Max Planck Institute for Gravitational Physics

A bstract Two fundamentally distinct types of quantities are both called “eikonal” in present amplitudes literature. The unitarity of the S-matrix ensures it can be written as the exponential of a Hermitian operator. The eikonal generator or Magnusian , which is the classical limit of the expectation value of that operator, generates all scattering observables. The leading order classical behavior of the phase of an S-matrix element is called the classical eikonal phase, and it coincides with a classical on-shell action. We demonstrate that the eikonal generator (Magnusian) and the eikonal phase (classical on-shell action) are inequivalent and find the exact general relationship between them. That relationship explains the special case of integrable scattering in which the two do coincide up to a Legendre transformation and explains why such a correspondence fails in general when spin or radiation are included.

Abstract We report the discovery and timing of two pulsars from a sample of four circularly polarized sources identified in radio continuum images taken as part of the Australian SKA Pathfinder Variables and Slow Transients survey. Observations with the Parkes (Murriyang) radio telescope confirmed both sources as normal pulsars with high dispersion measures (DMs). PSR J1646−4451 has a spin period of 217 ms and a DM of 928 cm −3 pc, while PSR J1837−0616 exhibits a spin period of 118 ms and a DM of 793 cm −3 pc. These pulsars show extreme pulse broadening due to scattering, with measured scattering timescales of 117 ms and 75 ms at observing frequencies of ∼1.8 GHz, respectively. These measurements imply extrapolated scattering timescales at 1 GHz of ∼1346 ms and 740 ms, placing them among the most heavily scattered known pulsars. Our findings underscore the potential of using circular polarization in radio continuum images as a tool for identifying highly scattered pulsars. Future wide-field radio continuum surveys are poised to uncover a broader population of extreme pulsars, particularly those that are heavily scattered at 1.4 GHz, intrinsically faint, or residing in binaries—offering valuable insights into both pulsar demographics and the complex structure of the ionized interstellar medium.

Since 2002, GRACE and GRACE-FO have recorded valuable data on changes in the Earth mass distribution, indicating melting ice caps, a rising sea level and redistributions of groundwater. The continuation of this data collection is of high interest for climate research. Future gravity missions, such as NGGM, GRACE-C and TianQin-2 are currently under development and will use a Laser Ranging Instrument (LRI) to measure the main observable – distance variations between two satellites which are orbiting the Earth in a separation of 200 km.To support studies for future gravity missions, we developed a novel LRI Level 1A data simulator that uses orbit files containing the satellite positions and velocities, as well as attitude datasets providing satellite orientations. Under consideration of physical principles and instrument characteristics of laser interferometers in space, the simulator derives LRI phase measurements and LRI inter-satellite pointing angles in a format similar to GRACE-FO level1a files. The data is further processed to level1b using the same software used for the processing of GRACE-FO LRI flight data. The simulator is already capable of deriving realistic LRI ranging data and led to improvements in our GRACE-FO LRI level1b processing chain.In this poster presentation we provide an overview of which effects are already considered in the simulator, explain the data validation strategy, and present a tone-error analyses from different contributors.

The ESA-led Next Generation Gravity Mission, as the successor to the GRACE-FO mission, will use a Laser Tracking Instrument (LTI) as its primary and only inter-satellite ranging instrument, which will be developed entirely in Europe. The Instrument Control Unit (ICU), as one development to replace prior US contributions, is expected to acquire range information through phase readout of the laser interference, control the Optical Bench Electronics, stabilize the laser frequency, and communicate with the Onboard Computer. As a joint venture development with the Laser Interferometer Space Antenna (LISA) at AEI, an improved algorithm for Differential Wave Front (DWS) sensing is implemented, featuring higher robustness due to independent gain settings for ranging and DWS information. In addition, LTI pointing angles of the optical bench are used as a sensor to control satellite attitude, and the Scale-Factor Measurement System is included in the ICU as a major difference to the GRACE-C mission.Here we present the ICU Engineering Model (ICU EM) design, its most important performance requirements, and first results from the test campaign, which aims to achieve a two times more ambitious ranging noise requirement by means of phase-tracking with a noise below 40nm/rtHz x NSF(f) and DWS of 5nrad/rtHz x NSF. These measurements require a stabilized 80MHz system clock referenced with less than 50psec/rtHz x NSF(f) to a 10MHz ultra stable oscillator of the spacecraft. The laser frequency is stabilized either to a cavity with an absolute laser frequency accuracy below 20 ppb or locking to the incoming laser frequency with 13MHz offset, depending on the satellite's role.We specifically address the development and features of the FPGA firmware, which comprises, next to the digital signal processing pipelines for phase tracking, steering mirror, and laser control, also house-keeping and diagnostic functionalities. The first results from electrical and optical testing suggest that the ICU will meet the performance requirements and enable uninterrupted range measurements with sub-nanometer resolution, hence, continue the laser ranging dataset that has been initiated with the GRACE-FO mission.

