24 research outputs found
Localizing merging black holes with sub-arcsecond precision using gravitational-wave lensing
The current gravitational-wave localization methods rely mainly on sources
with electromagnetic counterparts. Unfortunately, a binary black hole does not
emit light. Due to this, it is generally not possible to localize these objects
precisely. However, strongly lensed gravitational waves, which are forecasted
in this decade, could allow us to localize the binary by locating its lensed
host galaxy. Identifying the correct host galaxy is challenging because there
are hundreds to thousands of other lensed galaxies within the sky area spanned
by the gravitational-wave observation. However, we can constrain the lensing
galaxy's physical properties through both gravitational-wave and
electromagnetic observations. We show that these simultaneous constraints allow
one to localize quadruply lensed waves to one or at most a few galaxies with
the LIGO/Virgo/Kagra network in typical scenarios. Once we identify the host,
we can localize the binary to two sub-arcsec regions within the host galaxy.
Moreover, we demonstrate how to use the system to measure the Hubble constant
as a proof-of-principle application.Comment: 5 pages (main text) + 5 pages (methods+references), 5 figures.
Accepted to MNRA
Probing wave-optics effects and dark-matter subhalos with lensing of gravitational waves from massive black holes
The Laser Interferometer Space Antenna (LISA) will detect gravitational waves
(GWs) emitted by massive black hole binaries (MBHBs) in the low-frequency
(mHz) band. Low-mass lenses, such as dark-matter (DM) subhalos, have
sizes comparable to the wavelength of these GWs. Encounters with these lenses
produce wave-optics (WO) effects that alter waveform phase and amplitude. Thus,
a single event with observable WO effects can be used to probe the lens
properties. In this paper, we first compute the probability of observing WO
effects in a model-agnostic way. We perform parameter estimation over
approximately 1000 MBHBs with total mass, mass ratio, and redshift spanning the
ranges relevant to LISA. We then calculate lensing rates using three
semi-analytical models of MBHB populations. In both cases, we use a waveform
model that includes merger, ringdown, and higher-order modes. We use two lens
population models: the theory-based Press-Schechter halo mass function and an
observation-based model derived from Sloan Digital Sky Survey, called the
measured velocity function. We find that the probability of detecting WO
effects can be as large as , , and at
, , and confidence levels, respectively. The most
optimistic MBHB population model yields , , and events
at the same confidence levels, while the rates drop to in the more
pessimistic scenarios. The most likely lens masses probed by LISA are in the
range , and the most probable redshifts are in the
range . Therefore, LISA observations of WO effects can probe DM
subhalos, complementing strong lensing and other observations.Comment: 24 pages, 15 figures. Comments are welcom
Subtracting Compact Binary Foregrounds to Search for Subdominant Gravitational-Wave Backgrounds in Next-Generation Ground-Based Observatories
Stochastic gravitational-wave backgrounds (SGWBs) derive from the
superposition of numerous individually unresolved gravitational-wave (GW)
signals. Detecting SGWBs provides us with invaluable information about
astrophysics, cosmology, and fundamental physics. In this paper, we study SGWBs
from binary black-hole (BBH) and binary neutron-star (BNS) coalescences in a
network of next-generation ground-based GW observatories (Cosmic Explorer and
Einstein Telescope) and determine how well they can be measured; this then
limits how well we can observe other subdominant astrophysical and cosmological
SGWBs. We simulate all-Universe populations of BBHs and BNSs and calculate the
corresponding SGWBs, which consist of a superposition of (i) undetected
signals, and (ii) the residual background from imperfect removal of resolved
sources. The sum of the two components sets the sensitivity for observing other
SGWBs. Our results show that, even with next-generation observatories, the
residual background is large and limits the sensitivity to other SGWBs. The
main contributions to the residual background arise from uncertainties in
inferring the coalescence phase and luminosity distance of the detected
signals. Alternative approaches to signal subtraction would need to be explored
to minimize the BBH and BNS foreground in order to observe SGWBs from other
