Harrison F.A.,Mathematics and Astronomy |
Boggs S.,Uc Berkeley Space Science Laboratory |
Christensen F.,Technical University of Denmark |
Craig W.,Uc Berkeley Space Science Laboratory |
And 30 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010
The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (6 - 80 keV) telescope to orbit. NuSTAR will offer a factor 50 - 100 sensitivity improvement compared to previous collimated or coded mask imagers that have operated in this energy band. In addition, NuSTAR provides sub-arcminute imaging with good spectral resolution over a 12-arcminute field of view. After launch, NuSTAR will carry out a two-year primary science mission that focuses on four key programs: studying the evolution of massive black holes through surveys carried out in fields with excellent multiwavelength coverage, understanding the population of compact objects and the nature of the massive black hole in the center of the Milky Way, constraining the explosion dynamics and nucleosynthesis in supernovae, and probing the nature of particle acceleration in relativistic jets in active galactic nuclei. A number of additional observations will be included in the primary mission, and a guest observer program will be proposed for an extended mission to expand the range of scientific targets. The payload consists of two co-aligned depth-graded multilayer coated grazing incidence optics focused onto a solid state CdZnTe pixel detectors. To be launched in early 2012 on a Pegasus rocket into a low-inclination Earth orbit, NuSTAR largely avoids SAA passage, and will therefore have low and stable detector backgrounds. The telescope achieves a 10.14-meter focal length through on-orbit deployment of an extendable mast. An aspect and alignment metrology system enable reconstruction of the absolute aspect and variations in the telescope alignment resulting from mast exure during ground data processing. Data will be publicly available at GSFC's High Energy Archive Research Center (HEASARC) following validation at the science operations center located at Caltech. © 2010 SPIE.
Wik D.R.,NASA |
Wik D.R.,Johns Hopkins University |
Lehmer B.D.,NASA |
Lehmer B.D.,Johns Hopkins University |
And 23 more authors.
Astrophysical Journal | Year: 2014
Prior to the launch of NuSTAR, it was not feasible to spatially resolve the hard (E > 10 keV) emission from galaxies beyond the Local Group. The combined NuSTAR data set, comprised of three ∼165 ks observations, allows spatial characterization of the hard X-ray emission in the galaxy NGC 253 for the first time. As a follow up to our initial study of its nuclear region, we present the first results concerning the full galaxy from simultaneous NuSTAR, Chandra, and Very Long Baseline Array monitoring of the local starburst galaxy NGC 253. Above ∼10 keV, nearly all the emission is concentrated within 100″ of the galactic center, produced almost exclusively by three nuclear sources, an off-nuclear ultraluminous X-ray source (ULX), and a pulsar candidate that we identify for the first time in these observations. We detect 21 distinct sources in energy bands up to 25 keV, mostly consisting of intermediate state black hole X-ray binaries. The global X-ray emission of the galaxy - dominated by the off-nuclear ULX and nuclear sources, which are also likely ULXs - falls steeply (photon index ≳3) above 10 keV, consistent with other NuSTAR-observed ULXs, and no significant excess above the background is detected at E > 40 keV. We report upper limits on diffuse inverse Compton emission for a range of spatial models. For the most extended morphologies considered, these hard X-ray constraints disfavor a dominant inverse Compton component to explain the γ-ray emission detected with Fermi and H.E.S.S. If NGC 253 is typical of starburst galaxies at higher redshift, their contribution to theE > 10 keV cosmic X-ray background is <1%. © 2014. The American Astronomical Society. All rights reserved.
Lehmer B.D.,Johns Hopkins University |
Lehmer B.D.,NASA |
Wik D.R.,NASA |
Hornschemeier A.E.,NASA |
And 19 more authors.
