Recursos de colección

Caltech Authors (163.728 recursos)

Repository of works by Caltech published authors.

Group = NuSTAR

Mostrando recursos 1 - 20 de 558

  1. New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei

    Baloković, M.; Brightman, M.; Harrison, F. A.; Comastri, A.; Ricci, C.; Buchner, J.; Gandhi, P.; Farrah, D.; Stern, D.
    The basic unified model of active galactic nuclei (AGNs) invokes an anisotropic obscuring structure, usually referred to as a torus, to explain AGN obscuration as an angle-dependent effect. We present a new grid of X-ray spectral templates based on radiative transfer calculations in neutral gas in an approximately toroidal geometry, appropriate for CCD-resolution X-ray spectra (FWHM ≥ 130 eV). Fitting the templates to broadband X-ray spectra of AGNs provides constraints on two important geometrical parameters of the gas distribution around the supermassive black hole: the average column density and the covering factor. Compared to the currently available spectral templates, our...

  2. The NuSTAR Extragalactic Surveys: X-Ray Spectroscopic Analysis of the Bright Hard-band Selected Sample

    Zappacosta, L.; Harrison, F. A.
    We discuss the spectral analysis of a sample of 63 active galactic nuclei (AGN) detected above a limiting flux of S(8-24 keV) = 7 x 10^(-14) erg s^(-1) cm^(-2 in the multi-tiered NuSTAR extragalactic survey program. The sources span a redshift range z = 0-2.1 (median (z) = 0.58). The spectral analysis is performed over the broad 0.5–24 keV energy range, combining NuSTAR with Chandra and/or XMM-Newton data and employing empirical and physically motivated models. This constitutes the largest sample of AGN selected at 〉 10 keV to be homogeneously spectrally analyzed at these flux levels. We study the distribution...

  3. On the Nature of the High-Energy Rollover in 1H 0419-577

    Turner, T. J.; Reeves, J. N.; Braito, V.; Costa, M.
    A NuSTAR/Swift observation of the luminous Seyfert 1 galaxy 1H 0419-577 taken during 2015 reveals one of the most extreme high energy cut-offs observed to date from an AGN - an origin due to thermal Comptonization would imply a remarkably low coronal temperature $kT \sim 15$ keV. The low energy peak of the spectrum in the hard X-ray NuSTAR band, which peaks before the expected onset of a Compton hump, rules out strong reflection as the origin of the hard excess in this AGN. We show the origin of the high energy rollover is likely due to a combination of both thermal Comptonization and an intrinsically steeper continuum,...

  4. The outflow structure of GW170817 from late time broadband observations

    Troja, E.; Piro, L.; Ryan, G.; van Eerten, H.; Ricci, R.; Wieringa, M.; Lotti, S.; Sakamoto, T.; Cenko, S. B.
    We present our broadband study of GW170817 from radio to hard X-rays, including Chandra and NuStar observations, and a multi-messenger analysis including LIGO constraints. The data are compared with predictions from a wide range of models, providing the first detailed comparison between non-trivial cocoon and jet models. Homogeneous and power-law shaped jets, as well as simple cocoon models are ruled out by the data, while both a Gaussian shaped jet and a cocoon with energy injection are found to be consistent with the present data. We propose that these models can be unambiguously discriminated by future observations measuring the post-peak behaviour, with temporal slope -1.2 for the cocoon and...

  5. A deep X-ray view of the bare AGN Ark 120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes

    Porquet, D.; Reeves, J. N.; Matt, G.; Marinucci, A.; Nardini, E.; Braito, V.; Lobban, A.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Dauser, T.; Farrah, D.; García, J.; Hailey, C. J.; Harrison, F.; Stern, D.; Tortosa, A.; Ursini, F.; Zhang, W. W.
    Context. The physical characteristics of the material closest to supermassive black holes (SMBHs) are primarily studied through X-ray observations. However, the origins of the main X-ray components such as the soft X-ray excess, the Fe Kα line complex, and the hard X-ray excess are still hotly debated. This is particularly problematic for active galactic nuclei (AGN) showing a significant intrinsic absorption, either warm or neutral, which can severely distort the observed continuum. Therefore, AGN with no (or very weak) intrinsic absorption along the line of sight, so-called “bare AGN”, are the best targets to directly probe matter very close to the...

