外部リンク

AAPPS DACG

JSPS Core-to-Core program

東京大学ハラスメント相談所

Tsvi Piran

(Hebrew University of Jerusalem)

Tidal Disruption Events - a being is devoured by a black hole

Stephane Colombi

(Institut Astrophysique de Paris/OAR)

Vlasov versus N-body

Dark matter in the Universe can be considered as a collisionless self-gravitating fluid obeying the Vlasov-Poisson equations. In practice, resolving dark matter dynamics relies on a N-body approach, but with the advent of exaflopic computers it becomes now possible to solve directly Vlasov dynamics in six-dimensional phase-space. In this talk I will compare particle-mesh simulations to Vlasov runs in the framework of the formation of dark matter microhalos. I will also discuss recent results obtained for the profile of microhalos, notably the appearance of "prompt cusps" which could survive until the present time and increase the probability of indirect detection of dark matter compared to standard calculations.

Alfredo Luminari

(INAF IAPS/OAR)

Time-Evolving Photoionisation in the XRISM era

Photoionisation is one of the main mechanisms shaping the gaseous environment of bright astrophysical sources, including Active Galactic Nuclei (AGNs), Gamma-Ray Bursts (GRBs) and compact sources. Much information on the gas physics, chemistry and kinematics, as well as on the ionising source itself, can be gathered through optical to X-ray spectroscopy. Just to name a few examples, mildly relativistic, photoionised outflows from AGNs transfer a significant amount of the accretion-liberated energy to the host galaxy scale, possibly driving its evolution. In X-Ray Binaries, gas feeding is regulated through massive winds outflowing from the accretion disc. In GRBs, spectroscopy of the ionised circumburst gas gives unique insights on the progenitor star and on the ISM, even at cosmological distances. Finally, the evolution of the gas reservoir at galactic and cluster scales is regulated by its radiative and collisional heating and cooling balance.
For all these cases, several public time equilibrium photoionisation codes are available to analyse the spectroscopic imprint of the gas in the observations. However, as most (if not all) the sources discussed above are intrinsically variable, such codes are only able to offer an average description of the gas properties and, in the most extreme cases, can lead to an erroneous diagnostic of its density, physics and geometry. In all these cases, time-evolving photoionisation is necessary to properly analyse the observations and derive the gas properties consistently, and thus its impact on the environment.
In this talk I will present our new Time-Evolving Photoionisation Device (TEPID; Luminari+23), a new code that self-consistently solves the time evolving photoionisation equations and accurately follows the response of the gas to changes of the ionising source. TEPID produces time-resolved gas absorption spectra that can be directly fitted to optical to X-ray observations. Time evolving ionisation offers a unique channel to directly constrain the gas number density, which is a totally degenerate quantity at equilibrium, and thus is necessary to properly estimate the gas mass load and the energy budget. Such time-evolving codes are especially needed in light of the recently-launched XRISM satellite, whose microcalorimeter Resolve will perform unprecedented high-resolution spectroscopy through the entire X-ray band and will make equilibrium codes obsolete.
Finally, I will present two applications of TEPID to dramatically different environments - AGN ionised absorbers and the circumburst environments of GRBs - to offer a glimpse of the unique capabilities offered by time-evolving photoionisation.

Ajit Kembhavi

(Inter-University Center for Astronomy and Astrophysics, Pune, India)

Artificial Intelligence and Machine Learning in Astronomy

Machine Learning, Deep Learning, and other Artificial Intelligence (AI) techniques have now become an integral part of development in every sphere of activity. The techniques are particularly important in astronomy, where powerful telescopes routinely generate vast quantities of data. In my talk I will describe some interesting applications of these techniques to a variety of problems in astronomy including galaxy morphology, identification of very compact galaxies, determining the nature of the compact objects in Low-Mass X-ray Binaries etc. I will also mention some applications beyond astronomy.

Stefan Ballmer

(Syracuse University)

The Next Leap in Gravitational-Wave Astronomy

The Gravitational-Wave Transient Catalog from the Advanced LIGO and Advanced Virgo observation run for the first time provides a non-trivial sample of actual gravitational-wave sources. Thus for the first time we can design the next-generation detectors with good guidance on the observable signals. This talk will discuss the latest results, and then focus on the detector technology currently used in Advanced LIGO, its sensitivity limitations and the plans for the next-generation detectors Cosmic Explorer and Einstein Telescope. In partiucular, it will highlight the technology developments needed for those detectors.

Atsush Takada

(Kyoto University)

Dawn of MeV gamma-ray astronomy with electron-tracking Compton camera

MeV gamma-ray from universe is an unique window for direct observation of nucleo synthesis. From the early days of high-energy astrophysics, the line gamma-rays from radioisotopes, electron-positron annihilation line, and de-excitation line are expected to become probes for the nucleosynthesis in supernovae, diffusion of matter in galaxy, and existence of low-energy cosmic-rays. However, there is a little progress in the observation after COMPTEL. For open the window of MeV gamma-ray astronomy, we are developing an electron-tracking Compton camera (ETCC), which is consist of a gaseous electron tracker as a Compton-scattering target and the surrounding scintillators as the absorber for the scattered gamma ray. In 2018, we performed one-day balloon flight (SMILE-2+) for demonstrating the observation of celestial objects and succeeded to detect Crab nebula and Galactic center region with the significance of 4 sigmas and ~10 sigmas, respectively. In addition, the event rate and spectrum at the level flight were explained by the summing of extragalactic diffuse, atmospheric gamma-rays, and instrumental gamma-rays. This fact says that our ETCC can realize the low-noise observation under the space condition, and it is the first designable telescope having a wide field of view in MeV band. In this talk, we will present the results of SMILE-2+ and the future observation plans using long-duration balloons or satellites.

Shingo Kazama

(Nagoya University)

Direct Dark Matter Search with XENON

Direct dark matter searches using xenon dual-phase time projection chamber have shown a great potential to detect WIMPs (Weakly Interacting Massive Particles) via elastic scattering off the target nuclei. With steadily growing target masses the XENON experiment (most recently the XENON1T) set the most stringent limits on WIMP-nucleon interactions over a broad mass range (0.1 GeV to 10 TeV). Its ultra-low backgrounds and the tonne-year exposure also enabled searches for rare nuclear processes, the coherent elastic scattering of solar neutrinos and alternative dark matter candidates such as axion-like particle (ALP). Recently, an excess of low-energy electronic recoil events was observed, but its origin is still not yet determined. This will be explored with the next experiment XENONnT. It is aimed at improving the WIMP sensitivity by more than an order of magnitude beyond current limits with the 20 times longer exposure and 20% of XENON1T background level. In this seminar, I will highlight the recent XENON1T results and give an overview of XENONnT's construction, status and physics reach.