Astrophysical Journal | Year: 2013
We present results from three nearly simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) and Chandra monitoring observations between 2012 September 2 and 2012 November 16 of the local star-forming galaxy NGC 253. The 3-40 keV intensity of the inner ∼20 arcsec (∼400 pc) nuclear region, as measured by NuSTAR, varied by a factor of ∼2 across the three monitoring observations. The Chandra data reveal that the nuclear region contains three bright X-ray sources, including a luminous (L2-10 keV ∼ few × 1039 erg s-1) point source located ∼1 arcsec from the dynamical center of the galaxy (within the 3σ positional uncertainty of the dynamical center); this source drives the overall variability of the nuclear region at energies ≳3 keV. We make use of the variability to measure the spectra of this single hard X-ray source when it was in bright states. The spectra are well described by an absorbed (NH ≈ 1.6 × 1023 cm-2) broken power-law model with spectral slopes and break energies that are typical of ultraluminous X-ray sources (ULXs), but not active galactic nuclei (AGNs). A previous Chandra observation in 2003 showed a hard X-ray point source of similar luminosity to the 2012 source that was also near the dynamical center (θ ≈ 0.4 arcsec); however, this source was offset from the 2012 source position by ≈1 arcsec. We show that the probability of the 2003 and 2012 hard X-ray sources being unrelated is ≫99.99% based on the Chandra spatial localizations. Interestingly, the Chandra spectrum of the 2003 source (3-8 keV) is shallower in slope than that of the 2012 hard X-ray source. Its proximity to the dynamical center and harder Chandra spectrum indicate that the 2003 source is a better AGN candidate than any of the sources detected in our 2012 campaign; however, we were unable to rule out a ULX nature for this source. Future NuSTAR and Chandra monitoring would be well equipped to break the degeneracy between the AGN and ULX nature of the 2003 source, if again caught in a high state. © 2013. The American Astronomical Society. All rights reserved..
Zhang K.,Mathematics and Astronomy |
Isella A.,Mathematics and Astronomy |
Carpenter J.M.,Mathematics and Astronomy |
Blake G.A.,California Institute of Technology
Astrophysical Journal | Year: 2014
We present ALMA observations of the 880 μm continuum and CO J = 3-2 line emission from the transition disk around [PZ99] J160421.7-213028, a solar mass star in the Upper Scorpius OB association. Analysis of the continuum data indicates that 80% of the dust mass is concentrated in an annulus extending between 79 and 114 AU in radius. Dust is robustly detected inside the annulus, at a mass surface density 100 times lower than that at 80 AU. The CO emission in the inner disk also shows a significantly decreased mass surface density, but we infer a cavity radius of only 31 AU for the gas. The large separation of the dust and gas cavity edges, as well as the high radial concentration of millimeter-sized dust grains, is qualitatively consistent with the predictions of pressure trap models that include hydrodynamical disk-planet interactions and dust coagulation/fragmentation processes. © 2014. The American Astronomical Society. All rights reserved..
Vogel J.K.,Lawrence Livermore National Laboratory |
Pivovaroff M.J.,Lawrence Livermore National Laboratory |
Nagarkar V.V.,Radiation Monitoring Devices, Inc. |
Kudrolli H.,Radiation Monitoring Devices, Inc. |
And 4 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012
Recent technological innovations now make it feasible to construct hard x-ray telescopes for space-based astronomical missions. Focusing optics are capable of improving the sensitivity in the energy range above 10 keV by orders of magnitude compared to previously used instruments. The last decade has seen focusing optics developed for balloon experiments  and they will soon be implemented in approved space missions such as the Nuclear Spectroscopic Telescope Array (NuSTAR)  and ASTRO-H . The full characterization of x-ray optics for astrophysical and solar imaging missions, including measurement of the point spread function (PSF) as well as scattering and reflectivity properties of substrate coatings, requires a very high spatial resolution, high sensitivity, photon counting and energy discriminating, large area detector. Novel back-thinned Electron Multiplying Charge-Coupled Devices (EMCCDs)  are highly suitable detectors for ground-based calibrations. Their chip can be optically coupled to a microcolumnar CsI(Tl) scintillator  via a fiberoptic taper. Not only does this device exhibit low noise and high spatial resolution inherent to CCDs, but the EMCCD is also able to handle high frame rates due to its controllable internal gain. Additionally, thick CsI(Tl) yields high detection efficiency for x-rays . This type of detector has already proven to be a unique device very suitable for calibrations in astrophysics: such a camera was used to support the characterization of the performance for all NuSTAR optics -. Further optimization will enable similar cameras to be improved and used to calibrate x-ray telescopes for future space missions. In this paper, we discuss the advantages of using an EMCCD to calibrate hard x-ray optics. We will illustrate the promising features of this detector solution using examples of data obtained during the ground calibration of the NuSTAR telescopes performed at Columbia University during 2010/2011. Finally, we give an outlook on ongoing development and optimizations, such as the use of single photon counting mode to enhance spectral resolution. © 2011 IEEE.
Ruan J.J.,University of Washington |
Anderson S.F.,University of Washington |
MacLeod C.L.,University of Washington |
MacLeod C.L.,U.S. Naval Academy |
And 9 more authors.
