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Can someone tell me how I can find the star brightness data to study exoplanet using transit method? The file should be in comma separated value (CSV) format or any other formats that can be latter converted to that format.

The following sample data shows the star brightness along with time. By using this data we can plot the transit curve. I want such over of data for actual star:

![Table](https://i.stack.imgur.com/O8SxG.jpg)

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    $\begingroup$ Welcome to astronomy SE! As you probably know from How to Ask, it would be good if you shared what research you did so far. In addition to that, the current formulation sounds rather demanding and could be put in friendlier words, I guess. I am happy to retract my down- and/or my close-vote if you edit your question a bit. $\endgroup$
    – B--rian
    Jun 16, 2021 at 8:23
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    $\begingroup$ @B--rian Research in this particular case can't be quite done easily. Do you want him to add "I did some googling"? Because the research can't be quite explained here like that: "First, I googled 'exoplanet archive'. Then I tried with 'exoplanets data'..." $\endgroup$
    – User123
    Jun 16, 2021 at 14:01
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    $\begingroup$ @B--rian Actually I'm in my final year of M.Sc. and wanted to do my dissertation on exoplanets. I know most of all the theory but the thing is I can't find the data. I know about NASA Exoplanet Archive, but don't know how to use it. What type of data I need is that the brightness of host star vs time. So I can use the data to create a python code and make transit curve. And same thing for Radial velocity. $\endgroup$
    – Priyash Mistry
    Jun 16, 2021 at 15:35
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    $\begingroup$ Are you aware of simbad.u-strasbg.fr/simbad ? All these comments show though, that your question shows quite a lack of explaining your question and your own research on the question - and more important: make clear what you really need $\endgroup$
    – planetmaker
    Jun 16, 2021 at 16:33
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    $\begingroup$ For the brightest apparent host stars you can obtain a data series even yourself with amateur equipment. With a 20cm telescope and even a reasonable camera you can get a light curve for those stars to analyse. It's a nice practical student exercise on the topic. $\endgroup$
    – planetmaker
    Jun 17, 2021 at 11:36

1 Answer 1

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I don't know of a source for the CSV data directly but if you are OK with a little bit of Python, this can be done with the NASA Exoplanet Archive. Looking at one famous example (HD 189733b), if you do a search for this object on the front page it should bring you to a page of detailed information and links to datasets. Expanding the 'Ancillary Information' section will show the links for the data (this link should be equivalent)

The data files are in IPAC table format but this is easily readable by AstroPy's Table class. A short example of this is below:

from astropy.table import Table
import matplotlib.pyplot as plt

# Read photometric table
phot_table = Table.read("https://exoplanetarchive.ipac.caltech.edu/data/ExoData/0098/0098505/data/UID_0098505_PLC_025.tbl", format="ipac")

# Subtract off integer part of first JD to make plotting easier
t0 = int(phot_table['HJD'][0])

plt.figure()
plt.errorbar(phot_table['HJD']-t0, phot_table['Relative_Flux'], yerr=phot_table['Relative_Flux_Uncertainty'], color='r', fmt="+", capsize=3)
plt.minorticks_on()
plt.xlabel('HJD-{:.1f} [days]'.format(t0))
plt.ylabel("Relative Flux") 
plt.title("HD 189733b Transit Light Curve")
plt.savefig("transit_lc.png")

# Read radial velocity data
rv_table = Table.read("https://exoplanetarchive.ipac.caltech.edu/data/ExoData/0098/0098505/data/UID_0098505_RVC_001.tbl", format="ipac")
t0 = int(rv_table['JD'][0])

plt.clf()
plt.errorbar(rv_table['JD']-t0, rv_table['Radial_Velocity'], yerr=rv_table['Radial_Velocity_Uncertainty'], color='r', fmt='+')
# Zoom in on one of the nights where Rossiter_McLaughlin effect was being measured
plt.xlim(395.45, 395.70)
plt.minorticks_on()
plt.xlabel('JD-{:.1f} [days]'.format(t0))
plt.ylabel('Radial Velocity [m/s]')
plt.title("HD 189733b Radial Velocity Curve")
plt.savefig("transit_rv.png")

# Example export to CSV format
rv_table.write("transit_RV.csv", format='csv')

Lightcurve of HD 189733b (from Winn et al. 2007) Radial velocity curve of HD189733b (from Triaud et al. 2009)

The top part of the exported CSV file looks like:

JD,Radial_Velocity,Radial_Velocity_Uncertainty
2453946.612661,-2167.93,0.89
2453946.620219,-2155.63,0.85
2453946.627291,-2142.88,0.78

if this is easier for further analysis.

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  • $\begingroup$ Amazing job! Thansk so much for your effort! $\endgroup$
    – B--rian
    Jun 18, 2021 at 11:43
  • $\begingroup$ No problem, I used to work on these in an earlier stage of my career (WASP-16b is "my" exoplanet...); hopefully it's helpful to the OP $\endgroup$
    – astrosnapper
    Jun 18, 2021 at 16:40
  • $\begingroup$ I don't think it's appropriate for me to suggest research topics to you, particularly if it's part of a formal qualification (if this was for general background information or self-learning it might be different). This is something that needs to be agreed after consultation with your supervisor or other faculty at your institution if there are issues with your relationship with your supervisor. $\endgroup$
    – astrosnapper
    Jun 18, 2021 at 19:29
  • $\begingroup$ Possible but very unlikely - I certainly wouldn't bet a dissertation on it... Those archives are meant as repositories of the final published details of the planet and star parameters so the data has been well looked at by the original authors. While it may in theory be possible to find e.g. a long-term trend in a RV curve of a published planet, indicating a longer period planet, the RV team likely knows about it too and are getting extra data. Could also be new transits in an existing lc but again not very likely. Need to look at lots of data in new ways e.g. PlanetHunters-TESS to find a few. $\endgroup$
    – astrosnapper
    Jun 21, 2021 at 16:30

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