We present the discovery of KELT-21b, a hot Jupiter transiting the V=10.5 A8V star HD 332124. The planet has an orbital period of P=3.6127647±0.0000033 days and a radius of 1.586 0.040 0.039 -+ R J . We set an upper limit on the 1 planetary mass of M 3.91 P < M J at 3s confidence. We confirmed the planetary nature of the transiting companion using this mass limit and Doppler tomographic observations to verify that the companion transits HD 332124. These data also demonstrate that the planetary orbit is well-aligned with the stellar spin, with a sky-projected spinorbit misalignment of 5.6 1.91.7 . High-resolution imaging observations revealed the presence of a pair of stellar companions to KELT-21, located at a separation of 1 2 and with a combined contrast of K 6.39 0.06 S D =  with respect to the primary. Although these companions are most likely physically associated with KELT-21, we cannot confirm this with our current data. If associated, the candidate companions KELT-21 B and C would each have masses of ∼0.12 M ☉ , a projected mutual separation of ∼20 au, and a projected separation of ∼500 au from KELT-21. KELT-21b may be one of only a handful of known transiting planets in hierarchical triple stellar systems.

We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by SOFIA with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 Aug 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hours. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies.

A map of surface molecular water was derived from long slit spectroscopy of the south polar region of the Moon using the Faint Object infraRed CAmera for the SOFIA Telescope spectrometer on the Stratospheric Observatory for Infrared Astronomy. Mean water abundances detected are about 250 μg/g over that of a mare reference surface at Mare Fecunditatis. Water abundances are locally anticorrelated with temperature. The distribution of water is consistent with derivation of water from pre‐existing hydroxyl subsequently trapped in impact glass, provided hydroxyl increases with latitude as some models and measurements suggest. The detected water cannot be in equilibrium with the exosphere because insufficient water is present in the exosphere to maintain the surface abundance. The data are consistent with a high latitude water‐bearing mineral host that may be a precursor to recently detected high latitude hematite.

We report on the analysis of 34 years of photometric observations of the pulsating helium atmosphere white dwarf GD358. The complete data set includes archival data from 1982-2006, and 1195.2 hours of new observations from [2007][2008][2009][2010][2011][2012][2013][2014][2015][2016]. From this data set, we extract 15 frequencies representing g-mode pulsation modes, adding 4 modes to the 11 modes known previously. We present evidence that these 15 modes are ℓ = 1 modes, 13 of which belong to a consecutive sequence in radial overtone k. We perform a detailed asteroseismic analysis using models that include parameterized, complex carbon and oxygen core composition profiles to fit the periods. Recent spectroscopic analyses place GD358 near the red edge of the DBV instability strip, at 24,000 ± 500 K and a log g of 7.8 ± 0.08 dex.The surface gravity translates to a mass range of 0.455 to 0.540 M ⊙ . Our best fit model has a temperature of 23,650 K and a mass of 0.5706 M ⊙ . That is slightly more massive than suggested by most the recent spectroscopy. We find a pure helium layer mass of 10 −5.50 , consistent with the result of previous studies and the outward diffusion of helium over time. Subject headings: Stars: oscillations -Stars: variables: general -white dwarfs spectroscopic temperature (T eff = 24000 ± 500 K) and log g = 7.8 places GD358 near the red edge of the instability strip. GD358's pulsation spectrum contains a series of independent radial overtones, and many have complex frequency structure. For one epoch of data taken during the Whole Earth Telescope (WET) run XCOV25, models involving magnetic fields and oblique rotation are proposed to explain such structure (Montgomery et al. 2010). Since the XCOV25 WET run reported in Provencal et al. (2009), we have maintained an active observing program of this complex star. These new observations have successfully identified additional periods in GD358's pulsation spectrum, bringing the total known independent radial overtones to 15. Thirteen of these modes belong to a consecutive ℓ = 1 sequence, the longest sequence observed in a DBV. Paradoxically, among the DBVs with enough detected periods to be fitted asteroseismically, GD358 is the only one that has not been analyzed using the complex C/O profiles adapted and parameterized from stellar evolution calculations (e.g. Salaris et al. (1997); Althaus et al. (2005)). The most recent fits of GD358 (Metcalfe et al. 2003b) wereperformed using 11 observed modes and simple models where the oxygen abundance drops linearly from its central value to zero. This study was plagued by a symmetric asteroseismic signature from the core and the envelopes in the models and was subsequently unable to derive a unique fit to the period spectrum. We present here a new detailed asteroseismic analysis employing more sophisticated interior chemical profiles.With these profiles, we are able to remove the degeneracy in the best fit parameters and better constrain the asteroseismic fits.The present analysis also allows us to place GD358 in...