  6. A deep X-ray view of the bare AGN Ark 120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes

    Porquet, D.; Reeves, J. N.; Matt, G.; Marinucci, A.; Nardini, E.; Braito, V.; Lobban, A.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Dauser, T.; Farrah, D.; García, J.; Hailey, C. J.; Harrison, F.; Stern, D.; Tortosa, A.; Ursini, F.; Zhang, W. W.
    Context. The physical characteristics of the material closest to supermassive black holes (SMBHs) are primarily studied through X-ray observations. However, the origins of the main X-ray components such as the soft X-ray excess, the Fe Kα line complex, and the hard X-ray excess are still hotly debated. This is particularly problematic for active galactic nuclei (AGN) showing a significant intrinsic absorption, either warm or neutral, which can severely distort the observed continuum. Therefore, AGN with no (or very weak) intrinsic absorption along the line of sight, so-called “bare AGN”, are the best targets to directly probe matter very close to the...

  7. Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR

    Xu, Yanjun; Harrison, Fiona A.; García, Javier A.; Fabian, Andrew C.; Fürst, Felix; Gandhi, Poshak; Grefenstette, Brian W.; Madsen, Kristin K.; Miller, Jon M.; Parker, Michael L.; Tomsick, John A.; Walton, Dominic J.
    We report on a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently discovered bright black hole candidate MAXI J1535-571. NuSTAR observed the source on MJD 58003 (five days after the outburst was reported). The spectrum is characteristic of a black hole binary in the hard state. We observe clear disk reflection features, including a broad Fe Kα line and a Compton hump peaking around 30 keV. Detailed spectral modeling reveals a narrow Fe Kα line complex centered around 6.5 keV on top of the strong relativistically broadened Fe Kα line. The narrow component is consistent with distant reflection from...

  8. NuSTAR hard x-ray optics

    Koglin, Jason E.; Christensen, Finn E.; Craig, William W.; Decker, Todd R.; Hailey, Charles J.; Harrison, Fiona A.; Hawthorn, Colin; Jensen, Carsten P.; Madsen, Kristin K.; Stern, Marcela; Tajiri, Gordon; Taylor, Michael D.
    The Nuclear Spectroscopic Telescope Array (NuSTAR) is a small explorer (SMEX) mission currently under an extended Phase A study by NASA. NuSTAR will be the first satellite mission to employ focusing optics in the hard X-ray band (8-80 keV). Its design eliminates high detector backgrounds, allows true imaging, and permits the use of compact high performance detectors. The result: a combination of clarity, sensitivity, and spectral resolution surpassing the largest observatories that have operated in this band by orders of magnitude. We present an overview of the NuSTAR optics design and production process. We also describe the progress of several...

  9. NuSTAR hard x-ray optics

    Koglin, Jason E.; Christensen, Finn E.; Craig, William W.; Decker, Todd R.; Hailey, Charles J.; Harrison, Fiona A.; Hawthorn, Colin; Jensen, Carsten P.; Madsen, Kristin K.; Stern, Marcela; Tajiri, Gordon; Taylor, Michael D.
    The Nuclear Spectroscopic Telescope Array (NuSTAR) is a small explorer (SMEX) mission currently under an extended Phase A study by NASA. NuSTAR will be the first satellite mission to employ focusing optics in the hard X-ray band (8-80 keV). Its design eliminates high detector backgrounds, allows true imaging, and permits the use of compact high performance detectors. The result: a combination of clarity, sensitivity, and spectral resolution surpassing the largest observatories that have operated in this band by orders of magnitude. We present an overview of the NuSTAR optics design and production process. We also describe the progress of several...

  10. Hard x-ray optics: from HEFT to NuSTAR

    Koglin, Jason E.; Chen, C. M. Hubert; Chonko, Jim C.; Christensen, Finn E.; Craig, William W.; Decker, Todd R.; Hailey, Charles J.; Harrison, Fiona A.; Jensen, Carsten P.; Madsen, Kristin K.; Pivovaroff, Michael J.; Stern, Marcela; Windt, David L.; Ziegler, Eric
    Focusing optics are now poised to dramatically improve the sensitivity and angular resolution at energies above 10 keV to levels that were previously unachievable by the past generation of background limited collimated and coded-aperture instruments. Active balloon programs (HEFT), possible Explorer-class satellites (NuSTAR - currently under Phase A study), and major X-ray observatories (Con-X HXT) using focusing optics will play a major role in future observations of a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters. These instruments call for low cost, grazing incidence optics coated with depth-graded multilayer films that can be nested...