Masaomi Tanaka

(Astronomical Institute, Tohoku University)

Kilonova: Electromagnetic signature of heavy-element nucleosynthesis

Coalescence of binary neutron stars (NSs) gives rise to kilonova, thermal emission powered by radioactive decays of newly synthesized heavy elements. Multi-messenger observations of the NS merger event GW170817 revealed that heavy elements are synthesized in the NS merger. Observational properties of kilonova are largely affected by opacities of heavy-elements. It is thus important to understand atomic properties of heavy elements to link the observed signals with nucleosynthesis in NS mergers. In this talk, I will briefly review the basic physics of NS mergers and kilonovae, and introduce the latest studies on the atomic properties of heavy elements. Then, I will discuss prospects for element identification in kilonova spectra.

Kazuyuki Sugimura

(Astronomical Institute, Tohoku University)

Formation of the First-star Binaries

The first stars in the Universe, born at the redshift z ～ 20-30, bring an end to the dark ages of the Universe. While the first stars are thought to be born as massive stars, we know little about their multiplicity or related properties. In this talk, I will present the results of our recent radiation hydrodynamics simulations of cosmological first star formation, in which we follow gas accretion considering the ionization/dissociation feedback from multiple protostars with a newly developed adaptive mesh refinement (AMR) code with the adaptive ray tracing method, SFUMATO-RT. In all of the three systems we examined, we found that the first stars form as massive binaries. I will also shortly discuss a possible link of our results to gravitational wave events by BH mergers.

Bunyo Hatsukade

(Institute of Astronomy, The University of Tokyo)

Radio constraints on the nature of superluminous supernovae and their host galaxies

Superluminous supernovae (SLSNe) are extremely luminous explosions (>10-100x brighter than ordinary Type Ia and core-collapse SNe), and their energy source and progenitor are still a matter of debate. Radio observations provide useful constraints on physical properties and environments of SLSNe. We have conducted late-time radio continuum observations of a sample of SLSNe and their host galaxies by using VLA, constraining radio light curves and obscured star formation in the hosts. We found a time variability in one of the targets. This is the first report of a variability of late-time radio emission in an SLSN, and plausible scenarios are a low-luminosity AGN or a magnetar wind nebulae. We have also conducted molecular line observations of an SLSN host to understand ISM properties of environments producing SLSNe. I will present our radio studies on SLSNe and future prospects.

Akira Okumura

(ISEE, KMI, Nagoya University)

CTA Small-Sized Telescopes for PeVatron Search

The origin of galactic cosmic rays with energies up to about 3 PeV has been one of mysteries in high-energy astrophysics. Cosmic-ray detectors clearly shows a spectrum cutoff at this energy, but they cannot locate the accelerators, so-called PeVatrons, because of the interstellar magnetic field and bent cosmic-ray trajectories. Instead of direct cosmic-ray observations, observing gamma rays produced by hadronic interaction between cosmic-ray protons and interstellar medium makes it possible to locate PeVatrons. Ground-based gamma-ray telescopes (Cherenkov telescopes) and array-type detectors have recently detected sub-PeV gamma rays and found possible PeVatron candidates with a limited angular resolution and photon statistics. The Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray telescope, is expected to join this PeVatron search race in 2020s with its wide energy coverage from 20 GeV to 300 TeV, and its large effective area of a few km^2. I will talk about the current development status of CTA and future prospects of our PeVatron search.

Kiwamu Izumi

(JAXA Institute of Space and Astronautical Science International Top Young Fellow)

Experimental activities for space gravitational wave observations

Observations of gravitational waves at frequencies below 10 Hz are expected to yield a rich variety of new astronomical and astrophysical insight. In order to achieve such observations, the detectors are essentially required to be put in space. LISA is one of such space missions to be launched in 2034 and will open the unexplored frequency window at around 1 mHz. LISA will shed light on the growth mechanisms of super massive black holes and the nature of gravity. In this talk, I am going to give an overview of the LISA science and mission, and recent status with the instrument development including the one carried out by the LISA Japan instrument group. Additionally, I will introduce a new technology demonstration mission, named SILVIA, which was recently proposed for a JAXA's competitive M-class mission opportunity.

Hiroki Akamatsu

(SRON Netherlands Institute for Space Research)

Energetics of galaxy clusters and cryogenic probes for future astronomical applications

Galaxy clusters are the largest gravitationally bound structures that grow via accretion and mergers. Such mergers introduce shock structures and turbulence in the intracluster medium (ICM). Although these processes are important to understand cluster energetics and their evolving history, the detailed nature is largely unknown. I will talk about X-ray (Suzaku/XMM-Newton/Chandra) and radio (mainly LOFAR) multi-wavelength approach on these issues. I will also touch on recent findings of an interplay between AGN jet and (compressed) cluster magnetic field revealed by MeerKAT radio telescope. In the last part of this contribution, I will briefly report recent progress on cryogenic instruments toward X-ray, infrared astronomy, and exoplanet investigations. New instruments will bring us new ways to study the universe. Transition Edge Sensors (TESs) spectrometers/bolometers are one of the most promising candidates for future applications. TESs are thermistors working at a rather low temperature around 100 mK at the edge of superconducting transition. The sharp transition makes spectrometers sensitive for various wavelengths (infrared, optical, and X-ray). In the coming decades, the cryogenic spectrometer will be a mainstream of astronomical instrumentations.

Takaaki Tanaka

(Kyoto University)

Recent X-ray Studies of Supernova Remnants and Beyond

X-ray observations of supernova remnants provide insight into particle acceleration at their expanding shocks, the mechanisms of the supernova explosions, nucleosynthesis in the explosions, and so on. I will talk about our recent results on Tycho's supernova remnant based on observational data obtained in 2000-2015 with the Chandra X-ray Observatory. Thanks to the superb angular resolution of Chandra, we discovered fine features of synchrotron X-rays showing variability in a short timescale of ~ yr. Such variability indicates that particle acceleration and synchrotron cooling of X-ray-emitting electrons proceed in the ~ yr timescale with a substantially amplified magnetic field. Chandra is a powerful tool also to measure the expansion rate of Tycho's supernova remnant with the highest precision ever. We found that the expansion was abruptly decelerated, which provides us with important clues about the progenitor system of the Type Ia supernova that created the remnant. In the last part of my talk, I will shortly talk about our detector development aiming for the future X-ray mission FORCE, which will achieve an unprecedented angular resolution in the hard X-ray band.

