A5023276561- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Porphyrin and Phthalocyanine Chemistry
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Photodynamic Therapy Research Studies
- Geophysics and Gravity Measurements
- Geomagnetism and Paleomagnetism Studies
- Spacecraft and Cryogenic Technologies
- Scientific Research and Discoveries
- Metal-Catalyzed Oxygenation Mechanisms
- Photochemistry and Electron Transfer Studies
- Isotope Analysis in Ecology
- Astronomical Observations and Instrumentation
- Porphyrin Metabolism and Disorders
- Radiation Effects and Dosimetry
- Oxidative Organic Chemistry Reactions
- Electron Spin Resonance Studies
- Advanced NMR Techniques and Applications
Hebrew University of Jerusalem
2012-2024
University of California, Berkeley
2019-2022
California Institute of Technology
2022
A. N. Nesmeyanov Institute of Organoelement Compounds
2006
Russian Academy of Sciences
1987
Ashland (United States)
1987
Institute of Biophysics
1974-1975
Recent observations identify a valley in the radius distribution of small exoplanets, with planets range 1.5–2.0 R⊕ significantly less common than somewhat smaller or larger planets. This may suggest bimodal population rocky that are either engulfed by massive gas envelopes enlarge their radius, do not have detectable atmospheres at all. One explanation such is atmospheric erosion high-energy stellar photons. We investigate an alternative mechanism: luminosity cooling core, which can...
ABSTRACT Some recently discovered short-period Earth- to Neptune-sized exoplanets (super-Earths) have low observed mean densities that can only be explained by voluminous gaseous atmospheres. Here, we study the conditions allowing accretion and retention of such We self-consistently couple nebular gas onto rocky cores subsequent evolution envelopes following dispersal protoplanetary disk. Specifically, address mass-loss due both photo-evaporation cooling planet. find planets shed their outer...
ABSTRACT A convective dynamo operating during the crystallization of white dwarfs is one promising channels to produce their observed strong magnetic fields. Although magnitude fields generated by dynamos uncertain, timing may serve as an orthogonal test this channel’s contribution. The carbon–oxygen cores $M\approx 0.5-1.0\, {\rm M}_{\odot }$ begin crystallize at age tcryst ∝ M−5/3, but field initially trapped in convection zone – deep inside CO core. Only once a mass mcryst has...
Observations from the last decade have indicated existence of a general class superluminous supernovae (SLSNe), in which peak luminosity exceeds 1044 erg s−1. Here we focus on subclass these events, where light curve is also tens days wide, so total radiated energy order 1051 erg. If origin SLSNe core-collapse-driven explosion massive star, then mechanism that converts into radiation must be very efficient (much more than typical core-collapse SNe, this efficiency 1%). We examine scenario...
We present K-band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. obtained spectra and 100 $\mu$as precision astrometry both b c in two epochs, as well spatially resolving hot inner disk around star. Rejecting unstable orbits, we found a nonzero eccentricity for $0.17 \pm 0.06$, near-circular orbit c, an orbital configuration that is consistent planets migrating into 2:1 mean motion resonance. Enforcing dynamical stability, 95% upper...
Abstract We present L ’-band imaging of the PDS 70 planetary system with Keck/NIRC2 using new infrared pyramid wave front sensor. detected both b and c in our images, as well rim circumstellar disk. After subtracting off a model disk, we measured astrometry photometry planets. Placing priors based on dynamics system, estimated to have semimajor axis <?CDATA ${20}_{-4}^{+3}$?> au ${34}_{-6}^{+12}$?> (95% credible interval). fit spectral energy distribution (SED) For b, were able place better...
It has been recently suggested that white dwarfs generate magnetic fields in a process analogous to the Earth. The crystallization of core creates compositional inversion drives convection, and combined with rotation, this can sustain dynamo. We reanalyse dynamo mechanism, arising from slow core, find convective turnover times $t_{\rm conv}$ weeks months - longer by orders magnitude than previously thought. With dwarf spin periods $P\ll t_{\rm conv}$, crystallization-driven dynamos are...
