Large Binocular Telescope Interferometer Adaptive Optics: On-sky performance and lessons learned

The Large Binocular Telescope Interferometer is a high contrast imager and interferometer that sits at the combined bent Gregorian focus of the LBTs dual 8.4~m apertures. The interferometric science drivers dictate 0.1 resolution with $10^3-10^4$ contrast at $10~mu m$, while the $4~mu m$ imaging science drivers require even greater contrasts, but at scales $>$0.2. In imaging mode, LBTIs Adaptive Optics system is already delivering $4~mu m$ contrast of $10^4-10^5$ at $0.3-0.75$ in good conditions. Even in poor seeing, it can deliver up to 90% Strehl Ratio at this wavelength. However, the performance could be further improved by mitigating Non-Common Path Aberrations. Any NCPA remedy must be feasible using only the current hardware: the science camera, the wavefront sensor, and the adaptive secondary mirror. In preliminary testing, we have implemented an ``eye doctor grid search approach for astigmatism and trefoil, achieving 5% improvement in Strehl Ratio at $4~mu m$, with future plans to test at shorter wavelengths and with more modes. We find evidence of NCPA variability on short timescales and discuss possible upgrades to ameliorate time-variable effects

Does the Debris Disk around HD 32297 Contain Cometary Grains?

We present an adaptive optics imaging detection of the HD 32297 debris disk at L (3.8 microns) obtained with the LBTI/LMIRcam infrared instrument at the LBT. The disk is detected at signal-to-noise per resolution element ~ 3-7.5 from ~ 0.3-1.1 (30-120 AU). The disk at L is bowed, as was seen at shorter wavelengths. This likely indicates the disk is not perfectly edge-on and contains highly forward scattering grains. Interior to ~ 50 AU, the surface brightness at L rises sharply on both sides of the disk, which was also previously seen at Ks band. This evidence together points to the disk containing a second inner component located at $lesssim$ 50 AU. Comparing the color of the outer (50 $< r$/AU $< 120$) portion of the disk at L with archival HST/NICMOS images of the disk at 1-2 microns allows us to test the recently proposed cometary grains model of Donaldson et al. 2013. We find that the model fails to match the disks surface brightness and spectrum simultaneously (reduced chi-square = 17.9). When we modify the density distribution of the model disk, we obtain a better overall fit (reduced chi-square = 2.9). The best fit to all of the data is a pure water ice model (reduced chi-square = 1.06), but additional resolved imaging at 3.1 microns is necessary to constrain how much (if any) water ice exists in the disk, which can then help refine the originally proposed cometary grains model.

Directly Imaged L-T Transition Exoplanets in the Mid-Infrared

Gas-giant planets emit a large fraction of their light in the mid-infrared ($gtrsim$3$mu$m), where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. Of particular importance are the L and M-band atmospheric windows (3-5$mu$m), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT AO images of the HR 8799 planetary system in six narrow-band filters from 3-4$mu$m, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3$mu$m band. These systems encompass the five known exoplanets with luminosities consistent with L$rightarrow$T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature (spanned by the narrowband filters and encompassed by the broader 3.3$mu$m filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the objects appearance. For the HR 8799 planets, we present new models that suggest the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.

A Thermal Infrared Imaging Study of Very Low-Mass, Wide Separation Brown Dwarf Companions to Upper Scorpius Stars: Constraining Circumstellar Environments

We present a 3-5um LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low-masses/mass ratios (M_BD < 25M_Jup; M_BD / M_star ~ 1-2%), and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4um and 24um photometry to constrain the properties of the BDs and identify evidence for circumprimary/secondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24um excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4um excess, nor does its primary; however, the system as a whole has a modest 24um excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4um colors of HIP 78530B match a spectral type of M3+-2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5M_Jup beyond 175AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering.

The Gray Needle: Large Grains in the HD 15115 Debris Disk from LBT/PISCES/Ks and LBTI/LMIRcam/L Adaptive Optics Imaging

We present diffraction-limited ks band and lprime adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At ks band the disk is detected at signal-to-noise per resolution element (SNRE) about 3-8 from about 1-2fasec 5 (45-113 AU) on the western side, and from about 1.2-2fasec 1 (63-90 AU) on the east. At lprime the disk is detected at SNRE about 2.5 from about 1-1fasec 45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 microns . At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at ks band, but not at lprime . The surface brightness at ks band declines inside 1asec (about 45 AU), which may be indicative of a gap in the disk near 1asec. The ks - lprime disk color, after removal of the stellar color, is mostly grey for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 microns -sized grains on the east side and 1-10 microns dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.

