المؤلفون: Padovani, P., Resconi, E., Ajello, M., Bellenghi, C., Bianchi, S., Blasi, P., Huang, K. -Y., Gabici, S., Rosas, V. Gámez, Niederhausen, H., Peretti, E., Eichmann, B., Guetta, D., Lamastra, A., Shimizu, T.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies

الوصف: We present a comprehensive multi-messenger study of NGC 1068, the prototype Seyfert II galaxy recently associated with high-energy IceCube neutrinos. Various aspects of the source, including its nuclear activity, jet, outflow, and starburst region, are analyzed in detail using a multi-wavelength approach and relevant luminosities are derived. We then explore its gamma-ray and neutrino emissions and investigate potential mechanisms underlying these phenomena and their relations with the different astrophysical components to try to understand which one is responsible for the IceCube neutrinos. By first using simple order-of-magnitude arguments and then applying specific theoretical models, we infer that only the region close to the accretion disc around the supermassive black hole has both the right density of X-ray photons needed to provide the targets for protons to sustain neutrino production and of optical/infrared photons required to absorb the associated but unobserved gamma rays. We conclude by highlighting ongoing efforts to constrain a possible broad connection between neutrinos and active galactic nuclei, as well as future synergies between astronomical and neutrino facilities.
Comment: 18 pages, 4 figures, review paper accepted for publication in Nature Astronomy; authors' version before editorial review

الوصول الحر: http://arxiv.org/abs/2405.20146Test

المؤلفون: Circiello, A., McDaniel, A., Drlica-Wagner, A., Karwin, C., Ajello, M., Di Mauro, M., Sánchez-Conde, M.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Recent results from numerical simulations and models of galaxy formation suggest that recently discovered ultra-faint compact stellar systems (UFCSs) in the halo of the Milky Way (MW) may be some of the smallest and faintest galaxies. If this is the case, these systems would be attractive targets for indirect searches of weakly interacting massive particle (WIMP) dark matter (DM) annihilation due to their relative proximity and high expected DM content. In this study, we analyze 14.3 years of gamma-ray data collected by the Fermi-LAT coincident with 26 UFCSs. No significant excess gamma-ray emission is detected, and we present gamma-ray flux upper limits for these systems. Assuming that the UFCSs are dark-matter-dominated galaxies consistent with being among the faintest and least massive MW dwarf spheroidal (dSphs) satellite galaxies, we derive the projected sensitivity for a dark matter annihilation signal. We find that observations of UFCSs have the potential to yield some of the most powerful constraints on DM annihilation, with sensitivity comparable to observations of known dSphs and the Galactic center. This result emphasizes the importance of precise kinematic studies of UFCSs to empirically determine their DM content.
Comment: 11 pages, 4 figures, 1 table, submitted to ApJL

الوصول الحر: http://arxiv.org/abs/2404.01181Test

المؤلفون: Rajguru, Garima, Marcotulli, L., Ajello, M., Tramacere, A.

المصدر: The Astrophysical Journal, 965:112, 2024 April 20

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Active galactic nuclei (AGNs) can power relativistic jets, which are called blazars when pointed close to our line of sight. Depending on the presence or absence of emission lines in their optical spectra, blazars are categorized into flat spectrum radio quasars (FSRQs) or BL Lacertae (BL Lacs) objects. According to the 'blazar sequence', as synchrotron peak frequency ($\nu^{sy}_{pk}$) shifts to higher energies, the synchrotron peak luminosity decreases. This means that BL Lacs as luminous as FSRQs, and with synchrotron peak frequencies $\nu^{sy}_{pk}>10^{15}$ Hz, should not exist. Detected as a high-synchrotron peak (HSP; $\nu^{sy}_{pk}>10^{15}$ Hz) BL Lac, 4FGL J1520.8-0348 shows high gamma-ray luminosity ($L_{\gamma}>10^{46}\,\rm erg~s^{-1}$), being at a high redshift of $z=$1.46. Since it is an outlier in the 'blazar sequence', the process of its jet acceleration and power may be different from bona fide BL Lacs. In this work, we constrain its spectral energy distribution (SED) by modeling the multi-wavelength data from infrared to $\gamma$-ray regime. Simultaneous X-ray data was obtained from X-ray Multi-Mirror Mission and Nuclear Spectroscopic Telescope Array to constrain the synchrotron emission and underlying electron distribution. On undertaking the SED modeling of the source, including the effect of extragalactic background light, we conclude that the source is more likely to be a 'blue FSRQ' or 'masquerading BL Lac' where the BL Lac is actually a FSRQ in disguise.