Abstract The observation of gravitational waves (GWs) from merging black holes and neutron stars provides a unique opportunity to discern information about their astrophysical environment. Two signatures that are considered powerful tracers to distinguish between different binary formation channels are general relativistic spin-induced orbital precession and orbital eccentricity. Both effects leave characteristic imprints in the GW signal that can be extracted from observations. To date, neither precession nor eccentricity has been confidently discerned in merging neutron star–black hole binaries. Here we report the measurement of orbital eccentricity in a neutron star–black hole merger. Using, for the first time, a waveform model that incorporates precession and eccentricity, we perform Bayesian inference on the GW event GW200105 and infer a median orbital eccentricity of e 20 ∼ 0.145 at an orbital period of 0.1 s, ruling out eccentricities smaller than 0.028 with 99.5% confidence. We find inconclusive evidence for the presence of precession, consistent with previous, noneccentric results, but a more unequal mass ratio. Our result implies a fraction of these binaries will exhibit orbital eccentricity even at small separations, suggesting formation through mechanisms involving dynamical interactions beyond isolated binary evolution. Future observations will reveal the contribution of eccentric neutron star–black hole binaries to the total merger rate across cosmic time.

Abstract The binary black hole merger GW231123 is both the most massive gravitational-wave event observed and has the highest component spins measured to date. The dimensionless spins of the more massive (primary) and less massive (secondary) black holes are measured to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>χ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.9</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.19</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>χ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.8</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.51</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.20</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> (90% credible intervals), respectively. Its large mass and extremal spins are challenging to explain through standard binary stellar physics, though a flurry of hypothetical scenarios have been proposed. Hierarchical assembly—i.e., mergers of black holes that are themselves formed from previous generations of mergers—is generally a promising way to explain massive and rapidly spinning black holes. Here, we investigate the possibility that GW231123 was assembled hierarchically in a dense star cluster as the merger of two second-generation black holes. Taking the inferred spin values at face value, we find that it is possible ( p ≈ 5%) that a compact binary with component spins like GW231123 could form in a cluster from hierarchical assembly.

Abstract Children with a disability require a greater level of care, which may profoundly affect the lives of their parents as their primary caregivers. However, empirical evidence to quantify the parental care burden of child disability remains scarce. This study aims to uncover the extent to which a child’s disability affects the parental care burden by investigating fathers’ and mothers’ time spent on housework and childcare. Exploiting data from the German Socio-Economic Panel (SOEP) and applying propensity-score matching, we compare the individual time fathers and mothers spend on parental care for children with and without a disability, as well as the division of parental care time within couples. Our findings indicate a parental care burden of child disability of an additional 19 minutes per day for fathers and 26 minutes per day for mothers. This extra burden is most significant for mothers of children with a disability aged 0 to 2, with 1 hour and 25 minutes per day. Furthermore, the parental care burden is particularly pronounced in fathers of later birth cohorts, and parents with a lower educational attainment level, with multiple children, or residing in West Germany. While the parental care burden of child disability is disproportionally higher for mothers than fathers, we find no evidence for an association with the division of parental care time within couples. Our study is the first to provide quantitative evidence for the increased parental care burden of child disability from a population perspective, potentially explaining adverse spillover effects on family dynamics and all family members’ wellbeing and health.

Abstract Accurate pulsar astrometric estimates are essential to almost all high-precision pulsar timing experiments. Traditional pulsar timing techniques refine these estimates by including them as free parameters when fitting a model to observed pulse time-of-arrival measurements. However, reliable submilliarcsecond astrometric estimations require years of observations. Even then, power from red noise can be inadvertently absorbed into astrometric parameter fits. This effect biases the resulting estimates and reduces the sensitivity to red noise processes, including gravitational waves (GWs). In this work, we seek to mitigate these shortcomings by using pulsar astrometric estimates derived from very long baseline interferometry (VLBI) as priors for the timing fit. First, we used VLBI and timing astrometric estimates of 18 millisecond pulsars to calibrate a rotation between the reference frames used in timing and VLBI, with a precision of ∼0.7 mas. Through this frame tie, we combined timing- and VLBI-based probabilities to obtain a maximum-posterior astrometric solution. We found offsets between our results and the timing-based astrometric solutions, which, if real, would lead to the absorption of spectral power at the frequencies of interest for single-source GW searches. However, we do not find significant power absorption due to astrometric fitting at the low-frequency domain of the GW background.