Astrophysics Program Research Articles

Nuclear astrophysics at n_TOF: focus on neutron sources in stars

Since 2001, the neutron time-of-flight facility n_TOF at CERN has carried out a large number of cross section measurements of interest for several research fields, including Nuclear Astrophysics. The results of these measurements have improved our knowledge on the nucleosynthesis of chemical elements. Particularly relevant for the s process, reported cross sections were used to constrain the Big Bang nucleosynthesis, to benchmark stellar models against nucleosynthesis in quiet and explosive scenarios, to interpret meteoritic abundances, as well as to study the neutron source reactions in Red Giant stars. After a brief description of the n_TOF facility and the related astrophysical program, the research activities about the 13C(a,n)16O and 22Ne(a,n)25Mg neutron source reactions are discussed.

Hyper-Kamiokande detector and its capabilities in astrophysical neutrino search

Hyper-Kamiokande (Hyper-K) is a next generation underground large water Cherenkov detector. Its tank will be filled with 260000 metric tons of ultra-pure water with a fiducial volume of 0.19 Mtons, which is about 8 times larger than that of its predecessor Super-Kamiokande. In its water volume, Cherenkov light will be produced by neutrino interactions and detected by newly developed photo sensors installed in a dedicated frame.Two different kinds of photo-detectors systems are considered for Hyper-K: 20-inch PMT and multi-PMT (mPMT). In particular, the mPMT system consists of a pressure sealed vessel with 19 3-inch PMTs installed inside. This configuration was implemented for the first time in the KM3NeT experiment, and has been demonstrated to improve the Hyper-K physics capabilities [1, 2].Hyper-K will be located in the Kamioka mine (Japan), where a dedicated cavern under a 600m-high mountain is being excavated for the installation of the detector. With its fruitful physics research program, Hyper-K will play a highly significant role in the next neutrino physics frontier, in particular for the CP violation, and including the neutrino astrophysics program, providing important information from its measurements.The physics potential of the Hyper-K neutrino astrophysics program will be discussed in this contribution.

Finding Quasars behind the Galactic Plane. II. Spectroscopic Identifications of 204 Quasars at ∣b∣ < 20°

Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source crowding in the Galactic plane. In this paper, we present a sample of 204 spectroscopically confirmed GPQs at ∣b∣ < 20°, 191 of which are new discoveries. This GPQ sample covers a wide redshift range from 0.069 to 4.487. For the subset of 230 observed GPQ candidates, the lower limit of the purity of quasars is 85.2%, and the lower limit of the fraction of stellar contaminants is 6.1%. Using a multicomponent spectral fitting, we measure the emission line and continuum flux of the GPQs, and estimate their single-epoch virial black hole masses. Due to selection effects raised from Galactic extinction and target magnitude, these GPQs have higher black hole masses and continuum luminosities in comparison to the SDSS DR7 quasar sample. The spectral-fitting results and black hole mass estimates are compiled into a main spectral catalog, and an extended spectral catalog of GPQs. The successful identifications prove the reliability of both our GPQ selection methods and the GPQ candidate catalog, shedding light on the astrometric and astrophysical programs that make use of a large sample of GPQs in the future.

Interior Structure of Solar-like Star τ Ceti

τ Ceti, a G8-V class star, has similar physical properties with our sun, even though most values are smaller and not as active as the sun. It has also been widely reviewed that this metal-poor population II star has terrestrial planetary systems, some of which are in the Habitable Zone. This paper aims to build the interior structure of τ Ceti through modeling experiments with Modules for Experiments in Stellar Astrophysics (MESA) program. The work began with the determination of several fundamental parameters obtained from previous observations of both interferometry and spectroscopy on several references, and also from basic calculations which are then used as input to build the model in MESA. Structural modeling has been carried out in accordance with current star conditions, which is in the main sequence phase. Finally, the result various physical parameters so-called stellar interior structure such as mass, luminosity, pressure, temperature, radius, and age, as well as zonal division of nuclear core (R < 0.23 R⊙,), radiative (0.23 < R⊙ < 0.54), and convective zone (0.54 < R⊙ < 0.775) were obtained.

