The typical extinction curve for the Small Magellanic Cloud (SMC), in contrast to that for the Galaxy, has no bump at 2175Å and has a steeper rise into the far ultraviolet. For the Galaxy the interpretation of the extinction and, therefore, the dust content of the interstellar medium has been greatly assisted by measurements of the wavelength dependence of the polarization. To the present no such measurements existed for the SMC.Therefore, to further elucidate the dust properties in the SMC we have for the first time measured linear polarization in five colors in the optical region of the spectrum Each star has been observed, sometimes more than once, in each of the two wavelength ranges. The reductions were made using the RDAF and IUEIDL packages at the University of

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We present results derived from the first multi-chord stellar occultations by the transneptunian object (50000) Quaoar, observed on 2011 May 4 and 2012 February 17, and from a single-chord occultation observed on 2012 October 15. If the timing of the five chords obtained in 2011 were correct, then Quaoar would possess topographic features (crater or mountain) that would be too large for a body of this mass. An alternative model consists in applying time shifts to some chords to account for possible timing errors. Satisfactory elliptical fits to the chords are then possible, yielding an equivalent radius R equiv = 555±2.5 km and geometric visual albedo p V = 0.109±0.007. Assuming that Quaoar is a Maclaurin spheroid with an indeterminate polar aspect angle, we derive a true oblateness of = 0.087 +0.0268 −0.0175 , an equatorial radius of 569 +24 −17 km, and a density of 1.99 ± 0.46 g cm −3 . The orientation of our preferred solution in the plane of the sky implies that Quaoar's satellite Weywot cannot have an equatorial orbit. Finally, we detect no global atmosphere around Quaoar, considering a pressure upper limit of about 20 nbar for a pure methane atmosphere.

Aims. The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, our goal was to reconstruct the star-formation history of the CMa R1 region, including the previously unknown older, fainter low-mass stellar population, using X-rays. Methods. We analyzed images obtained with the ROSAT satellite, covering ∼5 sq. deg. Complementary VRI photometry was performed with the Gemini South telescope. Colour-magnitude and colour-colour diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources.Results. The ROSAT images show two distinct clusters. One is associated with the known optical clusters near Z CMa, to which ∼40 members are added. The other, which we name the "GU CMa" cluster, is new, and contains ∼60 members. The ROSAT sources are young stars with masses down to M ∼ 0.5 M , and ages up to 10 Myr. The mass functions of the two clusters are similar, but the GU CMa cluster is older than the cluster around Z CMa by at least a few Myr. Also, the GU CMa cluster is away from any molecular cloud, implying that star formation must have ceased; on the contrary (as already known), star formation is very active in the Z CMa region.