NAME

Astro::Catalog::Star - A generic star object in a stellar catalogue.

SYNOPSIS

  $star = new Astro::Catalog::Star( ID         => $id, 
                                    Coords     => new Astro::Coords(),
                                    Magnitudes => \%magnitudes,
                                    MagErr     => \%mag_errors,
                                    Colours    => \%colours,
                                    ColErr     => \%colour_errors,
                                    Quality    => $quality_flag,
                                    Field      => $field,
                                    GSC        => $in_gsc,
                                    Distance   => $distance_to_centre,
                                    PosAngle   => $position_angle,
                                    X          => $x_pixel_coord,
                                    Y          => $y_pixel_coord,
                                    Comment    => $comment_string
				    SpecType   => $spectral_type,
				    StarType   => $star_type,
				    LongStarType=> $long_star_type,
				    MoreInfo   => $url,
				  );

DESCRIPTION

Stores generic meta-data about an individual stellar object from a catalogue.

If the catalogue has a field center the Distance and Position Angle properties should be used to store the direction to the field center, e.g. a star from the USNO-A2 catalogue retrieived from the ESO/ST-ECF Archive will have these properties.

REVISION

$Id: Star.pm,v 1.17 2003/08/26 19:53:02 aa Exp $

METHODS

Constructor

new

Create a new instance from a hash of options

  $star = new Astro::Catalog::Star( ID         => $id, 
                                    Coords     => new Astro::Coords(),
                                    Magnitudes => \%magnitudes,
                                    MagErr     => \%mag_errors,
                                    Colours    => \%colours,
                                    ColErr     => \%colour_errors,
                                    Quality    => $quality_flag,
                                    Field      => $field,
                                    GSC        => $in_gsc,
                                    Distance   => $distance_to_centre,
                                    PosAngle   => $position_angle,
                                    X          => $x_pixel_coord,
                                    Y          => $y_pixel_coord,
                                    Comment    => $comment_string
				    SpecType   => $spectral_type,
				    StarType   => $star_type,
				    LongStarType=> $long_star_type,
				    MoreInfo   => $url,
				  );

returns a reference to an Astro::Catalog::Star object.

The coordinates can also be specified as individual RA and Dec values (sexagesimal format) if they are known to be J2000.

Accessor Methods

id

Return (or set) the ID of the star

$id = $star->id();
$star->id( $id );

If an Astro::Coords object is associated with the Star, the name field is set in the underlying Astro::Coords object as well as in the current Star object.

coords

Return or set the coordinates of the star as an Astro::Coords object.

$c = $star->coords();
$star->coords( $c );

The object returned by this method is the actual object stored inside this Star object and not a clone. If the coordinates are changed through this object the coordinate of the star is also changed.

Currently, if you modify the RA or Dec through the ra() or dec() methods of Star, the internal object associated with the Star will change.

Returns undef if the coordinates have never been specified.

If the name() field is defined in the Astro::Coords object the id() field is set in the current Star object. Similarly for the comment field.

ra

Return (or set) the current object R.A. (J2000).

$ra = $star->ra();

If the Star is associated with a moving object such as a planet, comet or asteroid this method will return the J2000 RA associated with the time and observer position associated with the coordinate object itself (by default current time, longitude of 0 degrees). Returns undef if no coordinate has been associated with this star.

$star->ra( $ra );

The RA can be changed using this method but only if the coordinate object is associated with a fixed position. Attempting to change the J2000 RA of a moving object will fail. If an attempt is made to change the RA when no coordinate is associated with this object then a new Astro::Coords object will be created (with a Dec of 0.0).

RA accepted by this method must be in sexagesimal format, space or colon-separated. Returns a space-separated sexagesimal number.

dec

Return (or set) the current object Dec (J2000).

$dec = $star->dec();

If the Star is associated with a moving object such as a planet, comet or asteroid this method will return the J2000 Dec associated with the time and observer position associated with the coordinate object itself (by default current time, longitude of 0 degrees). Returns undef if no coordinate has been associated with this star.

$star->dec( $dec );

The Dec can be changed using this method but only if the coordinate object is associated with a fixed position. Attempting to change the J2000 Dec of a moving object will fail. If an attempt is made to change the Dec when no coordinate is associated with this object then a new Astro::Coords object will be created (with a Dec of 0.0).

