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/