ORCID Profile
0000-0002-8598-0815
Current Organisation
University of Birmingham
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Publisher: American Astronomical Society
Date: 26-08-2020
Publisher: Springer Science and Business Media LLC
Date: 28-09-2020
DOI: 10.1007/S41114-020-00026-9
Abstract: We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star–black hole, and binary black hole systems. The ability to localize the sources is given as a sky-area probability, luminosity distance, and comoving volume. The median sky localization area (90% credible region) is expected to be a few hundreds of square degrees for all types of binary systems during O3 with the Advanced LIGO and Virgo (HLV) network. The median sky localization area will improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo, and KAGRA (HLVK) network. During O3, the median localization volume (90% credible region) is expected to be on the order of $$10^{5}, 10^{6}, 10^{7}\\mathrm {\\ Mpc}^3$$ 10 5 , 10 6 , 10 7 Mpc 3 for binary neutron star, neutron star–black hole, and binary black hole systems, respectively. The localization volume in O4 is expected to be about a factor two smaller than in O3. We predict a detection count of $$1^{+12}_{-1}$$ 1 - 1 + 12 ( $$10^{+52}_{-10}$$ 10 - 10 + 52 ) for binary neutron star mergers, of $$0^{+19}_{-0}$$ 0 - 0 + 19 ( $$1^{+91}_{-1}$$ 1 - 1 + 91 ) for neutron star–black hole mergers, and $$17^{+22}_{-11}$$ 17 - 11 + 22 ( $$79^{+89}_{-44}$$ 79 - 44 + 89 ) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3 (HLVK network during O4). We evaluate sensitivity and localization expectations for unmodeled signal searches, including the search for intermediate mass black hole binary mergers.
Publisher: Springer Science and Business Media LLC
Date: 03-11-2021
DOI: 10.1038/S41467-021-26648-3
Abstract: The only martian rock s les on Earth are meteorites ejected from the surface of Mars by asteroid impacts. The locations and geological contexts of the launch sites are currently unknown. Determining the impact locations is essential to unravel the relations between the evolution of the martian interior and its surface. Here we adapt a Crater Detection Algorithm that compile a database of 90 million impact craters, allowing to determine the potential launch position of these meteorites through the observation of secondary crater fields. We show that Tooting and 09-000015 craters, both located in the Tharsis volcanic province, are the most likely source of the depleted shergottites ejected 1.1 million year ago. This implies that a major thermal anomaly deeply rooted in the mantle under Tharsis was active over most of the geological history of the planet, and has s led a depleted mantle, that has retained until recently geochemical signatures of Mars’ early history.
Publisher: American Physical Society (APS)
Date: 18-10-2019
Publisher: American Astronomical Society
Date: 19-03-2020
Abstract: On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from to ( – if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the in idual binary components being neutron stars. However, both the source-frame chirp mass and the total mass of this system are significantly larger than those of any other known binary neutron star (BNS) system. The possibility that one or both binary components of the system are black holes cannot be ruled out from gravitational-wave data. We discuss possible origins of the system based on its inconsistency with the known Galactic BNS population. Under the assumption that the signal was produced by a BNS coalescence, the local rate of neutron star mergers is updated to 250–2810 .
Publisher: American Physical Society (APS)
Date: 08-10-2024
Publisher: American Astronomical Society
Date: 18-12-2017
Publisher: American Astronomical Society
Date: 10-2020
Abstract: We present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (PSR J0437−4715, PSR J0711−6830, and PSR J0737−3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835−4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their first and second observing runs. For the first time, we are able to match (for PSR J0437−4715) or surpass (for PSR J0711−6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10 −8 . For each of the five pulsars, we perform targeted searches that assume a tight coupling between the gravitational-wave and electromagnetic signal phase evolution. We also present constraints on PSR J0711−6830, the Crab pulsar, and the Vela pulsar from a search that relaxes this assumption, allowing the gravitational-wave signal to vary from the electromagnetic expectation within a narrow band of frequencies and frequency derivatives.
