Pulsars, SNRs, and Plerions
Meeting, 4
April 2006
“status report
and discussion of Pulsar studies with DC2”
INTRODUCTION: Since the KickOff one month ago, various
people have looked at the EGRET pulsars, and some other pulsars, using the DC2
data and the Science Tools. Lots of things work well and people are enjoying
practicing for real data. Some problems have also surfaced, some of which may
limit our reaching some of the DC2 goals.
In the
following, we tour various results posted to confluence. Click on the links as
we work through the items.
1. The six EGRET pulsars
a. VELA
Vela is the
brightest, so we’ll start there. Dave Thompson pointed out that the light
curves look more ragged than they do for EGRET data:
https://confluence.slac.stanford.edu/display/DC2/Problem+with+DC2+Pulsar+Timing
Thierry
Reposeur elaborated on this: he plots photon energy versus phase and obtains a
highly non-physical plot:
https://confluence.slac.stanford.edu/display/DC2/2006/03/31/Vela+energy+spectrum
In his
posting, Thierry refers to Luis Reye’s posting that first alerted us to the
strange energy spectra:
Here, Denis
Dumora shows how Vela’s light curve changes depending on whether you let
gtpphase take the timing parameters from the DC2 database, or you type them in
by hand, using the output that gtephcomp gave you. Johan Bregeon added some
comments to the subject.
https://confluence.slac.stanford.edu/display/DC2/2006/03/09/gtpphase+and+VELA+pulsar
A problem
in the DC2 ephemerides database seems to be that some (most?) of the positions
are rounded off (truncated?) to the nearest hundredth of a degree. For Vela,
but even more so for some of the others seen below, taking the pulsar position
from for example the Simbad database improves the light curve significantly.
Nota
bene the energy
spectrum problem is unrelated to the position problem. This is illustrated
best in the Geminga link, below.
This
coordinate issue is illustrated in the following posting by Thierry Reposeur.
Denis Dumora verified the sensitivity to the source coordinate position by
taking some CELESTE Crab optical pulsar data, changing the source coordinates a
hair, and seeing the light curve degrade.
https://confluence.slac.stanford.edu/display/DC2/2006/04/04/gtbary+source+coordinates+dependency
Andrea
Caliandro and Vela – lovely presentation (link in section 4a, below).
b. GEMINGA
Geminga
gives a nice strong signal except that P2 and P1 are inverted as compared
to EGRET data. Here is Denis Dumora’s posting:
https://confluence.slac.stanford.edu/display/SCIGRPS/DC2+Analysis+of+Geminga+pulsar
Inverted… Or rotated by about 0.7 in phase – depends
on how you look at it. Johan Bregeon also saw Geminga.
c. CRAB
Pat Nolan
sees the Crab, and has started cleaning it up:
https://confluence.slac.stanford.edu/display/DC2/Adaptive+smoothing+of+light+curves
In that
same page he has results for Geminga and Vela.
After the
meeting, Pat sent the following comment --
“This
morning in the VRVS I should have pointed to this:
https://confluence.slac.stanford.edu/display/SCIGRPS/Crab+frequency+is+still+a+bit+off
when you
mentioned the quality of my Crab light curve. I had to fudge the
frequency. This might be due to my
use of
coordinates correct to 4 decimal places, rather than the truncated coordinates
in the ephemeris file.”
d. 1706-44
Dave
Thompson made a posting at
https://confluence.slac.stanford.edu/display/SCIGRPS/DC2+Analysis+of+PSR+B1706-44+pulsar
e. 1055-52
Andrea
Caliandro made the following posting:
https://confluence.slac.stanford.edu/display/SCIGRPS/DC2+Analysis+of+PSR+B1055-52+pulsar
On that page there is also
Andrea Caliandro https://confluence.slac.stanford.edu/download/attachments/10329/PSR1055quickAnalysis.ppt
f. 1951+32
Damien
Parent (senior thesis student in Bordeaux)
has what might be a few sigma for P2 but no P1. In progress…
2. Other pulsars
Dave
Thompson posted two other pulsars at :
These are PSR J1420-6048 and PSR J2229+6114.
3. Searching for ATNF counterparts to the DC2 LAT Catalog
In Bordeaux
we applied the Toulouse group’s gtsrcid tool and found that 34 ATNF pulsars have
good associations with DC2 LAT catalogue sources:
https://confluence.slac.stanford.edu/display/DC2/2006/04/03/ATNF+vs+LAT+catalogs+using+gtsrcid
4. Various other remarks
a. Better angle cuts
(Better
than cookie cutter? see Pat Nolan’s
comment at the bottom of this page:)
https://confluence.slac.stanford.edu/display/SCIGRPS/Data+Challenge+2+Activities
We (Bordeaux) were thinking “energy dependent
angle cut”, and we started to build our own PSF. But it depends on the photon
angle relative to the LAT as well. Does anyone know how to use the Official
IRF’s to extract a photon-by-photon angle cut?
Meanwhile,
go to https://confluence.slac.stanford.edu/display/DC2/PULSEPH
and look at Andrea Caliandro’s contribution called Three alternatives way to investigate Vela Light Curve There’s a lot of material in here, but I
only found this page a few minutes before today’s meeting. We in Bordeaux will
be using some of Andre’s ideas. In particular, he points out the PSF’s shown by
Jim Chiang at the KickOff.
b. Need to re-generate the energy spectra, don’t we?
Do we agree
that we’re not going to be able to do phase resolved spectroscopy, or any
spectroscopy, with the energy plots discussed above? If the bug hasn’t been
found yet, call for volunteers to track it down.
c. Absolute phases of P1’s not yet nailed down
Especially
in Geminga but also in Vela, the postings above don’t always have their peaks
just where we expect them from EGRET.
d. Blind searches: help wanted
Go to the
following page. There is a list of topics such as PULSNOEPH and SOURCELOC that
are untouched.
https://confluence.slac.stanford.edu/display/DC2/DC2+Analysis+Results
e. Hearty thanks to Max Razzano and/or his cohorts.
Some
problems have surfaced, nevertheless let us not lose from sight that the people
who generated the simulated pulsar data set were sometimes isolated beginners
and did a very big job which we are profiting from immensely. Some people who
volunteered to help with this big task never showed up (yours truly, for
instance).The pulsar simulators should feel very good about the job they’ve
done.