Akira Endo

(Delft University of Technology, on behalf of the DESHIMA collaboration)

DESHIMA: Integrated Superconducting Spectrometer for Wideband Submillimeter Astronomy

The integrated superconducting spectrometer (ISS) enables ultra-wideband, large field-of-view integral-field-spectrometer designs for mm-submm wave astronomy. DESHIMA (Deep Spectroscopic High-redshift Mapper) is a single-pixel ISS spectrometer for the ASTE 10-m telescope, designed to observe the 220-440 GHz band in a single shot, corresponding to a [CII]-line redshift range of z=3.3-7.6.In this colloquium I will present the instrument concept, design, and first on-sky results of DESHIMA, obtained from October to December 2017 on the ASTE telescope. On the ISS chip of DESHIMA, the signal is captured by a lens-antenna and subsequently travels through a coplanar waveguide made of superconducting NbTiN, from which NbTiN bandpass filters branch out to divide the signal into separate frequency channels. At the output of each filter is a NbTiN/Al hybrid microwave kinetic inductance detector (MKID). The first generation of DESHIMA (DESHIMA 1.0) is a 1-pixel spectrometer that covers the 332-377 GHz band with 49 spectral channels, offering a spectral resolution F/dF ~ 380. We present detection of molecular emission lines from various sources, including a weakly redshifted CO line from the luminous infrared galaxy VV 114. The on-sky performance shows excellent agreement between the design and laboratory measurement in terms of the sensitivity, optical efficiency and beam pattern. In addition, we present wideband spectral maps of extended sources to demonstrate the potential of the ISS technology towards spectroscopic direct imaging. Ongoing upgrades towards the octave-bandwidth full system (DESHIMA 2.0) include the development of a filterbank chip with ~350 channels and higher optical efficiency, a wideband quasioptical design, and observing methods for efficiently removing the atmosphere. DESHIMA is a collaboration between the Netherlands (TU Delft, SRON, Leiden University, +) and Japan (University of Tokyo, Nagoya University, Kitami Institute of Technology, NAOJ, +)

Reference

• Endo et al., "First light demonstration of the integrated superconducting spectrometer," Nature Astronomy 3, 989-996 (2019) https://arxiv.org/abs/1906.10216
• DESHIMA website: http://deshima.ewi.tudelft.nl

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Gilles Ferrand

(Astrophysical Big Bang Laboratory (ABBL), Cluster for Pioneering Researchand Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS)RIKEN)

From the thermonuclear supernova to the supernova remnant

Recent progress in the simulation of supernovae (SNe) has shown the importance of turbulence and asymmetries in successful explosions, which prompts us to revisit the subsequent phase, the supernova remnant (SNR). Can we use the SNR morphology as a probe of the explosion mechanism? Recent work has shown the interest of this approach for a core-collapse SNR like Cas A. Here we argue for the case of a Type Ia SNR like Tycho. Our project is making the link between two communities, the one studying the explosion and the one studying the remnant. We have run 3D simulations of a SNR starting from the output of 3D simulations of the thermonuclear explosion of a Chandrasekhar-mass white dwarf. By analyzing the wavefronts we have quantified the imprint of the explosion on the remnant over time. Assuming a uniform ambient medium, we find that the impact of the SN on the SNR may still be visible after hundreds of years. We will present a first comparative study of different explosions models bearing different levels of asymmetry. We will conclude on prospects for comparisons with X-ray observations of young Galactic SNRs.

Felix Aharonian

(Dublin Institute for Advanced Studies, School of Cosmic Physics, Ireland)

Cosmic TeVatrons, PeVatrons, and ZeVatrons

Cosmic Rays constitute, after the matter, radiation and magnetic fields, the 4th substance of the visible Universe. The Cosmic Ray factories, the sites where relativistic electrons, protons and nuclei are produced/accelerated, are linked to almost all types of astronomical objects - from stars to pulsars and supernova remnants, from Active Galactic Nuclei to Galaxy Clusters. Some of these factories are characterised by extreme (close to 100 %) efficiencies in the sense of both (i) conversion of the available energy in different initial forms (e.g. the rotational energy of pulsars and black holes and kinetic energy of supernovae explosions and accretion shocks) to nonthermal relativistic plasma and (ii) boosting the energy of individual particles to the absolute limits allowed by theory. I will discuss the properties of several types of TeVatrons and PeVatrons in the context of recent gamma-ray observations, and ZeVatrons in the context of highest energy Cosmic Rays.

Joseph Gelfand

(NYU Abu Dhabi)

The Extreme Physics of Pulsar Wind Nebulae

Abstract:The universe excels at creating objects whose properties are beyond anything achievable on Earth. A prime example of this are pulsar wind nebulae (PWNe) - which are powered by the rotational energy of a strongly magnetized (>10^12 Gauss), rapidly rotating (rotation period P ~ 10 ms - 1s), neutron star (~1.5x the mass of the Sun and the diameter of Tokyo-Yokohama), and contain particles ~100x more energetic than currently produced at the CERN LHC. In this talk I will describe what we have learned about the formation of neutron stars and the production of such high-energy particles by fitting the observed properties of a PWN with a simple model for its dynamical and radiative evolution.

Richard Shaw

(University of Liverpool)

Probing Dark Energy with CHIME

Abstract:CHIME will use Intensity Mapping of the 21cm line of neutral hydrogen to map large-scale structure between redshifts of 0.8 and 2.5. By measuring Baryon Acoustic Oscillations (BAO) we will place constraints on the dark energy equation of state as it begins to dominate the expansion of the Universe, particularly at redshifts poorly probed by current BAO surveys. In this talk I will introduce CHIME, a transit radio interferometer designed specifically for this purpose. I will discuss the promise and pitfalls of Intensity Mapping and describe how we plan to confront the many challenges of such observations, in particular removal of astrophysical foregrounds which are six orders of magnitude larger than the 21cm signal. CHIME started operating at the DRAO in Penticton, BC at the end of 2018 and I will report on current progress and lessons already learned.

Kenneth C. Wong

(Kavli IPMU)

A 2.4% Measurement of H0 from Lensed Quasars

Abstract: Strong gravitational lens systems with time delays between the multiple images are a powerful probe of cosmology, particularly of the Hubble constant (H0) that is key to probing dark energy, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. The H0 Lenses In COSMOGRAIL's Wellspring (H0LiCOW) project has measured H0 from lensed quasars using deep Hubble Space Telescope and AO imaging, precise time delay measurements from the COSMOGRAIL monitoring project, a measurement of the velocity dispersion of the lens galaxies, and a characterization of the mass distribution along the line of sight. Our latest results from a total of six lenses constrains H0 to be 73.3(-1.8,+1.7) km/s/Mpc for a flat Lambda CDM cosmology, which is a measurement to 2.4% precision. These results are consistent with independent determinations of H0 using type Ia supernovae calibrated by the distance ladder method, and are in 3.1-sigma tension with the results of Planck CMB measurements. Combined with the latest distance ladder results from the SH0ES project, we find a 5.3-sigma tension between Planck and late-Universe probes, hinting at possible new physics beyond the standard LCDM model and highlighting the importance of this independent probe.

