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Caltech Authors (147.820 recursos)

Repository of works by Caltech published authors.

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. 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...

5. 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...

6. SNLS spectroscopy: testing for evolution in type Ia supernovae

Bronder, T. J.; Hook, I. M.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R. G.; Conley, A.; Fouchez, D.; Guy, J.; Howell, D. A.; Neill, J. D.; Pain, R.; Perrett, K.; Pritchet, C. J.; Regnault, N.; Sullivan, M.; Baumont, S.; Fabbro, S.; Filliol, M.; Perlmutter, S.; Ripoche, P.
Aims. We present a quantitative study of a new data set of high redshift Type Ia supernovae spectra, observed at the Gemini telescopes during the first 34 months of the Supernova Legacy Survey. During this time 123 supernovae candidates were observed, of which 87 have been identified as SNe Ia at a median redshift of z=0.720. Spectra from the entire second year of the survey and part of the third year (59 total SNe candidates with 46 confirmed SNe Ia) are published here for the first time. The spectroscopic measurements made on this data set are used determine if these...

7. BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission

Lamperti, Isabella; Koss, Michael; Trakhtenbrot, Benny; Schawinski, Kevin; Ricci, Claudio; Oh, Kyuseok; Landt, Hermine; Riffel, Rogério; Rodríguez-Ardila, Alberto; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Mushotzky, Richard; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain
We provide a comprehensive census of the near-infrared (NIR, 0.8–2.4 μm) spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei (AGN), selected in the hard X-ray band (14–195 keV) from the Swift-Burst Alert Telescope survey. With the launch of the James Webb Space Telescope, this regime is of increasing importance for dusty and obscured AGN surveys. We measure black hole masses in 68 per cent (69/102) of the sample using broad emission lines (34/102) and/or the velocity dispersion of the Ca ii triplet or the CO band-heads (46/102). We find that emission-line diagnostics in the NIR are ineffective at...

8. 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...

9. The Golden Standard Type Ia Supernova 2005cf: Observations from the Ultraviolet to the Near-Infrared Wavebands

Wang, X.; Li, W.; Filippenko, A. V.; Foley, R. J.; Kirshner, R. P.; Modjaz, M.; Bloom, J.; Brown, P. J.; Carter, D.; Friedman, A. S.; Gal-Yam, A.; Ganeshalingam, M.; Hicken, M.; Krisciunas, K.; Milne, P.; Silverman, J. M.; Suntzeff, N. B.; Wood-Vasey, W. M.; Cenko, S. B.; Challis, P.; Fox, D. B.; Kirkman, D.; Li, J. Z.; Li, T. P.; Malkan, M. A.; Moore, M. R.; Reitzel, D. B.; Rich, R. M.; Serduke, F. J. D.; Shang, R. C.; Steele, T. N.; Swift, B. J.; Tao, C.; Wong, D. S.; Zhang, S. N.
We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal Type Ia supernova (SN Ia) 2005cf. The optical photometry, performed at eight different telescopes, shows a 1σ scatter of ≾0.03 mag after proper corrections for the instrument responses. From the well-sampled light curves, we find that SN 2005cf reached a B-band maximum at 13.63 ± 0.02 mag, with an observed luminosity decline rate Δm _(15)(B) = 1.05 ± 0.03 mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded...

10. 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)...

11. Validation of the effect of cross-calibrated GOES solar proton effective energies on derived integral fluxes by comparison with STEREO observations

Rodriguez, J. V.; Sandberg, I.; Mewaldt, R. A.; Daglis, I. A.; Jiggens, P.
The derivation of integral fluxes from instrument coincidence rates requires accurate knowledge of their effective energies. Recent cross calibrations of GOES with the high-energy-resolution Interplanetary Monitoring Platform (IMP) 8 Goddard Medium Energy Experiment (GME) (Sandberg et al., Geophys. Res. Lett, 41, 4435, 2014a) gave significantly lower effective energies than those currently used by the NOAA Space Weather Prediction Center to calculate solar proton integral fluxes from GOES rates. This implies systematically lower integral fluxes than currently produced. This paper quantifies the differences between the current and the cross-calibrated GOES integral fluxes and validates the latter. Care is taken to rule...