الوصول الحر: http://arxiv.org/abs/2403.10703Test

المؤلفون: Pizzetti, A., Torres-Alba, N., Marchesi, S., Buchner, J., Cox, I., Zhao, X., Neal, S., Sengupta, D., Silver, R., Ajello, M.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present the multi-epoch analysis of 13 variable, nearby (z<0.1), Compton-thin (22Comment: Submitted to ApJ

الوصول الحر: http://arxiv.org/abs/2403.06919Test

المؤلفون: Peñil, P., Otero-Santos, J., Ajello, M., Buson, S., Domínguez, A., Marcotulli, L., Torres-Albà, N., González, J. Becerra, Acosta-Pulido, J. A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Blazars present highly variable $\gamma$-ray emission. This variability, which can range from a few minutes to several years, is also observed at other wavelengths across the entire electromagnetic spectrum. We make use of the first 12 years of data from the Fermi Large Area Telescope (LAT), complemented with multiwavelength (MWL) archival data from different observatories and facilities in radio, infrared and optical bands, to study the possible periodic emission from 19 blazars previously claimed as periodic candidates. A periodicity analysis is performed with a pipeline for periodicity searches. Moreover, we study the cross-correlations between the $\gamma$-ray and MWL light curves. Additionally, we use the fractional variability and the structure function to evaluate the variability timescales. We find five blazars showing hints of periodic modulation with $\geq$3.0$\sigma$ ($\approx$0$\sigma$ post-trials), with periods ranging from 1.2 to 4 years, both in their $\gamma$-ray and MWL emission. The results provide clues for understanding the physical mechanisms generating the observed periodicity.
Comment: 21 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2403.01520Test

المؤلفون: Peñil, P., Westernacher-Schneider, J. R., Ajello, M., Domínguez, A., Buson, S., Otero-Santos, J., Marcotulli, L., Torres-Albà, N., Zrake, J.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Blazars display variable emission across the entire electromagnetic spectrum, with timescales that can range from a few minutes to several years. Our recent work has shown that a sample of five blazars exhibit hints of periodicity with a global significance $\gtrsim2\,\sigma$ at $\gamma$-ray energies, in the range of 0.1~GeV$<$E$<$800~GeV. In this work, we study their multiwavelength (MWL) emission, covering the X-ray, ultraviolet, optical, and radio bands. We show that three of these blazars present similar periodic patterns in the optical and radio bands. Additionally, fluxes in the different bands of the five blazars are correlated, suggesting a co-spatial origin. Moreover, we detect a long-term ($\approx$10 year) rising trend in the light curves of PG~1553+113, and we use it to infer possible constraints on the binary black hole hypothesis.
Comment: 20 pages, 10 figures, 7 tables

الوصول الحر: http://arxiv.org/abs/2310.12754Test

المؤلفون: Domínguez, A., Láinez, M., Paliya, V. S., Álvarez-Crespo, N., Ajello, M., Finke, J., Nievas-Rosillo, M., Contreras, J. L., Desai, A.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics

الوصف: The extragalactic high-energy $\gamma$-ray sky is dominated by blazars, which are active galactic nuclei with their jets pointing towards us. Distance measurements are of fundamental importance yet for some of these sources are challenging because any spectral signature from the host galaxy may be outshone by the non-thermal emission from the jet. In this paper, we present a method to constrain redshifts for these sources that relies only on data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This method takes advantage of the signatures that the pair-production interaction between photons with energies larger than approximately 10 GeV and the extragalactic background light leaves on $\gamma$-ray spectra. We find upper limits for the distances of 303 $\gamma$-ray blazars, classified as 157 BL Lacertae objects, 145 of uncertain class, and 1 flat-spectrum-radio quasar, whose redshifts are otherwise unknown. These derivations can be useful for planning observations with imaging atmospheric Cherenkov telescopes and also for testing theories of supermassive black hole evolution. Our results are applied to estimate the detectability of these blazars with the future Cherenkov Telescope Array, finding that at least 21 of them could be studied in a reasonable exposure of 20 h.
Comment: 13 pages, 7 figures, 1 table; Accepted by MNRAS