2018 NASA Laboratory Astrophysics Workshop: Scientific Organizing Committee Report

This report provides detailed findings on the critical laboratory astrophysics data needs that are required to maximize the scientific return for NASA's current and near-term planned astrophysics missions. It also provides prioritized rankings on said laboratory astrophysics data, generally by waveband. The Report is based on community input gathered at the 2018 NASA Laboratory Astrophysics Workshop (LAW) from presentations, from discussions during workshop breakout sessions, and from other solicited input deemed appropriate by the Scientific Organizing Committee (SOC) obtained prior to and after the meeting. Hence, the Report is a direct reflection of the spirit and participant make-up of LAW 2018. The Report also outlines specific opportunities and threats facing NASA's Laboratory Astrophysics Program, and articulates concrete actions by which the Agency can capitalize on the opportunities and mitigate the challenges. The Report was prepared by the SOC, with help from some invited speakers, and input and review from community members.

Creation of Space Segments of Astrophysical Observatories

The article presents a retrospective view on the history of the development of the first national space astrophysics programs in comparison with world trends. The special features of such programs are shown and the analysis of the potential problems during their development is provided.

Gender and the Career Outcomes of Ph.D. Astronomers in the United States

We analyze the postdoctoral career tracks of a nearly complete sample of astronomers from 28 United States graduate astronomy and astrophysics programs spanning 13 graduating years (). A majority of both men and women (65% and 66%, respectively) find long-term employment in astronomy or closely related academic disciplines. We find no significant difference in the rates at which men and women are hired into these jobs following their Ph.D.s or in the rates at which they leave the field. Applying a two-outcome survival analysis model to the entire data set, we measure a relative academic hiring probability ratio for women versus men at a common year -post-Ph.D. of and a leaving probability ratio of (95% CI). These are both consistent with equal outcomes for both genders () and rule out more than minor gender differences in hiring or in the decision to abandon an academic career. They suggest that despite discrimination and adversity, women scientists are successful at managing the transition between Ph.D., postdoctoral, and faculty/staff positions.

Quantitative atomic spectroscopy, a review of progress in the optical-UV region and future opportunities

The development of tunable dye lasers and a simple atomic and ionic beam source for all elements were critical in establishing a reliable absolute scale for atomic transition probabilities in the optical to near UV regions. The laboratory astrophysics program at the University of Wisconsin - Madison (UW) concentrates on neutral and singly-ionized species transitions that are observable in astronomical spectra of cool stars, emphasizing the rare earth n(eutron)-capture elements and the Fe-group elements that are important inputs to early Galactic nucleosynthesis studies. The UW program is one of several productive efforts on atomic transition probabilities. These programs generally use time-resolved laser-induced-fluorescence (TR-LIF) to accurately measure total decay rates and data from high resolution Fourier transform spectrometers (FTSs) to determine emission branching fractions (BFs). The UW laboratory results almost always are directly linked to astronomical chemical composition efforts. There are good opportunities to extend similar research to other wavelength regions.

Generation of quasi continuous-wave electron beams in an L-band normal conducting pulsed RF injector for laboratory astrophysics experiments

We report on an approach to produce quasi continuous-wave (cw) electron beams with an average beam current of milliamperes and a mean beam energy of a few MeV in a pulsed RF injector. Potential applications are in the planned laboratory astrophysics programs at DESY. The beam generation is based on field emission from a specially designed metallic field emitter. A quasi cw beam profile is formed over subsequent RF cycles at the resonance frequency of the gun cavity. This is realized by debunching in a cut disk structure accelerating cavity (booster) downstream of the gun. The peak and average beam currents can be tuned in beam dynamics simulations by adjusting operation conditions of the booster cavity. Optimization of the transverse beam size at specific positions (e.g., entrance of the plasma experiment) is performed by applying magnetic focusing fields provided by solenoids along the beam line. In this paper, the design of a microtip field emitter is introduced and characterized in electromagnetic field simulations in the gun cavity. A series of particle tracking simulations are conducted for multi-parametric optimization of the parameters of the produced quasi cw electron beams. The obtained results will be presented and discussed. In addition, measurements of the parasitic field emission (PFE) current (dark current) in the PITZ gun will be exemplarily shown to distinguish its order of magnitude from the produced beam current by the designed field emitter.

