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Presentation on theme: " NEAT pipeline for transients Ashish Mahabal, Joshua Dickerson, George Djorgovski and the Caltech group."— Presentation transcript:

1 NEAT pipeline for transients Ashish Mahabal, Joshua Dickerson, George Djorgovski and the Caltech group

2 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

3 NEAT NEAT is a program to look for Near Earth Asteroids (Mike Brown et al.) o Palomar observatory o 48-inch Oschin Schmidt telescope o Palomar-QUEST camera - 112 CCDs o Point and shoot mode

4 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

5 The NEAT mode o Triplets 20 or 90 minutes apart o Single filter (R) used o Subroutine looks for possible transients o Lot of junk ensuring real candidates are retained o Several tens per night

6 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: Alerts sent off for most promising ones

7 First attempt o Take a triplet o Obtain catalogs using sextractor o Throw out extended objects o Compare seeing based object numbers o Check if central object shows big magnitude swing

8 Data Flow NEAT.tar Files MEFs Images IRAF SExtractor Catalog 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

9 Transient Criteria Object history, h i Visibility/seeing, v i Stellarity, s i Detected? D j j th Candidate is ranked by probability, p j Image 1Image 2Image 3Possible Transient 0000 0011 0101 (Best case) 0111 1001 1010 1101 1110

10 Complicating Factors Faint stars near detection threshold CCD defects Satellites, airplanes Crowded fields Asteroids Known variables

11 Example artifacts o CCD defects o Reflections o Grazing CRs o Partially uncorrected bad columns o unknowns

12 More artifacts


14 Some reasons o Sextractors S/G classification is not the best o In crowded areas and with variable seeing sextractor gets easily confused

15 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

16 Result o Much better clean-up o A very small fraction of possibly real candidates get thrown out o Smaller proportion of contaminants o Script now ready as a blackbox to unleash transients o Advanced cog-sci still needed to assign significance values to events

17 Specimen

18 And couple more

19 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 HyperAtlas o To be real time in the near future


21 Asteroids in the Big Picture Tile b07 740 Cantabia

22 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

23 The Big Picture: Tile C12 (M87) Zoom-in

24 Big Picture - Detail

25 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 …

26 Examples (Priya Kollipara)


28 Conclusions for part I We are ready to start producing events. Lots of them. It is now important to have ways to Attach significance values to different Events. (Entities like aggregators will not be intelligent unless we make them so)

29 Event Synthesis Engine Pairitel Palomar 60 Raptor PQ next-day pipelines catalog Palomar-Quest known Variables known asteroids SDSS 2MASS PQ Event Factory remote archives baseline sky eStar VOEventNet VOEventNet: a Rapid-Response Telescope Grid VOEvent database

30 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 ellipse o Get solar system objects, variables and a sky survey image o Allow overplotting of other possibly interesting source types like X-ray and radio sources.

31 bin/grand_aladin3.cgi Currently uses aladin. Images from DPOSS for northern sky and DSS for southern sky could be used ent/ ent/ has the collective list

32 GUI (RESTful) String DateTime SIAP like

33 Output

34 Currently as cgi Directly callable Can consume feeds directly Events stored as an HTML page

35 Current tentative URLs NEAT VOEvents: Solar System objects/Variables: bin/grand_aladin3.cgi bin/grand_aladin3.cgi

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