Instructor: Prof. Dong Lai

• Office: 618 SSB. Email: dl57_at_cornell.edu
• Office hours: After each lecture; can schedule other times; best contact by email, will usually answer email within 24 hours

Time & Place: Tuesday, Thursday 10:10 - 11:25 am, in 622 Space Science Building

Course website: https://donglai6.github.io/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, TDEs, 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.

Organization:

Weekly lectures. There will be about 6-8 problem sets. No final exam (the last problem set may serve as take-home final exam). There will a student project during the second half of the semester (TBD). Grades will be determined by these HWs, project and participations in class. Either Letter or S/U grade option is possible. (S = attend lectures and do 70% of HWs and project with passing grades)

Recommended Books: We will not follow any book too closely, but here are some books you can consult:

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

"Introduction to High-Energy Astrophysics" (2007) by Stephan Rosswog and Marcus Bruggen

"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!)

Here are the topics covered in 2022 . We will cover many of the topics, and may add some new topics

• 1/21: 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.
• 1/23: 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);
• 1/28: physics at the low-mass end, Coulomb effect (estimate, WS cell). 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
• 1/30: Neutron stars: free npe gas in beta-equilibrium. Neutron stars: maximum mass (Oppenheimer-Volkoff). NS structure (atmosphere, crust and liquid core).
• 1/31 (Friday) Brief review of BPS, BBP EOS for crust (the idea and method), neutron drip, inner-outer crust. NS mass-radius relation vs EOS. Pulsar Introduction. 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. Reading: Ascenzi...Rea "Neutron-star measurements in the multi-messenger Era".
• 2/4: Pulsar as a unipolar inductor. Isolated NS magnetospheres: Goldreich-Julian argument (E field outside a rotating spehere in vacuum). Corotating magentosphere, Goldreich-Julian density, Poynting flux of aligned rotator. Radio emission: brightness temperature (explained), coherent vs incoherent radiation. Reading: For a review of pulsar magnetosphere, see see Spitkovsky 2008; For a review of pulsar radio emission, see see Philippov and Kramer 2022
• 2/6: Pair cascade. Curvature radiation, pulsar death line. Pulsar wave propagation in ISM: dispersion (derived), Faraday rotation, scintillation. NS formation (massive star evolution), core collapse energetics, neutrino emission.
• 2/7 (Friday): neutrino-matter interaction cross-section and mean free path. NS cooling: Internal energy, Urca process vs modified Urca process. Hydro equations. Sound waves and shock waves: shock Formation (piston problem).
• 2/11: 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.
• 2/13: Magnetar intro. 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. Dynamics of a test mass around a BH (equations derived from variational principle, conserved quantities and their meanings. Reading: Quick intro to GR: ST Chap.12
• 2/14 (Friday): Test mass moving around BH. ISCO. Photon trajectory: black hole shawdow. Kerr BH: Event horizon, ZAMO frame, cosmic censorship conjecture. Particle motion round Kerr BH: motion on equatorial plane, circular orbit, ISCO, radiative efficiency of thin disk, angular frequency.
• 2/20: Particle motion round Kerr BH (continued): Angular frequency. Non-equatorial orbit, Carter's constant. Concept of radial/vertical epicyclic frequencies. Negative energy orbit, Penrose process. BH area theorem and the maximum efficiency of energy extraction from BH.
• 2/21 (Friday): Blandford-Znajek process: impedance of BH and free space, impedance matching. Gravitomagnetic field and Lense-Thirring precession.
• 2/25: 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.
• 2/27 Thursday: No class
• 3/4
• 3/6
• 3/7 (Friday)
• 3/11
• 3/13 Thursday: No class
• 3/14 (Friday??
• 3/18
• 3/20
• 3/21 (Friday)
• 3/25

• Kip Thorne's GW course.
• Zombeck's Handbook of Space Astronomy and Astrophysics.
• Chapters in the book "Compact Stellar X-ray Sources"