voeventnet.caltech.edu neat pipeline for transients ashish mahabal, joshua dickerson, george...
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voeventnet.caltech.edu
NEAT pipeline for transients
Ashish Mahabal, Joshua Dickerson, George Djorgovski and the Caltech group
• Transients from NEAT data
• Extensible: PQ (+ other surveys)• Complimentary to other approaches (e.g. catalog domain)
• Brief update on Solar System objects/Variables associated with VOEvent error ellipses
NEAT
NEAT is a program to look for Near Earth Asteroids(Mike Brown et al.)
o Palomar observatoryo 48-inch Oschin Schmidt telescopeo Palomar-QUEST camera - 112 CCDso Point and shoot mode
The Palomar-Quest (PQ) and NEAT Surveys
P48
done with the Yale/IU Quest-2 112-CCD camera at the Palomar 48” Oschin Schmidt
telescope
The NEAT mode
o Triplets 20 or 90 minutes aparto Single filter (R) usedo Subroutine looks for possible
transientso Lot of junk ensuring real candidates
are retainedo Several tens per night
Process flow A NEAT tar file arrives nightly Script detects new arrival - springs in to
action Valid candidates identified and transformed
on to a web page - tentatively it is: http://www.astro.caltech.edu/~dposs/NEAT
Alerts sent off for most promising ones
First attempt
o Take a tripleto Obtain catalogs using sextractoro Throw out extended objectso Compare seeing based object
numberso Check if central object shows big
magnitude swing
Data Flow
NEAT.tar Files
MEFs Images
IRAF
SExtractorCatalog
Matching
Possible Transien
t?
FITS Files 1, 2 & 3
Catalogs 1, 2 & 3
Filter Against Documented Sources, etc.
Generate Report, Send
Alerts.
Database
Figure 1. Transient Discovery Flowchart
History Extraction(010)…
Filter against Seeing
Transient Criteria
Object history, hi
Visibility/seeing, vi
Stellarity, si
Detected? Dj
jth Candidate is ranked by probability, pj
Image 1 Image 2 Image 3 Possible Transient
0 0 0 0
0 0 1 1
0 1 0 1 (Best case)
0 1 1 1
1 0 0 1
1 0 1 0
1 1 0 1
1 1 1 0
{ ( )ji
hshvj dp ii
ii ⎥⎦
⎤⎢⎣
⎡= ∏
=
==
3
1
1,0,
Complicating Factors
Faint stars near detection threshold CCD defects Satellites, airplanes Crowded fields
Asteroids Known variables
Example artifactso CCD defectso Reflectionso Grazing CRso Partially
uncorrected bad columns
o unknowns
More artifacts
Some reasons
o Sextractor’s S/G classification is not the best
o In crowded areas and with variable seeing sextractor gets easily confused
Modifications
o Better statistics - sigma clipping to determine typical variation (non-intrinsic)
o Use checkimage and the extent of object it defines to better estimate the magnitude
o Obtain stellarity measure independently
Result
o Much better clean-upo A very small fraction of possibly real
candidates get thrown outo Smaller proportion of contaminantso Script now ready as a blackbox to
unleash transientso Advanced cog-sci still needed to
assign significance values to events
Specimen
And couple more
Complimentary work
Current work is clearly extensible to other surveys, and especially our own Drift Scan data from the Palomar-QUEST survey.
o Basic work based on mosaicing carried out for the Griffith Observatory picture has been started
o Being extended using HyperAtlaso To be “real time” in the near future
Asteroids in the Big Picture
Tile b07
740 Cantabia
The Big Picture A 152 ft 20 ft mural produced for Griffith Observatory
from PQ survey BRI images A swath of 15.2 2.0 swath through the center of the
Virgo cluster, sampled at 0.4 arcsec/pixel, giving a 136,800 18,000 pixel image
Computed at CACR using HyperAtlas and a custom data cleaning pipeline
Reproduced on 114 steel-backed porcellain plates, expected to last many decades
Will be seen by millions of visitors Associated website will include NVO outreach
The Big Picture:Tile C12 (M87)Zoom-in
Big Picture - Detail
Catalog domain
Another complimentary area is the catalog domain
o Started a basic program using single epoch catalogs from the Yale pipeline
o Awaiting new and improved catalogs from Caltech pipeline which is now up and running
o This is “next day” stuff …
Examples (Priya Kollipara)
Conclusions for part I
We are ready to start producing events.Lots of them.
It is now important to have ways toAttach significance values to differentEvents. (Entities like aggregators will
not be intelligent unless we make them so)
Event Synthesis Engine
Pairitel
Palomar 60”
Raptor
PQ next-daypipelines
catalog
Palomar-Quest
knownVariables
knownasteroids
SDSS2MASS
PQ Event Factory
remote archives
baselinesky
eStar
VOEventNet
VOEventNet: a Rapid-Response Telescope Grid
VOEventdatabase
Solar system objects/Variables
Known asteroids and variables can masquerade as transients. These can easily be eliminated by overplotting the error ellipse with solar system objects and variables.
o Get epoch, coordinates, error ellipseo Get solar system objects, variables and a
sky survey imageo Allow overplotting of other possibly
interesting source types like X-ray and radio sources.
http://avyakta.caltech.edu:8080/cgi-bin/grand_aladin3.cgiCurrently uses aladin. Images from
DPOSS for northern sky and DSS for southern sky could be used
http://avyakta.caltech.edu:8080/nvoevent/
has the collective list
GUI (RESTful) String
DateTime
SIAP like
Output
Currently as cgiDirectly callable
Can consume feeds directlyEvents stored as an HTML page
Current tentative URLs
NEAT VOEvents: http://www.astro.caltech.edu/~dposs/NEAT
Solar System objects/Variables:
http://avyakta.caltech.edu:8080/cgi-bin/grand_aladin3.cgi
http://avyakta.caltech.edu:8080/nvoevent/