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Planet formation and clearing of protoplanetary disks is one of the long standing problems in disk evolution theory. The best test of clearing scenarios is observing systems that are most likely to be actively forming planets: the transitional disks with large inner dust cavities. We present the first results of our ALMA (Atacama Large Millimeter/submillimeter Array) Cycle 0 program using Band 9, imaging the Herbig Ae star Oph IRS 48 in CO 6−5 and the submillimeter continuum in the extended configuration. The resulting ~0.2″ spatial resolution completely resolves the cavity of this disk in the gas and the dust. The gas cavity of IRS 48 is half as large as the dust cavity, ruling out grain growth and photoevaporation as the primary cause of the truncation. On the other hand, the continuum emission reveals an unexpected large azimuthal asymmetry and steep edges in the dust distribution along the ring, suggestive of dust trapping. We will discuss the implications of the combined gas and dust distribution for planet formation at a very early stage. This is one of the first transition disks with spatially resolved gas inside the cavity, demonstrating the superb capabilities of the Band 9 receivers.

We investigate the coronal structure of rapidly-rotating, solar-like stars using Chandra HETGS spectra of the short-period binary ER Vul, and by comparison with X-ray observations of the Sun and other dwarf stars. ER Vul consists of two solar-like (G0 + G5) dwarfs with rotation rates ~ 40 times that of the Sun. This binary is not interacting and these stars are the fastest rotating G dwarfs suitable for high resolution X-ray spectroscopy. X-ray (1.8-40 Å) spectra were obtained on 2001 March 29-30 along with 10.5 hours of simultaneous VLA monitoring at 3.6 and 20 cm. These spectra show hot, multi-temperature coronal emission with emission lines ranging in temperature from O VII (2 MK) to Fe XXIV (30 MK). ER Vul showed only low-level variability during the X-ray observation. Unlike the behaviour of longer period active binaries, no large, long-duration flares were detected, consistent with previous X-ray observations of this binary. No evidence for eclipses is seen in either the X-ray or radio emission. The coronal emission measure distribution and elemental abundances were derived for ER Vul.