ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    facet.materialart.
    Unknown
    A Giant Radio Halo in a Low-Mass Sz-selected Galaxy Cluster: ACT-CLJ0256.5+0006 (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)- selected merging galaxy cluster ACT-CL J0256.5+ 0006 (z = 0.363), observed with the Giant Metrewave Radio Telescope at 325 and 610 MHz. We find this cluster to host a faint (S610 = 5.6 +/- 1.4mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest mass systems, M500, SZ = (5.0 +/- 1.2) 10(exp14) M, found to host a GRH. We measure the GRH at lower significance at 325 MHz (S325 = 10.3 +/- 5.3mJy), obtaining a spectral index measurement of 610 325 = 1.0+ 0.7 0.9. This result is consistent with the mean spectral index of the population of typical radio haloes, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P1.4 GHz = (1.0 +/- 0.3) 10(exp 24)W/Hz, placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the intracluster medium morphology, suggest that ACT-CL J0256.5+ 0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of v = 1880 +/- 210 km/s. We construct a simple merger model to infer relevant time-scales in the merger. From its location on the P1.4GHz-LX scaling relation, we infer that we observe ACT-CL J0256.5+ 0006 just before first core crossing.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN40455 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-8711); 459; 4; 4240-4258
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC Waves, ULF Pulsations, and an Electron Flux Dropout (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We examined an electron flux dropout during the 12-14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A (P5), Cluster 2, and Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 h from 12 to 14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12-13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ electromagnetic ion cyclotron (EMIC) waves from just inside geosynchronous orbit out to the magnetopause across the dayside to the dusk flank. The second interval of reduced 0.8 MeV electron fluxes on 13-14 November was associated with a solar sector boundary crossing and development of a geomagnetic storm with Dst〈100 nT. At the start of the recovery phase, both the 0.8 and 2.0 MeV electron fluxes finally returned to near prestorm values, possibly in response to strong ultralow frequency (ULF) waves observed by the Van Allen Probes near dawn. A combination of adiabatic effects, losses to the magnetopause, scattering by EMIC waves, and acceleration by ULF waves can explain the observed electron behavior.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN40269 , Journal of Geophysical Research: Space Physics (ISSN 2169-9380) (e-ISSN 2169-9402); 121; 3; 1990–2008
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    Prompt Electromagnetic Transients from Binary Black Hole Mergers (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Binary black hole (BBH) mergers provide a prime source for current and future interferometric gravitational wave observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jetlike emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 1 0 Exp 45) 10(exp 46) (sub 13) M(sub 8)(exp 2) erg s(exp 1), with BBH mass scaled to M(sub 8) M / ( 10 8 M ) and ambient density 13 / ( 10(exp 13) g cm(sub 3)). We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN54261 , Physical Review D - Particles, Fields, Gravitation and Cosmology (ISSN 1550-7998) (e-ISSN 1550-2368); 96; 12; 123003
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unknown
    Prompt Electromagnetic Transients from Binary Black Hole Mergers (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Binary black hole (BBH) mergers provide a prime source for current and future interferometric GW observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jet-like emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 10(exp 45) - 10(exp 46) (p-13) M(sub 8)(exp 2) erg/s, with BBH mass scaled to M(sub 8) defined to be equal to M=(10(exp 8) solar mass) and ambient density p -13 defined to be equal to p/(10(exp -13) g/cu.cm). We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN51364 , Physical Review D - Particles, Fields, Gravitation and Cosmology (ISSN 1550-7998) (e-ISSN 1550-2368); 96; 12; 123003
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...