12. 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...

13. The high-Eddington NLS1 Ark 564 has the coolest corona

Kara, E.; Garcia, J. A.; Lohfink, A.; Fabian, A. C.; Reynolds, C. S.; Tombesi, F.; Wilkins, D. R.
Ark 564 is an archetypal Narrow line Seyfert 1 that has been well observed in soft X-rays from 0.3-10 keV, revealing a steep spectrum, strong soft excess, iron K emission line and dramatic variability on the order of hours. Because of its very steep spectrum, observations of the source above 10 keV have been sparse. We report here on the first NuSTAR observation of Ark 564. The source was observed for 200 ks with NuSTAR, 50 ks of which were concurrent with Suzaku observations. NuSTAR and Suzaku observed a dramatic flare, in which the hard emission is clearly delayed with respect to the soft emission, consistent with previous...

14. Coronal properties of the luminous radio-quiet quasar QSO B2202–209

Kammoun, E. S.; Risaliti, G.; Stern, D.; Jun, H. D.; Graham, M.; Celotti, A.; Behar, E.; Elvis, M.; Harrison, F. A.; Matt, G.; Walton, D. J.
We present an analysis of the joint XMM–Newton and NuSTAR observations of the radio-quiet quasar QSO B2202–209. Using an optical observation from the Hale Telescope at the Palomar Observatory, we revise the redshift of the source from the previously reported z = 1.77 to z = 0.532, and we estimate the mass of the central black hole, log (M_(BH)/M_⊙) = 9.08 ± 0.18. The X-ray spectrum of this source can be well described by a power law of photon index Γ = 1.82 ± 0.05 with E_(cut) = 152^(+103)_(−54) keV, in the rest frame of the source. Assuming a Comptonization model,...

15. A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

Ponti, G.; George, E.; Scaringi, S.; Zhang, S.; Jin, C.; Dexter, J.; Terrier, R.; Clavel, M.; Degenaar, N.; Eisenhauer, F.; Genzel, R.; Gillessen, S.; Goldwurm, A.; Habibi, M.; Haggard, D.; Hailey, C.; Harrison, F. A.; Merloni, A.; Mori, K.; Nandra, K.; Ott, T.; Pfuhl, O.; Plewa, P. M.; Waisberg, I.
We present the first fully simultaneous fits to the NIR and X-ray spectral slope (and its evolution) during a very bright flare from Sgr A⋆, the supermassive black hole at the Milky Way’s center. Our study arises from ambitious multi-wavelength monitoring campaigns with XMMNewton, NuSTAR and SINFONI. The average multi-wavelength spectrum is well reproduced by a broken power-law with ΓN IR = 1.7 ± 0.1 and ΓX = 2.27 ± 0.12. The difference in spectral slopes (∆Γ = 0.57 ± 0.09) strongly supports synchrotron emission with a cooling break. The flare starts first in the NIR with a flat and bright NIR spectrum, while X-ray radiation is...

16. The Phoenix galaxy as seen by NuSTAR

Masini, A.; Comastri, A.; Puccetti, S.; Baloković, M.; Gandhi, P.; Guainazzi, M.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Koss, M. J.; LaMassa, S. M.; Ricci, C.; Stern, D.; Walton, D. J.; Zhang, W. W.
Aims. We study the long-term variability of the well-known Seyfert 2 galaxy Mrk 1210 (also known as UGC 4203, or the Phoenix galaxy). Methods. The source was observed by many X-ray facilities in the last 20 yr. Here we present a NuSTAR observation and put the results in the context of previously published observations. Results. NuSTAR observed Mrk 1210 in 2012 for 15.4 ks. The source showed Compton-thin obscuration similar to that observed by Chandra, Suzaku, BeppoSAX and XMM-Newton over the past two decades, but different from the first observation by ASCA in 1995, in which the active nucleus was caught in a low...

