mult_ephem_RR-Lyr.ipynb

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   "source": [
    "# RR Lyrae\n",
    "\n",
    "[RR Lyrae](https://en.wikipedia.org/wiki/RR_Lyrae) is the prototype of a class of variable stars with radial pulsations. The pulsation period is related to the stellar luminosity, and a second, lower frequency variation can be seen on longer timescales, known as the [Blazkho effect](https://en.wikipedia.org/wiki/Blazhko_effect). \n",
    "\n",
    "* **Last Updated**: August 21, 2024\n",
    "* **lcviz version**: 0.4.2\n",
    "\n",
    "RR Lyrae itself was in the Kepler field, so let's load one Kepler Quarter of long-cadence observations, and inspect the periods:"
   ]
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  {
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   "source": [
    "import astropy.units as u\n",
    "from astropy.time import Time\n",
    "from lightkurve import search_lightcurve\n",
    "\n",
    "from lcviz import LCviz\n",
    "\n",
    "# Download three quarters of long cadence observations from Kepler:\n",
    "lc = search_lightcurve(\n",
    "    target=\"RR Lyra\", \n",
    "    mission=\"Kepler\", \n",
    "    quarter=2, \n",
    "    cadence=\"long\", \n",
    "    author=\"Kepler\"\n",
    ").download_all().stitch(\n",
    "    # stitch together the quarters after normalizing each one:\n",
    "    lambda x: x.normalize()\n",
    ")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "74d491b0-b59f-43bb-b24b-ba530d1185bb",
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   "source": [
    "Now we'll start `LCviz`:"
   ]
  },
  {
   "cell_type": "code",
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   "source": [
    "lcviz = LCviz()\n",
    "\n",
    "lcviz.load_data(lc)\n",
    "\n",
    "# we'll make use of these plugins later:\n",
    "eph = lcviz.plugins['Ephemeris']\n",
    "plot_options = lcviz.plugins['Plot Options']\n",
    "freq_analysis = lcviz.plugins['Frequency Analysis']\n",
    "freq_analysis.auto_range = False\n",
    "freq_analysis.xunit = 'period'\n",
    "\n",
    "lcviz.show()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ab983eb0-6da0-45ee-a343-edfa1155f384",
   "metadata": {},
   "source": [
    "Compute the peak power at periods near 13 hours using the `Frequency Analysis` plugin, and use the `Ephemeris` plugin to add a new viewer that's phase-folded at the pulsation period:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "17261527-c741-4cc7-a08c-4df10a9daef6",
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   "source": [
    "# compute pulsation period:\n",
    "freq_analysis.minimum = 0.1\n",
    "freq_analysis.maximum = 1.0\n",
    "ls = freq_analysis.periodogram\n",
    "period_pulsation = 1 / ls.frequency[ls.power.argmax()]\n",
    "\n",
    "# update Ephemeris:\n",
    "eph.rename_component('default', 'pulsation')\n",
    "eph.period = period_pulsation.to_value(u.d)\n",
    "eph.t0 = 0.26\n",
    "\n",
    "print(f\"Pulsation period: {period_pulsation:.3f}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "d0132512-d62e-45bb-9b25-61d9e3664f45",
   "metadata": {},
   "source": [
    "Compute the peak power at periods near 36 days using the `Frequency Analysis` plugin, and add an `Ephemeris` component for the Blazkho effect:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2bcb8d93-e9d0-4219-9539-d797099a172d",
   "metadata": {
    "tags": []
   },
   "outputs": [],
   "source": [
    "# compute Blazkho period:\n",
    "freq_analysis.minimum = 20.0\n",
    "freq_analysis.maximum = 55.0\n",
    "ls = freq_analysis.periodogram\n",
    "period_blazkho = 1 / ls.frequency[ls.power.argmax()]\n",
    "\n",
    "# update Ephemeris:\n",
    "eph.add_component('blazkho')\n",
    "eph.period = period_blazkho.to_value(u.d)\n",
    "eph.t0 = 23\n",
    "\n",
    "print(f\"Blazkho period: {period_blazkho:.3f}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "087ffb91-d24e-49e7-ba9a-14c6df0510ce",
   "metadata": {},
   "source": [
    "Color each point in the light curve in each viewer by the phase of the Blazkho effect, using the `Plot Options` plugin:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "39108e3e-b84c-4c21-9861-007f3a0ab2da",
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   "source": [
    "for viewer in plot_options.viewer.choices:\n",
    "    plot_options.viewer = viewer\n",
    "    plot_options.marker_color_mode = 'Linear'\n",
    "    plot_options.marker_colormap = 'Viridis'\n",
    "    plot_options.marker_color_col = 'phase:blazkho'"
   ]
  },
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   "execution_count": null,
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   "source": []
  }
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