Publisher: American Physical Society (APS)
Date: 02-04-2020
Publisher: Copernicus GmbH
Date: 22-07-2021
DOI: 10.5194/EPSC2021-710
Abstract: & & & & & strong& Introduction: & /strong& A possible source of seismic activity on Mars is meteoroid impacts [5]. Nevertheless, in the first Martian year of the the NASA InSight Mission [2] no signal has been unambiguously associated with an impact event [4]. This calls for further investigation of meteorite strikes and the relationship between impact conditions and the seismic signals they generate. One of the ways to understand the seismic signature of meteoroid impacts is to analyze already existing data from other planetary bodies.& & & & During the Apollo era, over one thousand seismic signals were recorded on the Moon [e.g. 12]. Part of the Apollo seismic experiments were artificial impacts of Lunar modules (LM) and Saturn booster drops (S-IVB). Artificial impacts are considered large scale controlled experiments, because the exact position of the crater and the impactor parameters that made it are known. In this work, we model S-IVB artificial impacts on the Moon, using the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. We simulated both the crater formation and the pressure wave propagation and attenuation. We examined size of the crater, cratering efficiency, impact momentum transferred to the target and two seismic parameters: seismic efficiency and seismic moment, and compared these measurements to the existing data [e.g., 10, 8, 7].& & & & One challenge with modelling the S-IVB artificial impacts is the realistic presentation of the projectile. The Apollo S-IVB boosters were hollow aluminum cylinders, with a very low bulk density of 23 gcm& em& & sup& & #8722 & /sup& & /em& & sup& & /sup& and mass of 14 t. The booster was 17.8 m long and 6.6 m in radius. The impact speed at the ground level was 2.54-2.66 kms& em& & sup& & #8722 & /sup& & /em& & sup& & /sup& . The drop angle was reported to be between 13.2& em& & sup& & #9702 & /sup& & /em& & em& & /em& and 35& em& & sup& & #9702 & /sup& & /em& & em& & /em& from vertical. [e.g., 14, 19]. There were five such impacts, and they all impacted into mare basalts and made elliptical craters (long and short axis in between 29.71 m and 38.7 m) with a central mound (crater depth was roughly estimated to 2-3 m) [e.g., 14].& & & & & strong& Numerical modelling: & /strong& All simulations in this work used the iSALE-2D shock physics hydrocode [e.g., 1, 3, 21]. To exclude any influence of target properties, all simulations used the same uniform target model of a 44% porous basaltic regolith [20, 15]. The mass and impact velocity of the projectile in our simulations were the same in all simulations and consistent with the experi- ments. Given the axial symmetry of the mesh geometry employed, we investi- gated five simplified representations of the irregularly shaped projectile. Three cases had a geometry of right-cylinder, with 90% porosity and different dimen- sions: 1. 11.7 m radius and height 0.5 m 2. 5.8 m radius and 2 m height 3. 0.992 m radius and 16.7 m height. The last two cases were spheroids: one was non-porous aluminum sphere with 1.06 m radius and the other one was 90% porous and had a radius of 2.3 m [13,21]. To calculate momentum transfer, the vertical component of the seismic moment and seismic efficiency we use approaches described extensively in previous studies [9, 7, 20, 15].& & & / & & & Here, we focus only on the vertical component of the seismic moment Mz [11, 7, 20]. To calculate seismic efficiency we used the same approach described in numerous previous work [e.g., 9, 20, 15].& & & & & strong& Results: & /strong& The shape of the projectile has a substantial effect on crater for- mation but little effect on the seismic signature of the impact. The largest crater was formed in Case 3, while the best agreement with observed crater properties was provided by Case 1 (for depth) and Case 5 (diameter). The porosity of the projectile affected the size of the mound at the bottom of the crater, which supports the idea that the observed central mounds at the bottom of the ob- served craters are projectile remenants [14]. The seismic efficiency & em& k & /em& & em& & sup& & #8722 & /sup& & /em& & sup& & /sup& and seismic moment & em& M& sub& z& /sub& & /em& 10& sup& & /sup& Nm were of the same order of magnitude for all cases. This seismic efficiency is in agreement with lower estimates of [10], and the seismic moment is consistent with the scaling proposed in [17, 16, 20, 6].