Manami Sasaki

(Dr. Karl Remeis Observatory, Bamberg, Friedrich-Alexander-University Erlangen-Nurnberg)

The eROSITA View of Stellar Endpoints

eROSITA (extended ROentgen survey with an Imaging Telescope Array) is an X-ray telescope onboard the Russian Spektrum-RG satellite, which will carry out the first imaging all-sky survey in the X-ray band of 0.2 - 10.0 keV. It will thus bridge the gap between the soft X-ray survey, performed with the German Rontgen Satellite (ROSAT, 0.1-2.4keV), and the hard X-ray to gamma-ray surveys of the Rossi X-ray Timing Explorer Mission (3-20 keV), International Gamma-Ray Astrophysics Laboratory (17-60 keV), or Fermi Gamma-ray Space Telescope (1 GeV). In the soft X-ray band (0.5-2 keV), eRASS will be 20-30 times more sensitive than the ROSAT all-sky survey. I will give an overview of the mission and discuss science objectives of eRASS, in particular focussing on the study of galactic X-ray sources.

Renyue Cen

(Princeton University)

Computing the Universe: from Intergalactic to Interstellar Medium

This talk will highlight some progress made based on our efforts of computing the universe, in order to understand the dynamics of gas in the universe, from intergalactic to interstellar medium. Select observables presented include the cosmic web from redshift zero to z=2-4, and the escape fraction of Lyman continuum photons from galaxies at the epoch of reionization, an essential parameter underlying the feasibility of stellar reionization of the universe.

Eiichiro Komatsu

(Director of Max Planck Institute for Astrophysics)

Non-Gaussian gravitational waves from inflation

It has been widely assumed that detection of primordial gravitational waves from inflation in, for example, B-mode polarisation of the cosmic microwave background, immediately implies discovery of the quantum nature of spacetime. While this statement is true for the vacuum solution (left hand side of Einstein's equation), it does not apply if the gravitational waves originate from the matter fields (right hand side). How can we distinguish between these two origins? The answer is non-Gaussinaity. We show that the gravitational waves from SU(2) gauge fields coupled to a spectator axion field during inflation are highly non-Gaussian with a characteristic shape, whereas those from the vacuum are only weakly non-Gaussian.

Toshiki Sato

(RIKEN)

The Origin of the X-ray Clumpy Ejecta in Type Ia Supernova Remnants

X-ray-emitting clumpy structures are generally observed in young Type Ia supernova remnants although the origin is still obscure. There are two candidates for explaining the formation of clumps; initial clumpiness in ejecta at the explosion (i.e., clumpy ejecta model) or hydrodynamic instabilities made from smooth ejecta profile (i.e., smooth ejecta model). This information should reflect the initial ejecta structure of SNe Ia, so it is important for understanding the Type Ia explosion itself. Our preliminary investigations into constraining the structure of SN Ia remnants using Fourier and wavelet-transform analyses did not turn out to be sufficiently powerful at discriminating the two hydro models and the observed Tycho image from each other. This led us to investigate an approach that would be more sensitive to patterns in the distribution of clumps and holes in the images, such as the "genus statistic".

In this study, for the first time, the genus statistics have been applied to a famous type Ia remnant, Tycho (SN 1572) to understand the formation of the clumps by comparing with hydrodynamical models (Sato et al. 2019, arXiv: 1903.00764). We found the genus curve from Tycho's supernova remnant strongly indicates a skewed non-Gaussian distribution of the ejecta clumps, which is similar to that of a hydrodynamical model for the clumpy ejecta model. In contrast, a hydrodynamical model for the smooth ejecta model has a genus curve that is similar to that of a random Gaussian distribution. Thus, our results support the initial clumpiness in the Type Ia ejecta is more reasonable for the origin of the clumps and demonstrate usefulness of the genus statistics for this field. In addition, we will also discuss the origin of "Fe-rich" ejecta clumps in Type Ia SNRs in this seminar.

Tilman Troester

(University of Edinburgh)

Weak gravitational lensing, baryons, and deep learning

Baryonic processes that alter the large-scale distribution of gas, and thus the matter power spectrum, such as AGN feedback, are one of the main systematics in current and future weak lensing surveys. Left uncorrected, these effects will bias the inferred properties of dark matter and dark energy that these surveys are designed to measure. Characterising the distribution of gas is thus of vital importance if these surveys are to be exploited to their full potential.

In this talk, I will present ongoing work on joint analyses of weak lensing and tracers of diffuse gas, specifically the tSZ effect. We measure the tomographic cross-correlations between the tSZ effect and preliminary weak lensing data from the KiDS-1000 data set. We model the signal with a new code, based on HMCode, that can jointly predict the matter and pressure distributions and thus fit cosmology and parameters describing baryonic effects, such as the strength of AGN feedback, at the same time. I will then show how a joint analysis of cosmic shear and tSZ cross-correlations breaks degeneracies of the individual probes and can significantly improve the constraints on cosmological parameters compared to cosmic shear alone.

Finally, I will show how we use a class of machine learning methods -- deep generative models -- to augment N-body simulations with gas. Specifically, I will show how conditional variational autoencoders and generative adversarial networks trained on the BAHAMAS hydrodynamical simulations can be used "paint" pressure fields on the SLICS suite of N-body simulations to produce consistent lensing and tSZ maps for use in the estimation of the cross-correlation covariance.

Anna Lisa Varri

(Dept. of Astronomy, University of Tokyo)

Phase space complexity of star clusters: fresh observables for old and new questions

Our traditional paradigm of the internal dynamics of globular clusters has been recently revolutionised by a series of discoveries about their chemical, structural, and kinematic properties. The empirical evidence that their phase space structure is much more complex than usually expected encourages us to use them as refreshingly novel playgrounds for some long-forgotten aspects of collisional gravitational dynamics. Such a realisation, coupled with the discovery that the stars in clusters were not all born at once in a single population, makes them challenging 'chemodynamical' puzzles, with a suite of new questions to be addressed.

This renaissance is stimulated and enabled by significant advancements on the observational side. Precision astrometry now available from Gaia DR2 is complemented by decades-long HST campaigns and recent ESO spectroscopic surveys. The timeline of the forthcoming Gaia data releases is accompanied by the promise of future facilities (such as WEAVE, 4MOST, and MOONS), which will provide crucial spectroscopic follow-ups. And there is much hope that the opportunity to characterise the properties of 'proto-clusters' in the early universe will finally be within reach, thanks to JWST and E-ELT.

In this thriving context, I will discuss our current understanding of the internal dynamics of these collisional stellar systems and present some new theoretical insight emerging from a more realistic description of their phase space, with emphasis on the distinction between signatures resulting from the early formation stage ('primordial features') and from long-term dynamical processes ('evolutionary features'). Specific attention will be given to the interplay between internal rotation and tidal effects, with analogies to spin-orbit coupling in planetary dynamics. The final goal of this synergy between 'remastered' theory and fresh observables will be a deeper understanding of the role of 'small scales' in the assembly of cosmic structures in our universe.

