47 research outputs found
The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager
Using the Gemini Planet Imager, we have resolved the circumstellar debris disk around HD 111520 at a projected range of ~30–100 AU in both total and polarized H-band intensity. The disk is seen edge-on at a position angle of 165° along the spine of emission. A slight inclination and asymmetric warp are covariant and alter the interpretation of the observed disk emission. We employ three point-spread function subtraction methods to reduce the stellar glare and instrumental artifacts to confirm that there is a roughly 2:1 brightness asymmetry between the NW and SE extension. This specific feature makes HD 111520 the most extreme example of asymmetric debris disks observed in scattered light among similar highly inclined systems, such as HD 15115 and HD 106906. We further identify a tentative localized brightness enhancement and scale height enhancement associated with the disk at ~40 AU away from the star on the SE extension. We also find that the fractional polarization rises from 10% to 40% from 0.”5 to 0.”8 from the star. The combination of large brightness asymmetry and symmetric polarization fraction leads us to believe that an azimuthal dust density variation is causing the observed asymmetry
The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager
Using the Gemini Planet Imager, we have resolved the circumstellar debris disk around HD 111520 at a projected range of ~30–100 AU in both total and polarized H-band intensity. The disk is seen edge-on at a position angle of 165° along the spine of emission. A slight inclination and asymmetric warp are covariant and alter the interpretation of the observed disk emission. We employ three point-spread function subtraction methods to reduce the stellar glare and instrumental artifacts to confirm that there is a roughly 2:1 brightness asymmetry between the NW and SE extension. This specific feature makes HD 111520 the most extreme example of asymmetric debris disks observed in scattered light among similar highly inclined systems, such as HD 15115 and HD 106906. We further identify a tentative localized brightness enhancement and scale height enhancement associated with the disk at ~40 AU away from the star on the SE extension. We also find that the fractional polarization rises from 10% to 40% from 0.”5 to 0.”8 from the star. The combination of large brightness asymmetry and symmetric polarization fraction leads us to believe that an azimuthal dust density variation is causing the observed asymmetry
Gemini Planet Imager Observational Calibrations III: Empirical Measurement Methods and Applications of High-Resolution Microlens PSFs
The newly commissioned Gemini Planet Imager (GPI) combines extreme adaptive
optics, an advanced coronagraph, precision wavefront control and a
lenslet-based integral field spectrograph (IFS) to measure the spectra of young
extrasolar giant planets between 0.9-2.5 um. Each GPI detector image, when in
spectral model, consists of ~37,000 microspectra which are under or critically
sampled in the spatial direction. This paper demonstrates how to obtain
high-resolution microlens PSFs and discusses their use in enhancing the
wavelength calibration, flexure compensation and spectral extraction. This
method is generally applicable to any lenslet-based integral field spectrograph
including proposed future instrument concepts for space missions.Comment: 10 pages, 6 figures. Proceedings of the SPIE, 9147-282 v2: reference
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Disk-Loss and Disk Renewal Phases in Classical Be Stars II. Detailed Analysis of Spectropolarimetric Data
In Wisniewski et al. 2010, paper I, we analyzed 15 years of spectroscopic and
spectropolarimetric data from the Ritter and Pine Bluff Observatories of 2 Be
stars, 60 Cygni and {\pi} Aquarii, when a transition from Be to B star
occurred. Here we anaylize the intrinsic polarization, where we observe
loop-like structures caused by the rise and fall of the polarization Balmer
Jump and continuum V-band polarization being mismatched temporally with
polarimetric outbursts. We also see polarization angle deviations from the
mean, reported in paper I, which may be indicative of warps in the disk, blobs
injected at an inclined orbit, or spiral density waves. We show our ongoing
efforts to model time dependent behavior of the disk to constrain the
phenomena, using 3D Monte Carlo radiative transfer codes.Comment: 2 pages, 6 figures, IAU Symposium 27
Bringing "The Moth" to Light: A Planet-Sculpting Scenario for the HD 61005 Debris Disk
The HD 61005 debris disk ("The Moth") stands out from the growing collection
of spatially resolved circumstellar disks by virtue of its unusual swept-back
morphology, brightness asymmetries, and dust ring offset. Despite several
suggestions for the physical mechanisms creating these features, no definitive
answer has been found. In this work, we demonstrate the plausibility of a
scenario in which the disk material is shaped dynamically by an eccentric,
inclined planet. We present new Keck NIRC2 scattered-light angular differential
imaging of the disk at 1.2-2.3 microns that further constrains its outer
morphology (projected separations of 27-135 AU). We also present complementary
Gemini Planet Imager 1.6 micron total intensity and polarized light detections
that probe down to projected separations less than 10 AU. To test our
planet-sculpting hypothesis, we employed secular perturbation theory to
construct parent body and dust distributions that informed scattered-light
models. We found that this method produced models with morphological and
photometric features similar to those seen in the data, supporting the premise
of a planet-perturbed disk. Briefly, our results indicate a disk parent body
population with a semimajor axis of 40-52 AU and an interior planet with an
eccentricity of at least 0.2. Many permutations of planet mass and semimajor
axis are allowed, ranging from an Earth mass at 35 AU to a Jupiter mass at 5
AU.Comment: Accepted to AJ; added Figure 5 and minor text edit
Disk Loss and Disk Renewal Phases in Classical Be Stars I: Analysis of Long-Term Spectropolarimetric Data
(Abridged) Classical Be stars occasionally transition from having a gaseous
circumstellar disk (''Be phase'') to a state in which all observational
evidence for the presence of these disks disappears (''normal B-star phase'').
