Alex Wolszczan

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 ms pulsar, PSR B1257+12, has been regularly timed with the Arecibo telescope since late 1990. Assuming the standard pulsar mass of 1.4 M_☉, the derived masses of planets B and C are 4.3 ± 0.2 and 3.9 ± 0.2 M_⊕, respectively. The corresponding orbital inclinations of 53° ± 4° and 47° ± 3° (or 127° and 133°) 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 systems long-term stability is guaranteed by the low Earth-like masses of planets B and C.

A Massive Neutron Star in the Globular Cluster M5

We report the results of 19 years of Arecibo timing for two pulsars in the globular cluster NGC 5904 (M5), PSR B1516+02A (M5A) and PSR B1516+02B (M5B). This has resulted in the measurement of the proper motions of these pulsars and, by extension, that of the cluster itself. M5B is a 7.95 ms pulsar in a binary system with a >0.13 M☉ companion and an orbital period of 6.86 days. In deep HST images, no optical counterpart is detected within ~2.5 σ of the position of the pulsar, implying that the companion is either a white dwarf or a low-mass main-sequence star. The eccentricity of the orbit (e = 0.14) has allowed a measurement of the rate of advance of periastron: = 0.0142° ± 0.0007° yr −1. We argue that it is very likely that this periastron advance is due to the effects of general relativity, the total mass of the binary system then being 2.29 ± 0.17 M☉. The small measured mass function implies, in a statistical sense, that a very large fraction of this total mass is contained in the pulsar: Mp = 2.08 ± 0.19 M☉ (1 σ); there is a 5% probability that the mass of this object is <1.72 M☉ and a 0.77% probability that 1.2 M☉ ≤ Mp ≤ 1.44 M☉. Confirmation of the median mass for this neutron star would exclude most soft equations of state for dense neutron matter. Millisecond pulsars (MSPs) appear to have a much wider mass distribution than is found in double neutron star systems; about half of these objects are significantly more massive than 1.44 M☉. A possible cause is the much longer episode of mass accretion necessary to recycle a MSP, which in some cases corresponds to a much larger mass transfer.

THE ARECIBO DETECTION OF THE COOLEST RADIO-FLARING BROWN DWARF

Radio detection provides unique means to measure and study magnetic fields of the coolest brown dwarfs. Previous radio surveys have observed quiescent and flaring emission from brown dwarfs down to spectral type L3.5, but only upper limits have been established for even cooler objects. We report the detection of sporadic, circularly polarized flares from the T6.5 dwarf, 2MASS J1047+21, with the Arecibo radio telescope at 4.75 GHz. This is by far the coolest brown dwarf yet detected at radio frequencies. The fact that such an object is capable of generating observable, coherent radio emission, despite its very low, {approx}900 K temperature, demonstrates the feasibility of studies of brown dwarfs of the meagerly explored L, T, and Y spectral types, using radio detection as a tool.

BD+48 740-Li OVERABUNDANT GIANT STAR WITH A PLANET: A CASE OF RECENT ENGULFMENT?

We report the discovery of a unique object, BD+48 740, a lithium overabundant giant with A(Li) = 2.33 ? 0.04 (where A(Li) = log n Li/n H + 12), that exhibits radial velocity (RV) variations consistent with a 1.6 MJ companion in a highly eccentric, e = 0.67 ? 0.17, and extended, a = 1.89?AU (P = 771?days), orbit. The high eccentricity of the planet is uncommon among planetary systems orbiting evolved stars and so is the high lithium abundance in a giant star. The ingestion by the star of a putative second planet in the system originally in a closer orbit could possibly allow for a single explanation to these two exceptional facts. If the planet candidate is confirmed by future RV observations, it might represent the first example of the remnant of a multiple planetary system recently affected by stellar evolution.

Arecibo Timing and Single-Pulse Observations of Eighteen Pulsars

We present new results of timing and single-pulse measurements for 18 radio pulsars discovered in 1993-1997 by the Penn State/Naval Research Laboratory declination-strip survey conducted with the 305 m Arecibo Telescope at 430 MHz. Long-term timing measurements have led to significant improvements of the rotational and the astrometric parameters of these sources, including the millisecond pulsar, PSR J1709+2313, and the pulsar located within the supernova remnant S147, PSR J0538+2817. Single-pulse studies of the brightest objects in the sample have revealed an unusual bursting pulsar, PSR J1752+2359, two new drifting subpulse pulsars, PSR J1649+2533 and PSR J2155+2813, and another example of a pulsar with profile mode changes, PSR J1746+2540. PSR J1752+2359 is characterized by bursts of emission, which appear once every 3-5 minutes and decay exponentially on a ~45 s timescale. PSR J1649+2533 spends ~30% of the time in a null state with no detectable radio emission.