& & & & & strong& Conclusion: & /strong& We have successfully replicated the S-IVB artificial impacts on the moon with iSALE2D, producing craters that are consistent with obser- vations in their approximate dimensions and morphology. The simulations also constrain the seismic efficiency and seismic moment of the artificial impacts, which are relatively insensitive to the density and shape of the impactor. The low seismic efficiency determined here for artificial impacts on the Moon may help explain the non-detection of impacts by InSight in the first Martian year of operating. Moreover, the insensitivity of seismic moment to impactor density and shape suggests that results from the Apollo seismic experiment of these artificial impacts are useful analogs for small impacts on Mars that can be used to better inform their detectability by InSight [17, 16, 20, 6].& & & & & & [1]& & Amsden A.A. et al. 1980. Technical report.& & & / & & & [2] Banerdt B.W. et al. 2020. & em& Nature Geoscience& /em& , pages 1& #8211 .& & & & [3] Collins G.S. et a. 2004. & em& Meteoritics & Planetary Science& /em& , 39(2):217& #8211 & & & & [4] Daubar I.J. et al. 2020. & em& Journal of Geophysical Resear& /em& & em& ch: Planets& /em& 125(8).& & & & [5] Daubar I.J. et al. 2018. & em& Space Science Reviews& /em& , 214(8):1& #8211 .& & & & [6] Fernando B. et al. 2020& em& Journal of Geophys& /em& & em& ical Research: Planets& /em& .& & & & [7] Gudkova T. et al. 2015. & em& Earth and Planetary Science Letters& /em& , 427:57& #8211 .& & & & [8] Gudkova TV et al. 2011. & em& Icarus& /em& , 211(2):1049& #8211 .& & & & [9] Guldemeister & Wunnemann K.2017. & em& Icarus& /em& , 296:15& #8211 .& & & & [10] Latham G. et al. 1970. & em& Science& /em& , 170(3958):620& #8211 .& & & & [11] Lognonne P. et al. 2009. & em& Journal of & /em& & em& Geophysical Research: Planets& /em& , 114(E12).& & & & [12] Lognonne & & Mosser B.1993. & & em& Surveys& /em& & em& & /em& & em& in & /em& & em& Geophysics& /em& , 14(3):239& #8211 .& & & & [13] Lundborg N. 1968. & em& International Journal of & /em& & em& Rock Mechanics and Mining Sciences & Geomechanics Abstracts& /em& , volume 5, pages 427& #8211 .& & & & [14] Plescia J.B. et al. 2016. & em& Planetary and Space Science& /em& , 124:15& #8211 .& & & & [15] Rajsic A., et al. 2021. & em& Journal of Geophysical Research: Planets& /em& .& & & & [16] Teanby N.A. 2015. & em& Icarus& /em& , 256:49& #8211 .& & & & [17] Teanby N.A. & Wookey J. 2011. & em& Physics of the Earth and Planetary Interiors& /em& , 186(1-2):70& #8211 .& & & & [18] Tillotson J.H. Technical report.& & & & [19] Wagner RV., et al. 2017. & em& Icarus& /em& , 283:92& #8211 ,& & & & [20] Wojcicka N. et al. 2020. & em& Journal of Geophys& /em& & em& ical Research: Planets& /em& . 125(10)& & & & [21] Wunnemann K., et al. 2006. & em& Icarus& /em& 180(2).& &
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
DOI: 10.1038/NATURE24471
Abstract: On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
Publisher: Copernicus GmbH
Date: 21-07-2021
DOI: 10.5194/EPSC2021-459
Abstract: & & The crust on Mars has been structurally affected by various geologic processes such as impacts, volcanism, mantle flow and erosion. Previous observations and modelling point to a dynamically active interior in early Martian history, that for some reason was followed by a rapid drop in heat transport. Such a change has significantly influenced the geological, geophysical and geochemical evolution of the planet, including the history of water and climate. Impact-induced seismic signature is dependent on the target properties (conditions in the planetary crust and interior) at the time of crater formation Thus, we can use simulations of impact cratering mechanics as a tool to probe the interior properties of a planet.