subdominant astrophysical and cosmological sources.Comment: 19 pages, 10 figures, matches the published versio
Rotavirus Frequency in Children With Acute Gastroenteritis Who Were Hospitalized in Keçiören Education and Research Hospital Pediatric Clinic
Bu çalışmada hastanemizin pediatri servisinde akut gastroenterit tanısı alan hastalarda rotavirus sıklığının yaşa, cin- siyete, mevsimsel özelliklere göre dağılımının belirlenmesi, hastalığın seyrinin araştırılması ve nozokomiyal inf eksiyon sıklı- ğının saptanması amaçlanmıştır. Hastanemizin pediatri servisinde Ocak 2010-Aralık 2013 tarihleri arasında akut gastroen- terit tanısıyla izlenen 0-4 yaş arası 772 hastanın dışkı örneklerine ait kayıtlar retrospektif olarak incelenmiştir. Taze dışkı örneklerinde rotavirus antijenlerinin varlığı immünokromatograf ik test ile araştırılmıştır. Çalışmaya alınan 772 hastanın 174ünde (% 22.5) rotavirus antijeni pozitif olarak saptanmıştır. Pozitif lik saptanan hastaların yaş ortalaması 138 ay olup rotavirus antijen pozitif liği % 66.2 oranla en sık 2 yaş altında saptanmıştır. Hastaların 88inin (% 51) erkek, 86sının (% 49) kız olduğu gözlenmiştir. Kırk yedi hastada (% 27) yatıştan üç gün sonra rotavirus antijen pozitif liği bulunmuş ve nozokomiyal inf eksiyon olarak değerlendirilmiştir. Rotavirus antijeni pozitif olgu sayısında sonbahar ve kış mevsimlerinde artış izlenmiştir. Rotavirus inf eksiyonlarının özellikle çocukluk çağı akut gastroenteritleri arasında önemli bir sıklığa sahip olduğu bilinmektedir. Akut gastroenteritli hastalarda viral etkenlerin saptanması hem erken tanı ve semptomatik tedavi olanağı sağlayacak hem de ampirik antibiyotik kullanılmasını önleyecektir. Ülkemizde rotavirus sıklığının yüksek olması nedeniyle çocuklara rotavirus aşısının uygulanmasının bu inf eksiyondan korunmada yararlı olabile- ceği düşünülmüştür.This study aimed to determine the f requency of rotavirus acute gastroenteritis in pediatric patients who were hospitalized in our Pediatric Department, to evaluate distributions according to age, gender and seasonal f eatures, course of the disease and the incidence of nosocomial inf ections. The records of 772 patients between the ages of 0-4 years who were hospitalized in our Pediatric Department between January 2010 and December 2013 due to acute gastroenteritis were investigated retrospectively. Rotavirus antigens were detected in the f resh stool specimens by immunochromatographic test. Of 772 pediatric patients, 174 (22.5 %) were identif ed as positive f or rotavirus antigen, most f requently in 0-2 age group with a rate of 66.2 %. Of the 174 rotavirus antigen positive patients in this study, 96 (49 %) were f emale, 144 (51 %) were male and mean age was 13±8 months 47 of the patients (27 %) were positive f or rotavirus as nosocomial inf ections af ter three days on admis- sion. An increase in the number of cases with rotavirus antigen positivity was detected during autumn and winter. The results of this study indicated that rotavirus was a f requent cause of acute gastroenteritis in children. Detection of viral agents in patients with acute gastroenteritis will allow early diagnosis and symptomatic treatment as well as preventing inapproppria- te antibiotic use. Because of the high f requency of rotavirus in our country, rotavirus vaccination might be usef ul f or children in prevention of this inf ection
The Relationship Between Atherosclerotic Risk Factors and Coronary Artery Disease in Coronary Artery Ectasia
Aim: Coronary artery ectasia (CAE)is described as the dilatation of all or a portion of the coronary arteries by 1.5 times or more wider than the diameter of adjacent normal coronary artery segment. The incidence of CAE varies between 1.5 to 5%. Although the etiology of CAE has not been enlightened, it is generally considered to be a variant of coronary atherosclerosis. In our study, the association between atherosclerotic risk factors and coronary artery disease in patients with coronary artery ectasia was investigated. Methods: Between January 2008 - May 2012 , 5595 patients were screened retrospectively. Atherosclerotic risk factors were determined in all patients. Patients were grouped as the CAE with coronary artery disease (CAD) and the CAE who had no CAD. Results: CAE was diagnosed in 135 (2.4%) patients. The mean age was 62.2 years and 81.5% were male. 71.1% of the patients had CAD. In CAE patients with CAD, diabetes mellitus (DM) and hypertension (HT) was significantly higher in frequency than CAE patients without CAD. In logistic regression analysis, the presence of DM was increased the risk of CAD 2.59-fold, HT was increased the risk of CAD 3,39-fold. Between the two groups there was no significant difference for other atherosclerotic risk factors. Right coronary arteries were the most common vascular involvement (45.9%). Conclusion: In our study, the frequency of CAE was determined as 2.4%. DM and HT which are well-known risk factors for CAD, were seen more frequently in CAE patients with CAD