الوصول الحر: http://arxiv.org/abs/2307.10083Test

المؤلفون: Domínguez, A., Kirkeberg, P. Østergaard, Wojtak, R., Saldana-Lopez, A., Desai, A., Primack, J. R., Finke, J., Ajello, M., Pérez-González, P. G., Paliya, V. S., Hartmann, D.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics

الوصف: We present $\gamma$-ray optical-depth calculations from a recently published extragalactic background light (EBL) model built from multiwavelength galaxy data from the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (HST/CANDELS). CANDELS gathers one of the deepest and most complete observations of stellar and dust emissions in galaxies. This model resulted in a robust derivation of the evolving EBL spectral energy distribution up to $z\sim 6$, including the far-infrared peak. Therefore, the optical depths derived from this model will be useful for determining the attenuation of $\gamma$-ray photons coming from high-redshift sources, such as those detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, and for multi-TeV photons that will be detected from nearby sources by the future Cherenkov Telescope Array. From these newly calculated optical depths, we derive the cosmic $\gamma$-ray horizon and also measure the expansion rate and matter content of the Universe including an assessment of the impact of the EBL uncertainties. We find $H_{0}=61.9$ $^{+2.9}_{-2.4}$ km s$^{-1}$ Mpc$^{-1}$ when fixing $\Omega_{m}=0.32$, and $H_{0}=65.6$ $^{+5.6}_{-5.0}$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_{m}=0.19\pm 0.07$, when exploring these two parameters simultaneously.
Comment: 11 pages, 8 figures, 1 tables; Accepted by MNRAS

الوصول الحر: http://arxiv.org/abs/2306.09878Test

المؤلفون: Lesage, S., Veres, P., Briggs, M. S., Goldstein, A., Kocevski, D., Burns, E., Wilson-Hodge, C. A., Bhat, P. N., Huppenkothen, D., Fryer, C. L., Hamburg, R., Racusin, J., Bissaldi, E., Cleveland, W. H., Dalessi, S., Fletcher, C., Giles, M. M., Hristov, B. A., Hui, C. M., Mailyan, B., Malacaria, C., Poolakkil, S., Roberts, O. J., von Kienlin, A., Wood, J., Ajello, M., Arimoto, M., Baldini, L., Ballet, J., Baring, M. G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Blandford, R. D., Bonino, R., Bruel, P., Buson, S., Cameron, R. A., Caputo, R., Caraveo, P. A., Cavazzuti, E., Chiaro, G., Cibrario, N., Ciprini, S., Orestano, P. Cristarella, Crnogorcevic, M., Cuoco, A., Cutini, S., DAmmando, F., De Gaetano, S., Di Lalla, N., Di Venere, L., Dominguez, A., Fegan, S. J., Ferrara, E. C., Fleischhack, H., Fukazawa, Y., Funk, S., Fusco, P., Galanti, G., Gammaldi, V., Gargano, F., Gasbarra, C., Gasparrini, D., Germani, S., Giacchino, F., Giglietto, N., Gill, R., Giroletti, M., Granot, J., Green, D., Grenier, I. A., Guiriec, S., Gustafsson, M., Hays, E., Hewitt, J. W., Horan, D., Hou, X., Kuss, M., Latronico, L., Laviron, A., Lemoine-Goumard, M., Li, J., Liodakis, I., Longo, F., Loparco, F., Lorusso, L., Lovellette, M. N., Lubrano, P., Maldera, S., Manfreda, A., Marti-Devesa, G., Mazziotta, M. N., McEnery, J. E., Mereu, I., Meyer, M., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panzarini, G., Persic, M., Pesce-Rollins, M., Pillera, R., Piron, F., Poon, H., Porter, T. A., Principe, G., Raino, S., Rando, R., Rani, B., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Ryde, F., Sanchez-Conde, M., Parkinson, P. M. Saz, Scotton, L., Serini, D., Sgro, C., Sharma, V., Siskind, E. J., Spandre, G., Spinelli, P., Tajima, H., Torres, D. F., Valverde, J., Venters, T., Wadiasingh, Z., Wood, K., Zaharijas, G.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We report the discovery of GRB 221009A, the highest flux gamma-ray burst ever observed by the Fermi Gamma-ray Burst Monitor (GBM). This GRB has continuous prompt emission lasting more than 600 seconds which smoothly transitions to afterglow visible in the GBM energy range (8 keV--40 MeV), and total energetics higher than any other burst in the GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the GBM trigger time (t0; 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of the thermal, photospheric emission of shock-breakout, with significant emission up to $\sim$15 MeV. We characterize the onset of external shock at t0+600 s and find evidence of a plateau region in the early-afterglow phase which transitions to a slope consistent with Swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the GBM sample and find that this GRB has the highest total isotropic-equivalent energy ($\textrm{E}_{\gamma,\textrm{iso}}=1.0\times10^{55}$ erg) and second highest isotropic-equivalent luminosity ($\textrm{L}_{\gamma,\textrm{iso}}=9.9\times10^{53}$ erg/s) based on redshift of z = 0.151. These extreme energetics are what allowed us to observe the continuously emitting central engine of GBM from the beginning of the prompt emission phase through the onset of early afterglow.
Comment: 26 pages 7 figures - accepted for publication in ApJL

