The SERENDIP 2 SETI project: Current status

Over the past 30 years, interest in extraterrestrial intelligence has progressed from philosophical discussion to rigorous scientific endeavors attempting to make contact. Since it is impossible to assess the probability of success and the amount of telescope time needed for detection, Search for Extraterrestrial Intelligence (SETI) Projects are plagued with the problem of attaining the large amounts of time needed on the world's precious few large radio telescopes. To circumvent this problem, the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) instrument operates autonomously in a piggyback mode utilizing whatever observing plan is chosen by the primary observer. In this way, large quantities of high-quality data can be collected in a cost-effective and unobtrusive manner. During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on earth, a major element of the SERENDIP project involves identifying and rejecting spurious signals from these sources. Another major element of the SERENDIP Project (as well as most other SETI efforts) is detecting extraterrestrial intelligence (ETI) signals. Events selected as candidate ETI signals are studied further in a targeted search program which utilizes between 24 to 48 hours of dedicated telescope time each year

Radiative Transfer Analysis of Far-UV Background Observations Obtained with the Far-Ultraviolet Space Telescope (FAUST)

In 1992 the Far-Ultraviolet Space Telescope (FAUST) provided measurements of the ultraviolet (140-180nm) diffuse sky background at high, medium, and low Galactic latitudes. A significant fraction of the detected radiation was found to be of Galactic origin, resulting from scattering by dust in the diffuse interstellar medium. To simulate the radiative transfer in the Galaxy, we employed a Monte Carlo model which utilized a realistic, non-isotropic radiation field based on the measured fluxes (at 156nm) and positions of 58,000 TD-1 stars, and a cloud structure for the interstellar medium. The comparison of the model predictions with the observations led to a separation of the Galactic scattered radiation from an approximately constant background, attributed to airglow and extragalactic radiation, and to a well constrained determination of the dust scattering properties. The derived dust albedo a = 0.45 +/- 0.05 is substantially lower than albedos derived for dust in dense reflection nebulae and star-forming regions, while the phase function asymmetry g = 0.68 +/- 0.10 is indicative of a strongly forward directed phase function. We show the highly non-isotropic phase function to be responsible, in conjunction with the non-isotropic UV radiation field, for the wide range of observed correlations between the diffusely scattered Galactic radiation and the column densities of neutral atomic hydrogen. The low dust albedo is attributed to a size distribution of grains in the diffuse medium with average sizes smaller than those in dense reflection nebulae.Comment: 35 pages, 10 figures included, to be published in the Ap

Far Ultraviolet Absolute Flux of alpha Virginis

We present the far ultraviolet spectrum of alpha Virginis taken with EURD spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to 1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE spectra of alpha Vir and compared the extension of the model to our wavelengths with EURD data. This comparison shows that EURD fluxes are consistent with the prediction of the model within 20-30%, depending on the reddening assumed. EURD fluxes are consistent with Voyager observations but are ~60% higher than most previous rocket observations of alpha Vir.Comment: 13 pages, 4 figures. Submitted to The Astrophysical Journa

Catching the radio flare in CTA 102 I. Light curve analysis

Context: The blazar CTA 102 (z=1.037) underwent a historical radio outburst in April 2006. This event offered a unique chance to study the physical properties of the jet. Aims: We used multifrequency radio and mm observations to analyze the evolution of the spectral parameters during the flare as a test of the shock-in-jet model under these extreme conditions. Methods: For the analysis of the flare we took into account that the flaring spectrum is superimposed on a quiescent spectrum. We reconstructed the latter from archival data and fitted a synchrotron self-absorbed distribution of emission. The uncertainties of the derived spectral parameters were calculated using Monte Carlo simulations. The spectral evolution is modeled by the shock-in-jet model, and the derived results are discussed in the context of a geometrical model (varying viewing angle) and shock-shock interaction. Results: The evolution of the flare in the turnover frequency-turnover flux density plane shows a double peak structure. The nature of this evolution is dicussed in the frame of shock-in-jet models. We discard the generation of the double peak structure in the turnover frequency-turnover flux density plane purely based on geometrical changes (variation of the Doppler factor). The detailed modeling of the spectral evolution favors a shock-shock interaction as a possible physical mechanism behind the deviations from the standard shock-in-jet model.Comment: 15 pages, 12 figure