& & & & Contrary to large impacts happening in Mars& #8217 early geologic history, the present-day impact bombardment is limited to small meter-size crater-forming impacts (in the atmosphere and on the ground), which are also natural seismic sources (Daubar et al., 2018, 2020 Neidhart et al., 2020). Impact simulations, in tandem with NASA InSight seismic observations (Benerdt et al., 2020, Giardini et al., 2020), can help understand the crustal properties over the course of Mars& #8217 evolution, including the state of Mars& #8217 crust today. Our most recent numerical investigations include: estimating the seismic efficiency and moment from small meter-size impact events, tracking pressure propagation from the impact point into far field, transfer of impact energy into seismic energy, etc (Rajsic et al., 2020, Wojcicka et al., 2020). Understanding coupling between impact crater formation process with the generation and progression of seismic energy can help identify small impact everts in seismic data on Mars. We also looked at the same process on the Earth (Neidhart et al., 2020) and the Moon (Rajsic, et al., this issue).& & & & Since the landing of the NASA InSight mission on Mars, there was a dozen known new impacts (Miljkovic et al., 2021). However, all but one impact occurred much too far away (3000 to 8400 km distance from the InSight lander) to be within the detectability threshold estimates (Teanby et al., 2015 Wojcicka et al., 2020). About 50% of the observed craters were likely single impacts and the other 50% were evidently cluster craters with less than 40 in idual craters in the largest cluster. The largest single crater was ~14 m in diameter, and the largest crater in a cluster was ~13 m (Neidhart et al., this issue), consistent with crater cluster observations (Daubar et al., 2013). The one impact that had a possibility of being detected by SEIS was 1.5 m in diameter at 37 km distance (Daubar et al. 2020).& & & & Considering that orbital imaging is limited in space and time, these known new impacts represent only a fraction of the total number of impacts that have occurred on Mars in the last ~2 years. According to impact flux calculations (Teanby and Wookey, 2011), there should have been ~3000 detectable craters, larger than 1 m in diameter, formed on Mars since InSight landed. If any of these unobserved impacts have been large enough and close enough to InSight to detect seismically, we have not yet discerned them in the seismic data.& & & & References:& & & & Banerdt, W.B. et al. (2020) & em& Nature Geosci. & /em& , 183-189.& & & & Giardini, D. et al. (2020) & em& Nature Geosci. & /em& , 205-212.& & & & Daubar, I.J. et al. (2020) & em& J. Geophys. Res. Planets& /em& , 125: e2020JE006382.& & & & W& #243 jcicka, N. et al. (2020) & em& J. Geophys. Res. Planets& /em& , 125, e2020JE006540.& & & & Raj& #353 i& #263 et al. (2021) & em& J. Geophys. Res. Planets& /em& , 126, e2020JE006662.& & & & Daubar et al. (2013) & em& Icarus& /em& 225, 506-516.& & & & Teanby, N.A. & Wookey, J. (2011) & em& PEPI& /em& 186, 70-80.& & & & Neidhart, T. et al. (2020) & em& PASA& /em& , 38, E016.& & & & Teanby, N.A. et al. (2015) & em& Icarus& /em& 256, 46-62.& & & & Miljkovic, K. et al. (2021) & em& LPSC& /em& , LPI Contribution No. 1758.& &
Publisher: American Physical Society (APS)
Date: 04-09-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-10-2022
Abstract: Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.
Publisher: American Geophysical Union (AGU)
Date: 04-2023
DOI: 10.1029/2022JE007698
Abstract: Seismic activity generated by impacts depends on impact conditions and properties of the impact site. Here, we combined mapping of the regolith thickness with numerical impact simulations to better estimate the seismic efficiency and seismic moment generated in small impact events in the uppermost crust on Mars. We used mapping of crater morphology to determine the regolith thickness that craters formed in. We found that local regolith thickness in the late Amazonian units is between 4 and 9 m. Combined with previous estimates for the NASA InSight landing site, we composed a more realistic uppermost crust analog and implemented it in numerical impact simulations. We estimated the seismic efficiency and seismic moment for small craters on Mars impacting a non‐porous or fractured bedrock overlaid by 5, 10, or 15 m thick regolith. Seismic energy showed more dependence on target properties. Three orders of magnitude more energy were produced in stronger targets. The seismic moment does not depend on target properties, and we confirm that seismic moment is almost proportional to impact momentum. The resulting seismic moment is in agreement up to a factor of 4 between different target types. We improved the scaling relationships developed from numerical simulations used in seismic moment approximations by constraining its dependence on more realistic target properties.