Kenta Hotokezaka

(Princeton Univ.)

Electromagnetic counterparts to GW170817 and astrophysical implications

The neutron star merger GW170817 is the first gravitational-wave (GW) event accompanied by electromagnetic radiation: prompt gamma-rays, uv/optical/IR kilonova, and broadband non-thermal afterglow. The signatures of kilonova in GW170817 are consistent with the picture that a substantial amount of material is ejected at merger and the ejecta is composed of r-process nuclei. In particular, the light curve from 0.5 to 70 days after the merger can be explained well with the radioactive power of r-process nuclei. I will discuss what we can learn from this observation about the composition of the ejecta and also discuss the nebular emission of kilonvoae. The second part of my talk, I will focus on the superluminal jet in GW170817 observed by VLBI. Using the afterglow light curve data and VLBI images, the jet's Lorentz factor, kinetic energy, and viewing angle are determined. I will discuss the implication of this jet to short gamma-ray bursts and how these observations can improve the GW distance measurement, which leads to the improvement of the local Hubble constant measurement from the GW-only analysis.

Alexei A. Starobinsky

(Landau Institute)

Stochastic dark energy from inflationary quantum fluctuations

Late time quantum backreaction from inflationary fluctuations of a very light, non-minimally coupled scalar field which was a spectator one during inflation is studied. It is shown that this quantum field is a viable candidate for the present dark energy. The problem is solved by suitably adapting the stochastic inflationary formalism. This allows to account self-consistently for its potentially large backreaction on the background expansion rate of the present Universe. This framework is equivalent to that of semiclassical gravity in which the matter vacuum fluctuations are included at the one loop level while purely quantum gravitational fluctuations are neglected. The results show that dark energy in this model has a rather specific effective equation of state parameter as a function of redshift. This allows for testing the model using cosmological observational data on the Universe background evolution. (based on D. Glavan, T. Prokopec, and A. A. Starobinsky, Eur. Phys. J. C 78, 371 (2018); arXiv:1710.07824)

Yann Alibert

(Univ. of Bern)

A hybrid model for giant planet formation

In this talk, I will review the formation of gas giant planets, in particular in the core-accretion framework, assuming core formation by accretion of either large size planetesimals or small size pebbles. In both cases, I will show the success and limitations of the models, using recent results developed in our group. I will in a second part explain how the recent constrain on the growth history of Jupiter can be used to develop a new hybrid formation paradigm that solves some of the shortcomings of planetesimal-based and pebble based formation models.

Yusuke Tsukamoto

(Kagoshima University)

Does disk fragmentation by gravitational instability explain formation of the wide orbit planets?

In this talk, I will discuss planet formation via gravitational fragmentation of protoplanetary disk. Recent ALMA observations have found gaps at several tens of AU in protoplanetary disks (e.g., ALMA Partnership 15, Tsukagoshi+16) which are often regarded as a sign of planet formation in the disks (Dipiero+15, Kanagawa+16). Further more, gaseous planets with semi-major axis of several tens AU have been found by direction observations (e.g., HR 8799; Marois+08, GJ504; Kuzuhara+13). However, standard planet formation scenario i.e., core accretion scenario has difficulty to explain such wide-orbit planets. Disk fragmentation by gravitational instability is an alternative and plausible mechanism for formation scenario of planets at several tens of AU because it tends to happen in outer part of disk. In this talk, I will discuss the criterion of disk fragmentation and property of the fragments formed in the protoplanetary disks. Then, I will discuss the whether disk fragmentation can be a preferred mechanism to explain the wide-orbit planets or gaps in the disk.

Magnus Axelsson

(Stockholm Univ.)

Breaking the spectral degeneracies in black hole binaries using rapid variability

The spectra of black hole binaries in the low/hard state are complex, with evidence for multiple different Comptonisation regions contributing to the hard X-rays, in addition to a cool disc component. However, it is difficult to constrain the shapes of these components uniquely using spectral data alone. We show how additional information from fast variability can break this degeneracy. In GX 339-4 we focus on the strong variability features known as quasi-periodic oscillations (QPOs), and in Cygnus X-1 we study the broad-band variability. In both sources, the results not only require inhomogeneous Comptonization, but also allow us to constrain the spectral components. We discuss our results in the context of propagating fluctuations through a hot flow, and the implications for our picture of the accretion flow.

Shinsuke Takasao

(Nagoya Univ.)

Accretion from a magnetized disk onto a central star: New accretion mode

The accretion process in magnetized disks is a general topic which is relevant for black hole accretion disks and protoplanetary disks, for example. The central region of accretion disks is particularly important for the evolution of central objects. However, since these processes are associated with a global magnetic field configuration and a highly turbulent disk, the detailed physics still remains elusive. To reveal the accretion structure, we performed three-dimensional magnetohydrodynamic simulations of accretion from a disk to a central star, in the context of star formation. Traditionally it has been considered that a fast (>~100 km/s) accretion is an indication of the accretion controlled by a strong stellar magnetic field (magnetospheric accretion), and many studies estimated the accretion rate on the basis of this picture. However, we found that a fast accretion is possible even without a strong stellar field. We will discuss the physics and implication for observations.

Tsuguo Aramaki

(SLAC)

Hunting for Dark Matter with SuperCDMS, GAPS and GRAMS

The existence of dark matter has been indicated in many astrophysical phenomena, but the nature of dark matter still remains a great mystery. Complementary dark matter searches with different detection methods are crucial to illuminate the nature and the origin of dark matter. In this talk, I will be presenting my research on both the SuperCDMS (direct dark matter search) and the GAPS (indirect dark matter search) experiments as well as the scientific roles of the projects in the dark matter search. While SuperCDMS measures the dark matter scattering within the detector, GAPS focuses on low-energy antiprotons and antideuterons produced by dark matter annihilation and decay in the dark matter halo. Both projects are funded for a science run/flight and will begin taking data in 2020. I will also be introducing a new project/concept, GRAMS (gamma-ray and antimatter survey) that I have been developing over the past year. GRAMS is the first experiment aiming for both MeV gamma-ray observation and antimatter-based dark matter search using a LAr-TPC detector. Through GRAMS, we can explore astrophysical objects in the MeV energy domain ("MeV gap") while pursuing dark matter.

Stéphane Colombi

(IAP)

Some aspects of Vlasov-Poisson equations

Dark matter or stars in galaxies are ensembles of particles that can be approximated with a self-gravitating, collisionless fluid, of which the dynamics is described by Vlasov-Poisson equations. I will study some properties of these equations and how they are solved numerically with the traditional N-body method and direct solvers using “semi-Lagrangian” methods and sophisticated computational geometry techniques. Focusing here on the dynamical evolution of single objects, I will study what happens for various systems, evolving from an initially warm or initially cold state. The concept of mean field limit will be approached through comparisons between N-body and Vlasov codes that will show that it is sometimes difficult if not nearly impossible to disentangle numerical from physical effects. I will discuss as well theoretical predictions, in particular the early evolution of dark matter proto-halos using perturbation theory and “post-collapse” perturbation theory.

