Lightkurve

==================

- Added a ``method="quadratic"`` option to ``tpf.estimate_centroids()`` which
enables centroids to be estimated by fitting a bivariate polynomial to the
3x3 pixel core of the PSF. The method can also be called as a standalone
function via ``lightkurve.utils.centroid_quadratic()``. [544, 610]

- Fixed a bug in ``Seismology.plot_echelle()`` which caused the Echelle diagram
of a power spectrum to be rendered incorrectly. [602]

- Fixed a bug which caused ``lightkurve.utils`` to be incorrectly resolved to
``lightkurve.seismology.utils``. [606]

- Changed ``bkjd_to_astropy_time()`` and ``btjd_to_astropy_time()`` to accept
a single float and lists of floats in addition to numpy arrays. [608]

- Improved support for creating a ``LombScarglePeriodogram`` with an unevenly
sampled grid in frequency space. [614]

==================

- Added ``flux_unit`` and ``flux_quantity`` properties to the ``LightCurve``
class to enable users to keep track of a light curve's flux units. [591]

- Changed the default behavior of ``LightCurve.plot()`` to use ``normalize=False``,
ie. plots now display a light curve in its intrinsic units by default. [591]

- Added an optional ``unit`` argument to ``LightCurve.normalize()`` to make it
convenient to obtain a relative light curve in percent (``unit='percent'``),
parts per thousand (``unit='ppt'``) or parts per million (``unit='ppm'``). [591]

- Changed ``LombScarglePeriodogram.from_lightcurve()`` to not normalize the
input light curve by default. [591]

- Changed ``LightCurve.normalize()`` to emit a warning if the light curve
appears to be zero-centered. [589]

- Fixed an issue which caused the search functions to be incompatible with the
latest version of astroquery (v0.3.10). [598]

- Added support for performing mathematical operations involving ``LightCurve``
objects, e.g. two ``LightCurve`` objects can now be added together. [532]

- Updated the online tutorials (https://docs.lightkurve.org/tutorials) to
take all recent Lightkurve API changes into account. [596]

- Changed ``search_targetpixelfile()`` and ``search_lightcurvefile()`` to emit a
helpful warning if an ambigous target identifier is used, i.e. if a number is
entered in the range where the K2 EPIC and TESS TIC catalogs overlap. [558]

- Changed ``TargetPixelFile.plot()`` to always display the cadence number. [562]

- Changed ``TargetPixelFile.interact()`` to store light curves created using the
tool in the ``SAP_FLUX`` column rather than the ``FLUX`` column of the new
light curve file, for consistency with pipeline products. [559]

- Added ``scatter()`` and ``errorbar()`` methods to the ``LightCurveFile`` class
to make it consistent with the ``LightCurve`` class. [382]

- Fixed a bug in ``KeplerTargetPixelFile.from_fits_images()`` to ensure the
correct pixels are selected in cutout mode. [571]

- Fixed a series of minor documentation and code quality issues to enable
Lightkurve to receive the "code quality A" certification by codacy.com.
[557, 560, 564, 565, 566, 568, 573, 574, 575]

==================

- Added the ``lightkurve.seismology`` sub-package which enables quick-look
asteroseismic quantities to be extracted from ``Periodogram`` objects. [496]

- Added the ``stitch()`` method to ``LightCurveCollection`` and ``LightCurveFileCollection``
to enable multi-sector/multi-quarter data to be combined more easily. [548]

- Improved the ``LightCurve.fill_gaps()`` method to fill gaps in a light curve
with Gaussian noise proportional to the light curve's CDPP. [548]

- Added the ``TargetPixelFile.cutout()`` method which enables smaller Target
Pixel Files to be extracted from larger ones. [537]

- Added a ``pld_aperture_mask`` argument to ``PLDCorrector.correct()`` to enable
users to select the pixels used for creating the PLD basis vectors. [523]

- Added a new unit test module (test_synthetic_data.py) which utilizes
synthetic Target Pixel Files to validate Lightkurve features. [534]

- Added extra ``log.debug`` messages to ``lightkurve.search`` to enable users
to track the status of search and download operations. [547]

- Added several new usage examples to the docstrings of functions. [516]

- Removed seven methods which had been deprecated prior to v1.0: [515]
* removed ``lc.cdpp()`` in favor of ``lc.estimate_cdpp()``;
* removed ``lc.correct()`` in favor of ``lc.to_corrector().correct()``;
* removed ``lcf.from_fits()`` in favor of ``lightkurve.open()``;
* removed ``tpf.from_fits()`` in favor of ``lightkurve.open()``;
* removed ``lcf.from_archive()`` in favor of ``search_lightcurvefile()``;
* removed ``tpf.from_archive()`` in favor of ``search_targetpixelfile()``;
* removed ``tpf.centroids()`` in favor of ``tpf.estimate_centroids()``.

- Moved the ``Corrector`` systematics removal classes into their own
sub-package, named ``lightkurve.correctors``. [519]

- Fixed a bug which prevented ``lightkurve.open()`` from raising a
``FileNotFoundError`` when a file does not exist. [540]

- Fixed a bug which caused ``BoxLeastSquaresPeriodogram`` to ignore the
``period`` parameter. [514]

- Fixed a bug which prevented the ``t0`` argument of ``lc.fold()`` from being
an AstroPy Quantity object. [521]

==================

This is a minor bugfix release containing the following improvements:

- Fixed minor bugs in ``PLDCorrector.correct()`` [498],
``TargetPixelFile.create_threshold_mask()`` [502],
and ``LightCurve.bin()`` [503].

- Ensure users are alerted if a large number of cadences are masked out by
``quality_bitmask`` when opening data products. [495]

- ``CBVCorrector`` now accepts a ``KeplerLightCurve`` as input. [504]

- The ``lightkurve.search`` functions now provide a more helpful error message
if the download cache contains a corrupt file. [512]

- Switched continuous integration from Travis/Appveyor to Azure. [497]

==================

This is the first stable release of Lightkurve. It was prepared with the help
of 45 contributors!

This release contains major changes to the ``LombScarglePeriodogram`` class:

- Changed the default behavior of ``LombScarglePeriodogram.from_lightcurve()``
to use ``normalization='amplitude'`` and ``oversample_factor=5`` (the previous
defaults were ``normalization='psd'`` and ``oversample_factor=1``).
The docstring has been expanded to help users understand these options. [491]

- Added a ``LightkurveWarning`` to alert users of the changes to the default
behavior. [493]

- Deprecated the ``min_frequency``/``max_frequency`` arguments in favor of
``minimum_frequency``/``maximum_frequency`` to be consistent with the other
Periodogram classes. [478]

- Likewise, deprecated the ``min_period``/``max_period`` arguments in favor of
``minimum_period``/``maximum_period`` to be consistent with the other
Periodogram classes. [478]

Other changes are:

- Improved ``PLDCorrector`` to be more robust against the presence of NaNs.
[479, 488]

- Improved ``search_tesscut`` to avoid crashing in the event of an empty search
result, and to ensure that the files it returns carry the search string as
the ``targetid`` attribute. [475, 477]

- Various minor bug fixes. [488, 490, 494]