Long-Term Stability and Dynamical Environment of the PSR 1257+12 Planetary System

We study the long-term dynamics of the PSR 1257+12 planetary system. Using the recently determined accurate initial condition by Konacki & Wolszczan (2003) who derived the orbital inclinations and the absolute masses of the planets B and C, we investigate the system stability by long-term, 1 Gyr direct integrations. No secular changes of the semi-major axes, eccentricities and inclinations appear during such an interval. This stable behavior is confirmed with the fast indicator MEG NO. The analysis of the orbital stability in the neighborhood of the nominal initial condition reveals that the PSR 1257+12 system is localized in a wide stable region of the phase space but close to a few weak 2 and 3-body mean motion resonances. The long term stability is additionally confirmed by a negligible exchange of the Ang ular Momentum Deficit between the innermost planet A and the pair of the outer planets B and C. An important feature of the system that helps sustain the stability is the secular apsidal resonance (SAR) between the planets B and C with the center of libration about 180 o . We also find useful limits on the elements of the innermost pl anet A which are otherwise unconstrained by the observations. Specifically, we find that the line of nod es of the planet A cannot be separated by more than about ±60 ◦ from the nodes of the bigger companions B and C. This limits the relative inclination of the orbit of the planet A to the mean orbital plane of the planets B and C to moderate values. We also perform a preliminary study of the short-term dynamics of massless particles in the system. We find that a relatively extended stable zone exists between the planets A and B. Beyond the planet C, the stable zone appears already at distances 0.5 AU from the parent star. For moderately low eccentricities, beyond 1 AU, the motion of massless particles does not suffer from strong instabilities and this zone is ba sically stable, independent on the inclinations of the orbits of the test particles to the mean orbital plane of the s ystem. It is an encouraging result supporting the search for a putative dust disk or a Kuiper belt, especially w ith the SIRTF mission. Subject headings:celestial mechanics, stellar dynamics—methods: numerical, N-body simulations—planetary systems—stars: individual (PSR 1257+12)

The habitable zone planet finder: a proposed high-resolution NIR spectrograph for the Hobby Eberly Telescope to discover low-mass exoplanets around M dwarfs

The Habitable Zone Planet Finder (HZPF) is a proposed instrument for the 10m class Hobby Eberly telescope that will be capable of discovering low mass planets around M dwarfs. HZPF will be fiber-fed, provide a spectral resolution R~ 50,000 and cover the wavelength range 0.9-1.65μm, the Y, J and H NIR bands where most of the flux is emitted by midlate type M stars, and where most of the radial velocity information is concentrated. Enclosed in a chilled vacuum vessel with active temperature control, fiber scrambling and mechanical agitation, HZPF is designed to achieve a radial velocity precision < 3m/s, with a desire to obtain <1m/s for the brightest targets. This instrument will enable a study of the properties of low mass planets around M dwarfs; discover planets in the habitable zones around these stars, as well serve as an essential radial velocity confirmation tool for astrometric and transit detections around late M dwarfs. Radial velocity observation in the near-infrared (NIR) will also enable a search for close in planets around young active stars, complementing the search space enabled by upcoming high-contrast imaging instruments like GPI, SPHERE and PALM3K. Tests with a prototype Pathfinder instrument have already demonstrated the ability to recover radial velocities at 7-10 m/s precision from integrated sunlight and ~15-20 m/s precision on stellar observations at the HET. These tests have also demonstrated the ability to work in the NIR Y and J bands with an un-cooled instrument. We will also discuss lessons learned about calibration and performance from our tests and how they impact the overall design of the HZPF.

DISCOVERY OF A LOW-MASS COMPANION TO A METAL-RICH F STAR WITH THE MARVELS PILOT PROJECT

We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot project. The host star has an effective temperature T_(eff) = 6135 ± 40 K, logg = 4.4 ± 0.1, and [Fe/H] = 0.32 ± 0.01, indicating a mass of M_⊙ = 1.25 ± 0.09 M_⊙ and R = 1.15 ± 0.15 R_⊙. The companion has an orbital period of 5.69449 ± 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M_J , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of Hot Jupiters. We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius ≳ 0.8 R_J at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer.

GEODETIC PRECESSION AND TIMING OF THE RELATIVISTIC BINARY PULSARS PSR B1534+12 AND PSR B1913+16

The pulsars B1534+12 and B1913+16 are two unique neutron star binaries exhibiting a wide range of relativistic phenomena that are impossible to detect in other systems. They constitute an exquisite observational ground on which theories can be tested. To date, the timing observations of B1534+12 and B1913+16 have been successfully used to test the strong field regime of relativistic gravity by measuring and then comparing with theory the evolution of the orbital elements of the pulsars. In this paper we develop a method that allows us to detect the timing signature of yet another relativistic phenomenon, the geodetic spin precession, and derive the misalignment angle between the orbital angular momentum and the spin vector of the pulsar, an important quantity that can be used to assess the degree of asymmetry of the supernova explosion that created the pulsar. Although we demonstrate that observations of PSR B1534+12—using the Penn State Pulsar Machine and the Mark III system—do not yet have a sufficient time span to detect precessional effects in the timing, we show that in about 10–25 years we will be able to get a good grasp on the misalignment angle of this pulsar. This may seem a long time to wait but in fact is typical for timing relativistic binary pulsars and, as in the case of PSR B1913+16, patient observing will eventually turn out to be very rewarding. Subject headings: binaries: close — pulsars: individual (B1534+12, B1913+1616) — relativity — stars: neutron

Improved timing formula for the psr b1257+12 planetary system

We present a new analysis of the dynamics of the planetary system around the pulsar B1257+12. A semianalytical theory of perturbation between terrestrial-mass planets B and C is developed and applied to improve the multiorbit timing formula for this object. We use numerical simulations of the pulse arrival times for PSR B1257+12 to demonstrate that our new timing model can serve as a tool to determine the masses of the two planets.