Instructor: Prof. Dong Lai

• Phone: 5-4936. Office: 618 SSB. Email: dong_at_astro.cornell.edu
• Office hours: After each lecture; best contact by email, will usually answer email within 24 hours

Time & Place: Monday, Wednesday 9:40 - 10:55 am, in 622 Space Science Building

Course website: http://hosting.astro.cornell.edu/~dong/a6511/a6511.html

Description:

This is a one-semester lecture course on high energy astrophysics, with focus on compact stars and related subjects (including supermassive black holes). Contemporary research problems will be discussed along the way. An important component of the course is to introduce/survey (generally in a quick and ``low-brow'' manner) the physics tools needed for understanding various astrophysical observations. Major topics to be covered include gravitational wave astrophysics (e.g. LIGO/LISA/PTA sources) and various EM transient phenomena (supernovae, GRBs and FRBs, etc).

The course is aimed at graduate students in astronomy and physics; senior undergraduates with strong physics background may also take it. The minimum prerequisites for this course are all of the physics at the upper division undergraduate level. (The more basic physics you have had at the graduate level, the easier the course will be for you.) No prior knowledge of General relativity is required -- Practical GR will be introduced along the way during the semester. Though helpful, no astronomy background is needed.

Tentative syllabus, plan, texts etc

Some books:

"BHs, WDs and NSs" (1983) by Shapiro and Teukolsky (online)

"High Energy Astrophysics" (2011) by M.Longair (online)

"High Energy Astrophysics" (2013) by T.J-L Courvoisier (online for Cornell students)

"High Energy Astrophysics: A Primer" (2022) by J.E. Horvath (online for Cornell students)

"Compact Objects in Astrophysics" (2007) by M.Camenzind (online for Cornell students)

Detailed Topics covered in each class: (suggested reading from ST=Shapiro-Teukolsky, etc, plus review papers. Note that I'll try to choose easier (shorter) papers that could be read by most people. If you are interested in digging deeper into a particular topic, ask me!)

• 8/22: Course overview. Stellar evolution quick review (what MS stars lead to what remnants, 8 M_sun mass boundary). WD basics (order-of-magnitude): zero-point energy, M-R relation, Chandrasekhar limit. Reading:
• 8/24: WD structure (more detail): Eqn of hydrostatic equilibrium, quick digression of degenrate electron gas, M-R relation. physics at the high-mass end (cold fusion, electron capture, GR); physics at the low-mass end, Coulomb effect (estimate, WS cell) Reading:
• 8/29: Coulomb effect (continued): M-R relation of cold objects (from planets to WDs). WD formation and cooling; Mestal cooling; crystalization and Debye cooling. Reading: For the physics of WD cooling, you can look at standard stellar structure text, or ST sect.4.1-4.2
• 8/31: Neutron stars: free npe gas in beta-equilibrium. Neutron stars: maximum mass (Oppenheimer-Volkoff).NS structure (atmosphere, crust and liquid core).
• 9/5: No class (Labor day)
• 9/7: Brief review of BPS, BBP EOS for crust (the idea and method), neutron drip, inner-outer crust. NS mass-radius relation vs EOS. Pulsar Intro. Reading: Miller et al. 2020 "Constraining the Equation of State of High-density Cold Matter Using Nuclear and Astronomical Measurements"
• 9/12: Pulsar Intro: Radio pulsar basics: spin down (dipole radiation formula), estimate B field and age. Origin of B (flux conservation, dynamo idea). Origin of spin (J consetvation, spinup, off-centered kick); Pulsar velocity. Pulsar as a unipoar inductor.
• 9/14: Isolated NS magnetospheres: Goldreich-Julian argument (E field outside a rotating spehere in vacuum). Corotating magentosphere, Goldreich-Julian density, Poynting flux of aligned rotator.
• 9/19: Radio emission: brightness temperature (explained), coherent vs incoherent radiation. Pair cascade. Curvature radiation, pulsar death line. Reading: For a review of pulsar magnetosphere, see see Spitkovsky 2008
• 9/21: Glitch (quick review of starquark, mention superfludity and vortices). Pulsar wave propagation in ISM: dispersion (derived), Faraday rotation, scintillation and pulse broadening.
• 9/26: Quick summary of other observational manifestations of isolated NSs: X-rays, CCO, gamma-ray emission; magnetars. NS formation (massive star evolution), core collapse energetics, neutrino emission, neutrino-matter interaction cross-section and mean free path.
• 9/28: NS cooling: Internal energy, Urca process vs modified Urca process. Sound waves and shock waves: shock Formation (piston problem).
• 10/3: Shock jump condition derived and applied to gamma-law gas. Supernovae: different types. Core-collapse SNe. prompt explosion, delayed explosion (neutrino heating of shocked material). Brief mention of convection and hydro instabilities.
• 10/5: Black hole basics: Basic concepts of general relativity. coordinate basis, orthonormal basis, dot product in 4-space. Schwarzschild metric, gravitational time dilation and redshift, event horizon.
• 10/10: Fall break
• 10/12: Black Holes (continued): Dynamics of a test mass around a BH (equations derived from variational principle, conserved quantities and their meanings, comparison with Newtonian theory). ISCO. Photon trajectory: black hole shadow.
• 10/17: Kerr BH: event horizon, ZAMO frame, cosmic censorship conjecture. Particle motion round Kerr BH: motion on equatorial plane, circular orbit, photon orbit, marginally bound orbit, ISCO, radiative efficiency of thin disk, angular frequency.
• 10/19: Motion of test mass in Kerr: non-equatorial plane, Carter's constant. concept of radial/vertical epicyclic frequency.
• 10/24: Motion in Kerr: Negative energy orbit, Penrose process. BH area theorem and the maximum efficiency of energy extraction from BH. Blandford-Znajek process (conceptual). Gravitomagnetic field and Lense-Thirring precession.
• 10/26: Acretion power in astrophysics: overview (Comapct x-ray binaries and AGNs); spherical accretion onto NS, efficiency, why X-rays? shock vs BB). Eddington Luminosity and accretion rate Eddington.
• 10/31: Bondi accretion (derive accretion rate), Holye-Lyttleton accretion. Mass transfer in binaries, Roche lobe, orbital evolution and stability of mass transfer.
• 11/2: Accretion disks: luminosity. Thin vs thick (radiative inefficient) disks (low Mdot and high Mdot). Thin disk equations: mass continuity, vertical balance, angular momentum, viscous torque, inner BC, energy generation.
• 11/7: Thin disk equations (continued): EOS, radiative transfer, Ansatz for viscosity (alpha viscosity), SS disks.
• 11/9: Disk spectra: Disk black-body. Scattering effects.
• 11/14: Disk coronae, power-law components of accreting BHs. Comptonization process. Accretion disk variability and timescales.
• 11/16: Disk instabilities: Dynamical, thermal, viscous instabilities, Limit cycle (equations derived).
• 11/21: Double compact object binaries. Binary pulsars. GR test, Binary evolution and formation of compact object binaries. Gravitational waves (intro): GR in weak gravity limit: Linearized field equations, explain mass-menergy tensor, derive the metric outside a stationary source.
• 11/28: GW theory: GW polarization, Quadrupole radiation: power and waveform. GWs from compact binary.
• 11/30: Supernova explosion and lightcurves.
• 12/5: Student presentation.