[seminar] Astro Journal Club on April 12th

[Lana Ceraj]

Dear all, 

Astro Journal club starts on Wednesday at 3 p.m. (sharp) in the seminar room F-201 of the Physics Department. 

Presenter: Krešimir Tisanić, mag. phys.

Title of paper: Are gravitational waves spinning down PSR J1023+0038?

Author: B. Haskell, A. Patruno (2017)

Abstract: 
The pulsar J1203+0038 rotates with a frequency ν≈592 Hz and has been observed to transition between a radio state, during which it is visible as a millisecond radio pulsar, and and a Low Mass X-ray Binary state, during which accretion powered X-ray pulsations are visible. Timing during the two phases reveals that during the LMXB phase the neutron star is spinning down at a rate of ν˙≈−3×10−15 Hz/s, which is approximately 27% faster than the rate measured during the radio phase, ν˙≈−2.4×10−15 Hz/s, and at odds with the predictions of accretion models. In this letter we suggest that the increase in spin-down rate is compatible with gravitational wave emission, and in particular to the creation of a `mountain' during the accretion phase. We show that asymmetries in pycno-nuclear reaction rates in the crust can lead to a large enough mass quadrupole to explain the observed spin-down rate, which so far has no other self-consistent explanation, and that radio timing at the onset of the next millisecond radio pulsar phase can test this scenario. Another possibility is that an unstable r-mode with amplitude α≈5×10−8 may be present in the system.
 
Link to paper: https://arxiv.org/abs/1703.08374 <https://arxiv.org/abs/1703.08374>

If you have recently read interesting astrophysics paper you would like to present, please contact me via e-mail: lceraj at phy.hr <mailto:lceraj at phy.hr>

See you on Wednesday.

Cheers,
Lana


P. S. 
We have set up a web page to function as a repository of AJC presentations.
It can be found at: https://lanaceraj.wixsite.com/ajc-main <https://lanaceraj.wixsite.com/ajc-main>
In case you run into some problem or bug, please let me know. Thank you. 
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