Improvements on Fresnel arrays for high contrast imaging

The Fresnel Diffractive Array Imager (FDAI) is based on a new optical concept for space telescopes, developed at Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse, France. For the visible and near-infrared it has already proven its performances in resolution and dynamic range. We propose it now for astrophysical applications in the ultraviolet with apertures from 6 to 30 meters, aimed at imaging in UV faint astrophysical sources close to bright ones, as well as other applications requiring high dynamic range. Of course the project needs first a probatory mission at small aperture to validate the concept in space. In collaboration with institutes in Spain and Russia, we will propose to board a small prototype of Fresnel imager on the International Space Station (ISS), with a program combining technical tests and astrophysical targets. The spectral domain should contain the Lyman-α line (λ = 121 nm). As part of its preparation, we improve the Fresnel array design for a better Point Spread Function in UV, presently on a small laboratory prototype working at 260 nm. Moreover, we plan to validate a new optical design and chromatic correction adapted to UV. In this article we present the results of numerical propagations showing the improvement in dynamic range obtained by combining and adapting three methods : central obturation, optimization of the bars mesh holding the Fresnel rings, and orthogonal apodization. We briefly present the proposed astrophysical program of a probatory mission with such UV optics.

NASA Astrophysics Program: Present and Future

NASA’s astrophysics program includes support of space-based gravitational wave research in the U.S. The future includes plans for NASA’s contributions as a minority partner to the ESA-led L3 Gravitational Wave Observatory.

Programme

Monday, 5th of September 2016Chair: M. ColpiS. VitaleThe LTP experiment on LISA Pathfinder and its first resultsK. DooleyAdvanced LIGO: news from the dark universeB. SchutzLIGOs Black Holes and Science in the LISA EraP. McNamaraLISA Pathfinder: First steps to observing gravitational waves from spaceM. HewitsonIn-flight Performance of the Optical Metrology System on LISA PathfinderW. WeberPhysical model of the LISA Pathfinder differential acceleration measurement and its application to LISAK. DanzmannThe Status of LISAChair: O. JennrichJ. MartinoOn-flight characterization of Coldgas micro-Newton thrusters for Lisa PathfinderM. NofrariasMagnetic force noise in LISA PathfinderL. FerraioliThe LISA Pathfinder GRS Front-End ElectronicsD. VetrugnoThe Δg workflow: from measured displacements to the differential external acceleration.A. WittchenCoupling of relative intensity noise and pathlength noise to the length measurement in the optical metrology system of LISA PathfinderS. PaczkowskiLaser frequency stabilisation and interferometer path length differences on LISA PathfinderR. GiusteriThe free-fall mode experiment on LISA Pathfinder: first resultsP. WassElectrostatic test-mass force-noise disturbances as measured by LISA PathfinderR. DolesiThe contribution of Brownian noise from viscous gas damping to the differential acceleration noise measured in LISA Pathfinder between two nominally free falling test massesC. TrenkelThe engineering of LISA Pathfinder – the quietest laboratory ever flown in spaceW. KlipsteinLISA-derived Flight Phasemeter on the GRACE Follow-On MissionP. LauferMEMS Ion Thruster Chips to Significantly Enhance Cold Gas Thruster Lifetime for LISAM. TintoEnhanced Gravitational Wave Science with LISA and gLISATuesday, 6th of September 2016Chair: P. McNamaraF. RicciAdvanced VIRGO: State of the ArtC. BelczynskiEvolutionary predictions in the advanced LIGO/Virgo eraA. SesanaThe promise of multi-band gravitational wave astronomyB. SathyaprakashExploring the Universe with third generation interferometersS. SatoThe status of DECIGOG. HeinzelSatellite interferometry from LTP and GRACE Follow-On to LISAP. BinetruyCosmology with LISAChair: S. VitaleA. Giménez CañeteBeyond LISA PathfinderP. HertzNASA Astrophysics Program: Present and FutureF. SafaESA activities towards the Gravitation Waves Space ObservatoryH. WardLPF Interferometry and route to LISAJ. CampDevelopment of a US Laser System for the Gravitational Wave Mission LISAT. SchwarzePerformance of an optical three-signal test for the LISA metrologyM. LaporteStatus of the eLISA on table (LOT) electro-optical simulator for space based gravitational waves observatoriesS. AppleUF Torsion Pendulum and GRS Technology DevelopmentJ. LivaseLISA Telescope In-field Pointing and Scattered Light StudyK. IsleifThe LISA backlink – comparing optical phase reference systemsWednesday, 7th of September 2016Chair: C. SopuertaT. AlexanderEMRIs and the relativistic loss coneR. SchoedelThe stellar cusp around the Milky Way’s central black holeJ. GairImpact of eLISA design on EMRI ScienceM. van de MeentModelling spinning EMRIs with Self-ForceA. GianninasA Progress Report on the Search for the Most Extreme Binary White DwarfsI. ThorpeInitial Results from ST7-Disturbance Reduction System on LISA PathfinderG. JinOngoing development of detection of gravitational waves in space in ChinaThursday, 8th of September 2016Chair: P. BinetruyR. BlandfordThe Future of Black Hole Astrophysics in the LISA-VIRGO-LPF EraC. MooreObserving black hole merger kicks directly with gravitational wavesN. TamaniniLate time cosmology with eLISAI. DvorkinA synthetic model of the gravitational wave background from evolving binary compact objectsA. PetiteauLISA science performance in the context of LISAPathfinder first results and simulation for LISAN. CornishFast, fully precessing frequency domain waveforms for analyzing black hole mergers with LISAA. KleinSupermassive Black Hole Observations with eLISAS. HughesMeasuring EMRIs: A reality checkChair: Ch. CapriniL. MayerMassive black hole mergers and their timescales: connecting galaxy formation with gravitational wave scienceS. BabakEnchilada: analysis of simulated eLISA data setA. RicciardonePrimordial Gravitational Waves and eLISAS. SanidasCan eLISA save the day? Hunting for cosmic strings in the SKA era.G. ServantProbing cosmological phase transitions with eLISAD. WeirAcoustic waves and the detectability of first-order phase transitions by eLISAM. BonettiPost-Newtonian Dynamics of Massive Black Holes TripletsJ. Garcia-BellidoGravitational waves from primordial black holes as dark matterT. RegimbauSearching for the stochastic gravitational-wave background with Advanced LIGO and Advanced VirgoM. PieroniPrimordial GW from universality classes of pseudo-scalar inflationFriday, 9th of September 2016Chair: G. MuellerK. Holley-BockelmannThe Known Unknowns: predicting the landscape of LISA black hole sourcesE. RossiSupermassive black hole seeds: updates on the quasi star modelC. MingarelliThe Gravitational-Wave Universe seen by Pulsar Timing ArraysS. SmarttSearching for the electromagnetic counterparts to gravitational wave sourcesJ. BergéMICROSCOPE: the first few months in orbitO. JennrichThe preparation for L3 – building on LISA Pathfinder

