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- Astropy v5.2.1 »
- Astronomical Coordinate Systems (`astropy.coordinates`) »
- GalacticLSR

# GalacticLSR

class astropy.coordinates.GalacticLSR(*args, copy=True, representation_type=None, differential_type=None, **kwargs)

  Bases: `BaseCoordinateFrame`

  A coordinate or frame in the Local Standard of Rest (LSR), axis-aligned to the Galactic frame.

  This coordinate frame is axis-aligned and co-spatial with `ICRS`, but has a velocity offset relative to the solar system barycenter to remove the peculiar motion of the sun relative to the LSR. Roughly, the LSR is the mean velocity of the stars in the solar neighborhood, but the precise definition of which depends on the study. As defined in Schönrich et al. (2010): “The LSR is the rest frame at the location of the Sun of a star that would be on a circular orbit in the gravitational potential one would obtain by azimuthally averaging away non-axisymmetric features in the actual Galactic potential.” No such orbit truly exists, but it is still a commonly used velocity frame.

  We use default values from Schönrich et al. (2010) for the barycentric velocity relative to the LSR, which is defined in Galactic (right-handed) cartesian velocity components \((U, V, W) = (11.1, 12.24, 7.25)~{{\rm km}}~{{\rm s}}^{{-1}}\). These values are customizable via the `v_bary` argument which specifies the velocity of the solar system barycenter with respect to the LSR.

  The frame attributes are listed under Other Parameters.

  Parameters:
    data `BaseRepresentation` subclass instance

      A representation object or `None` to have no data (or use the coordinate component arguments, see below).

    l `Angle`, optional, keyword-only

      The Galactic longitude for this object (`b` must also be given and `representation` must be None).

    b `Angle`, optional, keyword-only

      The Galactic latitude for this object (`l` must also be given and `representation` must be None).

    distance `Quantity` [:ref: ‘length’], optional, keyword-only

      The Distance for this object along the line-of-sight. (`representation` must be None).

    pm_l_cosb `Quantity` [:ref: ‘angular speed’], optional, keyword-only

      The proper motion in Galactic longitude (including the `cos(b)` term) for this object (`pm_b` must also be given).

    pm_b `Quantity` [:ref: ‘angular speed’], optional, keyword-only

      The proper motion in Galactic latitude for this object (`pm_l_cosb` must also be given).

    radial_velocity `Quantity` [:ref: ‘speed’], optional, keyword-only

      The radial velocity of this object.

    representation_type `BaseRepresentation` subclass, `python:str`, optional

      A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing `representation_type='cartesian'` will make the classes expect position data with cartesian names, i.e. `x, y, z` in most cases unless overridden via `frame_specific_representation_info`. To see this frame’s names, check out `<this frame>().representation_info`.

    differential_type `BaseDifferential` subclass, `python:str`, `python:dict`, optional

      A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing `differential_type='cartesian'` will make the classes expect velocity data with the argument names `v_x, v_y, v_z` unless overridden via `frame_specific_representation_info`. To see this frame’s names, check out `<this frame>().representation_info`.

    copy bool, optional

      If `True` (default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.

  Other Parameters:
    v_bary `CartesianDifferential`

      The velocity of the solar system barycenter with respect to the LSR, in Galactic cartesian velocity components.

  Attributes Summary

  `default_differential` | Default representation for differential data (e.g., velocity)
  `default_representation` | Default representation for position data
  `frame_attributes` |
  `frame_specific_representation_info` | Mapping for frame-specific component names
  `name` |
  `v_bary` |

  Attributes Documentation

  default_differential

    Default representation for differential data (e.g., velocity)

  default_representation

    Default representation for position data

  frame_attributes = {'v_bary': <astropy.coordinates.attributes.DifferentialAttribute object>}
  frame_specific_representation_info

    Mapping for frame-specific component names

  name = 'galacticlsr'
  v_bary = <CartesianDifferential (d_x, d_y, d_z) in km / s (11.1, 12.24, 7.25)>