Herschel discovery of a new class of cold, faint debris discs

We present Herschel PACS 100 and 160 μm observations of the solar-type stars α Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel open time key programme (OTKP) DUNES (DUst around NEarby Stars). Our observations show small infrared excesses at 160 μm for all three stars. HD 210277 also shows a small excess at 100 μm, while the 100 μm fluxes of α Men and HD 88230 agree with the stellar photospheric predictions. We attribute these infrared excesses to a new class of cold, faint debris discs. Both α Men and HD 88230 are spatially resolved in the PACS 160 μm images, while HD 210277 is point-like at that wavelength. The projected linear sizes of the extended emission lie in the range from ~115 to ≤ 250 AU. The estimated black body temperatures from the 100 and 160 μm fluxes are ≲22 K, and the fractional luminosity of the cold dust is L_dust/L_⋆ ~ 10^-6, close to the luminosity of the solar-system’s Kuiper belt. These debris discs are the coldest and faintest discs discovered so far around mature stars, so they cannot be explained easily invoking “classical” debris disc models.

The first extrasolar planet discovered with a new-generation high-throughput Doppler instrument

We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new-generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. The planet imparts radial velocity variability to the star with a semiamplitude of 63.4 ± 2.0 m s^-1 and a period of 4.11 days. The planetary minimum mass (m sin i) is 0.488MJ ± 0.015M_J. The planet was initially detected in the spring of 2005 with the Kitt Peak National Observatory (KPNO) 0.9 m coudé feed telescope. The detection was confirmed by radial velocity observations with the ET at the KPNO 2.1 m telescope and also at the 9 m Hobby-Eberly Telescope (HET) with its High Resolution Spectrograph. This planetary discovery with a 0.9 m telescope around a V = 8.05 magnitude star was made possible by the high throughput of the instrument: 49% measured from the fiber output to the detector. The ET's interferometer-based approach is an effective method for planet detection. In addition, the ET concept is adaptable to multiple-object Doppler observations or very high precision observations with a cross-dispersed echelle spectrograph to separate stellar fringes over a broad wavelength band. In addition to spectroscopic observations of HD 102195, we obtained brightness measurements with one of the automated photometric telescopes at Fairborn Observatory. Those observations reveal that HD 102195 is a spotted variable star with an amplitude of ~0.015 mag and a 12.3 ± 0.3 day period. This is consistent with spectroscopically observed Ca II H and K emission levels and line-broadening measurements but inconsistent with rotational modulation of surface activity as the cause of the radial velocity variability. Our photometric observations rule out transits of the planetary companion.

Absolute calibration and characterization of the multiband imaging photometer for Spitzer. I. The stellar calibrator sample and the 24 μm calibration

We present the stellar calibrator sample and the conversion from instrumental to physical units for the 24 μm channel of the Multiband Imaging Photometer for Spitzer (MIPS). The primary calibrators are A stars, and the calibration factor based on those stars is 4.54 × 10^-2 MJy sr^–1 (DN/s)^–1, with a nominal uncertainty of 2%. We discuss the data reduction procedures required to attain this accuracy; without these procedures, the calibration factor obtained using the automated pipeline at the Spitzer Science Center is 1.6% ± 0.6% lower. We extend this work to predict 24 μm flux densities for a sample of 238 stars that covers a larger range of flux densities and spectral types. We present a total of 348 measurements of 141 stars at 24 μm. This sample covers a factor of ~460 in 24 μm flux density, from 8.6 mJy up to 4.0 Jy. We show that the calibration is linear over that range with respect to target flux and background level. The calibration is based on observations made using 3 s exposures; a preliminary analysis shows that the calibration factor may be 1% and 2% lower for 10 and 30 s exposures, respectively. We also demonstrate that the calibration is very stable: over the course of the mission, repeated measurements of our routine calibrator, HD 159330, show a rms scatter of only 0.4%. Finally, we show that the point-spread function (PSF) is well measured and allows us to calibrate extended sources accurately; Infrared Astronomy Satellite (IRAS) and MIPS measurements of a sample of nearby galaxies are identical within the uncertainties.