Dec accepted by this method must be in sexagesimal format, space or colon-separated. Returns a space-separated sexagesimal number with a leading sign.

magnitudes

Set the UBVRIHK magnitudes of the object, takes a reference to a hash of magnitude values

my %mags = ( B => '16.5', V => '15.4', R => '14.3' );
$star->magnitudes( \%mags );

additional calls to magnitudes() will append, not replace, additional magnitude values, magnitudes for filters already existing will be over-written.

magerr

Set the error in UBVRIHK magnitudes of the object, takes a reference to a hash of error values

my %mag_errors = ( B => '0.3', V => '0.1', R => '0.4' );
$star->magerr( \%mag_errors );

additional calls to magerr() will append, not replace, additional error values, errors for filters already existing will be over-written.

Colours

Set the colour values for the object, takes a reference to a hash of colours

my %cols = ( 'B-V' => '0.5', 'B-R' => '0.4' );
$star->colours( \%cols );

additional calls to colours() will append, not replace, colour values, altough for colours which already have defined values, these values will be over-written.

ColErr

Set the colour error values for the object, takes a reference to a hash of colour errors

my %col_errors = ( 'B-V' => '0.02', 'B-R' => '0.05' );
$star->colerr( \%col_errors );

additional calls to colerr() will append, not replace, colour error values, altough for errors which already have defined values, these values will be over-written.

what_filters

Returns a list of the filters for which the object has defined values.

@filters = $star->what_filters();
$num = $star->what_filters();

if called in a scalar context it will return the number of filters which have defined magnitudes in the object.

what_colours

Returns a list of the colours for which the object has defined values.

@colours = $star->what_colours();
$num = $star->what_colours();

if called in a scalar context it will return the number of colours which have defined values in the object.

get_magnitude

Returns the magnitude for the supplied filter if available

$magnitude = $star->get_magnitude( 'B' );

get_errors

Returns the error in the magnitude value for the supplied filter if available

$mag_errors = $star->get_errors( 'B' );

get_colour

Returns the value of the supplied colour if available

$colour = $star->get_colour( 'B-V' );

get_colourerror

Returns the error in the colour value for the supplied colour if available

$col_errors = $star->get_colourerr( 'B-V' );

quality

Return (or set) the quality flag of the star

$quality = $star->quailty();
$star->quality( 0 );

for example for the USNO-A2 catalogue, 0 denotes good quality, and 1 denotes a possible problem object. In the generic case any flag value, including a boolean, could be used.

These quality flags are standardised sybolically across catalogues and have the following definitions:

STARGOOD
STARBAD

TBD. Need to provide quality constants and mapping to and from these constants on catalog I/O.

field

Return (or set) the field parameter for the star

$field = $star->field();
$star->field( '0080' );

gsc

Return (or set) the GSC flag for the object

$gsc = $star->gsc();
$star->gsc( 'TRUE' );

the flag is TRUE if the object is known to be in the Guide Star Catalogue, and FALSE otherwise.

distance

Return (or set) the distance from the field centre

$distance = $star->distance();
$star->distance( '0.009' );

e.g. for the USNO-A2 catalogue.

posangle

Return (or set) the position angle from the field centre

$position_angle = $star->posangle();
$star->posangle( '50.761' );

e.g. for the USNO-A2 catalogue.

x

Return (or set) the X pixel co-ordinate of the star

$x = $star->x();
$star->id( $x );

y

Return (or set) the Y pixel co-ordinate of the star

$y = $star->y();
$star->id( $y );

comment

Return (or set) a comment associated with the star

$comment = $star->comment();
$star->comment( $comment_string );

The comment is propogated to the underlying coordinate object (if one is present) if the comment is updated.

spectype

The spectral type of the Star.

$spec = $star->spectype;

startype

The type of star. Usually uses the Simbad abbreviation. eg. '*' for a star, 'rG' for a Radio Galaxy.

$type = $star->startype;

See also longstartype for the expanded version of this type.

longstartype

The full description of the type of star. Usually uses the Simbad text. If no text has been provided, a lookup will be performed using the abbreviated startype.

$long = $star->longstartype;
$star->longstartype( "A variable star" );

See also longstartype for the expanded version of this type.

moreinfo

A link (URL) to more information on the star in question. For example this might provide a direct link to the full Simbad description.

$url = $star->moreinfo;

General Methods

configure

Configures the object from multiple pieces of information.

$star->configure( %options );

Takes a hash as argument with the list of keywords. The keys are not case-sensitive and map to accessor methods.

Note that RA and Dec keys are allowed. The values should be sexagesimal.

COPYRIGHT

This program was written as part of the eSTAR project and is free software; you can redistribute it and/or modify it under the terms of the GNU Public License.

AUTHORS

Alasdair Allan <aa@astro.ex.ac.uk>, Tim Jenness <tjenness@cpan.org>,

To install Astro::Catalog, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Astro::Catalog

CPAN shell

perl -MCPAN -e shell
install Astro::Catalog

For more information on module installation, please visit the detailed CPAN module installation guide.

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