Research Notes

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09.16.2013 ~ 09.22.2013 (38th / 52)

Read

  • Goswami, S., Kiel, P. & Rasio, F. A. 2013, “Black Holes In Young Stellar Clusters”
    • runaway collisions during an early episode of core collapse (G ̈ rkan et al. 2004; Portegies Zwart et al. 2004; Freitag et al. 2006; Goswami et al. 2012) provide a way to form IMBHs in young star clusters.
    • According to stellar evolution calculations (Fryer 1999; Heger & Woosley 2002; Heger et al. 2003), a star with a final mass Mfin > 40 M immediately before collapse could avoid a SN explosion and directly collapse to a BH of almost the same mass.
    • It has also been observed that the metal poor Large Magellanic Cloud (LMC) has a lower ratio of LMXBs to high mass X-ray binaries (HMXBs) than the Milky Way which is metal rich (Cowley 1994; Iben et al. 1997).
  • Steiner, J. F., & McClintock, J. E. (2012). Modeling the Jet Kinematics of the Black Hole Microquasar XTE J1550-564: A Constraint on Spin-Orbit Alignment. The Astrophysical Journal, 745, 136. doi:10.1088/0004-637X/745/2/136;
    • Continuum-fitting method to measure the spin of Black hole. -> thermal emission from an accretion disk
    • it is reasonable to expect that, given a means of interaction, the spin of the black hole will eventually come into alignment with the orbital angular momentum
    • If there is an initial misalignment between the spin and the orbital angular momenta, then Lense–Thirring precession will cause the inner X-ray-emitting portion of the disk to line up with the spin of the black hole (Bardeen & Petterson 1975).
    • Heinz (2002) has proposed that black hole microquasars preferentially inhabit environments that are underdense compared to their supermassive (quasar) counterparts. Heinz offers several explanations, notably that microquasars may produce self-encasing low-density bubbles either as a remnant of the birthing supernova explosion or via persistent kinetic outflows from the compact source.
    • Theory predicts that accretion torques acting over time will have brought most black holes into alignment with the orbital plane of their binary hosts.

09.09.2013 ~ 09.15.2013 (37th / 52)

  • Attending 2013 IMPRS Summer school of High Energy Astrophysics operated by Max-Plank institute at Hidelberg University

09.02.2013 ~ 09.08.2013 (36th / 52)

08.26.2013 ~ 09.01.2013 (35th / 52)

08.19.2013 ~ 08.25.2013 (34th / 52)

08.12.2013 ~ 08.18.2013 (33th / 52)

08.05.2013 ~ 08.11.2013 (32rd / 52)

07.29.2013 ~ 08.04.2013 (31st / 52)

07.22.2013 ~ 07.28.2013 (30th / 52)

07.15.2013 ~ 07.21.2013 (29th / 52)

07.08.2013 ~ 07.14.2013 (28th / 52)

boundary_error.png

Weird things happened around left boundary in the simulation of PWNe with inclined discontinuity.

Still don't know what causes it, but it is resolved by merely 'restart'

07.01.2013 ~ 07.07.2013 (27th / 52)

Modify the paper.

06.24.2013 ~ 06.30.2013 (26th / 52)

Read:

  • Heinz, S. 2006, The Astrophysical Journal, 636, 316–322, “Composition, Collimation, Contamination: The Jet of Cygnus X-1”

Edit:

  • paper of jet bending by stellar wind

06.17.2013 ~ 06.23.2013 (25th / 52)

jetthick_450_comb.eps
jetthick_450_comb2.eps

(Resolution Test for the jet thickness (left) and jet bending angle (right))

06.10.2013 ~ 06.16.2013 (24th / 52)

Run:

  • Resolution test in jets for XRBs with Spherical wind

Read:

  • Christiansen, H. R. 2013,“High energy emission from galactic jets”
  • Palotti, M. L., Heitsch, F., Zweibel, E. G. & Huang, Y.-M. 2008, The Astrophysical Journal, 678, 234–244, "Evolution of Unmagnetized and Magnetized Shear Layers"

06.03.2013 ~ 06.09.2013 (23rd / 52)

05.27.2013 ~ 06.02.2013 (22nd / 52)

05.20.2013 ~ 05.26.2013 (21st / 52)

05.13.2013 ~ 05.19.2013 (20th / 52)

05.06.2013 ~ 05.12.2013 (19th / 52)

04.29.2013 ~ 05.05.2013 (18th / 52)

04.22.2013 ~ 04.28.2013 (17th / 52)

04.15.2013 ~ 04.21.2013 (16th / 52)

04.08.2013 ~ 04.14.2013 (15th / 52)

04.01.2013 ~ 04.07.2013 (14th / 52)

03.25.2013 ~ 03.31.2013 (13th / 52)

03.18.2013 ~ 03.24.2013 (12th / 52)

03.11.2013 ~ 03.17.2013 (11th / 52)

Activity:

  • Start writing the paper about Pulsar Wind Nebula moving through density continuity

Run:

  • develop 1d simulation to test wind model we've established in 2d runs. (purpose of checking the problem below)
pulsar_radi_comb.eps

The main reason why the bubble is not expanded enough is the velocity of the pulsar wind.
In case $v_w > 10^9 km s^{-1}$ (red & green), the tendancy of shell evolving is consistent with
the expanding bubble model suggested by Castor et al. 1975, (eq. (1)), that is energy driven expansion.

