Susan R. Trammell

Analysis of the Polarization and Flux Spectra of SN 1993J

Synthetic polarization and flux spectra are presented for aspherical, electron scattering-dominated photospheres of Type II supernovae (SN II) in general and the specific case of SN 1993J using a Monte Carlo scheme. The observed luminosity of a Type II supernova depends on the unknown inclination angle. Spectral analysis alone will fail to detect even strong deviations from spherical symmetry. Line scattering depolarizes incident polarized light, but the residual intrinsic polarization does not completely vanish because of electron scattering effects that depend on the electron density distribution. By combining results on the polarization and velocity structure of the emission lines, and the degree of polarization in the continuum, we place strong constraints on the degree of asphericity, the inclination of the system and the electron density distribution. Both the flux spectra and the percentage of polarization as a function of wavelength can be reproduced by an aspherical model with an axis ratio of 0.6, radial electron densities proportional to r**-5 and an effective temperature of 4800 K. In an oblate model, SN1993J is seen almost equator on. The line forming region is still within the hydrogen rich part of the envelope after 3 weeks, although the continuum may form in deeper layers. Although the residual polarization across Halpha is not zero, the interstellar component derived herein is consistent with that deduced by Trammell et al.(1993). The power of this technique for investigating the structure of other SN II, as a method for independently deriving the interstellar polarization, and the implications of these results on the use of SN II to determine distances through the Baade- Wesselink method are discussed.

Spectropolarimetry of SN 1993J in NGC 3031

We have obtained low-resolution optical spectropolarimetry of SN 1993J which shows a high continuum linear polarization and a 0.5% drop in polarization across the Ha emission line accompanied by a ∼15° position angle rotation. From these data we infer the presence of two distinct polarization components and conclude that at least part of the polarization is intrinsic to the supernova. We propose that the polarization observed at Hα is due to interstellar polarization within NGC 3031, while the continuum polarization is intrinsic to the object. After correcting the observed Stokes parameters for interstellar polarization, we find that the intrinsic continuum polarization is high, P=1.6%±0.1% at θ=49°±3°, and is wavelength independent

PROMPT: Panchromatic robotic optical monitoring and polarimetry telescopes

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Multiple Collimated Outflows in the Proto-Planetary Nebula GL 618

1.2M in grants and donations, we are now building PROMPT at CTIO. When completed in late 2005, PROMPT will consist of six 0.41-meter diameter Ritchey-Chretien telescopes on rapidly slewing mounts that respond to GRB alerts within seconds, when the afterglow is potentially extremely bright. Each mirror and camera coating is being optimized for a different wavelength range and function, including a NIR imager, two red-optimized imagers, a blue-optimized imager, an UV-optimized imager, and an optical polarimeter. PROMPT will be able to identify high-redshift events by dropout and distinguish these events from the similar signatures of extinction. In this way, PROMPT will act as a distance-finder scope for spectroscopic follow up on the larger 4.1-meter diameter SOAR telescope, which is also located at CTIO. When not chasing GRBs, PROMPT serves broader educational objectives across the state of North Carolina. Enclosure construction and the first two telescopes are now complete and functioning: PROMPT observed Swifts first GRB in December 2004. We upgrade from two to four telescope in February 2005 and from four to six telescopes in mid-2005.

Spectropolarimetry of the post-main-sequence bipolar nebulae GL 618, M2-56, and M1-92

We present narrowband Hα, [S II], and [O I] Hubble Space Telescope images of the young planetary nebula GL 618. This object is a compact, bipolar nebula that is currently undergoing the transition from asymptotic giant branch star to planetary nebula. Our images confirm the presence of at least three highly collimated outflows emanating from the central regions of GL 618. We also detect Hα emission close to the central dust lane and in an extended scattered light halo. The three outflows are occurring simultaneously in this object as opposed to being the result of a precessing jet. We derive an inclination for the brightest outflow in the east lobe of 39° ± 4°. This differs from the previous estimate of 45°. In addition, our results indicate that the outflows seen in GL 618 are probably not coplanar. Line strengths derived from the narrowband images indicate a shock velocity in the range of 40-100 km s-1. Based on the shock velocity, we estimate that the age of the outflows is less than 500 yr. The outflows seen in the optical images of GL 618 are related to features seen in near-IR, CO, and CS maps of this object. This relationship indicates that the outflows are playing a major role in the morphological evolution of this young planetary nebula, interacting with and shaping the neutral envelope surrounding GL 618. We discuss the implications of these jets and their interaction with the neutral envelope in the context of current models of planetary nebula formation.