Publisher: American Physical Society (APS)
Date: 02-09-2020
Publisher: Copernicus GmbH
Date: 21-07-2021
DOI: 10.5194/EPSC2021-12
Abstract: & & & strong& Introduction:& /strong& Martian meteorites are the only s les from the Red Planet available for in-depth laboratory analyses. More than 280 pieces of 152 unique s les, originating from at least 11 source craters, are curated in the world& #8217 s collections [1]. Ejection ages, based on cosmic ray exposure (CRE), vary from 0.7 to 20 Myr [2-4]. The ejection sites are still unknown, despite several previous propositions [5-7], motivated by the significance of establishing a link between the crystallization ages, and the chemical and mineralogical properties of these s les with surface geology.& & & & & strong& Secondary impact craters, the key to identify the meteorites ejection sites:& /strong& The formation of an impact crater generates debris ejected with speeds above and below the escape velocity on Mars (5 km/s). The fraction of ejecta material with a velocity higher than the escape velocity may get through the Martian atmosphere and into the interplanetary space. Numerical simulations suggest that impact events capable of producing such fragments would form craters larger than ~3 km in diameter on the Martian surface [8-9]. Material with a velocity lower than 5 km/s falls back to the surface in a radial pattern or rays around the primary source crater and forms secondary craters with a maximum size of about 2 to 5% of the primary crater diameter [10-12]. These secondaries are shallower than those formed by primary impacts and are rapidly eroded. Typically, a secondary crater of 100 m in diameter would be completely erased in about 50 Myr. Therefore, the occurrence of radial patterns of small secondaries is a diagnostic feature of young primary craters [6,13-14]. The use of high-resolution imagery would allow the identification of such small craters, but manual mapping of the tens of millions of secondary impact craters constellating the surface of Mars is not feasible.& & & & & strong& Machine learning approach to identify small craters on high-resolution images:& /strong& We adapted an automated Crater Detection Algorithm (CDA) [15] to identify craters smaller than 1 km in diameter across the entire surface of Mars. The algorithm was trained using High-Resolution Imagery System Experiment (HiRISE) images (25 cm ixel) and applied on the global Context Camera (CTX) mosaic [16] (6 m ixel), thus generating a database of more than 90 million detections (Figure 1).& & & & & img src=& quot ileStorageProxy.php?f=gnp.47e50ee6e99062688960261/sdaolpUECMynit/1202CSPE& app=m& a=0& c=2f4db6722d4cfeabbf1a09450cf5bd43& ct=x& n=gnp.elif& d=1& quot alt=& quot & quot & & & & & Figure 1: Crater Size-Frequency Distribution of the automatic crater database (in red) compared to the manual catalogue (in blue) from [11-12].& & & & We evaluated the performance of our model against ~1000 impact craters & m (10 pixels in diameter on CTX imagery) manually mapped on 6 different geological units, thus constituting the ground truth (GT). For craters & 100 m in diameter, it results in an average true positive detection rate (or & em& recall& /em& ) of more than 80% and an average precision of 96%. The diameter estimation derived from our model is within 25% of uncertainty compared to our ground truth (Figure 2), which is within the expected human performance [17].& & & & & img src=& quot ileStorageProxy.php?f=gnp.1a9cedf6e99067788960261/sdaolpUECMynit/1202CSPE& app=m& a=0& c=969cc49d5871573a6a5e5b1c373d57a1& ct=x& n=gnp.elif& d=1& quot alt=& quot & quot & & & & & Figure 2: Comparison between the difference in the diameter of craters estimated by the CDA and the ground truth (black crosses). The kernel density estimator shows that detections larger than 100m are estimated within 25% of uncertainties compared to manually identified impact craters.