1,026 research outputs found
Pulsar Timing Constraints on the Fermi Massive Black-Hole Binary Blazar Population
Blazars are a sub-population of quasars whose jets are nearly aligned with
the line-of-sight, which tend to exhibit multi-wavelength variability on a
variety of timescales. Quasi-periodic variability on year-like timescales has
been detected in a number of bright sources, and has been connected to the
orbital motion of a putative massive black hole binary. If this were indeed the
case, those blazar binaries would contribute to the nanohertz
gravitational-wave stochastic background. We test the binary hypothesis for the
blazar population observed by the \textit{Fermi} Gamma-Ray Space Telescope,
which consists of BL Lacertae objects and flat-spectrum radio quasars. Using
mock populations informed by the luminosity functions for BL Lacertae objects
and flat-spectrum radio quasars with redshifts , we calculate the
expected gravitational wave background and compare it to recent pulsar timing
array upper limits. The two are consistent only if a fraction of blazars hosts a binary with orbital periods years. We
therefore conclude that binarity cannot significantly explain year-like
quasi-periodicity in blazars.Comment: 5 pages, 4 figures, accepted by MNRAS Letter
Quasi-periodicities of BL Lac Objects
We review the reports of possible year-long quasi-periodicities of BL Lac
objects in the -ray and optical bands, and present a homogeneous time
analysis of the light curves of PKS2155304, PG1553+113, and BL Lac. Based on
results from a survey covering the entire Fermi -ray sky we have
estimated the fraction of possible quasi-periodic BL Lac objects. We compared
the cyclical behaviour in BL Lac objects with that derived from the search of
possible optical periodicities in quasars, and find that at z1 the
cosmic density of quasi-periodic BL Lac objects is larger than that of
quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a
supermassive binary black hole (SBBH) scenario, there could be a tension with
the upper limits on the gravitational wave background measured by the pulsar
timing array. The argument clearly indicates the difficulties of generally
associating quasi-periodicities of BL Lac objects with SBBHs.Comment: In publication on A&A, 6 pages, 4 figure (11 plots). Minor
corrections adde
Examining the Effects of Dark Matter Spikes on Eccentric Intermediate Mass Ratio Inspirals Using -body Simulations
Recent studies have postulated that the presence of dark matter (DM) spikes
around IMBHs could lead to observable dephasing effects in gravitational wave
(GW) signals emitted by Intermediate Mass Ratio Inspirals (IMRIs). While prior
investigations primarily relied on non-self-consistent analytic methods to
estimate the influence of DM spikes on eccentric IMRIs, our work introduces the
first self-consistent treatment of this phenomenon through -body
simulations. Contrary to previous studies, which suggested that dynamical
friction (DF), a cumulative effect of two-body encounters, is the primary
mechanism responsible for energy dissipation, we reveal that the slingshot
mechanism, a three-body effect, plays a more significant role in driving the
binary system's energy loss and consequent orbital shrinkage, similar to
stellar loss cone scattering in Massive Black Hole (MBH) binaries. Furthermore,
our work extends its analysis to include rotation in DM spikes, a factor often
overlooked in previous studies. We find that binaries that counter-rotate with
respect to the spike particles merge faster, while binaries that co-rotate
merge slower, in opposition to the expectation from DF theory. While our models
are idealistic, they offer findings that pave the way for a more comprehensive
understanding of the complex interactions between DM spikes, IMRIs, GW
emission, and the ability to constrain DM microphysics. Our work systematically
includes Post-Newtonian (PN) effects until 2.5 order and our results are
accurate and robust.Comment: 19 pages, 15 figures. New version with results from non-softened
simulations. Comments welcome
Associating host galaxy candidates to massive black hole binaries resolved by pulsar timing arrays
We propose a novel methodology to select host galaxy candidates of future pulsar timing array (PTA) detections of resolved gravitational waves (GWs) from massive black hole binaries (MBHBs). The method exploits the physical dependence of the GW amplitude on the MBHB chirp mass and distance to the observer, together with empirical MBH massâhost galaxy correlations, to rank potential host galaxies in the massâredshift plane. This is coupled to a null-stream based likelihood evaluation of the GW amplitude and sky position in a Bayesian framework that assigns to each galaxy a probability of hosting the MBHB generating the GW signal. We test our algorithm on a set of realistic simulations coupling the likely properties of the first PTA resolved GW signal to synthetic all-sky galaxy maps. For a foreseeable PTA sky-localization precision of 100 deg2, we find that the GW source is hosted with 50%(90%) probability within a restricted number of Ⲡ50( Ⲡ500) potential hosts. These figures are orders of magnitude smaller than the total number of galaxies within the PTA sky error-box, enabling extensive electromagnetic follow-up campaigns on a limited number of targets
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