Confirmation of a Supernova Candidate

• launch Aladin, TOPCAT

• load the local image of NGC6946 (ngc6946.fit) taken by the Col Druscie Remote Observatory Supernovae Search (CROSS) programme
• to make the image clearer, modify the pixel distribution ("pixel" button, 3rd from the bottom in the vertical tool bar, right next to the image window -> Contrast)
  • you can change the colour map by selecting "pixel" again and then Color map
• the image has no astrometric calibration; the calibration can be done from within Aladin:
  • open the Server Selector by clicking on the Load button
  • select allVO; explore allVO for NGC6946
    • tick off Catalogues and Spectra and open the Server list (click on "Detailed list ...")
    • the button marked "?" next to each Registry will give information about the Registry
    • you can Filter the resources
  • select a few resources (e.g. Aladin image server, POSSII image) and "SUBMIT" the query.
  • the response will appear in the form of a tree in the Server selector window
  • pick the image of your choice ( tip: do not select large images!)
  • select a reference catalogue from the Catalogue Servers (e.g. 2MASS, USNO)
  • place both images (calibrated and non-calibrated) side by side by splitting the display window in two panels (click on the corresponding option at the bottom left of the display window - multiview)
  • highlight the non-calibrated image plane and select the properties button "prop", (or right-click on the image and select "Properties ...")
  • in the Astrometric Reduction section select New and select by matching stars
  • activate the cells under "x y" position (by clicking on them) and click on a few (3-4) stars on the uncalibrated image; then select the corresponding stars on the calibrated image after activating the cells under hh mm ss +dd mm ss and then click Create
• the local image is now calibrated and can be superposed on the POSSII (or other) image.

• We will now identify the Supernova by comparing the two images:
• go back to single view mode (showing one single image in the main Aladin window) and change the transparency of the POSSII image with the sliding bar appearing on the image logo to the right
• OR associate the two images (this can be done by clicking on the "assoc" icon, 6th from the bottom)
• "tag" the supernova (6th button from the top)

• measure the distance from the centre of the galaxy:
• Click on the "dist" icon, 4th from the top of the vertical tool bar
• then click on the centre of the galaxy and without releasing the mouse button, drag the pointer all the way to the supernova;
• the distance is displayed on the main window
• check for more SNe and other interesting objects in the same galaxy:
• load Simbad from the Server Selector, apply no filter
• clicking on either of the objects, the available information will appear in tabular form at the bottom of the Aladin window, linking directly to the Simbad query results on your browser - try it
• to see immediately the SNe, highlight the Simbad plane and click on the column named OTYPE
• the corresponding histogram (objects grouped per type) will appear in the little graphic window below the stacks; move the mouse over each bar to see the corresponding objects highlighted in the main Aladin window

• send the Simbad plane from Aladin to TOPCAT (right click on the plane and broadcast selected table to... TOPCAT)
• view the Simbad table selecting View -> Table Data
• view the column metadata selecting View -> Column Info
• place the cursor on any Simbad identification on the main Aladin window and see how the relevant column is highlighted in the TOPCAT Table Data

• in TOPCAT, you can create the SN sub-sample as follows:
  • click on Display row subset -> Define new subset using algebraic expression as equals(OTYPE,"SN")
• Alternatively, this can be done in Aladin with a filter:
  • click on "filter" within Aladin (make sure the Simbad plane is highlighted)
  • select advanced mode and define: $[src.class]="SN" {draw red square} (the SNe will appear in red); Click "Apply" and/or "Export"; a new plane with the filtered source has now been created

• Search in VizieR catalogues
• in the "Keywords" field type your constraints (e.g. x-rays, radio, gamma, supernovae) and select the resources to be queried
• put the objects name (NGC6946) in the "Object Name" field and query
• cross-correlate the resulting catalogues (either in TOPCAT or Aladin), check them against the images
• try to load other images from different archives, look for existing spectra, improvise!