integral field spectroscopy and mid-infrared spectroscopy. The models incorporate stellar evolution, spectral synthesis, and photoionization modeling, and are optimized for 1-45 micron observations of starburst galaxies. The data allow us to model the starburst regions on scales as small as 25 pc. We investigate the initial mass function (IMF) of the stars and constrain quantitatively the spatial and temporal evolution of starburst activity in M82. We find a typical decay timescale for individual burst sites of a few million years. The data are consistent with the formation of very massive stars (> 50-100 Msun) and require a flattening of the starburst IMF below a few solar masses assuming a Salpeter slope at higher masses. Our results are well matched by a scenario in which the global starburst activity in M82 occurred in two successive episodes each lasting a few million years, peaking about 10 and 5 Myr ago. The first episode took place throughout the central regions of M82 and was particularly intense at the nucleus while the second episode occurred predominantly in a circumnuclear ring and along the stellar bar. We interpret this sequence as resulting from the gravitational interaction M82 and its neighbour M81, and subsequent bar-driven evolution. The short burst duration on all spatial scales indicates strong negative feedback effects of starburst activity, both locally and globally. Simple energetics considerations suggest the collective mechanical energy released by massive stars was able to rapidly inhibit star formation after the onset of each episode.Comment: 48 pages, incl. 16 Postscript figures; accepted for publication in the Astrophysical Journa

A search for periodicity in the light curves of selected blazars

We present an analysis of multifrequency light curves of the sources 2223-052 (3C 446), 2230+114 (CTA 102), and 2251+158 (3C 454.3), which had shown evidence of quasi-periodic activity. The analysis made use of data from the University of Michican Radio Astronomy Observatory (USA) at 4.8, 8, and 14.5 GHz, as well as the Metsahovi Radio Astronomy Observatory (Finland) at 22 and 37 GHz. Application of two different methods (the discrete autocorrelation function and the method of Jurkevich) both revealed evidence for periodicity in the flux variations of these sources at essentially all frequencies. The periods derived for at least two of the sources -- 2223-052 and 2251+158-- are in good agreement with the time interval between the appearance of successive VLBI components. The derived periods for 2251+158 (P = 12.4 yr and 2223-052 (P = 5.8 yr) coincide with the periods found earlier by other authors based on optical light curves.Comment: 27 pages, 11 figures, accepted for publication in Astronomy Report

Measuring Black Hole Spin in OJ287

We model the binary black hole system OJ287 as a spinning primary and a non-spinning secondary. It is assumed that the primary has an accretion disk which is impacted by the secondary at specific times. These times are identified as major outbursts in the light curve of OJ287. This identification allows an exact solution of the orbit, with very tight error limits. Nine outbursts from both the historical photographic records as well as from recent photometric measurements have been used as fixed points of the solution: 1913, 1947, 1957, 1973, 1983, 1984, 1995, 2005 and 2007 outbursts. This allows the determination of eight parameters of the orbit. Most interesting of these are the primary mass of $1.84\cdot 10^{10} M_\odot$, the secondary mass $1.46\cdot 10^{8} M_\odot$, major axis precession rate $39^\circ.1$ per period, and the eccentricity of the orbit 0.70. The dimensionless spin parameter is $0.28\:\pm\:0.01$ (1 sigma). The last parameter will be more tightly constrained in 2015 when the next outburst is due. The outburst should begin on 15 December 2015 if the spin value is in the middle of this range, on 3 January 2016 if the spin is 0.25, and on 26 November 2015 if the spin is 0.31. We have also tested the possibility that the quadrupole term in the Post Newtonian equations of motion does not exactly follow Einstein's theory: a parameter $q$ is introduced as one of the 8 parameters. Its value is within 30% (1 sigma) of the Einstein's value $q = 1$. This supports the $no-hair theorem$ of black holes within the achievable precision. We have also measured the loss of orbital energy due to gravitational waves. The loss rate is found to agree with Einstein's value with the accuracy of 2% (1 sigma).Comment: 12 pages, 4 figures, IAU26

HST detection of spiral structure in two Coma Cluster dwarf galaxies

We report the discovery of (stellar) spiral-like structure in Hubble Space Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the Coma cluster. GMP 3629 is the faintest such galaxy detected in a cluster environment, and it is the first such galaxy observed in the dense Coma cluster. The large bulge and the faintness of the broad spiral-like pattern in GMP 3629 suggests that its disk may have been largely depleted. >We may therefore have found an example of the ``missing link'' in theories of galaxy evolution which have predicted that dwarf spiral galaxies, particularly in clusters, evolve into dwarf elliptical galaxies.Comment: Accepted for publication in AJ on July

A computer-generated galaxy model with long-lived two-armed spiral structure

A long-lived two-armed spiral has been generated in an N-body computer simulation of a galaxy with a static bulge and halo and an active disk composed of 60,000 particles. The spiral lasts for about three pattern revolutions without severe distortion and persists for at least two more revolutions with distortions and bifurcations resulting from an increasingly clumpy ISM. This suggests that two-armed grand design spirals in nonbarred noninteracting galaxies can be long-lived if star formation and other heat sources not present in the simulation maintain a steady interstellar medium

Tidal spiral arms in two-component galaxies - Density waves and swing amplification

The tidal spiral arms in galaxies are studied using the two-dimensional polar coordinate N-body program of Miller (1976, 1978) and a two-component disk galaxy perturbed by a point-mass model. The density wave theory, which explains spiral arms in the presence of differential rotation, and the components of the model and computer program are discussed. The spiral arms in the cold (spiral arm population) and hot (old stars) components and their velocity dispersions are examined, and consideration is given to density waves and swing amplification. The data reveal that a grand design spiral pattern can develop in the gaseous component of a disk galaxy as a result of tidal triggering from a companion, and the spiral pattern and kinematics of the particles correlate with predictions from the density wave theory

Tidal spiral arms in two-component galaxies - Density waves and swing amplification

The tidal spiral arms in galaxies are studied using the two-dimensional polar coordinate N-body program of Miller (1976, 1978) and a two-component disk galaxy perturbed by a point-mass model. The density wave theory, which explains spiral arms in the presence of differential rotation, and the components of the model and computer program are discussed. The spiral arms in the cold (spiral arm population) and hot (old stars) components and their velocity dispersions are examined, and consideration is given to density waves and swing amplification. The data reveal that a grand design spiral pattern can develop in the gaseous component of a disk galaxy as a result of tidal triggering from a companion, and the spiral pattern and kinematics of the particles correlate with predictions from the density wave theory

A computer-generated galaxy model with long-lived two-armed spiral structure

A long-lived two-armed spiral has been generated in an N-body computer simulation of a galaxy with a static bulge and halo and an active disk composed of 60,000 particles. The spiral lasts for about three pattern revolutions without severe distortion and persists for at least two more revolutions with distortions and bifurcations resulting from an increasingly clumpy ISM. This suggests that two-armed grand design spirals in nonbarred noninteracting galaxies can be long-lived if star formation and other heat sources not present in the simulation maintain a steady interstellar medium