  11. The nuclear spectroscopic telescope array (NuSTAR) high-energy X-ray mission

    Madsen, Kristin K.; Harrison, Fiona A.; An, Hongjun; Boggs, Steven E.; Christensen, Finn E.; Cook, Rick; Craig, William W.; Forster, Karl; Fuerst, Felix; Grefenstette, Brian; Hailey, Charles J.; Kitaguchi, Takao; Markwardt, Craig; Mao, Peter; Miyasaka, Hiromasa; Rana, Vikram; Stern, Daniel K.; Zhang, William W.; Zoglauer, Andreas; Walton, Dominic; Westergaard, Niels J.
    The Nuclear Spectroscopic Telescope Array (NuSTAR) mission was launched on 2012 June 13 and is the first focusing high-energy X-ray telescope in orbit operating above ~10 keV. NuSTAR flies two co-aligned Wolter-I conical approximation X-ray optics, coated with Pt/C and W/Si multilayers, and combined with a focal length of 10.14 meters this enables operation from 3-79 keV. The optics focus onto two focal plane arrays, each consisting of 4 CdZnTe pixel detectors, for a field of view of 12.5 arcminutes. The inherently low background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a...

  12. Through-Silicon-Vias (TSVs) for 3D readout of ASIC for nearly gapless CdZnTe detector arrays

    Hong, Jaesub; Allen, Branden; Grindlay, Jonathan; Miyasaka, Hiromasa; Burnham, Jill; Hong, Sankgi; Lei, Wesker; Barthelmy, Scott; Patti, Robert; Harrison, Fiona
    Wirebonds, although proven for space application and perceived necessary for hybrid sensors like CdZnTe (CZT) detectors, introduce assembly complexity and undesirable gaps between detector units. Thus, they pose a serious challenge in building a low cost large area detector. We are developing Through-Silicon Vias (TSVs) to make all connections (both power and data) through ASICs, which will eliminate wirebonds and enable simple direct flip-chip bonding between the ASIC and a substrate electronics layer. TSVs also enable a more compact layout of the ASIC, which reduces the inactive area of the detector plane, and thus enables nearly gaplessly tilable detector arrays....

  13. Through-Silicon-Vias (TSVs) for 3D readout of ASIC for nearly gapless CdZnTe detector arrays

    Hong, Jaesub; Allen, Branden; Grindlay, Jonathan; Miyasaka, Hiromasa; Burnham, Jill; Hong, Sankgi; Lei, Wesker; Barthelmy, Scott; Patti, Robert; Harrison, Fiona
    Wirebonds, although proven for space application and perceived necessary for hybrid sensors like CdZnTe (CZT) detectors, introduce assembly complexity and undesirable gaps between detector units. Thus, they pose a serious challenge in building a low cost large area detector. We are developing Through-Silicon Vias (TSVs) to make all connections (both power and data) through ASICs, which will eliminate wirebonds and enable simple direct flip-chip bonding between the ASIC and a substrate electronics layer. TSVs also enable a more compact layout of the ASIC, which reduces the inactive area of the detector plane, and thus enables nearly gaplessly tilable detector arrays....

  14. Development of focal plane detectors for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission

    Rana, Vikram R.; Cook, Walter R., III; Harrison, Fiona A.; Mao, Peter H.; Miyasaka, Hiromasa
    The Nuclear Spectroscopic Telescope Array (NuSTAR), scheduled for launch in 2011, is a NASA Small Explorer mission that will improve the current sensitivity for detection of faint astrophysical sources in the 6-80 keV band by two orders of magnitude. NuSTAR achieves high sensitivity by utilizing a hard X-ray focusing system. We have developed Cadmium Zinc Telluride (CdZnTe) pixel detectors optimized for good energy for the NuSTAR focal plane. Each of NuSTAR's two focal planes is comprised of hybrid detectors that consist of a CdZnTe pixel sensor with the anode contacts directly attached to corresponding readout circuits integrated on a custom...

  15. Development of focal plane detectors for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission

    Rana, Vikram R.; Cook, Walter R., III; Harrison, Fiona A.; Mao, Peter H.; Miyasaka, Hiromasa
    The Nuclear Spectroscopic Telescope Array (NuSTAR), scheduled for launch in 2011, is a NASA Small Explorer mission that will improve the current sensitivity for detection of faint astrophysical sources in the 6-80 keV band by two orders of magnitude. NuSTAR achieves high sensitivity by utilizing a hard X-ray focusing system. We have developed Cadmium Zinc Telluride (CdZnTe) pixel detectors optimized for good energy for the NuSTAR focal plane. Each of NuSTAR's two focal planes is comprised of hybrid detectors that consist of a CdZnTe pixel sensor with the anode contacts directly attached to corresponding readout circuits integrated on a custom...