Hubble Space Telescope and Ground-based Imaging of the Bipolar Proto-Planetary Nebula M1-92: Evidence for a Collimated Outflow

New high-quality spectropolarimetry of the post-main-sequence bipolar nebulae GL 618, M2-56, and M1-92 is presented which permits accurate separation of the scattered and unscattered components. Shock emission dominates the optical line spectrum of the three nebulae and probably plays a significant role in their dynamical evolution. The central H II region spectrum for GL 6189 is isolated and T(stellar) of 36,000-40,000 and log (N/O) = 0.0 +/- 0.2 are derived. GL 618 and M2-56 have shock velocities of 40-60 km/s; that of M1-92 is 60-100 km/s. Log (N/O) is derived for different regions of the three nebulae. There is an apparent correlation of outflow velocity with chemical abundance.

BV PHOTOMETRY OF RR LYRAE VARIABLES IN THE GLOBULAR CLUSTER M92

We present ground-based and Hubble Space Telescope narrowband images of M1-92. M1-92 is a bipolar proto-planetary nebula currently undergoing the transition from asymptotic giant branch star to planetary nebula. Previous spectropolarimetry of this object revealed that the line emission produced in the bipolar lobes is dominated by shock emission. The goal of the current observations is to determine the morphology of the shock-heated gas in order to better understand the origin of this emission. The ground-based images suggest that the shock emission is concentrated in diffuse knots in the bipolar lobes. Our high spatial resolution Wide Field Planetary Camera 2 images demonstrate that the shock emission is the result of a collimated outflow that originates near the central star and impacts the bipolar lobes. The outflow axis appears to be inclined with respect to the bipolar axis of M1-92, suggesting the presence of a precessing or wobbling jet. We discuss these findings in the context of the current models that seek to explain the planetary nebula formation process.

Fiber-optic manipulation of urinary stone phantoms using holmium:YAG and thulium fiber lasers

We present BV CCD photometry for 7 RR Lyrae variables in the globular cluster M92 (NGC 6341). New ephemerides are computed, and V, B, and B-V light curves are given. A color-magnitude diagram based on 2 V and 2 B short exposures is given, reaching from above the horizontal branch to below the main sequence turn-off. A comparison with results from other workers shows we agree with the photometry of Cathey (1974) and Stetson and Harris (1988). We study also the timing of the secondary bumps in the light curves of 5 of the RRab variables, finding it to be consistent with prediction from the echo model. Expansion radii derived from radial velocities are not consistent with the photospheric infall model of the secondary bump.

The distant globular cluster NGC 6229 and its relation to other outer halo clusters

Abstract. Fiber-optic attraction of urinary stones during laser lithotripsy may be exploited to manipulate stone fragments inside the urinary tract without mechanical grasping tools, saving the urologist time and space in the ureteroscope working channel. We compare thulium fiber laser (TFL) high pulse rate/low pulse energy operation to conventional holmium:YAG low pulse rate/high pulse energy operation for fiber-optic suctioning of plaster-of-paris (PoP) stone phantoms. A TFL (wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10 to 350 Hz) and a holmium laser (wavelength of 2120 nm, pulse energy of 35 to 360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz) were tested using 270-μm-core optical fibers. A peak drag speed of ∼2.5  mm/s was measured for both TFL (35 mJ and 150 to 250 Hz) and holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber-optic suctioning of urinary stone phantoms is feasible. TFL operation at high pulse rates/low pulse energies is preferable to holmium operation at low pulse rates/high pulse energies for rapid and smooth stone pulling. With further development, this novel technique may be useful for manipulating stone fragments in the urinary tract.

Using LED sources to selectively heat blood for enhanced mid-IR imaging of vascular structures

CCD-based BV photometry is presented for over 1100 stars in and around the globular cluster NGC 6229. For the first time, the clusters entire giant branch and its horizontal branch are delineated, from which metallicity (Fe/H about -1.4) and distance estimates ensue. NGC 6229 is found to have a relatively blue horizontal branch for its intermediate metallicity, which is unusual for an outer halo cluster. Its low R value hints that the blue color of its horizontal branch is due to a lower than average helium abundance. Three possible new variable stars are identified, including one RR Lyrae and two long-period variables. Among the 13 globular clusters lying more than 24 kpc from the Galactic center, the unusually red horizontal branch phenomenon is common only among the outermost clusters. An average R value for these clusters suggests the effect is not caused by an overabundance of helium. The Oosterhoff dichotomy apparently persists into the outer halo, although the number of clusters with RR Lyrae variables is small. 55 refs.