We present one of the most comprehensive spectropolarimetric views to date of
such a transition for two Be stars, pi Aquarii and 60 Cygni. 60 Cyg's disk loss
episode was characterized by a monotonic decrease in emission strength over a
time-scale of 1000 days, consistent with the viscous time-scale of the disk,
assuming alpha is 0.14. pi Aqr's disk loss was episodic in nature and occurred
over a time-scale of 2440 days. An observed time lag between the behavior of
the polarization and H-alpha in both stars indicates the disk clearing
proceeded in an ''inside-out'' manner. We determine the position angle of the
intrinsic polarization to be 166.7 +/- 0.1 degrees for pi Aqr and 107.7 +/- 0.4
degrees for 60 Cyg, and model the observed polarization during the quiescent
diskless phase of each star to determine the interstellar polarization along
the line of sight. Minor outbursts observed during the quiescent phase of each
star shared similar lifetimes as those previously reported for mu Cen,
suggesting that the outbursts represent the injection and subsequent viscous
dissipation of individual blobs of material into the inner circumstellar
environments of these stars. We also observe deviations from the mean intrinsic
polarization position angle during polarization outbursts in each star,
indicating deviations from axisymmetry. We propose that these deviations might
be indicative of the injection (and subsequent circularization) of new blobs
into the inner disk, either in the plane of the bulk of the disk material or in
a slightly inclined (non-coplanar) orbit.Comment: 30 pages, 14 figures; accepted in Ap
A Chromaticity Analysis and PSF Subtraction Techniques for SCExAO/CHARIS Data
We present an analysis of instrument performance using new observations taken with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instrument and the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system. In a correlation analysis of our data sets (which use the broadband mode covering the J band through the K band in a single spectrum), we find that chromaticity in the SCExAO/CHARIS system is generally worse than temporal stability. We also develop a point-spread function (PSF) subtraction pipeline optimized for the CHARIS broadband mode, including a forward modeling-based exoplanet algorithmic throughput correction scheme. We then present contrast curves using this newly developed pipeline. An analogous subtraction of the same data sets using only the H-band slices yields the same final contrasts as the full JHK sequences; this result is consistent with our chromaticity analysis, illustrating that PSF subtraction using spectral differential imaging (SDI) in this broadband mode is generally not more effective than SDI in the individual J, H, or K bands. In the future, the data processing framework and analysis developed in this paper will be important to consider for additional SCExAO/CHARIS broadband observations and other ExAO instruments which plan to implement a similar integral field spectrograph broadband mode.Natural Sciences and Engineering Council of Canada through the Postgraduate Scholarships-Doctoral discovery grant; Technologies for Exo-Planetary Science Collaborative Research and Training Experience programs; JSPS [23340051, 26220704, 23103002]; Astrobiology Center of the National Institutes of Natural Sciences, Japan; Mt. Cuba Foundation; directors contingency fund at Subaru Telescope; MEXT of the Japanese government [23103002]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The Peculiar Debris Disk of HD 111520 as Resolved by the Gemini Planet Imager
Using the Gemini Planet Imager (GPI), we have resolved the circumstellar
debris disk around HD 111520 at a projected range of ~30-100 AU in both total
and polarized -band intensity. The disk is seen edge-on at a position angle
of ~165 along the spine of emission. A slight inclination or
asymmetric warping are covariant and alters the interpretation of the observed
disk emission. We employ 3 point spread function (PSF) subtraction methods to
reduce the stellar glare and instrumental artifacts to confirm that there is a
roughly 2:1 brightness asymmetry between the NW and SE extension. This specific
feature makes HD 111520 the most extreme examples of asymmetric debris disks
observed in scattered light among similar highly inclined systems, such as HD
15115 and HD 106906. We further identify a tentative localized brightness
enhancement and scale height enhancement associated with the disk at ~40 AU
away from the star on the SE extension. We also find that the fractional
polarization rises from 10 to 40% from 0.5" to 0.8" from the star. The
combination of large brightness asymmetry and symmetric polarization fraction
leads us to believe that an azimuthal dust density variation is causing the
observed asymmetry.Comment: 9 pages, 8 Figures, 1 table, Accepted to Ap