<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">Dear all, </div><div class=""><div class=""><br class=""></div><div class="">Astro Journal club starts on Wednesday at 3 p.m. (sharp) in the seminar room F-201 of the Physics Department. </div><div class=""><br class=""></div><div class="">Presenter: Krešimir Tisanić, mag. phys.</div><div class=""><br class=""></div><div class="">Title of paper: Are gravitational waves spinning down PSR J1023+0038?</div><div class=""><br class=""></div><div class="">Author: B. Haskell, A. Patruno (2017)</div><div class=""><br class=""></div><div class="">Abstract: </div><div class=""><div class="">The pulsar J1203+0038 rotates with a frequency <span tabindex="0" id="MathJax-Element-1-Frame" class="MathJax"><nobr class=""><span style="width: 4.068em; display: inline-block;" id="MathJax-Span-1" class="math"><span style="display: inline-block; position: relative; width: 3.275em; height: 0px; font-size: 123%;" class=""><span style="position: absolute; clip: rect(1.74em, 1003.25em, 2.788em, -1000em); top: -2.597em; left: 0em;" class=""><span id="MathJax-Span-2" class="mrow"><span style="font-family: STIXGeneral; font-style: italic;" id="MathJax-Span-3" class="mi">ν</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-4" class="mo">≈</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-5" class="mn">592</span></span><span style="display: inline-block; width: 0px; height: 2.597em;" class=""></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.097em; border-left: 0px solid; width: 0px; height: 1.012em;" class=""></span></span></nobr></span> 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 <span tabindex="0" id="MathJax-Element-2-Frame" class="MathJax"><nobr class=""><span style="width: 7.851em; display: inline-block;" id="MathJax-Span-6" class="math"><span style="display: inline-block; position: relative; width: 6.38em; height: 0px; font-size: 123%;" class=""><span style="position: absolute; clip: rect(1.538em, 1006.38em, 2.907em, -1000em); top: -2.597em; left: 0em;" class=""><span id="MathJax-Span-7" class="mrow"><span id="MathJax-Span-8" class="texatom"><span id="MathJax-Span-9" class="mrow"><span id="MathJax-Span-10" class="munderover"><span style="display: inline-block; position: relative; width: 0.47em; height: 0px;" class=""><span style="position: absolute; clip: rect(3.398em, 1000.46em, 4.196em, -1000em); top: -4.009em; left: 0em;" class=""><span style="font-family: STIXGeneral; font-style: italic;" id="MathJax-Span-11" class="mi">ν</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span><span style="position: absolute; clip: rect(3.217em, 1000.22em, 3.655em, -1000em); top: -4.068em; left: 0.068em;" class=""><span style="font-family: STIXGeneral;" id="MathJax-Span-12" class="mo">˙</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span></span></span></span></span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-13" class="mo">≈</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-14" class="mo">−</span><span style="font-family: STIXGeneral;" id="MathJax-Span-15" class="mn">3</span><span style="font-family: STIXGeneral; padding-left: 0.25em;" id="MathJax-Span-16" class="mo">×</span><span style="padding-left: 0.25em;" id="MathJax-Span-17" class="msubsup"><span style="display: inline-block; position: relative; width: 2.266em; height: 0px;" class=""><span style="position: absolute; clip: rect(3.163em, 1000.98em, 4.192em, -1000em); top: -4.009em; left: 0em;" class=""><span style="font-family: STIXGeneral;" id="MathJax-Span-18" class="mn">10</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span><span style="position: absolute; top: -4.412em; left: 1em;" class=""><span id="MathJax-Span-19" class="texatom"><span id="MathJax-Span-20" class="mrow"><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-21" class="mo">−</span><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-22" class="mn">15</span></span></span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.597em;" class=""></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.243em; border-left: 0px solid; width: 0px; height: 1.406em;" class=""></span></span></nobr></span> Hz/s, which is approximately
27% faster than the rate measured during the radio phase, <span tabindex="0" id="MathJax-Element-3-Frame" class="MathJax"><nobr class=""><span style="width: 8.754em; display: inline-block;" id="MathJax-Span-23" class="math"><span style="display: inline-block; position: relative; width: 7.114em; height: 0px; font-size: 123%;" class=""><span style="position: absolute; clip: rect(1.538em, 1007.11em, 2.907em, -1000em); top: -2.597em; left: 0em;" class=""><span id="MathJax-Span-24" class="mrow"><span id="MathJax-Span-25" class="texatom"><span id="MathJax-Span-26" class="mrow"><span id="MathJax-Span-27" class="munderover"><span style="display: inline-block; position: relative; width: 0.47em; height: 0px;" class=""><span style="position: absolute; clip: rect(3.398em, 1000.46em, 4.196em, -1000em); top: -4.009em; left: 0em;" class=""><span style="font-family: STIXGeneral; font-style: italic;" id="MathJax-Span-28" class="mi">ν</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span><span style="position: absolute; clip: rect(3.217em, 1000.22em, 3.655em, -1000em); top: -4.068em; left: 0.068em;" class=""><span style="font-family: STIXGeneral;" id="MathJax-Span-29" class="mo">˙</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span></span></span></span></span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-30" class="mo">≈</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-31" class="mo">−</span><span style="font-family: STIXGeneral;" id="MathJax-Span-32" class="mn">2.4</span><span style="font-family: STIXGeneral; padding-left: 0.25em;" id="MathJax-Span-33" class="mo">×</span><span style="padding-left: 0.25em;" id="MathJax-Span-34" class="msubsup"><span style="display: inline-block; position: relative; width: 2.266em; height: 0px;" class=""><span style="position: absolute; clip: rect(3.163em, 1000.98em, 4.192em, -1000em); top: -4.009em; left: 0em;" class=""><span style="font-family: STIXGeneral;" id="MathJax-Span-35" class="mn">10</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span><span style="position: absolute; top: -4.412em; left: 1em;" class=""><span id="MathJax-Span-36" class="texatom"><span id="MathJax-Span-37" class="mrow"><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-38" class="mo">−</span><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-39" class="mn">15</span></span></span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.597em;" class=""></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.243em; border-left: 0px solid; width: 0px; height: 1.406em;" class=""></span></span></nobr></span> 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 <span tabindex="0" id="MathJax-Element-4-Frame" class="MathJax"><nobr class=""><span style="width: 0.511em; display: inline-block;" id="MathJax-Span-40" class="math"><span style="display: inline-block; position: relative; width: 0.395em; height: 0px; font-size: 123%;" class=""><span style="position: absolute; clip: rect(1.987em, 1000.4em, 2.766em, -1000em); top: -2.597em; left: 0em;" class=""><span id="MathJax-Span-41" class="mrow"><span style="font-family: STIXGeneral; font-style: italic;" id="MathJax-Span-42" class="mi">r<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.023em;" class=""></span></span></span><span style="display: inline-block; width: 0px; height: 2.597em;" class=""></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.069em; border-left: 0px solid; width: 0px; height: 0.681em;" class=""></span></span></nobr></span>-mode with amplitude <span tabindex="0" id="MathJax-Element-5-Frame" class="MathJax"><nobr class=""><span style="width: 6.665em; display: inline-block;" id="MathJax-Span-43" class="math"><span style="display: inline-block; position: relative; width: 5.42em; height: 0px; font-size: 123%;" class=""><span style="position: absolute; clip: rect(1.547em, 1005.42em, 2.791em, -1000em); top: -2.597em; left: 0em;" class=""><span id="MathJax-Span-44" class="mrow"><span style="font-family: STIXGeneral; font-style: italic;" id="MathJax-Span-45" class="mi">α</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-46" class="mo">≈</span><span style="font-family: STIXGeneral; padding-left: 0.313em;" id="MathJax-Span-47" class="mn">5</span><span style="font-family: STIXGeneral; padding-left: 0.25em;" id="MathJax-Span-48" class="mo">×</span><span style="padding-left: 0.25em;" id="MathJax-Span-49" class="msubsup"><span style="display: inline-block; position: relative; width: 1.913em; height: 0px;" class=""><span style="position: absolute; clip: rect(3.163em, 1000.98em, 4.192em, -1000em); top: -4.009em; left: 0em;" class=""><span style="font-family: STIXGeneral;" id="MathJax-Span-50" class="mn">10</span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span><span style="position: absolute; top: -4.412em; left: 1em;" class=""><span id="MathJax-Span-51" class="texatom"><span id="MathJax-Span-52" class="mrow"><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-53" class="mo">−</span><span style="font-size: 70.7%; font-family: STIXGeneral;" id="MathJax-Span-54" class="mn">8</span></span></span><span style="display: inline-block; width: 0px; height: 4.009em;" class=""></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.597em;" class=""></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.1em; border-left: 0px solid; width: 0px; height: 1.253em;" class=""></span></span></nobr></span> may be
present in the system.</div><div class=""> </div></div><div class=""><div class="">Link to paper: <a href="https://arxiv.org/abs/1703.08374" class="">https://arxiv.org/abs/1703.08374</a></div><div class=""><br class=""></div></div><div class="">If you have recently read interesting astrophysics paper you would like to present, please contact me via e-mail: <a href="mailto:lceraj@phy.hr" class="">lceraj@phy.hr</a></div><div class=""><br class=""></div><div class="">See you on Wednesday.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Lana</div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">P. S. </div><div class="">We have set up a web page to function as a repository of AJC presentations.</div><div class="">It can be found at: <a href="https://lanaceraj.wixsite.com/ajc-main" class="">https://lanaceraj.wixsite.com/ajc-main</a></div><div class="">In case you run into some problem or bug, please let me know. Thank you. </div></body></html>