Aims. HD 42527A is one of the most studied Herbig Ae/Be stars with a transitional disk, as it has the largest imaged gap in any protoplanetary disk: the gas is cleared from 30 to 90 AU. The HD 142527 system is also unique in that it has a stellar companion with a small mass compared to the mass of the primary star. This factor of ≈20 in mass ratio between the two objects makes this binary system different from any other YSO. The HD 142527 system could therefore provide a valuable test bed for understanding the impact of a lower mass companion on disk structure. This low-mass stellar object may be responsible for both the gap and dust trapping observed by ALMA at longer distances. Methods. We observed this system with the NACO and GPI instruments using the aperture masking technique. Aperture masking is ideal for providing high dynamic range even at very small angular separations. We present the spectral energy distribution (SED) for HD 142527A and B. Brightness of the companion is now known from the R band up to the M band. We also followed the orbital motion of HD 142527B over a period of more than two years. Results. The SED of the companion is compatible with a T = 3000 ± 100 K object in addition to a 1700 K blackbody environment (likely a circum-secondary disk). From evolution models, we find that it is compatible with an object of mass 0.13 ± 0.03 M , radius 0.90 ± 0.15 R , and age 1.0 +1.0 −0.75 Myr. This age is significantly younger than the age previously estimated for HD 142527A. Computations to constrain the orbital parameters found a semimajor axis of 140 +120 −70 mas, an eccentricity of 0.5 ± 0.2, an inclination of 125 ± 15 degrees, and a position angle of the right ascending node of −5 ± 40 degrees. Inclination and position angle of the ascending node are in agreement with an orbit coplanar with the inner disk, not coplanar with the outer disk. Despite its high eccentricity, it is unlikely that HD 142527B is responsible for truncating the inner edge of the outer disk.

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The Sagittarius dwarf galaxy (SDG) is visible in the background field of the globular cluster M55. We present a deep VI color-magnitude diagram (CMD) of M55, which shows a prominent sequence of stars some 3.5 mag below the cluster main sequence. Through a comparison with a similar CMD for the globular cluster M4, we show that the M55 background field is not the Galactic bulge or spheroid. The SDG main sequence is almost as blue as that of M55 and thus, if it is metal rich, it must be younger than M55, a typical old Galactic globular cluster. The results from isochrone fitting indicate that the age of the SDG is 10 -14 Gyr, similar to the ages inferred for the two associated globular clusters Ter 7 and Arp 2.

We describe the design, construction, and operation of the Carnegie Observatories Spectroscopic Multislit and Imaging Camera (COSMIC) for the prime focus of the Hale 5 m telescope at Palomar Observatory. COSMIC is a reimaging grism spectrograph with a 13.65 arcmin square field of view, which can also be used as a direct imaging camera with a 9.75 arcmin square field of view. The wavelength coverage extends from 350 nm to almost 1 mm; the detector is a thinned, back-illuminated SITe CCD with high quantum 2048 # 2048 efficiency and excellent cosmetics. Multislit aperture masks are produced photographically, with spectra of up to ∼50 objects fitted on a single row of a slit mask. The instrument exhibits very little flexure and uses an active thermal control to maintain focus over a wide range of ambient temperature. In direct mode COSMIC is typically used with Kron-Cousins, Gunn, and narrow bandpass filters. The instrument achieves throughputs of greater than 50% for direct imaging and, in spectroscopic mode, a peak efficiency at 5500 A ˚of slightly better than 24% of light falling on the 5 m mirror. COSMIC is optimized for faint-object imaging, down to Gunn mag, and r ϭ 26 multiobject spectroscopy, down to mag, with typically 30 objects per spectroscopic exposure. r ϭ 23

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