First Light LBT AO Images of HR 8799 bcde at 1.65 and 3.3 Microns: New Discrepancies between Young Planets and Old Brown Dwarfs

As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H-band and 3.3 microns with the new LBT adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3$ micron photometry of the innermost planet (for the first time) and put strong upper-limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 microns compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 microns due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres, but find that removing CH4 to fit the 3.3 micron photometry increases the predicted L (3.8 microns) flux enough that it is inconsistent with observations. In an effort to fit the SED of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity. In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown-dwarfs. Our mixed cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.

Direct Imaging Constraints on the Putative Exoplanet 14 Her c

We present results of deep direct imaging of the radial velocity (RV) planet-host star 14 Her (=GJ 614, HD 145675), obtained in the lprime ~band with the Clio-2 camera and the MMT adaptive optics system. This star has one confirmed planet and an unconfirmed outer companion, suggested by residuals in the RV data. The orbital parameters of the unconfirmed object are not well constrained since many mass/semimajor axis configurations can fit the available data. The star has been directly imaged several times, but none of the campaigns has ruled out sub-stellar companions. With about 2.5 hrs of integration, we rule out at 5$sigma$ confidence $gtrsim$ 18 mj ~companions beyond about 25 AU, based on the cite{baraffe} COND mass-luminosity models. Combining our detection limits with fits to the RV data and analytic dynamical analysis, we constrain the orbital parameters of 14 Her c to be: $3 lesssim m/$mj ~$lesssim 42$, $7 lesssim a/$AU $lesssim 25$, and $e lesssim 0.5$. A wealth of information can be obtained from RV/direct imaging overlap, especially with deep imaging as this work shows. The collaboration between RV and direct imaging will become more important in the coming years as the phase space probed by each technique converges. Future studies involving RV/imaging overlap should be sure to consider the effects of a potential planets projected separation, as quoting limits assuming face-on orientation will be misleading.

Constraints on Long-Period Planets from an L and M band Survey of Nearby Sun-Like Stars: Observations

We present the observational results of an L and M band Adaptive Optics (AO) imaging survey of 54 nearby, sunlike stars for extrasolar planets, carried out using the Clio camera on the MMT. We have concentrated more strongly than all other planet imaging surveys to date on very nearby F, G, and K stars, prioritizing stellar proximity higher than youth. Ours is also the first survey to include extensive observations in the M band, which supplement the primary L observations. Models predict much better planet/star flux ratios at the L and M bands than at more commonly used shorter wavelengths (i.e. the H band). We have carried out extensive blind simulations with fake planets inserted into the raw data to verify our sensitivity, and to establish a definitive relationship between source significance in $sigma$ and survey completeness. We find 97% confident-detection completeness for 10$sigma$ sources, but only 46% for 7$sigma$ sources -- raising concerns about the standard procedure of assuming high completeness at 5$sigma$, and demonstrating that blind sensitivity tests to establish the significance-completeness relation are an important analysis step for all planet-imaging surveys. We discovered a previously unknown, approximately 0.15 solar-mass stellar companion to the F9 star GJ 3876, at a projected separation of about 80 AU. Twelve additional candidate faint companions are detected around other stars. Of these, eleven are confirmed to be background stars, and one is a previously known brown dwarf. We obtained sensitivity to planetary-mass objects around almost all of our target stars, with sensitivity to objects below 3 Jupiter masses in the best cases. Constraints on planet populations based on this null result are presented in our Modeling Results paper.

Constraints on Long-Period Planets from an L and M band Survey of Nearby Sun-Like Stars: Modeling Results

We have carried out an L and M band Adaptive Optics (AO) extrasolar planet imaging survey of 54 nearby, sunlike stars using the Clio camera at the MMT. Our survey concentrates more strongly than all others to date on very nearby F, G, and K stars, in that we have prioritized proximity higher than youth. Our survey is also the first to include extensive observations in the M band, which supplemented the primary L observations. These longer wavelength bands are most useful for very nearby systems in which low temperature planets with red IR colors (i.e. H - L, H - M) could be detected. The survey detected no planets, but set interesting limits on planets and brown dwarfs in the star systems we investigated. We have interpreted our null result by means of extensive Monte Carlo simulations, and constrained the distributions of extrasolar planets in mass $M$ and semimajor axis $a$. If planets are distributed according to a power law with $dN propto M^{alpha} a^{beta} dM da$, normalized to be consistent with radial velocity statistics, we find that a distribution with $alpha = -1.1$ and $beta = -0.46$, truncated at 110 AU, is ruled out at the 90% confidence level. These particular values of $alpha$ and $beta$ are significant because they represent the most planet-rich case consistent with current statistics from radial velocity observations. With 90% confidence no more than 8.1% of stars like those in our survey have systems with three widely spaced, massive planets like the A-star HR 8799. Our observations show that giant planets in long-period orbits around sun-like stars are rare, confirming the results of shorter-wavelength surveys, and increasing the robustness of the conclusion.