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Caltech Authors (147.820 recursos)

Repository of works by Caltech published authors.

Group = NuSTAR

Mostrando recursos 1 - 20 de 360

  1. The NuSTAR View of the Seyfert 2 Galaxy NGC 4388

    Kamraj, N.; Rivers, E.; Harrison, F. A.; Brightman, M.; Baloković, M.
    We present analysis of NuSTAR X-ray observations in the 3-79 keV energy band of the Seyfert 2 galaxy NGC 4388, taken in 2013. The broadband sensitivity of NuSTAR, covering the Fe K$\alpha$ line and Compton reflection hump, enables tight constraints to be placed on reflection features in AGN X-ray spectra, thereby providing insight into the geometry of the circumnuclear material. In this observation, we found the X-ray spectrum of NGC 4388 to be well described by a moderately absorbed power law with non-relativistic reflection. We fit the spectrum with phenomenological reflection models and a physical torus model, and find the source to be absorbed by Compton-thin material (N$_{H}...

  2. Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured

    Ricci, C.; Bauer, F. E.; Treister, E.; Schawinski, K.; Privon, G. C.; Blecha, L.; Arevalo, P.; Armus, L.; Harrison, F. A.; Ho, L. C.; Iwasawa, K.; Sanders, D. B.; Stern, D.
    Mergers of galaxies are thought to cause significant gas inflows to the inner parsecs, which can activate rapid accretion on to supermassive black holes (SMBHs), giving rise to active galactic nuclei (AGN). During a significant fraction of this process, SMBHs are predicted to be enshrouded by gas and dust. Studying 52 galactic nuclei in infrared-selected local luminous and ultraluminous infrared galaxies in different merger stages in the hard X-ray band, where radiation is less affected by absorption, we find that the amount of material around SMBHs increases during the last phases of the merger. We find that the fraction of Compton-thick (CT, NH ≥ 10^(24) cm^−2) AGN...

  3. Galactic Sources Detected in the NuSTAR Serendipitous Survey

    Tomsick, John A.; Lansbury, George B.; Rahoui, Farid; Clavel, Maïca; Fornasini, Francesca M.; Hong, Jaesub; Aird, James; Alexander, David M.; Bodaghee, Arash; Chiu, Jeng-Lun; Grindlay, Jonathan E.; Hailey, Charles J.; Harrison, Fiona A.; Krivonos, Roman A.; Mori, Kaya; Stern, Daniel
    The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and Universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3-24 keV band using 13 deg2 of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify eight of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminosities for three of them. There are four CVs...

  4. CO excitation in the Seyfert galaxy NGC7130

    Pozzi, F.; Vallini, L.; Vignali, C.; Talia, M.; Gruppioni, C.; Mingozzi, M.; Massardi, M.; Andreani, P.
    We present a coherent multi-band modelling of the CO Spectral Energy Distribution of the local Seyfert Galaxy NGC7130 to assess the impact of the AGN activity on the molecular gas. We take advantage of all the available data from X-ray to the sub-mm, including ALMA data. The high-resolution (~0.2") ALMA CO(6-5) data constrain the spatial extension of the CO emission down to ~70 pc scale. From the analysis of the archival CHANDRA and NuSTAR data, we infer the presence of a buried, Compton-thick AGN of moderate luminosity, L_2-10keV ~ 1.6x10^{43} ergs-1. We explore photodissociation and X-ray-dominated regions (PDRs and XDRs) models to reproduce the CO emission. We find...

  5. Sagittarius A* High Energy X-ray Flare Properties During NuSTAR Monitoring of the Galactic Center from 2012 to 2015

    Zhang, Shuo; Baganoff, Frederick K.; Ponti, Gabriele; Neilsen, Joseph; Tomsick, John A.; Dexter, Jason; Clavel, Maïca; Markoff, Sera; Hailey, Charles J.; Mori, Kaya; Barrière, Nicolas M.; Nowak, Michael A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Grefenstette, Brian W.; Harrison, Fiona A.; Madsen, Kristin K.; Stern, Daniel; Zhang, William W.
    Understanding the origin of the flaring activity from the Galactic center supermassive black hole, Sagittarius A^* , is a major scientific goal of the NuSTAR Galactic plane survey campaign. We report on the data obtained between July 2012 and April 2015, including 27 observations on Sgr A^* with a total exposure of = 1 Ms. We found a total of ten X-ray flares detected in the NuSTAR observation window, with luminosities in the range of L_3_(−79 keV) ∼ (0.2–4.0)×10^(35) erg s^−1 . With this largest hard X-ray Sgr A^* flare dataset to date, we studied the flare spectral properties. Seven flares are detected above 5σ significance, showing a...

