Browsing by Author "Balokovic, M."

Now showing 1 - 18 of 18
  • No Thumbnail Available
    Item
    A GROWTH-RATE INDICATOR FOR COMPTON-THICK ACTIVE GALACTIC NUCLEI
    (2016) Brightman, M.; Masini, A.; Ballantyne, D. R.; Balokovic, M.; Brandt, W. N.; Chen, C. -T.; Comastri, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Ricci, C.; Stern, D.; Walton, D. J.
    Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, lambda(Edd), and the X-ray power-law index, Gamma, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic Gamma is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic Gamma values and X-ray luminosities, L-X. With a simple bolometric correction to L-X to calculate lambda(Edd), we find a statistically significant correlation between Gamma and lambda(Edd) (p = 0.007). A linear fit to the data yields Gamma = (0.41 +/- 0.18)log(10)lambda(Edd) + (2.38 +/- 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M-BH approximate to 10(6)-10(7) M-circle dot) and are highly inclined, our results extend the Gamma-lambda(Edd) relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of Gamma as a growth-rate indicator for accreting black holes, even for CT AGNs.
  • Thumbnail Image
    Item
    A new population of compton-thick AGNs identified using the spectral curvature above 10 keV.
    (2016) Koss, M.; Bauer, Franz Erik; Ricci, Claudio; Treister, Ezequiel; Assef T., Roberto; Balokovic, M.; Stern, Daniel.; Gandhi, P.; Lamperti, I.; Alexander, D. M.
  • No Thumbnail Available
    Item
    BASS. XXXIII. Swift-BAT Blazars and Their Jets through Cosmic Time
    (2022) Marcotulli, L.; Ajello, M.; Urry, C. M.; Paliya, V. S.; Koss, M.; Oh, K.; Madejski, G.; Ueda, Y.; Balokovic, M.; Trakhtenbrot, B.; Ricci, F.; Ricci, C.; Stern, D.; Harrison, F.; Powell, M. C.
    We derive the most up-to-date Swift-Burst Alert Telescope (BAT) blazar luminosity function in the 14-195 keV range, making use of a clean sample of 118 blazars detected in the BAT 105 month survey catalog, with newly obtained redshifts from the BAT Active Galatic Nucleus Spectroscopic Survey. We determine the best-fit X-ray luminosity function for the whole blazar population, as well as for flat-spectrum radio quasars (FSRQs) alone. The main results are: (1) at any redshift, BAT detects the most luminous blazars, above any possible break in their luminosity distribution, which means we cannot differentiate between density and luminosity evolution; (2) the whole blazar population, dominated by FSRQs, evolves positively up to redshift z similar to 4.3, confirming earlier results and implying lower number densities of blazars at higher redshifts than previously estimated. The contribution of this source class to the cosmic X-ray background at 14-195 keV can range from 5%-18%, while possibly accounting for 100% of the MeV background. We also derived the average 14 keV-10 GeV spectral energy distribution for BAT blazars, which allows us to predict the number counts of sources in the MeV range, as well as the expected number of high-energy (>100 TeV) neutrinos. A mission like COSI will detect 40 MeV blazars, of which two may have coincident neutrino detections. Finally, taking into account beaming selection effects, the distribution and properties of the parent population of these extragalactic jets are derived. We find that the distribution of viewing angles is quite narrow, with most sources aligned within <5 degrees of the line of sight. Moreover, the average Lorentz factor, Gamma = 8-12, is lower than previously suggested for these powerful sources.
  • Thumbnail Image
    Item
    Determining the covering factor of compton-thick active galactic nuclei with NuSTAR
    (2015) Brightman, M.; Balokovic, M.; Stern, D.; Arevalo, P.; Ballantyne, D. R.; Bauer, Franz Erik; Bogg, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; Lamassa, S.; Fuerst, F.; Puccetti, S.; Rivers, E.; Vasudevan, R.; Walton, D. J.; Zhang, W. W.