17. Metrology system for measuring mast motions on the NuSTAR mission

Liebe, Carl Christian; Burnham, Jill; Cook, Rick; Craig, Bill; Decker, Todd; Harp, D. Isaiah; Kecman, Branislav; Meras, Patrick; Raffanti, Mike; Scholz, Christopher; Smith, Christopher; Waldman, Jeff; Wu, James
A metrology system designed and built for the NuSTAR mission is described. The NuSTAR mission is an orbiting X-ray telescope with a 10 meter focal length. The system consists of two laser pointers mounted rigidly together with a star tracker and the X-ray optics. The focused laser beams illuminates two metrology detectors mounted rigidly with the X-ray detectors. The detectors and optics/lasers are separated by a ∼10 meter deployable (and somewhat flexible) carbon fiber mast. Details about the implementation of the metrology system is discussed in this paper.

18. The response of relativistic outflowing gas to the inner accretion disk of a black hole

Parker, Michael L.; Pinto, Ciro; Fabian, Andrew C.; Lohfink, Anne M.; Buisson, Douglas J. K.; Alston, William N.; Kara, Erin; Cackett, Edward M.; Chiang, Chia-Ying; Dauser, Thomas; De Marco, Barbara; Gallo, Luigi C.; García, Javier A.; Harrison, Fiona A.; King, Ashley L.; Middleton, Matthew J.; Miller, Jon M.; Miniutti, Giovanni; Reynolds, Christopher S.; Uttley, Phil; Vasudevan, Ranjan; Walton, D. J.; Wilkins, Daniel R.; Zoghbi, Abderahmen
The brightness of an active galactic nucleus is set by the gas falling onto it from the galaxy, and the gas infall rate is regulated by the brightness of the active galactic nucleus; this feedback loop is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts1. Gas outflows (in the form of disk winds) release huge quantities of energy into the interstellar medium2, potentially clearing the surrounding gas. The most extreme (in terms of speed and energy) of these—the ultrafast outflows—are the subset of X-ray-detected outflows with velocities higher than...

19. Evidence for Relativistic Disk Reflection in the Seyfert 1h Galaxy/ULIRG IRAS 05189–2524 Observed by NuSTAR and XMM-Newton

Xu, Yanjun; Baloković, Mislav; Walton, Dominic J.; Harrison, Fiona A.; García, Javier A.; Koss, Michael J.
We present a spectral analysis of the NuSTAR and XMM-Newton observations of the Seyfert 1h galaxy/ULIRG IRAS 05189–2524 taken in 2013. We find evidence for relativistic disk reflection in the broadband X-ray spectrum: a highly asymmetric broad Fe Kα emission line extending down to 3 keV and a Compton scattering component above 10 keV. Physical modeling with a self-consistent disk reflection model suggests that the accretion disk is viewed at an intermediate angle with a supersolar iron abundance, and a mild constraint can be put on the high-energy cutoff of the power-law continuum. We test the disk reflection modeling under...

20. Particle acceleration and reconnection in the solar wind

Zank, G. P.; Hunana, P.; Mostafavi, P.; le Roux, J. A.; Webb, G. M.; Khabarova, O.; Cummings, A. C.; Stone, E. C.; Decker, R. B.
An emerging paradigm for the dissipation of magnetic turbulence in the supersonic solar wind is via localized quasi-2D small-scale magnetic island reconnection processes. An advection-diffusion transport equation for a nearly isotropic particle distribution describes particle transport and energization in a region of interacting magnetic islands [1; 2]. The dominant charged particle energization processes are 1) the electric field induced by quasi-2D magnetic island merging, and 2) magnetic island contraction. The acceleration of charged particles in a “sea of magnetic islands” in a super-Alfvénic flow, and the energization of particles by combined diffusive shock acceleration (DSA) and downstream magnetic island reconnection...

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