Masses and orbital inclinations of planets in the PSR B1257+12 system

We present measurements of the true masses and orbital inclinations of the two Earth-mass planets in the PSR B1257+12 system, based on the analysis of their mutual gravitational perturbations detectable as microsecond variations of the arrival times of radio pulses from the pulsar. The 6.2-millisecond pulsar, PSR B1257+12, has been regularly timed with the Arecibo telescope since late 1990. Assuming the standard pulsar mass of 1.4 M_Sun, the derived masses of planets B and C are 4.3 +/- 0.2 M_Earth and 3.9 +/- 0.2 M_Earth, respectively. The corresponding orbital inclinations of 53.4 and 47.3 deg (or 127 and 133 deg) imply that the two orbits are almost coplanar. This result, together with the known near 3:2 resonance between the orbits of the two planets, strongly supports the hypothesis of a disk origin of the PSR B1257+12 planetary system. The system's long-term stability is guaranteed by the low, Earth-like masses of planets B and C.Comment: 2 figures, to appear in ApJ

A Search for Cold Dust around Neutron Stars

We present observations of nine radio pulsars using the Heinrich-Hertz-Telescope at \lambda 0.87mm and the IRAM 30-m telescope at \lambda 1.2mm in search for a cold dust around these sources. Five of the program pulsars have been observed for the first time at the mm-wavelengths. The results are consistent with the absence of circumpulsar disks that would be massive enough ($\ge 0.01 M_{\odot}$) to support planet formation according to the scenarios envisioned for solar-type stars, but they do not exclude lower mass ($\le 10-100 M_{\oplus}$) disks for a wide range of grain sizes. These conclusions confirm the previously published results and, together with the current lack of further detections of pulsar planets, they suggest that planet formation around neutron stars is not a common phenomenon.Comment: 5 pages, 1 figure, accepted for publication in A&

Radial velocity measurements of a sample of K-giants with the Hobby-Eberly telescope

We present motivation and initial results of a large RV survey of K giants aimed at a detection of low-mass companions. The survey, performed with the Hobby-Eberly Telescope, utilizes high resolution (60,000) spectra for high precision radial velocity measurements. The primary goal of the survey is the selection of astrometrically stable reference stars for the Extrasolar Planet Interferometric Survey key project to be carried out with the Space Interferometry Mission