الوصول الحر: http://arxiv.org/abs/2303.14172Test

المؤلفون: Hood II, J. C., Simpson, A., McDaniel, A., Foster, A., Ade, P. A. R., Ajello, M., Anderson, A. J., Austermann, J. E., Beall, J. A., Bender, A. N., Benson, B. A., Bianchini, F., Bleem, L. E., Carlstrom, J. E., Chang, C. L., Chaubal, P., Chiang, H. C., Chou, T-L., Citron, R., Moran, C. Corbett, Crawford, T. M., Crites, A. T., de Haan, T., Dobbs, M. A., Everett, W., Gallicchio, J., George, E. M., Gupta, N., Halverson, N. W., Hilton, G. C., Holder, G. P., Holzapfel, W. L., Hrubes, J. D., Huang, N., Hubmayr, J., Irwin, K. D., Knox, L., Lee, A. T., Li, D., Lowitz, A., Madejski, G., Malkan, M., McMahon, J. J., Meyer, S. S., Montgomery, J., Natoli, T., Nibarger, J. P., Noble, G., Novosad, V., Omori, Y., Padin, S., Patil, S., Pryke, C., Reichardt, C. L., Ruhl, J. E., Saliwanchik, B. R., Schaffer, K. K., Sievers, C., Smecher, G., Stark, A. A., Tucker, C., Veach, T., Vieira, J. D., Wang, G., Whitehorn, N., Wu, W. L. K., Yefremenko, V., Zebrowski, J. A., Zhang, L.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies

الوصف: Including millimeter-wave (mm-wave) data in multi-wavelength studies of the variability of active galactic nuclei (AGN) can provide insights into AGN physics that are not easily accessible at other wavelengths. We demonstrate in this work the potential of cosmic microwave background (CMB) telescopes to provide long-term, high-cadence mm-wave AGN monitoring over large fractions of sky. We report on a pilot study using data from the SPTpol instrument on the South Pole Telescope (SPT), which was designed to observe the CMB at arcminute and larger angular scales. Between 2013 and 2016, SPTpol was used primarily to observe a single 500 deg^2 field, covering the entire field several times per day with detectors sensitive to radiation in bands centered at 95 and 150 GHz. We use SPT 150 GHz observations to create AGN light curves, and we compare these mm-wave light curves to those at other wavelengths, in particular gamma-ray and optical. In this Letter, we focus on a single source, PKS 2326-502, which has extensive, day-timescale monitoring data in gamma-ray, optical, and now mm-wave between 2013 and 2016. We find PKS 2326-502 to be in a flaring state in the first two years of this monitoring, and we present a search for evidence of correlated variability between mm-wave, optical R band, and gamma-ray observations. This pilot study is paving the way for AGN monitoring with current and upcoming CMB experiments such as SPT-3G, Simons Observatory, and CMB-S4, including multi-wavelength studies with facilities such as VRO-LSST.
Comment: 9 pages, 3 figures, accepted to Astrophysical Journal Letters

الوصول الحر: http://arxiv.org/abs/2302.14749Test