Kohei Kamada

(IBS-CTPU)

Cosmological Magnetic Fields: a Frontier in Cosmology and Particle Physics

Recent observations of gamma-ray from blazars by Fermi-LAT identified the deficit of secondary cascade GeV photons. A natural explanation is intergalactic magnetic fields, which bend the direction of the cascade. This motivates to explore the possibilities that magnetic fields are generated in the early Universe. In particular, helical (hyper)magnetic fields before the electroweak symmetry breaking are interesting objects since they interact with the Standard Model fermions nontrivially through the chiral anomaly. Thus cosmological magnetic fields can be a possible field of study both in cosmology and particle physics. In this talk, I will discuss the impact of the chiral plasma instability that is caused by the chiral magnetic effect on the generation of cosmological magnetic fields and explore their possible connection to the baryon asymmetry of the Universe. I will show that the baryogenesis model from SU(5) Grand Unified Theory, which has been thought not to work, can be an indirect origin of the present baryon asymmetric Universe through these phenomena.

Kazuyuki Sugimura

(Tohoku University)

Accretion onto seed BHs: the impacts of radiation anisotropy and gas angular momentum

Seed black hole (BH) growth by gas accretion is supposed to play a crucial role in the formation of supermassive BHs. In this talk, I will present the results of our simulations that follow gas accretion onto seed BHs under radiation feedback considering the radiation anisotropy and gas angular momentum. We find that the effects of radiation anisotropy and gas angular momentum can significantly change the accretion rate. I will also discuss the growth of Pop III remnant BHs based on our findings.

Kyohei Kawaguchi

(ICRR, Univ. of Tokyo)

Gravitational-wave templates for inspiralling binary neutron stars

On 17th of August 2017, three ground-based gravitational-wave detectors, advanced LIGO and advanced Virgo, reported the first detection of gravitational waves from a binary neutron star merger. Gravitational waves from binary neutron stars contain rich information of the neutron stars, in particular, of the equation of state through so-called the tidal deformability. To extract the tidal deformability of neutron stars from the observed gravitational-wave data, an accurate theoretical waveform template is crucial. In this talk, I will present our recent result developing a model for frequency-domain gravitational waveforms from inspiraling binary neutron stars based on the latest numerical-relativity simulations and analytic models, and discuss the measurability of the tidal deformability from gravitational waves from binary neutron stars in future observation.

Peter Behroozi

(University of Arizona)

Automated Physics Recovery from Galaxy Observations

I discuss new methods that allow computers to recover the underlying physics of galaxy formation using only galaxy observations and dark matter simulations, and show how these methods have already changed our understanding of galaxy formation physics (including why galaxies stop forming stars). Basic extensions to the same techniques allow constraining internal galaxy processes, including coevolution between galaxies and supermassive black holes as well as time delays for supernova / GRB progenitors. Finally, I discuss how these methods will benefit from the enormous amount of upcoming data in widefield (HETDEX, LSST, Euclid, WFIRST) and targeted (JWST, GMT) observations, as well as ways they can benefit observers, including making predictions for future telescopes (especially JWST) and testing which of many possible targeted observations would best constrain galaxy formation physics.

Roxanne Ligi

(INAF-Astronomical Observatory of Brera)

Detection and characterization of exoplanetary systems: The contribution of high angular resolution

The quest of exoplanets is driven by our search for habitability and our understanding of planetary formation. Whatever the detection method used, the exoplanets parameters are strongly linked to stellar properties. Thus, to know the planet, we have to know the star. However, characterising stars is not an easy task, as direct measurements are limited to bright stars and stellar models meet degeneracies. I will show how high angular resolution can be used both for exoplanetary detection and characterisation. In particular, I will show how interferometry is precious to derive global stellar parameters, and can lead to the determination of internal structure of exoplanets. Finally, direct imaging is a good solution for bringing insights in planetary formation theories.

Aurélien Crida

(Univ. Côte d'Azur/Obs. Côte d'Azur)

Satellite formation from rings

The world of Saturn is fascinating. Cassini's stunning pictures have revealed an extraordinary diversity in the satellites and the rings. However, one intriguing feature appears to link them: the mass of the satellites increases as a power law of their distance to the rings. This can not be explained in the classical model of satellite formation in a gaseous disk around the planet, like a mini-solar system. In this seminar, I will show that Saturn's satellites are actually formed from the spreading of the rings beyond the Roche radius. Starting from basic notions, this model will be explained. In particular, it will be demonstrated how this mechanism explains the mass - distance feature. The history of the evolution of the rings and the satellites can then be revisited. Finally, I will argue that this mechanism can be generalized to all planets of the Solar System (except Jupiter), and that most regular satellites are born from the spreading of massive planetary ring!

Mark Hindmarsh

(University of Sussex)

Gravitational waves from phase transitions in the early Universe

About 10 picoseconds after the beginning of the Universe, the Higgs field turned on. In extensions of the Standard Model of particle physics, this could have been a first order phase transition, with the spontaneously nucleated bubbles of the Higgs phase expanding and colliding at relativistic speeds. I will discuss how sound waves from colliding bubbles generate gravitational radiation, prospects for observing the radiation at the future space-based gravitational wave detector LISA, and outline how LISA complements the LHC as a probe of physics beyond the Standard Model.

George Hobbs

(CSIRO)

Pulsar and transients observations at Parkes and towards the SKA

I will describe historical and on-going pulsar observing projects with the Parkes telescope. This will include a discussion on the Parkes Pulsar Timing Array (PPTA) project that aims to use pulsars to detect ultra-low-frequency gravitational waves and the various pulsar search projects that had led to Parkes being used to discover more than half of the known pulsars. I will describe how the SKA will be used to search for and study pulsars and highlight various technical challenges relating to the SKA.

Kipp Cannon
Masaomi Tanaka

(RESCEU
NAOJ)

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Electromagnetic Wave Observations of GW170817

On August 17, 2017 at 12:41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made the first observation of a compact object collision consistent the the inspiral and merger of a pair of neutron stars. 1.7 s later GRB 170817A was detected by Fermi-GBM, and 10.5 h later supernova SSS17a was identified the 1M2H team using the 1 m Swope Telescope, both in the same part of the sky from which the GWs originated. Many hundreds of observations of the event have followed, marking the dawn of the era of joint gravitational and electromagnetic astronomy. I will present a summary of the gravitational wave discovery and what we have learned from the signal.

