Second Einstein@Home newsletter

News on the gravitational-wave search (M. Alessandra Papa)
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The Einstein@Home all-sky search for continuous gravitational wave
signals in the gravitational-wave frequency range from 50 Hertz to 510
Hertz is in its final stages. Thanks to your continued support we had
enough processing power to implement a hierarchy of follow-ups. Each
step was more sensitive than the previous one and would zoom in to a
signal, if present, and discard, at each step, more and more false
alarms (random fluctuations of noise mimicking a signal).

At the time of the first newsletter we were completing the first
follow-up (FU1), which looked at a total of 16 million candidates. Out
of these, the next stage (FU2) followed up about 5.5 million, using a
different set-up to increase the sensitivity. The data were split into
40 segments, each with a longer coherent observation time, namely 140
hours versus the 60 hours used in FU1. About one in every five
candidates that was looked at with FU2 was deemed worthy of being
further inspected with the third follow-up stage (FU3).

The third and final stage uses data segments of 140 hours coherent
observation time (like FU2) but with a much finer grid in parameter
space, again zooming in and increasing the sensitivity. According to
our studies, this should give us at least a 40% increase in
signal-to-noise ratio. This is sufficient to confidently separate a
possible signal from the background. In fact we expect to have no more
than a few candidates coming out of FU3, which could be confirmed or
discarded based on specific candidate-tailored studies.

FU3 is a short run, of order a few weeks, and ended in late
September. If we see something it will be extremely exciting! If we do
not, we will be able to set the most constraining upper limit on the
amplitude of continuous gravitational waves ever. And finally, the
upgraded and more sensitive Advanced LIGO detectors are coming online
these days, and we cannot wait to look at this new data.

News on the binary radio pulsar search (Benjamin Knispel)
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Our currently most active radio pulsar search is a more sensitive
re-analysis of the Parkes Multi-beam Pulsar Survey (PMPS). It covers a
larger parameter space than analyzed in a previous Einstein@Home
search of the same data set. Since the start in March we have
processed roughly 30% of all observations. So far no new discoveries
have been made, but we have seen some interesting candidates and
re-discovered many known pulsars.

Whenever we get ‘fresh’ data from the PALFA survey with the Arecibo
telescope, we sent them out to your GPUs and Android devices
immediately. Over the past months we received four batches of new
data. In the latest data, we have made new radio pulsar
discoveries. Three of them (J1955+29, J1853+00, and J1853+0029) have
already been confirmed by the required follow-up observation. Congrats
to Przemek Wisialski and Gary S. Grant II, robert dolezal and Jim
Trettel, and [TiDC] Chulma - S'inergy and boinc_qc whose computers
found the pulsars with the highest statistical significance! The
follow-up observations for one remaining candidate will be done soon
with the Arecibo radio telescope.

Finally, a paper reporting on an earlier Einstein@Home radio pulsar
discovery in PALFA data has been published in The Astrophysical
Journal [3]. You can read it for free on the arXiv preprint server
[4]. The paper presents the discovery of a millisecond pulsar in a
surprisingly eccentric orbit, and looks at how this system and the
four known similar ones might have formed. In any case, they cannot
have formed through what has been thought to be the standard way of
making millisecond pulsars, i.e., through spinning up an older pulsar
by transfer of matter from a companion star. You can read more
background info at [5].

News on the gamma-ray pulsar search (Holger Pletsch)
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The various improvements offered by the latest, still ongoing, survey
of unidentified gamma-ray sources have borne first fruit. Earlier this
month we announced the Einstein@Home discovery of a new gamma-ray
pulsar hidden in plain sight in data from the Fermi Gamma-ray Space
Telescope, which has been published in the Astrophysical Journal
Letters [6] (open-access preprint available at [7], accompanying press
release at [8]). Further exciting candidate discoveries are currently
being studied in detail. We also examining the feasibility of
expanding the survey to other pulsar system types not yet searched on
Einstein@Home.

News from the project administration (Bernd Machenschalk)
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For the gamma-ray pulsar search we issued new application versions
that include a minor bug fix (typo in numerical constant) and feature
checkpointing during the last (“follow-upâ€) stage of a task, which was
previously not interruptable. This allows us to now slightly increase
the number of follow-up candidates to squeeze the last bit of
sensitivity out of the computation.

The “S6Bucket Follow-Up run #2†has ended (see above) and the third
stage of the follow-up will run until the end of September. After the
end of the third stage, there will be no new gravitational-wave search
for a while, and the project's CPUs will run 100% gamma-ray pulsar
search.

The binary radio pulsar search applications have been updated as well:
Optimizations that mainly reduce the amount of data that needs to be
shifted between GPU and CPU memory were implemented for both BRP4
(Arecibo data) and BRP6 (Barkes data), in application versions
1.52. The optimizations resulted in a speedup of up to 50%. There are
also CUDA application versions currently in Beta test with an updated
version of CUDA (5.5 instead of previously used 3.2). The speedup
gained from using these versions highly depends on the card used, it
varies between zero and another 50%.

For the general server infrastructure we performed additional numerous
system software and security updates, and am in the process of
replacing old servers that have become unreliable by modern hardware.

[1] http://www.ligo.org/magazine/LIGO-magazine-issue-7.pdf#page=18
[2] http://jobs.uwm.edu/postings/23976
[3] http://iopscience.iop.org/0004-637X/806/1/140/
[4] http://arxiv.org/abs/1504.03684
[5] http://einsteinathome.org/node/198055
[6] http://iopscience.iop.org/2041-8205/809/1/L2/
[7] http://arxiv.org/abs/1508.00779/
[8] http://www.aei.mpg.de/1689618/EatHGPSRHidden