Last week I was gone on a hike! It was wonderful, but as a result, there wasn’t a massive amount of work produced on the project. Before I left however, I briefly began working with the Pleiades magnitude data and created a Delta V vs. (V-K) CMD, shown below.

The (V-K) and V magnitudes were given by the data set. The Delta V values were calculated as the difference between each Pleiades point and the Kamai V vs (V-K) isochrone. Note that Delta V values above 0.375 are excluded as those points are assumed to be binary stars and would be irrelevant for fitting a simple starspot model.

The plot itself does not tell us much on its own, but coming up, I will be working to finding a reasonable range of spot temperatures and filling factors to bound the data. Further out into the future, I would like to create an automated routine to find the best fit parameters. This brute force method will give us a good idea of whether the values the later code returns reasonable values, plus it will cut down run time by allowing us to exclude certain temperature and filling factor ranges. I haven’t looked much into automated fitting functions yet. We’ll see if I can have that done by the end of next week.

I am now to the point where the high resolution magnitude code is implemented and working correctly, meaning that I can create useful CMDs for photometric analysis. The Kepler band is still not available as I have yet to apply/find the zero-point flux to the code, but that has not been a problem yet. Included here is a CMD for V vs. (V-K) as a function of photospheric temperature and fractional spot temperature.

Each color in the gradient represents  the same photospheric temperature range, 7000K to 3200K. The gradient is a range of spot temperatures, fractionally compared to the photo temperature in the legend. The star was modeled with a 30% filling factor. The trends here show that for a cooler spot, the V(mag) is lower and the (V-K) color separation becomes greater. Looking far forward, I will be attempting to find a set of parameters, i.e. spot size and temp, that recreate the data from (Figure 1) from Kevin’s 2016 Pleiades paper, a V(mag) vs. (V-K) diagram for Pleiades members.

 

The past two weeks have been quite productive despite my absence! The first run at creating color magnitude diagram was close to correct, but points showed up around M=-60 for all bands. The incorrect values were due to the units of the Phoenix file, which were not matched with the scale that Dr. Larson had used in here photometry code. To make the simple conversion just about doubled the length of my jupyter notebook, but now that it’s done, the magnitudes are being reported correctly; I confirmed this by checking a temperature spectrum close to that of the Sun. Here is the plot that I ended up with. This was for a temperature of 5800K, as close as I could get to the Sun. The V mag is reported as +4.7, and my value is just below 5! Very close!

Moving forward I am working on adding the SDSS and Kepler bands to the photometry routines. Unfortunately, all of the data corresponding to those bands is on the AB magnitude system rather than Vega, so it will take a little more conversion to bring everything together. After I can create a color magnitude plot from the low resolution routine, I will get the high res working and we can start doing some photometric analysis! We are close!

Note: the low resolution code approximates each filter curve as a normalized box, where the high res will use the real curves. The data will obviously be more accurate once I can use the high resolution, I’m curious to see how much things change.

I’ll be out for a good chunk of this next week, but I’ll still have access to my laptop which I will try and get some work out of while I’m away. The main goal right now is to implement Dr. Larson’s magnitude calculation scripts into my routine, i.e. no more pysynphot, hooray! I spent much of the past week banging my head against the above mention package to no avail, but now I’ve made good progress on creating some cleaner, more organized python notebooks to run the final calculations from. There has been some trouble trying to read functions in from outside files, but I should be able to clear that up soon, or I can just copy the functions into one main file. The Phoenix files do not have linearly spaced wavelength points, I was able to change that so now the data will be compatible with Dr. Larson’s code. And again, always more to read!

Week one has been spent getting myself oriented in my project and setting up the necessary accounts and folders to work with. I’ve read a few papers on photometry to gain a better understanding of the filters I’ll be using to analyze the Phoenix spectra, which has gone well so far, but I wouldn’t consider myself an expert yet. Working in my Jupyter notebook, I have been able to create a function to read in a data file from the Phoenix collection, as well as model a spotted star with a certain filling factor (see figure below).

The figure here is the modeled spectra from the python routine, photospheric and spot temperatures and the filling factor are given in the legend. Later in the week I was allowed access in to Jim’s GitHub repository for the starspot project and was able to tick off the above mentioned work from the to-do list.

Things to do for the next week: read and re-read the photometry related papers; look more into pysysphot for synthetic photometry on our Phoenix spectra, eventually be able to load the correct bandpass filter and spectra (including spotted stars) and create a magnitude vs wavelength plot; extend that routine to return spectra through all useful filters.

Just a quick test to see that everything is working. I’m excited to start my research project!