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# LSR

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

  Bases: `BaseRADecFrame`

  A frame in the Local Standard of Rest (LSR).

  For Earth-bound observers it is often convenient to use a reference frame that is tied to the Solar System barycenter, but such frames are not very useful for describing galactic dynamics. The dynamical LSR is instead tied to the circular velocity at the Sun’s location, but defining a circular velocity in a non-axisymmetric galaxy requires non-trivial averaging. The kinematic LSR is understood as a frame in which the average motion of the stars in the solar neighborhood is zero, but in practice that is not straightforward either because the average motion is different for different spectral types.

  The default parameters of this frame are those of the dynamical LSR of Schönrich et al. (2010), meaning the Galactic (right-handed) Cartesian velocity components of the solar motion are \((U, V, W) = (11.1, 12.24, 7.25)~{{\rm km}}~{{\rm s}}^{{-1}}\), but a different solar motion can be specified with the `v_bary` argument. The frame is axis-aligned and co-spatial with `ICRS`.

  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).

    ra `Angle`, optional, keyword-only

      The RA for this object (`dec` must also be given and `representation` must be None).

    dec `Angle`, optional, keyword-only

      The Declination for this object (`ra` 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_ra_cosdec `Quantity` [:ref: ‘angular speed’], optional, keyword-only

      The proper motion in Right Ascension (including the `cos(dec)` factor) for this object (`pm_dec` must also be given).

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

      The proper motion in Declination for this object (`pm_ra_cosdec` 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 `CartesianRepresentation`

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

    .. versionchanged:: 8.0

      `v_bary` is now a `CartesianRepresentation` rather than a `CartesianDifferential`.

  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` | The relative velocity of the solar-system barycenter

  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.CartesianRepresentationAttribute object>}
  frame_specific_representation_info

    Mapping for frame-specific component names

  name = 'lsr'
  v_bary

    The relative velocity of the solar-system barycenter

    Default: (11.1, 12.24, 7.25) km / s