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ARNIE Version 4.0 - Tutorial

ARNIE is a hypertext interface to the databases of the Leicester Database and Archive Service. This tutorial shows you how the system works. Following this tutorial will be easier if you clone yourself a second window and display the tutorial in one window whilst following the instructions on the other.

There are two ways to begin your ARNIE session; via the Standard ARNIE start-up page, or by the ARNIE Index page. There is no functional difference between these two methods, they differ only in the way they organise the 200-odd databases available, and in the amount of information given about each database. Start by clicking on "Standard ARNIE" at left.

On the front page of Standard ARNIE, there is a list in the middle-left frame of the different groups of databases that you can access. The databases are grouped by mission and general astronomical waveband. Click on the ROSAT link, on the middle-right frame you will then see all the databases associated with ROSAT (ROentgen SATellite). The databases have been grouped into categories to make it easier to select the database you require. In this tutorial we are going to search the ROSPUBLIC database, which appears in the "X-ray Telescope" section of the page because it contains the list of public data associated with the detectors on the ROSAT X-ray Telescope. Click on the "ARNIE" button next to ROSPUBLIC, and a new page will appear in the right-hand frame containing a form. This form is the Database Browser with ROSPUBLIC as the selected database.

Now try using the ARNIE Index; click on "ARNIE Index" at left. A large page will appear, which lists all the LEDAS database tables grouped by mission. There are no sub-categories as on the Standard ARNIE pages. In addition, the number of parameters and the number of entries for each database is shown. Simply click on the "ARNIE" button next to ROSPUBLIC and the ARNIE database query form for the ROSPUBLIC database will load.

The form has a number of links which display help information. These are;

  • Database Help: displays information on the currently selected database giving an overview, definitions of the database parameters and some ancillary information.
  • Name Resolver Help: Instructions on how to use the name resolver.
  • Cone Search Help: Instructions on how to perform cone searches.
  • Filter Search Help: Instructions on how to apply a filter search.
  • Parameter Help: A list of the database parameters.
You can apply two types of search to a database. A Cone Search and a Filter Search. They can be applied separately or simultaneously.

A Cone Search simply selects all database records within a certain angular distance of your input coordinates. Clicking on the System and Equinox checkboxes allows you to change the default coordinate system or equinox. You can set the cone search radius using checkboxes or an input box. The input coordinates are typed into the Coords box. A number of coordinate formats are allowed and these are listed in the Cone Search Help.

The system also contains a Name Resolver. You simply type in the name of an astronomical object into the Name box. If you then click on "Resolve Name" the system connects to the Simbad database which returns the coordinates of your object. Unfortunately, network links between the UK and Europe can be slow at times, so to avoid excessive delays there is an option which allows you to timeout the resolver after a certain time. If your resolve query is successful, the coordinates of the object you typed will appear in the Cone Search section of the form.

Filter Searches can either be Inclusive or Exclusive (selected using checkboxes) and can be used to select all database records where,

parameter (not) equal to value

or select all database records where

min (>)<= parameter (<)>= max.

Note that when searching on parameters that are character strings, the wildcard characters asterix (*) and percent (%) match any string of characters of any length, and an underscore (_) matches any single character.

Assume we are interested in ROSAT observations of the Galactic Centre. Select the Galactic coordinates checkbox next to "Coord. System". Now type "0, 0" (don't forget the comma) into the Coords box. Select the Other checkbox against "Radius" and set the search radius to 120 arcminutes in the input box.

There is one "hidden" feature of ARNIE to note: to request all entries in the database, leave all fields on the database query form blank.

Now click on either Submit Query button. In a few moments the Results of Database Search page will load, which shows (1) how many entries your query has matched, (2) the existing filters applied to the database, in this case:

Galactic Cone Search at (0.000000, 0.000000), radius 120 arcmin.

(3) two paragraphs which tell you that the database has associated on-line and near-line data products with instructions on how to access these products and (4) a table showing the results of the search. Note that the Max Display input box on the query form sets the default for the maximum number of displayed entries. Therefore not all the matched entries are shown here (unless you changed the number to something larger). You are advised not to attempt to display too many found entries, as the additional time taken to build the larger page slows down the speed of your query.

In order to look at the on-line products for one of the entries, simply click on the "PROD" button next to that entry. The on-line files associated with ROSPUBLIC are images, stored in gif, compressed HDS and FITS format. Clicking on an HDS or FITS file name will cause a the file to be automatically decompressed and transferred over network. Clicking on a gif image file name will cause the image to be displayed. HDS files are written in the UK ASTERIX/HDS image format and can be displayed using the ASTERIX image display and analysis package. FITS images can be displayed using utilities such as SAOIMAGE or XIMAGE.

Now lets assume we want to apply an additional filter to our search results. Click on the "Back" button of your browser until the Results of Database Search is displayed again. Now click on "Refine Query". The original Database Query form will reload, but included at the top is the list of Existing Filters, each with an associated checkbox. When the filter checkbox is checked the filter is active for the subsequent search. You can turn the filter on or off by clicking on the checkbox.

ROSAT observations typically have exposure times ranging from a few tens of seconds up to several hundred thousand seconds. Assume we are only interested in observations with long exposures. Select the Exposure option from the Parameter menu. Next, select the Exclusive checkbox from the Search Type section. Finally, type 0 and 9999 into the two Range input boxes (i.e. we are excluding all observations with exposure times less than 10 kseconds).

Click on the Submit Query button again. The Results of Database Search page is shown again, but now the number of entries found has changed and a second filter has appeared in the Existing Filters list.

The Results of Database Search page also provides the means to request near-line data which are stored on CD-ROM if, as in the case of ROSPUBLIC, there is any associated with the database. The first column of the table, CD, contains a series of checkboxes which are used to request the near-line products. This is done by clicking on one or more of the checkboxes corresponding to the product you require, then typing a valid return e-mail address into the input box provided.

A handy tool for requesting large numbers of datasets is the yellow "Invert Selection" button at the top of the column. This reverses the sense of the individual checkboxes, so that the ones that are checked are excluded. For example, to request all but the first entry you only need to click the first two checkboxes in the column.

When you click on the Submit Request button, the system automatically copies the requested files to the anonymous ftp site ledas-ftp.star.le.ac.uk. You will be sent an e-mail message in acknowledgement once the data have been made available. The message contains information on the location of the files and any necessary ancillary information. Please do not abuse the system by submitting lots of unnecessary requests. For ROSPUBLIC, the near-line products consist of the entire observation dataset (event files, images, and housekeeping files).

Note that if a database has no associated near-line or on-line products, the checkboxes and "PROD" links will not be displayed.

If you have comments about ARNIE, including suggestions for improvements or general queries, please contact ledas-help@star.le.ac.uk.


 
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