The first gravitational wave (GW) observation from a neutron star merger was successfully made for GW170817. The detection triggered electromagnetic (EM) wave observations over the entire wavelength range, which enebled the first identification of an EM counterpart of a GW source. I review EM observations of GW170817 and discuss implications from observations and open questions.

Misao Sasaki

(Kyoto University)

Inflationary massive gravity

Inflation is a natural platform for modified gravity. Here we present a new massive gravity theory in which the gravitational wave (GW) modes become massive during inflation. Then we discuss its observational signatures, which are particularly intriguing in this coming era of GW physics/astronomy.

Kent Yagi

(Princeton University)

Probing Extreme Gravity with Gravitational Waves

The binary black hole merger events recently discovered by the LIGO and Virgo Collaboration offer us excellent testbeds for exploring extreme (strong and dynamical-field) gravity that was previously inaccessible. In this talk, I will first review the current status of testing such gravity with GW150914 and GW151226, in particular, explaining how well one can probe various fundamental pillars in General Relativity. I will then describe what comes next in terms of testing gravity with gravitational waves. Regarding black-hole based tests of gravity, I will discuss how one can stack multiple ringdown events to probe black hole no-hair property. Regarding neutron star based tests of gravity, I will use approximate universal relations ("I-Love-Q relations") among certain neutron star observables that are almost insensitive to the unknown stellar internal structure, and describe how one can extract extreme gravity information by combining future gravitational wave and binary pulsar observations. I will conclude with a summary of important future directions.

Bernard Carr

(Queen Mary University of London)

Primordial black holes as dark matter and seeds for cosmic structure

The possibility that the dark matter comprises primordial black holes (PBHs) is considered, with particular emphasis on the currently allowed mass windows at 10¹⁶ - 10¹⁷g, 10²⁰ - 10²⁴g and 10 - 10³ M_☉. The last possibility is of special interest in view of the recent detection of black-hole mergers by LIGO. All relevant constraints (lensing, dynamical, large-scale structure and accretion) are considered and various effects necessary for a precise calculation of the PBH abundance (non-Gaussianity, non-sphericity, critical collapse) are accounted for. It is difficult to put all the dark matter in PBHs if their mass function is monochromatic but this is still possible if the mass function is extended, as expected in many scenarios. A novel procedure for confronting observational constraints with an extended PBH mass spectrum is therefore introduced and this is applied for two inflationary models. Even if PBHs provide only a small fraction of the dark matter, they could generate cosmological structure through either the 'seed' effect on small scales or the 'Poisson' effect on large scales. For example, if supermassive PBHs with much less than the critical density seed galaxies, this naturally explains the proportionality between the mass of the central black hole and the galactic mass. On the other hand, if intermediate mass PBHs provide the dark matter, the first bound clouds of 10⁶ M_☉ would form through Poisson fluctuations much earlier than usual. In principle, an extended PBH mass spectrum could permit them to fulfill all of these roles - providing the dark matter, the first bound clouds and galaxies. The gravitational wave background from the PBHs would then extend from the LIGO frequency (due to dark matter black holes) to the LISA frequency (due to galactic nuclei black holes).

Alexei Starobinsky

(Landau Institute for Theoretical Physics RAS and RESCEU)

From generic classical curvature singularity in GR and f(R) gravity to inflation

I discuss how generic is the onset of inflation from generic classical curvature singularity preceding it in GR and f(R), and which conditions are needed for it. For viable inflationary models in these kinds of gravity theory, the inflaton potential in the Einstein frame is not important near the singularity. Thus, its boundedness in models producing the best fit to observational data does not reduce the degree of generality of inflation. Space-time is asymptotically locally homogeneous near the singularity, despite the absence of causal connection, due to the very structure of field equations. However, an intermediate period when spatial gradients become important may well occur before the beginning of inflation. As a whole it seems that, for inflation to begin inside a patch including the observable part of the Universe, causal connection inside the whole patch is not necessary. However, it becomes obligatory for a graceful exit from inflation in order to have practically the same number of e-folds during inflation inside this patch. Also, the fact that inflation does not "solve" the singularity problem, i.e. it does not remove a curvature singularity preceding it, can be an advantage, not its weakness.

Stefan Ballmer

(Syracuse University/LIGO)

What comes next for Gravitational-Wave Astronomy

One year ago the Advanced LIGO detectors provided the first observation of gravitational waves from merging black holes. They just started to observe again this fall. I will discuss what we learned from the initial discovery, and where the detector sensitivity stands for the current observation run. Then I will look into the future, describing the next sensitivity upgrades for the detectors, and what we hope to observe with them. I will conclude by looking at possible future gravitational-wave observatories capable of observing binary mergers from an era when the first stars just started to form.

Gonjie Li

(Harvard University)

Interactions of Planetary Systems with passing Stars and Binaries

N/A

Surhud More

(Kavli IPMU)

Detection of halo assembly bias and the splashback radius of galaxy clusters

Dark matter halos are the basic building blocks that form the large scale structure in the Universe. I will present an overview of our knowledge about the internal structure of these halos, their large scale distribution, and the connection between the two, based on numerical simulations of cold dark matter in the concordance cosmological model. I will talk about some of the recent theoretical developments regarding the physical boundaries of dark matter halos, and their connection to the assembly history of these halos. I will present observational evidence supporting these new developments. In particular, I will highlight the recent detections of halo assembly bias on galaxy cluster scales, and the edges of galaxy clusters, and how these advances will help us to further our understanding of galaxy formation and the challenges they present to cosmological inferences.

Krzysztof M. Gorski

(JPL/Kavli IPMU)

The Future of Cosmology with the CMB

Observational cosmology has seen a remarkable quarter century of space exploration of the cosmic microwave background with the satellite missions COBE, WMAP, and Planck. I will briefly review the advances that these effort brought about, and discuss current prospects for the future, polarization measurements oriented CMB satellite proposals, including LiteBIRD in Japan, and the forthcoming suborbital CMB projects.

Kipp Cannon

(RESCEU)

Results From Advanced LIGO's First Science Run

In its first 400 hours of operation, Advanced LIGO had already surveyed a larger space-time volume than all previous gravitational-wave detection experiments combined. I will discuss some of the conclusions drawn from this early effort.

Francois R. Bouchet

(Institut d'Astrophysique de Paris)

Cosmology with the Planck satellite

Sketched out in 1992, selected by ESA in 1996, and launched in 2009, the Planck satellite was shut off in 2013, after a measuring mission that exceeded all expectations. The Planck collaboration delivered a first set of cosmological data and results in March 21st 2013, and the full set in February 2015. Part of the data delivery is a "definitive" map of the anisotropies of the Cosmic Microwave Background (CMB), its angular power spectrum together with their full statistical characterisation. The 2015 delivery also includes pioneering polarisation data. The temperature anisotropy map displays minuscule variations as a function of the observing direction, of rms ~100 microK, of the fossil radiation around its mean temperature of 2.725K. Other maps reveal the CMB polarisation. The anisotropies are the imprint of the primordial fluctuations which initiated the growth of the large scale structures of the Universe, as transformed by their evolution, in particular during the first 370 000 years. The polarisation is another imprint whose theoretical implications can then be confronted with those derived from the temperature field. I will describe some of our key results we obtained so far from temperature and polarisation data, both in terms of content of the universe and of characteristics of the primordial fluctuations, in particular concerning precision tests of key hypotheses of the standard model of cosmology, like the flat spatial geometry or Gaussianity, adiabaticity and per cent deviation from scale invariance of the primordial fluctuations.

