Adding JOSS paper

docs/paper.bib

@@ -0,0 +1,71 @@
+@ARTICLE{Astropy:2018,
+   author = {{Astropy Collaboration} and {Price-Whelan}, A.~M. and {Sip{\H o}cz}, B.~M. and
+	{G{\"u}nther}, H.~M. and {Lim}, P.~L. and {Crawford}, S.~M. and
+	{Conseil}, S. and {Shupe}, D.~L. and {Craig}, M.~W. and {Dencheva}, N. and
+	{Ginsburg}, A. and {VanderPlas}, J.~T. and {Bradley}, L.~D. and
+	{P{\'e}rez-Su{\'a}rez}, D. and {de Val-Borro}, M. and {Aldcroft}, T.~L. and
+	{Cruz}, K.~L. and {Robitaille}, T.~P. and {Tollerud}, E.~J. and
+	{Ardelean}, C. and {Babej}, T. and {Bach}, Y.~P. and {Bachetti}, M. and
+	{Bakanov}, A.~V. and {Bamford}, S.~P. and {Barentsen}, G. and
+	{Barmby}, P. and {Baumbach}, A. and {Berry}, K.~L. and {Biscani}, F. and
+	{Boquien}, M. and {Bostroem}, K.~A. and {Bouma}, L.~G. and {Brammer}, G.~B. and
+	{Bray}, E.~M. and {Breytenbach}, H. and {Buddelmeijer}, H. and
+	{Burke}, D.~J. and {Calderone}, G. and {Cano Rodr{\'{\i}}guez}, J.~L. and
+	{Cara}, M. and {Cardoso}, J.~V.~M. and {Cheedella}, S. and {Copin}, Y. and
+	{Corrales}, L. and {Crichton}, D. and {D'Avella}, D. and {Deil}, C. and
+	{Depagne}, {\'E}. and {Dietrich}, J.~P. and {Donath}, A. and
+	{Droettboom}, M. and {Earl}, N. and {Erben}, T. and {Fabbro}, S. and
+	{Ferreira}, L.~A. and {Finethy}, T. and {Fox}, R.~T. and {Garrison}, L.~H. and
+	{Gibbons}, S.~L.~J. and {Goldstein}, D.~A. and {Gommers}, R. and
+	{Greco}, J.~P. and {Greenfield}, P. and {Groener}, A.~M. and
+	{Grollier}, F. and {Hagen}, A. and {Hirst}, P. and {Homeier}, D. and
+	{Horton}, A.~J. and {Hosseinzadeh}, G. and {Hu}, L. and {Hunkeler}, J.~S. and
+	{Ivezi{\'c}}, {\v Z}. and {Jain}, A. and {Jenness}, T. and {Kanarek}, G. and
+	{Kendrew}, S. and {Kern}, N.~S. and {Kerzendorf}, W.~E. and
+	{Khvalko}, A. and {King}, J. and {Kirkby}, D. and {Kulkarni}, A.~M. and
+	{Kumar}, A. and {Lee}, A. and {Lenz}, D. and {Littlefair}, S.~P. and
+	{Ma}, Z. and {Macleod}, D.~M. and {Mastropietro}, M. and {McCully}, C. and
+	{Montagnac}, S. and {Morris}, B.~M. and {Mueller}, M. and {Mumford}, S.~J. and
+	{Muna}, D. and {Murphy}, N.~A. and {Nelson}, S. and {Nguyen}, G.~H. and
+	{Ninan}, J.~P. and {N{\"o}the}, M. and {Ogaz}, S. and {Oh}, S. and
+	{Parejko}, J.~K. and {Parley}, N. and {Pascual}, S. and {Patil}, R. and
+	{Patil}, A.~A. and {Plunkett}, A.~L. and {Prochaska}, J.~X. and
+	{Rastogi}, T. and {Reddy Janga}, V. and {Sabater}, J. and {Sakurikar}, P. and
+	{Seifert}, M. and {Sherbert}, L.~E. and {Sherwood-Taylor}, H. and
+	{Shih}, A.~Y. and {Sick}, J. and {Silbiger}, M.~T. and {Singanamalla}, S. and
+	{Singer}, L.~P. and {Sladen}, P.~H. and {Sooley}, K.~A. and
+	{Sornarajah}, S. and {Streicher}, O. and {Teuben}, P. and {Thomas}, S.~W. and
+	{Tremblay}, G.~R. and {Turner}, J.~E.~H. and {Terr{\'o}n}, V. and
+	{van Kerkwijk}, M.~H. and {de la Vega}, A. and {Watkins}, L.~L. and
+	{Weaver}, B.~A. and {Whitmore}, J.~B. and {Woillez}, J. and
+	{Zabalza}, V. and {Astropy Contributors}},
+    title = "{The Astropy Project: Building an Open-science Project and Status of the v2.0 Core Package}",
+  journal = {\aj},
+archivePrefix = "arXiv",
+   eprint = {1801.02634},
+ primaryClass = "astro-ph.IM",
+ keywords = {methods: data analysis, methods: miscellaneous, methods: statistical, reference systems },
+     year = 2018,
+    month = sep,
+   volume = 156,
+      eid = {123},
+    pages = {123},
+      doi = {10.3847/1538-3881/aabc4f},
+   adsurl = {http://adsabs.harvard.edu/abs/2018AJ....156..123A},
+  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
+}
+
+@ARTICLE{Numpy:2011,
+author={S. {van der Walt} and S. C. {Colbert} and G. {Varoquaux}},
+journal={Computing in Science Engineering},
+title={The NumPy Array: A Structure for Efficient Numerical Computation},
+year={2011},
+volume={13},
+number={2},
+pages={22-30},
+keywords={data structures;high level languages;mathematics computing;numerical analysis;numerical computation;numpy array;numerical data;high level language;Python programming language;Arrays;Numerical analysis;Performance evaluation;Computational efficiency;Finite element methods;Vector quantization;Resource management;Python;NumPy;scientific programming;numerical computations;programming libraries},
+doi={10.1109/MCSE.2011.37},
+ISSN={1558-366X},
+month={March}
+}
+