The Nuclear Astrophysics program at n_TOF (CERN)

An important experimental program on Nuclear Astrophysics is being carried out at the n_TOF since several years, in order to address the still open issues in stellar and primordial nucleosynthesis. Several neutron capture reactions relevant to s-process nucleosynthesis have been measured so far, some of which on important branching point radioisotopes. Furthermore, the construction of a second experimental area has recently opened the way to challenging measurements of (n, charged particle) reactions on isotopes of short half-life. The Nuclear Astrophysics program of the n_TOF Collaboration is here described, with emphasis on recent results relevant for stellar nucleosynthesis, stellar neutron sources and primordial nucleosynthesis.

X-ray emission produced in charge-exchange collisions between highly charged ions and argon: Role of the multiple electron capture

In this work we use the classical trajectory Monte Carlo method within an eight-electron scheme to theoretically study photonic spectra that follow charge-exchange processes between highly charged ions of charge states 10+, 17+, 18+, and 36+ with neutral argon. The energy range considered is 18 eV/amu to 4 keV/amu, covering typical electron beam ion traps and solar wind energies. The role played by multiple electron capture processes for the different collision systems under consideration is explicitly analyzed and its contribution separated as arising from radiative decay and autoionizing multiple capture. For the present collision systems we find that multiple electron capture is responsible for 50%--60% of the resulting x-ray spectra. The present results are of direct relevance to the astrophysical program.

