We present results derived from four stellar occultations by the plutino object (208996) 2003~AZ\(_{84}\), detected at January 8, 2011 (single-chord event), February 3, 2012 (multi-chord), December ...2, 2013 (single-chord) and November 15, 2014 (multi-chord). Our observations rule out an oblate spheroid solution for 2003~AZ\(_{84}\)'s shape. Instead, assuming hydrostatic equilibrium, we find that a Jacobi triaxial solution with semi axes \((470 \pm 20) \times (383 \pm 10) \times (245 \pm 8)\)~km % axis ratios \(b/a= 0.82 \pm 0.05\) and \(c/a= 0.52 \pm 0.02\), can better account for all our occultation observations. Combining these dimensions with the rotation period of the body (6.75~h) and the amplitude of its rotation light curve, we derive a density \(\rho=0.87 \pm 0.01\)~g~cm\(^{-3}\) a geometric albedo \(p_V= 0.097 \pm 0.009\). A grazing chord observed during the 2014 occultation reveals a topographic feature along 2003~AZ\(_{84}\)'s limb, that can be interpreted as an abrupt chasm of width \(\sim 23\)~km and depth \(> 8\)~km or a smooth depression of width \(\sim 80\)~km and depth \(\sim 13\)~km (or an intermediate feature between those two extremes).
We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance ...started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.
We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance ...started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1%-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and " Angkor," which persist on timescales from several days to weeks. Our main results so far are as follows: (i) there are no apparent changes of the stellar spectrum or polarization during the dips and (ii) the multiband photometry of the dips shows differential reddening favoring non-gray extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale << 1 mu m, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process.
We present the discovery from the TESS mission of two giant planets transiting M dwarf stars: TOI 4201 b and TOI 5344 b. We also provide precise radial velocity measurements and updated system ...parameters for three other M dwarfs with transiting giant planets: TOI 519, TOI 3629 and TOI 3714. We measure planetary masses of 0.525 +- 0.064 M_J, 0.243 +- 0.020 M_J, 0.689 +- 0.030 M_J, 2.57 +- 0.15 M_J, and 0.412 +- 0.040 M_J for TOI 519 b, TOI 3629 b, TOI 3714 b, TOI 4201 b, and TOI 5344 b, respectively. The corresponding stellar masses are 0.372 +- 0.018 M_s, 0.635 +- 0.032 M_s, 0.522 +- 0.028 M_s, 0.625 +- 0.033 M_s and 0.612 +- 0.034 M_s. All five hosts have super-solar metallicities, providing further support for recent findings that, like for solar-type stars, close-in giant planets are preferentially found around metal-rich M dwarf host stars. Finally, we describe a procedure for accounting for systematic errors in stellar evolution models when those models are included directly in fitting a transiting planet system.