docs/paper.md

@@ -0,0 +1,51 @@
+---
+title: 'linea: Fast linear detrending for CHEOPS photometry'
+tags:
+  - Python
+  - astronomy
+  - photometry
+authors:
+  - name: Brett M. Morris
+    orcid: 0000-0003-2528-3409
+    affiliation: "1"
+affiliations:
+ - name: Center for Space and Habitability, University of Bern, 
+         Gesellschaftsstrasse 6, CH-3012, Bern, Switzerland
+   index: 1
+date: 18 June 2020
+bibliography: paper.bib
+---
+
+# Summary
+
+The CHaracterizing ExOPlanets Satellite (CHEOPS) is a 30 cm telescope in orbit 
+around the Earth, which seeks to measure properties of exoplanets using 
+photometry, or brightness measurements of the planets and their host stars. The
+photometry collected with CHEOPS arrives on users machines in the form of FITS 
+files which contain photometry that inevitably contains trends as a function of 
+several variables; for example, the photometry is often covariant with the 
+stellar centroid position on the detector, the roll angle of the spacecraft, 
+the flux of contaminants within the aperture, the background and the 
+dark current.
+
+We present ``linea``, a linear detrending toolkit for CHEOPS photometry.  
+``linea`` features an efficient ``numpy`` implementation of linear least-squares 
+regression [@Numpy:2011] which can be used to quickly remove trends from CHEOPS
+photometry. The core principle of ``linea`` is that the vector of observed 
+fluxes observed by CHEOPS can be represented by a linear combination of some 
+observational vectors, like the roll angle and stellar centroid position. 
+
+The ``linea`` API has handy classes and methods for reading in the output files 
+produced by the CHEOPS Data Reduction Pipeline (DRP), assembling a design matrix
+of the housekeeping vectors, regressing the design matrix against the observed
+fluxes, and visualizing the results. We built-in two realistic, simulated 
+example light curves and tutorials on how to detrend them including the phase 
+curve of 55 Cnc e and four eclipses of WASP-189 b.
+
+The mathematical formalism of the ``linea`` algorithms are detailed in the 
+software's documentation. The ``linea`` package is built on the ``astropy`` 
+package template [@Astropy:2018]. ``linea`` is open source and contributions are
+welcome.
+
+# References
+

linea/core.py

@@ -379,8 +379,13 @@ def concatenate(self):
         extra_attrs = ['time', 'mask']
         c = namedtuple('ConcatenatedLightCurve', self.attrs + extra_attrs)
         for attr in self.attrs + extra_attrs:
-            setattr(c, attr, np.concatenate([getattr(lc, attr)
-                                             for lc in self]))
+            if attr is not 'time':
+                setattr(c, attr, np.concatenate([getattr(lc, attr)
+                                                 for lc in self]))
+            else:
+                setattr(c, attr, Time(np.concatenate([getattr(lc, attr).jd
+                                                      for lc in self]),
+                                      format='jd'))
         return c
 
     def _pad_shapes(self):