Lensing or luck? False alarm probabilities for gravitational lensing of gravitational waves
Strong gravitational lensing of gravitational waves (GWs) has been forecasted
to become detectable in the upcoming observing runs. However, definitively
distinguishing pairs of lensed sources from random associations is a
challenging problem. We investigate the degree to which unlensed events mimic
lensed ones because of the overlap of parameters due to a combination of random
coincidence and errors in parameter estimation. We construct a mock catalog of
lensed and unlensed events. We find that the false alarm probability (FAP)
based on coincidental overlaps of the chirp mass, sky location, and coalescence
phase are approximately , , and per pair, respectively.
Combining all three, the overall FAP per pair is . As the number
of events, , in the GW catalogs increases, the number of random pairs of
events increases as . Meanwhile, the number of lensed events will
increase linearly with , implying that for sufficiently high , the false
alarms will always dominate over the true lensing events. This issue can be
compensated for by placing higher thresholds on the lensing candidates (e.g.,
selecting a higher signal-to-noise ratio (SNR) threshold), which will lead to
better parameter estimation and, thus, lower FAP per pair -- at the cost of
dramatically decreasing the size of the lensing sample (by \sim
1/\mbox{SNR}^3). We show that with our simple overlap criteria for current
detectors at design sensitivity, the false alarms will dominate for realistic
lensing rates () even when selecting the highest SNR pairs.
These results highlight the necessity to design alternative identification
criteria beyond simple waveform and sky location overlap. Future GW detectors
Cosmic Explorer and Einstein Telescope may provide sufficient improvement in
parameter estimation, allowing for the conclusive detection of strong lensing
of GWs.Comment: 17 pages, 14 figure
Observability of lensing of gravitational waves from massive black hole binaries with LISA
The gravitational waves emitted by massive black hole binaries in the LISA band can be lensed. Wave-optics effects in the lensed signal are crucial when the Schwarzschild radius of the lens is smaller than the wavelength of the radiation. These frequency-dependent effects can enable us to infer the lens parameters, possibly with a single detection alone. In this work, we assess the observability of wave-optics effects with LISA by performing an information-matrix analysis using analytical solutions for both point-mass and singular isothermal sphere lenses. We use gravitational-waveform models that include the merger, ringdown, higher harmonics, and aligned spins to study how waveform models and source parameters affect the measurement errors in the lens parameters. We find that previous work underestimated the observability of wave-optics effects and that LISA can detect lensed signals with higher impact parameters and lower lens masses
Observability of lensing of gravitational waves from massive black hole binaries with LISA
The gravitational waves emitted by massive black hole binaries in the LISA
band can be lensed. Wave-optics effects in the lensed signal are crucial when
the Schwarzschild radius of the lens is smaller than the wavelength of the
radiation. These frequency-dependent effects can enable us to infer the lens
parameters, possibly with a single detection alone. In this work, we assess the
observability of wave-optics effects with LISA by performing an
information-matrix analysis using analytical solutions for both point-mass and
singular isothermal sphere lenses. We use gravitational-waveform models that
include the merger, ringdown, higher harmonics, and aligned spins to study how
waveform models and source parameters affect the measurement errors in the lens
parameters. We find that previous work underestimated the observability of
wave-optics effects and that LISA can detect lensed signals with higher impact
parameters and lower lens masses.Comment: 17 pages, 9 figures. All comments are welcom