  • Thumbnail Image
    Item
    Hard X-ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR
    (2016) Puccetti, S.; Comastri, A.; Bauer, Franz Erik; Brandt, W.; Fiore, E.; Harrison, F.; Luo, B.; Stern, D.; Urry, C.; Alexander, D.; Annuar, A.; Arevalo, P.; Balokovic, M.; Boggs, S.; Brightman, M.; Craig, W.; Ricci, Claudio
  • No Thumbnail Available
    Item
    Joint ALMA/X-ray monitoring of the radio-quiet type 1 active galactic nucleus IC 4329A
    (2024) Shablovinskaya, E.; Ricci, C.; Chang, C. -s.; Tortosa, A.; del Palacio, S.; Kawamuro, T.; Aalto, S.; Arzoumanian, Z.; Balokovic, M.; Bauer, F. E.; Gendreau, K. C.; Ho, L. C.; Kakkad, D.; Kara, E.; Koss, M. J.; Liu, T.; Loewenstein, M.; Mushotzky, R.; Paltani, S.; Privon, G. C.; Smith, K.; Tombesi, F.; Trakhtenbrot, B.
    The origin of a compact millimeter (mm, 100-250 GHz) emission in radio-quiet active galactic nuclei (RQ AGN) remains debated. Recent studies propose a connection with self-absorbed synchrotron emission from the accretion disk X-ray corona. We present the first joint ALMA (similar to 100 GHz) and X-ray (NICER/XMM-Newton/Swift; 2-10 keV) observations of the unobscured RQ AGN, IC 4329A (z = 0.016). The time-averaged mm-to-X-ray flux ratio aligns with recently established trends for larger samples, but with a tighter scatter (similar to 0.1 dex) compared to previous studies. However, there is no significant correlation on timescales of less than 20 days. The compact mm emission exhibits a spectral index of -0.23 +/- 0.18, remains unresolved with a 13 pc upper limit, and shows no jet signatures. Notably, the mm flux density varies significantly (by factor of 3) within four days, exceeding the contemporaneous X-ray variability and showing the largest mm variations ever detected in RQ AGN over daily timescales. The high amplitude variability rules out scenarios of heated dust and thermal free-free emission, pointing toward a synchrotron origin for the mm radiation in a source of similar to 1 light day (similar to 120 gravitational radii) size. While the exact source is not yet certain, an X-ray corona scenario emerges as the most plausible compared to a scaled-down jet or outflow-driven shocks.
  • Thumbnail Image
    Item
    NuSTAR AND XMM-NEWTON OBSERVATIONS OF LUMINOUS, HEAVILY OBSCURED, WISE-SELECTED QUASARS AT Z similar to 2
    (2014) Stern, D.; Lansbury, G.; Assef, R.; Brandt, W.; Alexander, D.; Ballantyne, D.; Balokovic, M.; Bauer, Franz Erik; Benford, D.
  • Thumbnail Image
    Item
    NuSTAR catches the unveiling nucleus of NGC 1068
    (2016) Bauer, Franz Erik; Ricci, Claudio; Marinucci, A.; Bianchi, S.; Matt, G.; Alexander, D.; Balokovic, M.; Brandt, W.; Gandhi, P.; Guainazzi, M.; Harrison, F.; Iwasawa, K.; Koss, M.; Madsen, K.; Nicastro, F.; Puccetti, S.; Stern, D.; Walton, D.
  • No Thumbnail Available
    Item
    NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?
    (OUP, 2020) Annuar, A.; Alexander, D. M.; Gandhi, P.; Lansbury, G. B.; Asmus, D.; Balokovic, M.; Ballantyne, D. R.; Bauer, Franz Erik; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Chen, C. T. J.; Del Moro, A.; Farrah, D.; Harrison, F. A.; Koss, M. J.; Lanz, L.; Marchesi, S.; Masini, A.; Nardini, E.; Ricci, Claudio; Stern, D.; Zappacosta, L.
    We present NuSTAR (Nuclear Spectroscopic Telescope Array) observations of four active galactic nuclei (AGNs) located within 15 Mpc. These AGNs, namely ESO 121-G6, NGC 660, NGC 3486, and NGC 5195, have observed X-ray luminosities of L 2–10 keV,obs ≲ 10 39 erg s −1 , classifying them as low-luminosity AGN (LLAGN). We perform broad-band X-ray spectral analysis for the AGN by combining our NuSTAR data with Chandra or XMM–Newton observations to directly measure their column densities (N H ) and infer their intrinsic power. We complement our X-ray data with archival and new high-angular resolution mid-infrared (mid-IR) data for all objects, except NGC 5195. Based on our X-ray spectral analysis, we found that both ESO 121-G6 and NGC 660 are heavily obscured (N H > 10 23 cm −2 ; L 2–10 keV,int ∼ 10 41 erg s −1 ), and NGC 660 may be Compton thick. We also note that the X-ray flux and spectral slope for ESO 121-G6 have significantly changed over the last decade, indicating significant changes in the obscuration and potentially accretion rate. On the other hand, NGC 3486 and NGC 5195 appear to be unobscured and just mildly obscured, respectively, with L 2–10 keV,int < 10 39 erg s −1 , i.e. genuine LLAGN. Both of the heavily obscured AGNs have L bol > 10 41 erg s −1 and λ Edd ≳ 10 −3 , and are detected in high-angular resolution mid-IR imaging, indicating the presence of obscuring dust on nuclear scale. NGC 3486, however, is undetected in high-resolution mid-IR imaging, and the current data do not provide stringent constraints on the presence or absence of obscuring nuclear dust in the AGN.