& & & & & strong& The ejection site of a group of Martian meteorites:& /strong& We analyzed the spatial and size distribution of craters smaller than 300 m by computing a crater density map from this dataset. The figure 3 presents the results obtained by combining three density maps with red, green, and blue channels corresponding to local crater density (in a 0.05& #176 grid) for three diameter size ranges, in order of decreasing range of diameter, respectively 150 & D & 300 m, 75 & D & 150 m and & 75 m. Using this map, we identified 19 secondary ray systems associated with large and recent primary craters (Figure 3).& & & & & img src=& quot ileStorageProxy.php?f=gepj.031f0117e99067988960261/sdaolpUECMynit/1202CSPE& app=m& a=0& c=8f76ba0bd509fe689fb19000bc0f57b3& ct=x& n=gepj.elif& d=1& quot alt=& quot & quot & & & & & Figure 3: Density map of craters & 300 m in diameter (89,054,458 entries). Colors indicate crater densities of specific diameter ranges (see text for details).& & & & Using crater counts on the ejecta blanket of each of those 19 impact craters and their surrounding terrains, we derived respectively the model age of those impacts and the age of the impacted material. Those results are compared with the ejection age of Martian meteorites as well as their crystallization ages. We found that two craters, both located in the Tharsis volcanic province, are the most likely source of depleted Shergottites launched ~1 Myr ago [3]. Considering the magmatic ages and the petrogenesis of these s les, this implies that a major thermal anomaly deeply rooted in the mantle under Tharsis was active over most of the geological history of the planet, and has s led a depleted mantle that has retained geochemical signatures of Mars& #8217 early history.& & & & & strong& References: & /strong& [1] eteor/metbull.php. [2] Herzog, G.F., & Caffee, M.W. & em& Treatise on Geochemistry& /em& , 1, 419-454 (2014). [3] Lapen, T.J., et al. & em& Sci. Adv.& /em& , 3(2), e1600922 (2017). [4] Udry, A., et al. & em& J. Geophys. Res.& /em& , 25, e2020JE006523 (2020). [5] Werner, S. C., et al., & em& Science& /em& , 343, 1343& #8211 (2014). [6] McEwen, A.S., et al. & em& Icarus& /em& , 176, pp. 351-381 (2005). [7] Mouginis-Mark, P.J. & Boyce, J.M. & em& Chemie der Erde - Geochemistry& /em& , 72, 1-23 (2012). [8] Artemieva, N., & Ivanov, B.A. & em& Icarus& /em& , 1, 84-101 (2004). [9] Head, J.N., et al., & em& Science& /em& , 298, 1752-1756 (2002). [10] Lagain, A., et al., in Reimold, W.U., and Koeberl, C., eds., & em& Large Meteorite Impacts and Planetary Evolution VI& /em& , 550, p. 1-16 (2021). [11] Robbins, S.J., & Hynek, B.M. J. Geophys. Res., 117, E05004, (2012). [12] Robbins, S.J. & Hynek, B.M. & em& J. Geophys. Res.& /em& , 116, E10003 (2011). [13] Hartmann, W.K., et al., & em& Icarus& /em& , 208, 621-635 (2010). [14] Tornabene, L.L., et al. & em& J. Geophys. Res.& /em& , 111, 1-25 (2006). [15] Benedix, G.K., et al. & em& Earth. Sp. Sci.& /em& , 7, e2019EA001005 (2020). [16] Dickson, J.L., et al., & em& & /em& & em& & sup& th& /sup& Lunar and Plan. Sci. Conf.& /em& (2019). [17] Robbins, S.J., et al. & em& Icarus& /em& , 234, 109& #8211 (2014).& &
Publisher: American Astronomical Society
Date: 16-10-2017
Publisher: American Physical Society (APS)
Date: 30-09-2019
Publisher: American Astronomical Society
Date: 04-09-2019
Publisher: American Astronomical Society
Date: 29-06-2021
Abstract: We report the observation of gravitational waves from two compact binary coalescences in LIGO’s and Virgo’s third observing run with properties consistent with neutron star–black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115 the first was observed by LIGO Livingston and Virgo and the second by all three LIGO–Virgo detectors. The source of GW200105 has component masses 8 . 9 − 1 . 5 + 1. 2 and 1. 9 − 0. 2 + 0. 3 M ⊙ , whereas the source of GW200115 has component masses 5. 7 − 2 . 1 + 1. 8 and 1. 5 − 0. 3 + 0. 7 M ⊙ (all measurements quoted at the 90% credible level). The probability that the secondary’s mass is below the maximal mass of a neutron star is 89%–96% and 87%–98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are 280 − 110 + 110 and 300 − 100 + 150 Mpc , respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of 45 − 33 + 75 Gpc − 3 yr − 1 when assuming that GW200105 and GW200115 are representative of the NSBH population or 130 − 69 + 112 Gpc − 3 yr − 1 under the assumption of a broader distribution of component masses.