Probing new physics with underground accelerators and radioactive sources

New light, weakly coupled particles can be efficiently produced at existing and future high-intensity accelerators and radioactive sources in deep underground laboratories. Once produced, these particles can scatter or decay in large neutrino detectors (e.g. Super-K and Borexino) housed in the same facilities. We discuss the production of weakly coupled scalars ϕ via nuclear de-excitation of an excited element into the ground state in two viable concrete reactions: the decay of the 0+ excited state of 16O populated via a (p,α) reaction on fluorine and from radioactive 144Ce decay where the scalar is produced in the de-excitation of 144Nd⁎, which occurs along the decay chain. Subsequent scattering on electrons, e(ϕ,γ)e, yields a mono-energetic signal that is observable in neutrino detectors. We show that this proposed experimental setup can cover new territory for masses 250 keV≤mϕ≤2me and couplings to protons and electrons, 10−11≤gegp≤10−7. This parameter space is motivated by explanations of the “proton charge radius puzzle”, thus this strategy adds a viable new physics component to the neutrino and nuclear astrophysics programs at underground facilities.

Highlights of the NASA Particle Astrophysics Program

The NASA Particle Astrophysics Program covers Origin of the Elements, Nearest Sources of Cosmic Rays, How Cosmic Particle Accelerators Work, The Nature of Dark Matter, and Neutrino Astrophysics. Progress in each of these topics has come from sophisticated instrumentation flown on long duration balloon (LDB) flights around Antarctica over the past two decades. New opportunities including Super Pressure Balloons (SPB) and International Space Station (ISS) platforms are emerging for the next major step. Stable altitudes and long durations enabled by SPB flights ensure ultra-long duration balloon (ULDB) missions that can open doors to new science opportunities. The Alpha Magnetic Spectrometer (AMS) has been operating on the ISS since May 2011. The CALorimetric Electron Telescope (CALET) and Cosmic Ray Energetics And Mass (CREAM) experiments are being developed for launch to the Japanese Experiment Module Exposed Facility (JEM-EF) in 2014. And, the Extreme Universe Space Observatory (EUSO) is planned for launch to the ISS JEM-EF after 2017. Collectively, these four complementary ISS missions covering a large portion of the cosmic ray energy spectrum serve as a cosmic ray observatory.

Tsinghua Center for Astrophysics and the Dark Universe

The Tsinghua Center for Astrophysics (THCA) was founded in 2001 by Prof. Li Tipei and Shang Rencheng. A distinguishing characteristic of THCA's astrophysics program is its emphasis on space X-ray and gamma-ray instrumentation, by taking advantage of Tsinghua's strong programs on nuclear physics, nuclear engineering, space and aeronautics engineering, as well as electronics and information technology. The main research directions in THCA include high energy astrophysics and cosmology with space and ground observations in X-rays and gamma-rays, and more recently in optical wavelengths, radio-astronomy, gravitational waves, dark matter and dark energy analyses and projects.

Astrophysics experiments with radioactive beams at ATLAS

Reactions involving short-lived nuclei play an important role in nuclear astrophysics, especially in explosive scenarios which occur in novae, supernovae or X-ray bursts. This article describes the nuclear astrophysics program with radioactive ion beams at the ATLAS accelerator at Argonne National Laboratory. The CARIBU facility as well as recent improvements for the in-flight technique are discussed. New detectors which are important for studies of the rapid proton or the rapid neutron-capture processes are described. At the end we briefly mention plans for future upgrades to enhance the intensity, purity and the range of in-flight and CARIBU beams.

“RadioAstron”-A telescope with a size of 300 000 km: Main parameters and first observational results

The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

TWINNING between Institutions in developed and less developed countries: an ideal way to set-up an astrophysics program

AbstractIt is very difficult to start from scratch a new Astrophysics program in a country with very little or no researchers in the field. In 2007, we began to set-up an Astrophysics program by TWINNING the Université de Ouagadougou with the Université de Montréal in Canada, the Université de Provence in France and the University of Cape Town in South Africa. Already, courses are given at the undergraduate and Master levels and a teaching Observatory has been built. A 1m research telescope was also moved from the La Silla Observatory in Chile to Burkina Faso and the infrastructure is being built at the moment on mount Djaogari in the north-eastern part of the country. In the meantime, 6 students are doing their PhD in Astrophysics overseas (Canada, France and South Africa) and will become the core of the research group at the Université de Ouagadougou. An engineer is also doing his PhD in Astronomical Instrumentation to help with the maintenance of the equipment on the Research Telescope.