However, in case of lower velocities, the evolution seems to be odd. It's because the extremely concentrated density
structure around the PWN is naturally higer than ambient density (we fixed the Spin-down Energy loss rate implying that
the density will be increased by decreasing velocity of the pulsar wind) so that the gas pressure pushes the shell in addition to
the energy driven. See below figures.

1d_v7_radi_0800.png
1d_v8_radi_0300.png

(left: $10^7$ cm/s, right: $10^8$ cm/s)

1d_v9_radi_0300.png
1d_v10_radi_0300.png

(left: $10^9$ cm/s, right: $10^{10}$ cm/s)

  • Another issue is that if we decrease the inner radius (star radius), the explosion starts at smaller radi so that adiabatic expension
    makes Mach number be dropped resulting in smaller expansion rate (but still observe the relationship $r \propto t^{3/5}$)
pulsar_radi2d_comp1d.png

03.04 ~ 03.10.2013 (10th / 52)

Issue:
dens_600kms.png
Bow shock structures are well established as seen in numerical results from Bucciantini's papers,
however, the expanding bubble structures are not grown (It's not good!!). We should figure out why it doesn't grow.

Read:

  • Psaltis, D. 2004, arXiv:astro-ph/0410536, "Accreting neutron stars and black holes: a decade of discoveries"

02.25 ~ 03.03.2013 (9th / 52)

Read:

  • Bucciantini, N., Amato, E. & Del Zanna, L. 2005, Astronomy and Astrophysics, 434, 189–199, "Relativistic MHD Simulation of pulsar bow-shock nebulae"
  • Bucciantini, N. 2010, arXiv:1005.4781, "MHD models of Pulsar Wind Nebulae"
  • Bucciantini, N. 2002, Astronomy and Astrophysics, 387, 1066–1073, "Pulsar bow-shock nebulae II. Hydrodynamical simulation"
  • Castor, J., McCray, R. & Weaver, R. 1975, The Astrophysical Journal Letters, 200, L107–L110, "Interstellar Bubbles"
(1)
\begin{align} R_{s} = 0.76 \left( \frac{\dot{E}_{0} t^{3}}{\rho_{0}} \right)^{1/5} \end{align}

02.18 ~ 02.24.2013 (8th / 52)

Read:

  • Bernstein, J. P. & Hughes, P. A. 2009, Journal of Computational Physics, 228, 6212–6230
  • Van Kerkwijk, M. H. & Ingle, A. 2008, The Astrophysical Journal Letters, 683, L159–L162, "Reconstructing the Guitar: Blowing Bubbles with a Pulsar Bow Shock BackFlow"

Run:

  • change the geometry of 2d PWN simulation. ("Cartesian" -> "Cylindrical")
    because physical quantities should evolve differently with geometry.

02.11 ~ 02.17.2013 (7th / 52)

Read:

  • Mirabel, I. F. 2002, arXiv:astro-ph/0211085, "Microquasars as sources of high energy phenomena"
  • Charles, P. in 2011, 447, 19, "LMXBs: An Overview"
  • Volker Beckmann & Chris R, Shrader, "The AGN phenomenon: open issues"

Run:

  • Animation of fast moving XRBs through density discontinuity (10 times higher or lower)
xrbs_jets_d10l_0700.png

-> movie clips of the simulations

  • Keep doing parameter studies for fast moving PWNe

02.04 ~ 02.10.2013 (6th / 52)

Read:

  • van Kerkwijk & Ingle 2008, ApJ 683, "Reconstructing the Guitar: Blowing Bubbles with a Pulsar Bow Shock Backflow"
  • Bernstein & Hughes 2009, JCoPh 228, "Refining a relativistic, hydrodynamic solver: Admitting ultra-relativistic flows"
  • Vigelius et al 2007, MNRAS 374, "Three-dimensional hydrodynamics simulations of asymmetric pulsar wind bow shocks"

Run:

  • develop 2D hydro for cases of fast moving PWNe
    user boundary for xl & yl (for yl boundary, we set the spherically injecting area at some spot and elsewhere reflecting boundary

100 km/s of PWN proper motion

PWN2d_100kms_0539.png

Pulsar is still inside the bubble.

01.27 ~ 02.03.2013 (5th / 52)

Activity:

  • Thesis Proposal (1/30) @ UW-Madison
    entitled - "The interaction of microquasar jets with ISM"