Doris Rosenbaum

Infrared Kuiper belt constraints

We compute the temperature and IR signal of particles of radius a and albedo α at heliocentric distance R, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of COBE DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance R, particle radius a, and particle albedo α. We then apply these results to a recently developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40<R<50-90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the solar system of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally, we compare Kuiper belt IR spectra for various parameter values. Results of this work include: (1) numerical limits on Kuiper belt dust as a function of (R, a, α) on the basis of four alternative sets of constraints, including those following from recent discovery of the cosmic IR background by Hauser et al.; (2) application to the two-sector Kuiper belt model, finding mass limits and spectrum shape for different values of relevant parameters including dependence on time elapsed since last passage through a molecular cloud cleared the outer solar system of dust; and (3) potential use of spectral information to determine time since last passage of the Sun through a giant molecular cloud.

Seismic search for strange quark nuggets

Bounds on masses and abundances of Strange Quark Nuggets (SQNs) are inferred from a seismic search on Earth. Potential SQN bounds from a possible seismic search on the Moon are reviewed and compared with Earth capabilities. Bounds are derived from the data taken by seismometers implanted on the Moon by the Apollo astronauts. We show that the Apollo data implies that the abundance of SQNs in the region of 10 kg to 1 ton must be at least an order of magnitude less than would saturate the dark matter in the solar neighborhood.

Charges on strange quark nuggets in space

Since Wittens seminal 1984 paper on the subject, searches for evidence of strange quark nuggets (SQNs) have proven unsuccessful. In the absence of experimental evidence ruling out SQNs, the validity of theories introducing mechanisms that increase their stability should continue to be tested. To stimulate electromagnetic SQN searches, particularly space searches, we estimate the net charge that would develop on a SQN in space exposed to various radiation baths (and showers) capable of liberating the SQNs less strongly bound electrons, taking into account recombination with ambient electrons. We consider, in particular, the cosmic microwave background, radiation from the sun, and diffuse galactic and extragalactic ultraviolet backgrounds. The largest charge, for the settings considered, develops on a solar system SQN exposed to a solar X-ray flare. A possible dramatic signal of SQNs in explosive astrophysical events is noted.

Millimeter-Wave Signature of Strange Matter Stars

One of the most important questions in the study of compact objects is the nature of pulsars, including whether they consist of neutron star matter or strange quark matter (SQM). However, few mechanisms for distinguishing between these two possibilities have been proposed. The purpose of this Letter is to show that a strange star (one made of SQM) will have a vibratory mode with an oscillation frequency of approximately 250 GHz (millimeter wave). This mode corresponds to motion of the center of the expected crust of normal matter relative to the center of the strange quark core, without distortion of either. Radiation from currents generated in the crust at the mode frequency would be an SQM signature. We also consider effects of stellar rotation, estimate power emission and signal-to-noise ratio, and discuss briefly the particularly important, but unsolved, question of possible mechanisms for exciting the mode.

Strange quark nuggets in space: Charges in seven settings

We have computed the charge that develops on an SQN in space as a result of balance between the rates of ionization by ambient gammas and capture of ambient electrons. We have also computed the times for achieving that equilibrium and binding energy of the least bound SQN electrons. We have done this for seven different settings. We sketch the calculations here and give their results in the Figure and Table II; details are in the Physical Review D.79.023513 (2009).

On the Mass of the Kuiper Belt

Evidence for the Kuiper Belt (of cometary material just past Neptune) and the processes that shape it are briefly reviewed. A summary of selected estimates of its mass is given. A two-sector model for the belt is summarized. A limit is placed on the amount of mass that could be present in the Kuiper Belt in the form of objects with sizes around a centimeter, from survival of the Pioneer 10 spacecraft’s propellant tank during a dozen years in the belt. Work in progress on the belt’s IR signal is reviewed: A useful formula is given for the IR signal from dust particles as a function of albedo, radius and heliocentric distance. Preliminary results are given for limits on the sector masses, in the two-sector model, as a function of time since last passage of the Sun through a giant molecular cloud. Possible indication for the time since such passage and possible support for the existence of a more massive outer sector are found in preliminary results for the ratios of the IR signal in the four different COBE DIRBE bands.