We present high spatial resolution images that demonstrate WASP-12b and HAT-P-8b orbit the primary star of hierarchical triple star systems. In each case, two distant companions with colors and brightness consistent with M dwarfs co-orbit the hot Jupiter planet host as well as one another. Our adaptive optics images spatially resolve the secondary around WASP-12, previously identified by Bergfors et al. (2011) andCrossfield et al. (2012), into two distinct sources separated by 84.3 ± 0.6 mas (21 ± 3 AU). We find that the secondary to HAT-P-8, also identified by Bergfors et al. (2011), is in fact composed of two stars separated by 65.3 ± 0.5 mas (15 ± 1 AU). Our follow-up observations demonstrate physical association through common proper-motion. HAT-P-8 C has a particularly low mass, which we estimate to be 0.18 ± 0.02 M ⊙ using photometry. Due to their hierarchy, WASP-12 BC and HAT-P-8 BC will enable the first dynamical mass determination for hot Jupiter stellar companions. These previously well-studied planet hosts now represent higher-order multi-star systems with potentially complex dynamics, underscoring the importance of diffraction-limited imaging and providing additional context for understanding the migrant population of transiting hot Jupiters.

Very high energy gamma‐ray flares from the Crab nebula detected by the AGILE and Fermi satellites challenge our understanding of the pulsar wind nebulae. The short duration of the flares, only a few days, is particularly puzzling since it is much shorter than the dynamical time‐scale of the nebula. In this work we investigate analytically and via numerical simulations the electromagnetic signatures expected from the large‐amplitude low‐frequency magnetosonic waves generated within the Crab nebula which induce the corrugation perturbations of the termination shock. As a result, the oblique termination shock produces a time‐dependent, mildly relativistic post‐shock flow. Using the relativistic magnetohydrodynamic version of the riemann code, we simulate the interaction of the termination shock with downstream perturbations. We demonstrate that mild Doppler boosting of the synchrotron emission in the post‐shock flow can produce bright, short time‐scale flares.

HD 19467 B is presently the only directly imaged T dwarf companion known to induce a measurable Doppler acceleration around a solar-type star. We present spectroscopy measurements of this important benchmark object taken with the Project 1640 integral field unit at Palomar Observatory. Our high-contrast R ≈ 30 observations obtained simultaneously across the JH bands confirm the cold nature of the companion as reported from the discovery article and determine its spectral type for the first time. Fitting the measured spectral energy distribution to SpeX/ IRTF T dwarf standards and synthetic spectra from BT-Settl atmospheric models, we find that HD 19467 B is a T5.5 ± 1 dwarf with effective temperature T eff = 978 +20 −43 K. Our observations reveal significant methane absorption affirming its substellar nature. HD 19467 B shows promise to become the first T dwarf that simultaneously reveals its mass, age, and metallicity independent from the spectrum of light that it emits.

We present new observations of the faint "Sirius-like" companion discovered to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared wavelengths using NIRC2 at Keck have resulted in a non-detection. Our new L'-band observations taken with the Large Binocular Telescope and LMIRCam recover the companion (∆L = 10.15 ± 0.15 mag, ρ = 0.675" ± 0.016") with a high signal-to-noise ratio (10 σ). This measurement represents the deepest L' high-contrast imaging detection at sub-arcsecond separations to date, including extrasolar planets. We confirm that HD 114174 B has near-infrared colors consistent with the interpretation of a cool white dwarf (J − L ′ = 0.76 ± 0.19 mag, K − L ′ = 0.64 ± 0.20). New model fits to the object's spectral energy distribution indicate a temperature T eff = 4260 ± 360 K, surface gravity log g = 7.94 ± 0.03, a cooling age t c ≈ 7.8 Gyr, and mass M = 0.54 ± 0.01 M ⊙ . We find that the cooling age given by theoretical atmospheric models do not agree with the age of HD 114174 A derived from both isochronological and gyrochronological analyses. We speculate on possible scenarios to explain the apparent age discrepancy between the primary and secondary. HD 114174 B is a nearby benchmark white dwarf that will ultimately enable a dynamical mass estimate through continued Doppler and astrometric monitoring. Efforts to characterize its physical properties in detail will test theoretical atmospheric models and improve our understanding of white dwarf evolution, cooling, and progenitor masses.

We present the first near infra-red spectrum of the faint white dwarf companion HD 114174 B, obtained with Project 1640. Our spectrum, covering the Y , J and H bands, combined with previous TRENDS photometry measurements, allows us to place further constraints on this companion. We suggest two possible scenarios; either this object is an old, low mass, cool H atmosphere white dwarf with T eff ∼ 3800 K or a high mass white dwarf with T eff > 6000 K, potentially with an associated cool (T eff ∼ 700 K) brown dwarf or debris disk resulting in an infra-red excess in the L band. We also provide an additional astrometry point for 2014 June 12 and use the modelled companion mass combined with the RV and direct imaging data to place constraints on the orbital parameters for this companion.