Astrophysical Journal | Year: 2012
We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ∼ 30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales . Imposing cuts on minimum τ and allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E ≥ 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8′. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ∼ 3years in the rest frame of the jet, in contrast with the 320day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics. © 2012. The American Astronomical Society. All rights reserved.
Estrada C.,Mathematics and Astronomy |
Marcolli M.,Mathematics and Astronomy
International Journal of Geometric Methods in Modern Physics | Year: 2013
We study the renormalization group flow for the Higgs self-coupling in the presence of gravitational correction terms. We show that the resulting equation is equivalent to a singular linear ODE, which has explicit solutions in terms of hypergeometric functions. We discuss the implications of this model with gravitational corrections on the Higgs mass estimates in particle physics models based on the spectral action functional. © 2013 World Scientific Publishing Company.
Kitaguchi T.,Mathematics and Astronomy |
Grefenstette B.W.,Mathematics and Astronomy |
Harrison F.A.,Mathematics and Astronomy |
Miyasaka H.,Mathematics and Astronomy |
And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011
The Nuclear Spectroscopic Telescope Array (NuSTAR) will be the first space mission to focus in the hard X-ray (5-80 keV) band. The NuSTAR instrument carries two co-aligned grazing incidence hard X-ray telescopes. Each NuSTAR focal plane consists of four 2 mm CdZnTe hybrid pixel detectors, each with an active collecting area of 2 cm x 2 cm. Each hybrid consists of a 32x32 array of 605 μm pixels, read out with the Caltech custom low-noise NuCIT ASIC. In order to characterize the spectral response of each pixel to the degree required to meet the science calibration requirements, we have developed a model based on Geant4 together with the Shockley-Ramo theorem customized to the NuSTAR hybrid design. This model combines a Monte Carlo of the X-ray interactions with subsequent charge transport within the detector. The combination of this model and calibration data taken using radioactive sources of 57Co, 155Eu and 241Am enables us to determine electron and hole mobility-lifetime products for each pixel, and to compare actual to ideal performance expected for defect-free material. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Ceyhan O.,University of Luxembourg |
Marcolli M.,Mathematics and Astronomy
Advances in Theoretical and Mathematical Physics | Year: 2014
This paper continues our previous study of Feynman integrals in configuration spaces and their algebro-geometric and motivic aspects. We consider here both massless and massive Feynman amplitudes, from the point of view of potential theory. We consider a variant of the wonderful compactification of configuration spaces that works simultaneously for all graphs with a given number of vertices and that also accounts for the external structure of Feynman graph. As in our previous work, we consider two version of the Feynman amplitude in configuration space, which we refer to as the real and complex versions. In the real version, we show that we can extend to the massive case a method of evaluating Feynman integrals, based on expansion in Gegenbauer polynomials, that we investigated previously in the massless case. In the complex setting, we show that we can use algebro-geometric methods to renormalize the Feynman amplitudes, so that the renormalized values of the Feynman integrals are given by periods of a mixed Tate motive. The regularization and renormalization procedure is based on pulling back the form to the wonderful compactification and replace it with a cohomologous one with logarithmic poles. A complex of forms with logarithmic poles, endowed with an operator of pole subtraction, determine a Rota-Baxter algebra on the wonderful compactifications. We can then apply the renormalization procedure via Birkhoff factorization, after interpreting the regularization as an algebra homomorphism from the Connes- Kreimer Hopf algebra of Feynman graphs to the Rota-Baxter algebra. We obtain in this setting a description of the renormalization group. We also extend the period interpretation to the case of Dirac fermions and gauge bosons. © 2014 International Press.
