| 161. |
- Szulkin, R, et al.
(författare)
-
Genome-wide association study of prostate cancer-specific survival
- 2015
-
Ingår i: Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology. - 1538-7755. ; 24:11, s. 1796-1800
-
Tidskriftsartikel (refereegranskat)
|
|
| 162. |
- Abramowicz, Marek A, 1945, et al.
(författare)
-
A note on the slope-shift anticorrelation in the neutron star kHz QPOs data
- 2005
-
Ingår i: n Proceedings of RAGtime 6/7: Workshops on black holes and neutron stars. - 807248334X
-
Konferensbidrag (refereegranskat)abstract
- Observations show that the upper νU and lower νL of the ``twin peak'' high frequency QPOs in neutron star sources vary along lines νU = AνL + B in a frequency-frequency plot, and that their ratios νU/νL cluster near the value 3/2. This behaviour is well consistent with the predictions of the non-linear resonance model for QPOs. In this Note, we further explore our recent finding that the coefficients A, B of the frequency-frequency lines for individual sources are anticorrelated. In the (A,B) plane, they occupy rather a narrow region along the line A = 3/2 - B/600 Hz. We show that this observational property of QPOs also follows from the resonance model
|
|
| 163. |
- Abramowicz, Marek A, 1945, et al.
(författare)
-
Epicyclic frequencies derived from the effective potential: simple and practical formulae
- 2005
-
Ingår i: Astrophys. Space Sci.. - : Springer Science and Business Media LLC. - 0004-640X. ; 300:1-3, s. 127-136
-
Tidskriftsartikel (refereegranskat)abstract
- We present and discuss a short and simple derivation of orbital epicyclic frequencies for circular geodesic orbits in stationary and axially symmetric spacetimes. Such spacetimes include as special cases analytically known black hole Kerr and Schwarzschild spacetimes, as well as the analytic Hartle-Thorne spacetime and all numerically constructed spacetimes relevant for rotating neutron stars. Our derivation follows directly from energy and angular momentum conservation and it uses the concept of the effective potential. It has never been published, except for a few special cases, but it has already become a part of the common knowledge in the field.
|
|
| 164. |
- Abramowicz, Marek A, 1945, et al.
(författare)
-
Mass of a Black Hole Firewall
- 2014
-
Ingår i: Physical Review Letters. - 0031-9007. ; 112:9
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum entanglement of Hawking radiation has been supposed to give rise to a Planck density "firewall" near the event horizon of old black holes. We show that Planck density firewalls are excluded by Einstein's equations for black holes of mass exceeding the Planck mass. We find an upper limit of 1/(8 pi M) to the surface density of a firewall in a Schwarzschild black hole of mass M, translating for astrophysical black holes into a firewall density smaller than the Planck density by more than 30 orders of magnitude. A strict upper limit on the firewall density is given by the Planck density times the ratio M-Pl/(8 pi M).
|
|
| 165. |
|
|
| 166. |
- Abramowicz, Marek A, 1945, et al.
(författare)
-
The Twin Peak QPOs in Neutron Star and Black Hole Sources: What is explained, and What is not
- 2007
-
Ingår i: Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias). ; 27, s. 8-17
-
Konferensbidrag (refereegranskat)abstract
- The resonance model proposed in 2000 by Kluzniak and Abra-mo-wicz, explains the twin peak, high frequency, quasi periodic oscillations (HF QPOs) observed in the X-ray flux from black hole and neutron stars, as a non-linear resonance in modes of oscillations of accretion flows in strong gravity. While several important physical questions remain unanswered, recent observations of HF QPOs provide direct evidence of non-linear resonances. This article gives an up to date (May 2006) review of what has been explained, and what has not been explained, by the resonance model.
|
|
| 167. |
- Abramowicz, Marek, 1945, et al.
(författare)
-
Twin peak QPOs frequencies in microquasars and Sgr A The resonance and other orbital models
- 2004
-
Ingår i: Proceedings of RAGtime. - 2336-5676 .- 2336-5668. ; , s. 1-23
-
Konferensbidrag (refereegranskat)abstract
- In all four microquasars which show twin peak kHz QPOs, the ratio of the two frequencies is 3:2. This rather strongly supports the suggestion by [Abramowicz and Kluźniak, 2001] that twin peak kHz QPOs are due to a resonance between some modes of accretion disk oscillations. Detailed studies of this suggestion revealed that several such non-linear resonances are present in nearly Keplerian disks in strong gravity. Here, we fit to observations predictions of the resonance hypothesis for two particular types of non-linear resonances between vertical and radial epicyclic frequencies. For three microquasars with known masses, the fits give an accurate estimate of the spin.
|
|
| 168. |
- Abramwicz, M A, et al.
(författare)
-
Possible Suppression of Magnetorotational Instability by Rapid Radial Flow
- 2013
-
Ingår i: Acta Astronomica. - 0001-5237. ; 63:2, s. 267-273
-
Tidskriftsartikel (refereegranskat)abstract
- By investigating the magnetorotational instability (MRI) in a region of rapidly varying accretion-disk thickness, e.g., in the ISCO region, we find a limit to the applicability of a recent finding by Balbus (2012) that the MRI is present also in the region of Rayleigh-unstable flow. RAMOWICZ MA, 1988, ASTROPHYSICAL JOURNAL, V332, P646
|
|
| 169. |
- Aharonian, F., et al.
(författare)
-
Constraints on the Intergalactic Magnetic Field Using Fermi-LAT and HESS Blazar Observations
- 2023
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 950:2
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetic fields in galaxies and galaxy clusters are believed to be the result of the amplification of intergalactic seed fields during the formation of large-scale structures in the universe. However, the origin, strength, and morphology of this intergalactic magnetic field (IGMF) remain unknown. Lower limits on (or indirect detection of) the IGMF can be obtained from observations of high-energy gamma rays from distant blazars. Gamma rays interact with the extragalactic background light to produce electron-positron pairs, which can subsequently initiate electromagnetic cascades. The gamma-ray signature of the cascade depends on the IGMF since it deflects the pairs. Here we report on a new search for this cascade emission using a combined data set from the Fermi Large Area Telescope and the High Energy Stereoscopic System. Using state-of-the-art Monte Carlo predictions for the cascade signal, our results place a lower limit on the IGMF of B > 7.1 x 10(-16) G for a coherence length of 1 Mpc even when blazar duty cycles as short as 10 yr are assumed. This improves on previous lower limits by a factor of 2. For longer duty cycles of 10(4) (10(7)) yr, IGMF strengths below 1.8 x 10(-14) G (3.9 x 10(-14) G) are excluded, which rules out specific models for IGMF generation in the early universe.
|
|
| 170. |
- Aharonian, F., et al.
(författare)
-
HESS Follow-up Observations of GRB 221009A
- 2023
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 946:1
-
Tidskriftsartikel (refereegranskat)abstract
- GRB 221009A is the brightest gamma-ray burst (GRB) ever detected. To probe the very-high-energy (VHE; >100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hr after the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection, after applying atmospheric corrections. The combined observations yield an integral energy flux upper limit of f(UL)(95%)=9.7x10(-12)ergcm(-2)s(-1) E-thr = 650 GeV. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the spectral energy distribution occurring above the X-ray band. Compared to the VHE-bright GRB 190829A, the upper limits for GRB 221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB 221009A, effectively ruling out an IC-dominated scenario.
|
|