Robert Wittenmyer

(The University of New South Wales)

The great unveiling: a new golden age of exoplanetary science

Less than a generation ago, we wondered, as we had for millions of years before, whether there were any other planetary systems at all. Now, we are privileged to be in the first generation of humans to know that many of the points of light dusting our night sky are host to orbiting worlds, some of which may be like our Earth. With that privilege comes the mighty task of our time, to unlock the secrets of the diversity of worlds. I will give an overview of the "discovery revolution" that brought us here. I will then describe the tremendous challenges and opportunities awaiting us in exoplanetary science over the next decade. The next revolution will be one of understanding - a "great unveiling" as we learn the detailed properties of the planetary systems in the Solar neighbourhood.

Giuseppe Bono

(Univ. of Rome Tor Vergata)

On the distribution of neutron capture elements across the Galactic thin disk using Cepheids

We present new results concerning the distribution of neutron capture (s-, r-) elements across the Galactic thin disk. We use young (classical Cepheids) stellar tracers for which we collected high spectral resolution, high signal to noise optical spectra with UVES at VLT (ESO). We found that the five (s: Y, La, Ce, Nd; r: Eu) investigated elements show well defined negative gradients when moving from the innermost to the outermost regions. Moreover, we also found that the gradients of the above elements are positive as a function of age/pulsation period. Thus suggesting a trend with age similar to alpha-elements. On the other hand, the slopes of [element/Fe] vs Galactocentric distance are more positive than for alpha-elements. We introduce plausible working hypothesis to take account of the difference, and perform a detailed comparison with similar abundances for dwarf and giant stars available in the literature. Finally, we discuss the abundance ratio between s- and r- elements (La/Eu) and between heavy and light s- elements (La/Y) and outline their impact on the chemical enrichment history of the Galactic thin disk.

Samaya Nissanke

(Radboud University Nijmegen, the Netherlands)

Follow the chirp: seeing and listening to the transient Universe

The mergers of binary compact objects (black holes, neutron stars, white dwarfs) are amongst some of the most violent events in the Universe. The physics driving these events in strongly curved spacetimes are extremely complex, rich but still remain elusive. These cosmic laboratories present us now with both a challenge and an opportunity. The challenge is to explain the physics at play in strong-field gravity in Universe. The opportunity is to detect the accompanying electromagnetic (EM) and gravitational radiation for the first time with a suite of time-domain telescopes and newly upgraded gravitational wave (GW) detectors.In this pivotal new era of strong-field gravity astronomy, the most compelling astrophysical sources are neutron star binary mergers, which should emit both in electromagnetic and GWs. I will first review the most recent advances in this blossoming field of EM + GW astronomy, which combines two active disciplines: time-domain astronomy and general relativity. I will discuss the promises of this new convergence by illustrating the wealth of astrophysical information that a combined EM+GW measurement would immediately bring. I will then outline the main challenges that lie ahead for this new field in pinpointing the sky location of neutron star mergers using GW detectors and optical and radio wide-field synoptic surveys.

Anupam Mazumdar

(Physics Department, Lancaster University)

Universal laws of Gravity without Singularity

I will discuss classical singularity theorem of General relativity, and then construct a general covariant theory of gravity which can avoid cosmological and blackhole singularities in the ultraviolet and reduces to the predictions of Einstein's theory of gravity in the infrared. I will also discuss how such an action may arise from string theory.

Shin'ichiro Ando

(GRAPPA, Univ. of Amsterdam)

Dark matter searches in anisotropic gamma-ray sky

As a viable candidate of dark matter, weakly interacting massive particle (WIMP) has been studied. WIMP is considered to annihilate with itself, and as its consequence, to produce high-energy gamma rays. Since dark matter has been annihilating (if ever happens) since the beginning of the structure formation, it gives contributions to the diffuse gamma-ray background measured with the Fermi satellite. The measurement of the gamma-ray background spectrum already gives one of the tightest constraints on the annihilation cross section. Since Fermi already collected more than 5 million photons from the whole sky (above 1 GeV), it is possible to discuss anisotropy* of the gamma-ray background. I will discuss (1) the angular power spectrum, (2) one-point PDF of the gamma-ray flux, and (3) cross correlation with local galaxy catalogs, and prospects on discovering dark matter particles in the near future in the gamma-ray data.

Kipp Cannon

(Canadian Institute for Theoretical Astrophysics / University of Toronto)

Challenges in Gravitational-Wave Astronomy

Gravitational radiation promises new knowledge about our world, but all attempts to observe gravitational waves (GWs) have been unsuccessful. There are many challenges to overcome in our quest to detect this elusive form of energy. I will describe how multivariate classifier techniques have been used to combat detector noise in searches for GWs from cosmic strings with LIGO and Virgo, and how the search for binary neutron star collisions has created new techniques for modeling collision waveforms.
Rapid detection of GWs will allow GW antennas like KAGRA to join a larger transient astronomy community and will provide exciting, new, information about the Universe. I will describe the analysis techniques used to achieve the extreme performance required to search for GWs from neutron star collisions with tens of seconds of latency. Finally, I will comment on some challenges that lay ahead for our community, and what might be done to address them.

Pisin Chen

(National Taiwan University)

Radiowave Detection of Ultra High Energy Cosmic Neutrinos and Cosmic Rays

There has been tremendous progress in the field of particle astrophysics in recent years, exemplified by the results from the Pierre Auger Observatory in Argentina on ultra high energy cosmic ray (UHECR) detection and the IceCube at the South Pole on PeV cosmic neutrino observation. Here we introduce a novel methodology based on the detection of the radio wave signals emitted by the ultra high energy cosmic neutrinos (UHECN) and cosmic rays. Such radio wave signals can be either triggered by the Askaryan effect or the geosynchrotron effect. In this talk we will review the several projects based on this approach, namely ANITA, ARA, and TAROGE, that have been pursued by the Leung Center for Cosmology and Particle Astrophysics (LeCosPA) at the National Taiwan University. We will first review the science potentials in astrophysics and particle physics through the detection of UHECR and UHECN. We will then report on the history, status and the future prospect of ANITA, ARA, and TAROGE observatories, including their scientific results obtained so far.