ProtoDESI: First On-Sky Technology Demonstration for the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the universe using the baryon acoustic oscillations technique. The spectra of 35 million galaxies and quasars over 14,000 square degrees will be measured during a 5-year survey. A new prime focus corrector for the Mayall telescope at Kitt Peak National Observatory will deliver light to 5,000 individually targeted fiber-fed robotic positioners. The fibers in turn feed ten broadband multi-object spectrographs. We describe the ProtoDESI experiment, that was installed and commissioned on the 4-m Mayall telescope from August 14 to September 30, 2016. ProtoDESI was an on-sky technology demonstration with the goal to reduce technical risks associated with aligning optical fibers with targets using robotic fiber positioners and maintaining the stability required to operate DESI. The ProtoDESI prime focus instrument, consisting of three fiber positioners, illuminated fiducials, and a guide camera, was installed behind the existing Mosaic corrector on the Mayall telescope. A Fiber View Camera was mounted in the Cassegrain cage of the telescope and provided feedback metrology for positioning the fibers. ProtoDESI also provided a platform for early integration of hardware with the DESI Instrument Control System that controls the subsystems, provides communication with the Telescope Control System, and collects instrument telemetry data. Lacking a spectrograph, ProtoDESI monitored the output of the fibers using a Fiber Photometry Camera mounted on the prime focus instrument. ProtoDESI was successful in acquiring targets with the robotically positioned fibers and demonstrated that the DESI guiding requirements can be met.Comment: Accepted versio

The cooling rate of neutron stars after thermonuclear shell flashes

Thermonuclear shell flashes on neutron stars are detected as bright X-ray bursts. Traditionally, their decay is modeled with an exponential function. However, this is not what theory predicts. The expected functional form for luminosities below the Eddington limit, at times when there is no significant nuclear burning, is a power law. We tested the exponential and power-law functional forms against the best data available: bursts measured with the high-throughput Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer. We selected a sample of 35 'clean' and ordinary (i.e., shorter than a few minutes) bursts from 14 different neutron stars that 1) show a large dynamic range in luminosity, 2) are the least affected by disturbances by the accretion disk and 3) lack prolonged nuclear burning through the rp-process. We find indeed that for every burst a power law is a better description than an exponential function. We also find that the decay index is steep, 1.8 on average, and different for every burst. This may be explained by contributions from degenerate electrons and photons to the specific heat capacity of the ignited layer and by deviations from the Stefan-Boltzmann law due to changes in the opacity with density and temperature. Detailed verification of this explanation yields inconclusive results. While the values for the decay index are consistent, changes of it with the burst time scale, as a proxy of ignition depth, and with time are not supported by model calculations.Comment: 10 pages, 7 figures, recommended for publication in A&

The kinetic temperature in a damped Lyman-alpha absorption system in Q2206-199 - an example of the warm neutral medium

By comparing the widths of absorption lines from OI, SiII and FeII in the redshift z=2.076 single-component damped Lyman alpha absorption system in the spectrum of Q2206-199 we establish that these absorption lines arise in Warm Neutral Medium gas at ~12000 +/- 3000K. This is consistent with thermal equilibrium model estimates of ~ 8000K for the Warm Neutral Medium in galaxies, but not with the presence of a significant cold component. It is also consistent with, but not required by, the absence of CII* fine structure absorption in this system. Some possible implications concerning abundance estimates in narrow-line WNM absorbers are discussed.Comment: 9 pages, 3 figures. MNRAS accepte

Position-sensitive ion detection in precision Penning trap mass spectrometry

A commercial, position-sensitive ion detector was used for the first time for the time-of-flight ion-cyclotron resonance detection technique in Penning trap mass spectrometry. In this work, the characteristics of the detector and its implementation in a Penning trap mass spectrometer will be presented. In addition, simulations and experimental studies concerning the observation of ions ejected from a Penning trap are described. This will allow for a precise monitoring of the state of ion motion in the trap.Comment: 20 pages, 13 figure