  6. Measurement of the Absolute Crab Flux with NuSTAR

    Madsen, Kristin K.; Forster, Karl; Grefenstette, Brian W.; Harrison, Fiona A.; Stern, Daniel
    We present results from a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Crab made at a large off-axis angle of 1 5. At these angles, X-rays do not pass through the optics and instead illuminate the detectors directly, due to incomplete baffling. Due to the simplicity of the instrument response in this configuration and the good absolute calibration of the detectors, we are able to measure the absolute intrinsic flux of the Crab to better than 4%. We find the spectral parameters of the power law to be Γ = 2.106 ± 0.006, N = 9.71 ± 0.16, in...

  7. An XMM-Newton and NuSTAR Study of IGR J18214-1318: A Non-pulsating High-mass X-Ray Binary with a Neutron Star

    Fornasini, Francesca M.; Tomsick, John A.; Bachetti, Matteo; Krivonos, Roman A.; Fürst, Felix; Natalucci, Lorenzo; Pottschmidt, Katja; Wilms, Jörn
    IGR J18214-1318, a Galactic source discovered by the International Gamma-Ray Astrophysics Laboratory, is a high-mass X-ray binary (HMXB) with a supergiant O-type stellar donor. We report on the XMM-Newton and NuSTAR observations that were undertaken to determine the nature of the compact object in this system. This source exhibits high levels of aperiodic variability, but no periodic pulsations are detected with a 90% confidence upper limit of 2% fractional rms between 0.00003–88 Hz, a frequency range that includes the typical pulse periods of neutron stars (NSs) in HMXBs (0.1–10^3 s). Although the lack of pulsations prevents us from definitively identifying...

  8. Analysis of NuSTAR and Suzaku observations of Cyg X-1 in the hard state: evidence for a truncated disc geometry

    Basak, Rupal; Zdziarski, Andrzej A.; Parker, Michael; Islam, Nazma
    The geometry of the accretion flow in black-hole X-ray binaries in the hard state, in particular the position of the disc inner edge, has been a subject of intense debate in recent years. We address this issue by performing a spectral study of simultaneous observations of Cyg X-1 in the hard state by {\it{NuSTAR}\} and {\it{Suzaku}}. The same data were analysed before, and modelled by a lamppost containing hybrid electrons and located very close to the horizon, which emission was incident on a surrounding disc extending almost to the innermost stable circular orbit. We re-analyse the incident continuum model and show that it suffers from the lack of...

  9. Detection of Cyclotron Resonance Scattering Feature in High Mass X-ray Binary Pulsar SMC X-2

    Jaisawal, Gaurava K.; Naik, Sachindra
    We report broadband spectral properties of the high mass X-ray binary pulsar SMC X-2 by using three simultaneous $NuSTAR$ and $Swift$/XRT observations during its 2015 outburst. The pulsar was significantly bright, reaching a luminosity up to as high as $\sim$5.5$\times$10$^{38}$~ergs~s$^{-1}$ in 1-70 keV range. Spin period of the pulsar was estimated to be 2.37 s. Pulse profiles were found to be strongly luminosity dependent. The 1-70 keV energy spectrum of the pulsar was well described with three different continuum models such as (i) negative and positive power-law with exponential cutoff, (ii) Fermi-Dirac cutoff power-law and (iii) cutoff power-law models. Apart from the presence of an iron line at $\sim$6.4...

  10. X-ray Intraday Variability of Five TeV Blazars with NuSTAR

    Pandey, Ashwani; Gupta, Alok C.; Wiita, Paul J.
    We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and PKS 2155-304. Four of the blazars showed intraday variability in the NuSTAR energy range of 3-79 keV. Using an auto correlation function analysis we searched for intraday variability timescales in these LCs and found indications of several between 2.5 and 32.8 ks in eight LCs of Mrk 421, a timescale around 8.0 ks for one LC of Mrk 501, and timescales of 29.6 ks and 57.4 ks in two LCs of PKS 2155-304. The other two blazars' LCs do not show any...