  16. Ground calibration of the spatial response and quantum efficiency of the CdZnTe hard x-ray detectors for NuSTAR

    Grefenstette, Brian W.; Bhalerao, Varun; Cook, W. Rick; Harrison, Fiona A.; Kitaguchi, Takao; Madsen, Kristin K.; Mao, Peter H.; Miyasaka, Hiromasa; Rana, Vikram
    Pixelated Cadmium Zinc Telluride (CdZnTe) detectors are currently flying on the Nuclear Spectroscopic Telescope ARray (NuSTAR) NASA Astrophysics Small Explorer. While the pixel pitch of the detectors is ≈ 605 μm, we can leverage the detector readout architecture to determine the interaction location of an individual photon to much higher spatial accuracy. The sub-pixel spatial location allows us to finely oversample the point spread function of the optics and reduces imaging artifacts due to pixelation. In this paper we demonstrate how the sub-pixel information is obtained, how the detectors were calibrated, and provide ground verification of the quantum efficiency of...

  17. Observational artifacts of Nuclear Spectroscopic Telescope Array: ghost rays and stray light

    Madsen, Kristin K.; Christensen, Finn E.; Craig, William W.; Forster, Karl W.; Grefenstette, Brian W.; Harrison, Fiona A.; Miyasaka, Hiromasa; Rana, Vikram
    The Nuclear Spectroscopic Telescope Array (NuSTAR) launched in June 2012, flies two conical approximation Wolter-I mirrors at the end of a 10.15-m mast. The optics are coated with multilayers of Pt/C and W/Si that operate from 3 to 80 keV. Since the optical path is not shrouded, aperture stops are used to limit the field of view (FoV) from background and sources outside the FoV. However, there is still a sliver of sky (∼1.0  deg to 4.0 deg) where photons may bypass the optics altogether and fall directly on the detector array. We term these photons stray light. Additionally, there are...

  18. Looking at A 0535+26 at low luminosities with NuSTAR

    Ballhausen, Ralf; Pottschmidt, Katja; Fürst, Felix; Wilms, Jörn; Tomsick, John A.; Schwarm, Fritz-Walter; Stern, Daniel; Kretschmar, Peter; Caballero, Isabel; Harrison, Fiona A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles J.; Zhang, William W.
    We report on two NuSTAR observations of the high-mass X-ray binary A 0535+26 taken toward the end of its normal 2015 outburst at very low 3–50 keV luminosities of ~1.4 × 10^(36) erg s^(-1) and ~5 × 10^(35) erg s^(-1), which are complemented by nine Swift observations. The data clearly confirm indications seen in earlier data that the source’s spectral shape softens as it becomes fainter. The smooth exponential rollover at high energies seen in the first observation evolves to a much more abrupt steepening of the spectrum at 20–30 keV. The continuum evolution can be nicely described with emission from a...

  19. Spectral and Timing Properties of IGR J17091–3624 in the Rising Hard State During Its 2016 Outburst

    Xu, Yanjun; García, Javier A.; Fürst, Felix; Harrison, Fiona A.; Walton, Dominic J.; Tomsick, John A.; Bachetti, Matteo; King, Ashley L.; Madsen, Kristin K.; Miller, Jon M.; Grinberg, Victoria
    We present a spectral and timing study of the NuSTAR and Swift observations of the black hole candidate IGR J17091–3624 in the hard state during its outburst in 2016. Disk reflection is detected in each of the NuSTAR spectra taken in three epochs. Fitting with relativistic reflection models reveals that the accretion disk is truncated during all epochs with R_(in) > 10 r_g, with the data favoring a low disk inclination of ~30°–40°. The steepening of the continuum spectra between epochs is accompanied by a decrease in the high energy cutoff: the electron temperature kT_e drops from ~64 to ~26...

  20. NuSTAR and Swift observations of Swift J1357.2-0933 during an early phase of its 2017 outburst

    Stiele, H.; Kong, A. K. H.
    We present a detailed spectral analysis of Swift and NuSTAR observations of the very faint X-ray transient and black hole system, Swift J1357.2–0933, during an early, low-hard state of its 2017 outburst. Swift J1357.2–0933 was observed at ~0.02% of the Eddington luminosity (for a distance of 2.3 kpc and a mass of 4 M_⊙). Despite the low luminosity, the broadband X-ray spectrum between 0.3 and 78 keV requires the presence of a disk blackbody component with an inner disk temperature of T_(in) ~ 0.06 keV in addition to a thermal Comptonization component with a photon index of Γ ~ 1.70....

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