Some extrasolar giant planets in close orbits---"hot Jupiters"---exhibit larger radii than that of a passively cooling planet. The extreme irradiation $L_{\rm eq}$ these hot Jupiters receive from their stars creates thick isothermal layer envelopes, which slows down convective cooling, allowing them to retain inflated size for longer. This is yet insufficient explain the observed sizes most planets. models invoke an additional power source, deposited deep planet's envelope. Here we present...
High energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry mass loss. The active $\sim 22$ Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity quantify the effects of stellar XUV irradiation on atmospheres as function both age orbital separation. In paper we present over 5 hours Far-UV (FUV) observations taken with Cosmic Origins Spectrograph (COS; 1070-1360 Angstrom)...
ABSTRACT Ultramassive white dwarfs with masses $M\gtrsim 1.1\, {\rm M}_{\odot }$ probe extreme physics near the Chandrasekhar limit. Despite rapid increase in observations, it is still unclear how many harbour carbon–oxygen (CO) versus oxygen–neon (ONe) cores. The origin of these and their strong magnetic fields – single stellar evolution or a merger another open question. steep mass–radius relation relativistic ultramassive shortens crystallization time $t_{\rm cryst}$, such that recently...
Short-period Earth to Neptune size exoplanets (super-Earths) with voluminous gas envelopes seem be very common. These atmospheres are thought have originated from the protoplanetary disk in which planets were embedded during their first few Myr. The accretion rate of surrounding nebula is determined by ability cool and radiate away its gravitational energy. Here we demonstrate that heat tidal interaction between star young (and therefore inflated) planet can inhibit cooling accretion....
The orbits of many observed hot Jupiters are decaying rapidly due to tidal interaction, eventually reaching the Roche limit. We analytically study ensuing coupled mass loss and orbital evolution during Roche-lobe overflow find two possible scenarios. Planets with light cores $M_c\lesssim 6M_\oplus$ (assuming a nominal dissipation factor $Q\sim 10^6$ for host star) transformed into Neptune-mass gas planets, orbiting at separation (relative stellar radius) $a/R_\star\approx 3.5$. heavier...
Gas giants are thought to form by runaway accretion: an instability driven the self-gravity of growing atmospheres that causes accretion rates rise superlinearly with planet mass. Why should stop at a Jupiter or any other mass is unknown. We consider proposal final masses controlled circumstellar disc gaps (cavities) opened planetary gravitational torques. develop fully time-dependent theory gap formation and couple it self-consistently growth rates. When first open, torques overwhelm...
Planets open gaps in discs. Gap opening is typically modeled by considering the planetary Lindblad torque which repels disc gas away from planet's orbit. But also clear because planet consumes local material. We present a simple, easy-to-use, analytic framework for calculating how deplete and disc's structure as whole changes combined action of repulsion consumption. The final mass to gap-embedded giant grows derived tandem. analytics are tested against 1D numerical experiments calibrated...
Some Jupiter-mass exoplanets contain $\sim$$100\, M_\oplus$ of metals, well above the $\sim$$10\, typically needed in a solid core to trigger giant planet formation by runaway gas accretion. We demonstrate that such `heavy-metal Jupiters' can result from planetary mergers near $\sim$10 au. Multiple cores accreting at rates gravitationally perturb one another onto crossing orbits average merger rate equals accretion rate. Concurrent and implies mass scales with total as $M_{\rm core} \propto...
Context. Period bouncers are cataclysmic variables (CVs) that have evolved past their orbital period minimum. The strong disagreement between theory and observations of the relative fraction is a severe shortcoming in understanding CV evolution. Aims. We test implications hypothesis magnetic braking (MB), which suggested to be an additional angular momentum loss (AML) mechanism for CVs below gap ( P orb ≲ 120 min), weakens around Methods. computed evolution donors using MESA code, assuming...