  11. A broadband self-consistent modelling of the X-ray spectrum of 4U 1626–67

    D'Aì, Antonino; Cusumano, Giancarlo; Del Santo, Melania; La Parola, Valentina; Segreto, Alberto
    The accretion-powered X-ray pulsar 4U 1626--67 is one of the few highly magnetized pulsars that accretes through Roche-lobe overflow from a low-mass companion. The characteristics of its broadband spectrum are similar to those of X-ray pulsars hosted in a high-mass X-ray binary systems, with a broad resonant cyclotron scattering feature (CRSF) at ~37 keV. In this work, we examine the pulse-resolved and the pulse-averaged broadband spectrum using data from NuSTAR and Swift. We use the Becker & Wolff model of bulk+thermal Comptonization to infer key physical parameters of the accretion column flow and a broadband model for the disk reflected...

  12. The weak Fe fluorescence line and long-term X-ray evolution of the Compton-thick active galactic nucleus in NGC 7674

    Gandhi, P.; Annuar, A.; Lansbury, G. B.; Stern, D.; Alexander, D. M.; Bauer, F. E.; Bianchi, S.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Del Moro, A.; Elvis, M.; Guainazzi, M.; Hailey, C. J.; Harrison, F. A.; Koss, M.; Lamperti, I.; Malaguti, G.; Masini, A.; Matt, G.; Puccetti, S.; Ricci, C.; Rivers, E.; Walton, D. J.; Zhang, W. W.
    We present NuSTAR X-ray observations of the active galactic nucleus (AGN) in NGC 7674. The source shows a flat X-ray spectrum, suggesting that it is obscured by Compton-thick gas columns. Based upon long-term flux dimming, previous work suggested the alternate possibility that the source is a recently switched-off AGN with the observed X-rays being the lagged echo from the torus. Our high-quality data show the source to be reflection-dominated in hard X-rays, but with a relatively weak neutral Fe Kα emission line (equivalent width [EW] of ≈ 0.4 keV) and a strong Fe xxvi ionized line (EW ≈ 0.2 keV). We...

  13. Magnetar Broadband X-ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE

    Enoto, Teruaki; Shibata, Shinpei; Kitaguchi, Takao; Suwa, Yudai; Uchide, Takahiko; Nishioka, Hiroyuki; Kisaka, Shota; Nakano, Toshio; Murakami, Hiroaki; Makishima, Kazuo
    Studies were made of the 1–70 keV persistent spectra of fifteen magnetars as a complete sample observed with Suzaku from 2006 to 2013. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at &10 keV with the 15–60 keV flux of ∼1–11 × 10−11 ergs s−1 cm−2. The hard X-ray luminosity Lh, relative to that of a soft-thermal surface radiation Ls, tends to become higher toward younger and strongly magnetized objects. Updated from the previous study, their hardness ratio, defined as ξ = Lh/Ls, is correlated with the measured spin-down rate P˙ as ξ = 0.62 × (P...

  14. The Broadband Spectral Variability of Holmberg IX X-1

    Walton, D. J.; Fürst, F.; Harrison, F. A.; Middleton, M. J.; Fabian, A. C.; Bachetti, M.; Barret, D.; Miller, J. M.; Ptak, A.; Rana, V.; Stern, D.; Tao, L.
    We present results from four new broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 (L_X > 10^(40) erg s^(−1)), performed by Suzaku and NuSTAR in coordination. Combined with the archival data, we now have broadband observations of this remarkable source from six separate epochs. Two of these new observations probe lower fluxes than seen previously, allowing us to extend our knowledge of the broadband spectral variability exhibited. The spectra are well fit by two thermal blackbody components that dominate the emission below 10 keV, as well as a steep (Γ ~ 3.5) power-law tail that dominates...

  15. High-redshift Blazars through NuSTAR Eyes

    Marcotulli, L.; Paliya, V. S.; Ajello, M.; Kaur, A.; Hartmann, D. H.; Gasparrini, D.; Greiner, J.; Rau, A.; Schady, P.; Baloković, M.; Stern, D.; Madejski, G.
    The most powerful sources among the blazar family are MeV blazars. Often detected at z > 2, they usually display high X- and γ-ray luminosities, larger-than-average jet powers, and black hole masses ≳10^9 M☉. In the present work, we perform a multiwavelength study of three high-redshift blazars: 3FGL J0325.5+2223 (z = 2.06), 3FGL J0449.0+1121 (z = 2.15), and 3FGL J0453.2−2808 (z = 2.56), analyzing quasi-simultaneous data from GROND, Swift-UVOT and XRT, Nuclear Spectroscopic Telescope Array (NuSTAR), and Fermi-LAT. Our main focus is on the hard X-ray band recently unveiled by NuSTAR (3–79 keV) where these objects show a hard spectrum...