  • Thumbnail Image
    Item
    NuSTAR observations of heavily obscured quasars at z 0.5
    (2014) Lansbury, G.B.; Alexander, D.M.; Del Moro, A.; Gandhi, P.; Assef, R.J.; Stern, D.; Aird, J.; Ballantyne, D.R.; Balokovic, M.; Bauer, Franz Erik
  • Thumbnail Image
    Item
    NuStar observations of the compton-thick active galactic nucleus and ultraluminous X-Ray source candidate in NGC 5643
    (2015) Annuar, A.; Gandhi, P.; Alexander, D.; Lansbury, G.; Arévalo, P.; Ballantyne, D.; Balokovic, M.; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Craig, W.; Del Moro, A.; Hailey, C.; Harrison, F.; Bauer, Franz Erik
  • Thumbnail Image
    Item
    NuStar reveals extreme absorption in z < 0.5 type 2 quasars
    (2015) Lansbury, G.; Gandhi, P.; Alexander, D.; Assef, R.; Aird, J.; Annuar, A.; Ballantyne, D.; Balokovic, M.; Bauer, Franz Erik; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Civano, F.; Comastri, A.; Craig, W.
  • Thumbnail Image
    Item
    NuStar spectroscopy of multiI-component X-Ray reflection from NGC 1068
    (2015) Bauer, Franz Erik; Arévalo, P.; Walton, D.; Koss, M.; Puccetti, S.; Gandhi, P.; Stern, D.; Alexander, D.; Balokovic, M.; Boggs, S.; Brandt, W.; Brightman, M.; Christensen, F.; Comastri, A.; Craig, W.; Del Moro, A.
  • Thumbnail Image
    Item
    NuSTAR unveils a Compton-thick type 2 quasar in Mrk 34
    (2014) Gandhi, P.; Lansbury, G.; Alexander, D.; Stern, D.; Arevalo, P.; Ballantyne, D.; Balokovic, M.; Bauer, Franz Erik; Boggs, S.; Brandt, W.
  • Thumbnail Image
    Item
    The NuSTAR view of nearby compton-thick active galactic nuclei: The cases of NGC 424, NGC 1320, and IC 2560
    (2014) Balokovic, M.; Comastri, A.; Harrison, F.; Alexander, D.; Ballantyne, D.; Bauer, Franz Erik; Boggs, S.; Brandt, W.; Brightman, M.
  • Thumbnail Image
    Item
    The Phoenix galaxy as seen by NuSTAR
    (2017) Masini, A.; Comastri, A.; Puccetti, S.; Balokovic, M.; Gandhi, P.; Guainazzi, M.; Boggs, S.; Ricci, Claudio; Bauer, Franz Erik; Boorman, P.; Brightman, M.; Christensen, F.; Craig, W.; Farrah, D.; Hailey, C.; Harrison, F.; Koss, M.
  • Thumbnail Image
    Item
    The Seyfert 2 galaxy NGC 2110 : hard X-ray emission observed by NuSTAR and variability of the iron Kα line
    (2015) Marinucci, A.; Matt, G.; Bianchi, S.; Lu, T. N.; Arévalo, P.; Balokovic, M.; Ballantyne, D.; Bauer, Franz Erik; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Harrison, F.; Puccetti, S.; Rivers, E.; Walton, D. J.; Stern, D.; Zhang, W.
  • Thumbnail Image
    Item
    X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei
    (2017) Brightman, M.; Balokovic, M.; Ballantyne, D. R.; Bauer, Franz Erik; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Ricci, Claudio