Many giant exoplanets in close orbits have observed radii which exceed theoretical predictions. One suggested explanation for this discrepancy is heat deposited deep inside the atmospheres of these "hot Jupiters". Here, we study extended power sources distribute from photosphere to interior planet. Our analytical treatment a generalization previous analysis localized "point sources". We model deposition profile as law optical depth and find that planetary cooling contraction halt when...
Black widows are close binary systems in which a millisecond pulsar is orbited by companion few per cent the mass of sun. It has been suggested that pulsar's rotationally powered $γ$-ray luminosity gradually evaporates companion, eventually leaving behind an isolated pulsar. The evaporation efficiency determined temperature $T_{\rm ch}\propto F^{2/3}$ to outflow heated flux $F$ on dynamical time-scale. Evaporation most efficient for companions fill their Roche lobes. In this case, dominated...
Understanding the anomalous radii of many transiting hot gas giant planets is a fundamental problem planetary science. Recent detections re-inflated warm Jupiters orbiting post-main-sequence stars and re-inflation while their host evolve on main-sequence may help constrain models for Jupiters. In this work, we present evolution studying giants to determine how varying depth intensity deposited heating affects both We find that deeper required re-inflate than needed suppress cooling,...
ABSTRACT During the runaway phase of their formation, gas giants fill gravitational spheres influence out to Bondi or Hill radii. When ends, planets shrink several orders magnitude in radius until they are comparable size present-day Jupiter; 1D models, contraction occurs on Kelvin–Helmholtz time-scale tKH, which is initially a few thousand years. However, if angular momentum conserved, cannot complete, as inevitably spun up breakup periods Pbreak. We consider how circumplanetary disc (CPD)...
Planets can open cavities (gaps) in the protoplanetary gaseous discs which they are born by exerting gravitational torques. Viscosity counters these torques and limits depletion of gaps. We present a simple one-dimensional scheme to calculate gas density profile inside gaps balancing viscous By generalizing results Goodman & Rafikov (2001), our properly accounts for propagation angular momentum waves. This method allows us easily study low-viscosity discs, challenging full hydrodynamical...
A nova eruption irradiates and heats the donor star in a cataclysmic variable to high temperatures $T_{\rm irr}$, causing its outer layers expand overflow Roche lobe. We calculate donor's heating expansion both analytically numerically, under assumption of spherical symmetry, find that irradiation drives enhanced mass transfer from at rate $\dot{m}\propto T_{\rm irr}^{5/3}$, which reaches $\dot{m}\sim 10^{-6}\textrm{ M}_\odot\textrm{ yr}^{-1}$ peak - about thousand times faster than during...
Recent observations suggest that some supernovae may be the result of an explosion into optically thick circumstellar material, product pre-explosion mass loss (wind) by progenitor star. This scenario has been studied previously both analytically and numerically. However, many previous studies base their analysis on diffusion approximation for radiation transfer, which is inappropriate in thin outer layers wind. Here we study deviations from calculate light curves more accurately using a...
Giant planets are thought to form by runaway gas accretion onto solid cores. Growth must eventually stop running away, ostensibly because open gaps (annular cavities) in their surrounding discs. Typical models artificially capping the rate and lowering it zero over an arbitrarily short time-scale. In reality, post-runaway persists as long disc remains. During this final possibly longest phase of formation, when planet is still emerging from disc, its mass can more than double, radius...
Abstract We present visible-light and ultraviolet ( UV ) observations of the supernova PTF 12glz. The SN was discovered monitored in near- R bands as part a joint GALEX Palomar Transient Factory campaign. It is among most energetic SNe IIn observed to date (≈10 51 erg). If radiated energy mainly came from thermalization shock kinetic energy, we show that 12glz surrounded by ∼1 M ⊙ circumstellar material (CSM) prior its explosive death. shows puzzling peculiarity: at early times, while freely...