  16. Multi-epoch analysis of the X-ray spectrum of the active galactic nucleus in NGC 5506

    Sun, Shangyu; Guainazzi, Matteo; Ni, Qingling; Wang, Jingchun; Qian, Chenyang; Shi, Fangzheng; Wang, Yu; Bambi, Cosimo
    We present a multi-epoch X-ray spectroscopy analysis of the nearby narrow-line Seyfert I galaxy NGC 5506. For the first time, spectra taken by Chandra, XMM-Newton, Suzaku, and NuSTAR - covering the 2000-2014 time span - are analyzed simultaneously, using state-of-the-art models to describe reprocessing of the primary continuum by optical thick matter in the AGN environment. The main goal of our study is determining the spin of the supermassive black hole (SMBH). The nuclear X-ray spectrum is photoelectrically absorbed by matter with column density $\simeq 3 \times 10^{22}$~cm$^{-2}$. A soft excess is present at energies lower than the photoelectric cut-off. Both photo-ionized and collisionally ionized components are required to...

  17. NuSTAR Hard X-ray Observations of the Energetic Millisecond Pulsars PSR B1821-24, PSR B1937+21, and PSR J0218+4232

    Gotthelf, E. V.; Bogdanov, S.
    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray timing and spectroscopy of the three exceptionally energetic rotation-powered millisecond pulsars PSRs B1821-24, B1937+21, and J0218+4232. By correcting the NuSTAR on-board clock for phase and frequency drifts between observation intervals, we are able to recover the intrinsic hard X-ray pulse profiles of all three pulsars with a resolution down to < 15 microsec. The substantial reduction of background emission relative to previous broad-band X-ray observations allows us to detect for the first time pulsed emission up to ~50 keV, ~20 keV, and ~25 keV, for the three pulsars, respectively. We conduct phase-resolved spectroscopy in the 0.5-79 keV range for all...

  18. Spectral and temporal properties of the ultra-luminous X-ray pulsar in M82 from 15 years of Chandra observations and analysis of the pulsed emission using NuSTAR

    Brightman, Murray; Harrison, Fiona; Walton, Dominic J.; Fuerst, Felix; Hornschemeier, Ann; Zezas, Andreas; Bachetti, Matteo; Grefenstette, Brian; Ptak, Andrew; Tendulkar, Shriharsh; Yukita, Mihoko
    The recent discovery by Bachetti et al. of a pulsar in M82 that can reach luminosities of up to 1040 erg s−1, a factor of ~100 times the Eddington luminosity for a 1.4 M⊙ compact object, poses a challenge for accretion physics. In order to better understand the nature of this source and its duty cycle, and in light of several physical models that have been subsequently published, we conduct a spectral and temporal analysis of the 0.5–8 keV X-ray emission from this source from 15 years of Chandra observations. We analyze 19 ACIS observations where the point-spread function (PSF)...

  19. The NuSTAR Hard X-Ray Survey of the Norma Arm Region

    Fornasini, Francesca M.; Forster, Karl; Grefenstette, Brian W.; Harrison, Fiona A.; Madsen, Kristin K.; Mao, Peter H.; Miyasaka, Hiromasa; Rana, Vikram
    We present a catalog of hard X-ray sources in a square-degree region surveyed by the Nuclear Spectroscopic Telescope Array (NuSTAR) in the direction of the Norma spiral arm. This survey has a total exposure time of 1.7 Ms, and the typical and maximum exposure depths are 50 ks and 1 Ms, respectively. In the area of deepest coverage, sensitivity limits of 5 × 10^(−14) and 4 × 10^(−14) erg s^(−1) cm^(−2) in the 3–10 and 10–20 keV bands, respectively, are reached. Twenty-eight sources are firmly detected, and 10 are detected with low significance; 8 of the 38 sources are expected...

  20. The infrared to X-ray correlation spectra of unobscured type 1 active galactic nuclei

    García-Bernete, I.; Ramos Almeida, C.; Landt, H.; Ward, M. J.; Baloković, M.; Acosta-Pulido, J. A.
    We use new X-ray data obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR), near-infrared (NIR) fluxes, and mid-infrared (MIR) spectra of a sample of 24 unobscured type 1 active galactic nuclei (AGN) to study the correlation between various hard X-ray bands between 3 and 80 keV and the infrared (IR) emission. The IR to X-ray correlation spectrum (IRXCS) shows a maximum at ~15-20 micron, coincident with the peak of the AGN contribution to the MIR spectra of the majority of the sample. There is also a NIR correlation peak at ~2 micron, which we associate with the NIR bump observed in some type 1 AGN at ~1-5 micron...

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