News Article | January 14, 2016
The Royal Swedish Academy of Sciences has announced the recipients of the 2016 Crafoord Prizes in Mathematics and Astronomy. The Crafoord Prize in Mathematics has been awarded to Yakov Eliashberg of Stanford University “for the development of contact and symplectic topology and groundbreaking discoveries of rigidity and flexibility phenomena.” The 2016 Crafoord Prize in Astronomy has been awarded to Roy Kerr of the University of Canterbury, Christchurch, New Zealand and to Roger Blandford of Stanford University “for fundamental work on rotating black holes and their astrophysical consequences.” The prize money is 6 million Swedish kronor per prize, and the Crafoord Prize in Astronomy is shared equally between the Laureates. The Royal Swedish Academy of Sciences, founded in 1739, is an independent organization whose overall objective is to promote the sciences and to strengthen their influence in society. The Academy states that it “takes special responsibility for the natural sciences and mathematics, but endeavors to promote the exchange of ideas between various disciplines.” The Academy awarded the Crafoord Prize for the first time in 1982 after receiving “a considerable donation” from the Lund industrialist Holger Crafoord and his wife Anna-Greta in 1980. This donation forms the basis of the Anna-Greta and Holger Crafoord Fund, whose aims are “to promote pure research in mathematics and astronomy, biosciences (in the first place ecology), geosciences and polyarthritis (rheumatoid arthritis).” These disciplines are chosen so as to complement those for which the Nobel Prizes are awarded. The prize sum of SEK 6 million makes the Crafoord one of the world´s largest scientific prizes. The international prize is awarded for one field per year in a fixed order to researchers who have made decisive contributions within their fields: Since 2012, there have been two separate prizes in astronomy and mathematics awarded at the same time. The prize in polyarthritis is awarded only when a special committee has shown that scientific progress in this field has been such that an award is justified. The laureates are announced in mid-January each year, and the prize is presented in April/May on “Crafoord Day." It is received from the hand of His Majesty the King of Sweden. In connection with Crafoord Day, a symposium in the discipline in question is arranged by the Royal Swedish Academy of Sciences. The Academy reports that Russian-American mathematician Yakov Eliashberg is one of the leading mathematicians of our time. For more than 30 years, he has helped to shape and research a field of mathematics known as symplectic geometry, and one of its branches in particular — symplectic topology. Eliashberg has solved many of the most important problems in the field and has found new and surprising results. He has further developed the techniques he used in contact geometry, a twin theory to symplectic geometry. While symplectic geometry deals with spaces with two, four or other even dimensions, contact theory describes spaces with odd dimensions. Both theories are closely related to current developments in modern physics, such as string theory and quantum field theory. Symplectic geometry’s link to physics has old roots. For example, it describes the geometry of a space in a mechanical system, the space phase. For a moving object, its trajectory is determined each moment by its position and velocity. Together, they determine a surface element that is the basic structure of symplectic geometry. The geometry describes the directions in which the system can develop; it describes movement. Physics becomes geometry. One of Eliashberg’s first, and perhaps most surprising, results was the discovery that there are regions where symplectic geometry is rigid and other regions where it is completely flexible. But where the boundary is between the flexible and the rigid regions, and how it can be described mathematically, is still a question awaiting an answer. Yakov Eliashberg was born in 1946 in St. Petersburg, Russia. He receiced his Ph.D. at Leningrad State University 1972. Eliashberg is the Herald L. and Caroline L. Ritch Professor of mathematics at Stanford University. The Academy explains in a background piece for this year’s prize that black holes are the source of the universe’s most powerful radiation, as well as of jets that can stretch many thousands of light years out into space. Roger Blandford’s theoretical work deals with the violent processes behind these phenomena. Roy Kerr laid the foundation for this research early on, when he discovered a mathematical description of rotating black holes. This became one of the most important theoretical discoveries in modern cosmology. The prediction of black holes is one of the perhaps strangest results of the general theory of relativity. When Albert Einstein finally presented his theory, in November 1915, he described gravity as a geometric property of space and time, spacetime. All objects with mass bend spacetime; they create a pit into which smaller objects can fall. The greater the mass, the deeper the pit. The mass of a black hole is so great that nothing that ends up in there can escape, not even light. It was not until 1963 that mathematician Roy Kerr succeeded in solving Einstein’s equations for rotating black holes. That the holes should rotate is feasible because the stars from which they originated should have rotated. At about the same time, astronomers discovered galaxies that emitted light and other electromagnetic radiation that was so strong it outshone several hundred ordinary galaxies. They were named quasars. Nothing other than a black hole could give the quasars their luminosity. So how is the strong light of rotating black holes created? This question was answered by Roger Blandford and his colleagues in the 1970s. Ever since, he has refined and made more realistic models of how gas surrounding a black hole flows towards it, is heated up and transforms some of its gravitational energy to radiation. While this is happening, electrically charged particles are sent millions of kilometers into space in the form of powerful jets. The source of all of this power is the rotational energy of the massive black hole. Roy Kerr was born in 1934 in Gore, New Zeeland. He received his Ph.D. in 1959 at the University of Cambridge. Kerr is an Emeritus Professor at the University of Canterbury, New Zeeland. Roger Blandford was born in 1949 in Grantham, Great Britain. He received his Ph.D. in 1974 at the University of Cambridge. Blandford is Luke Blossom Professor in the School of Humanities and Sciences, at Stanford University.