Publisher: Elsevier BV
Date: 2021
Publisher: American Astronomical Society
Date: 30-09-2019
Abstract: When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits ( e 0.1 at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template-based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates ≳100 Gpc −3 yr −1 for e 0.1, assuming a black hole mass spectrum with a power-law index ≲2.
Publisher: American Astronomical Society
Date: 11-09-2019
Publisher: American Geophysical Union (AGU)
Date: 29-11-2021
DOI: 10.1029/2021EA001887
Abstract: The third stage of the Saturn IV rocket used in the five Apollo missions made craters on the Moon ∼30 m in diameter. Their initial impact conditions were known, so they can be considered controlled impacts. Here, we used the iSALE‐2D shock physics code to numerically simulate the formation of these craters, and to calculate the vertical component of seismic moment (∼4 × 10 10 Nm) and seismic efficiency (∼10 −6 ) associated with these impacts. The irregular booster shape likely caused the irregular crater morphology observed. To investigate this, we modeled six projectile geometries, with footprint area between 3 and 105 m 2 , keeping the mass and velocity of the impactor constant. We showed that the crater depth and diameter decreased as the footprint area increased. The central mound observed in lunar impact sites could be a result of layering of the target and/or low density of the projectile. Understanding seismic signatures from impact events is important for planetary seismology. Calculating seismic parameters and validating them against controlled experiments in a planetary setting will help us understand the seismic data received, not only from the Moon, but also from the InSight Mission on Mars and future seismic missions.
Publisher: American Physical Society (APS)
Date: 11-07-2019
Publisher: American Physical Society (APS)
Date: 04-09-2019
Publisher: American Physical Society (APS)
Date: 24-08-2020
Publisher: Oxford University Press (OUP)
Date: 21-09-2020
Abstract: Gravitational waves provide a unique tool for observational astronomy. While the first LIGO–Virgo catalogue of gravitational-wave transients (GWTC-1) contains 11 signals from black hole and neutron star binaries, the number of observations is increasing rapidly as detector sensitivity improves. To extract information from the observed signals, it is imperative to have fast, flexible, and scalable inference techniques. In a previous paper, we introduced bilby: a modular and user-friendly Bayesian inference library adapted to address the needs of gravitational-wave inference. In this work, we demonstrate that bilby produces reliable results for simulated gravitational-wave signals from compact binary mergers, and verify that it accurately reproduces results reported for the 11 GWTC-1 signals. Additionally, we provide configuration and output files for all analyses to allow for easy reproduction, modification, and future use. This work establishes that bilby is primed and ready to analyse the rapidly growing population of compact binary coalescence gravitational-wave signals.
Publisher: SAGE Publications
Date: 18-06-0015
Abstract: Pain can elevate stress in people with dementia. Although salivary cortisol is used as a biomarker of stress in people with dementia, few studies have reported the feasibility of collection methods to assess salivary cortisol in nursing home residents with both dementia and chronic pain. To explore the feasibility of collecting cortisol via salivary swab as an indicator of stress in people with dementia and chronic pain. Participants ( N = 43) aged ≥ 65 years and living with dementia and chronic pain were randomly assigned to the PARO (in idual, nonfacilitated, 30-min sessions with the robotic seal PARO, 5 days per week for 6 weeks) or usual-care group using computer-generated random numbers. Salivary cortisol was collected in the early morning before the intervention (Week 0) and at the completion of the intervention (Week 6) for comparison. There were multiple challenges associated with saliva collection and analysis, including cognitive impairment of participants, ability to obtain repeated s les with saliva volume adequate for assay, and overall cost. Ultimately, adequate saliva was collected from only 8 participants (both pre- and post-intervention) for assay and quantitative analysis. Considering the multiple challenges involved in obtaining valid saliva s les in this population, salivary cortisol may not be a feasible biomarker of physiological stress in people with dementia and chronic pain.
Publisher: American Physical Society (APS)
Date: 04-12-2019
Publisher: American Physical Society (APS)
Date: 20-11-2019
Publisher: American Astronomical Society
Date: 26-06-2019
Publisher: American Geophysical Union (AGU)
Date: 10-2020
DOI: 10.1029/2020JE006540
Publisher: American Astronomical Society
Date: 20-04-2020
Publisher: American Geophysical Union (AGU)
Date: 08-2020
DOI: 10.1029/2020JE006382
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: Spain
No related grants have been discovered for Andrea Rajsic.