blog_log#11

I’m so sorry

Something struck me in the rear

I just ended up here

— Sokka

This week has been decently productive, it is indeed coming together in a inexplicably short amount of time. On the analysis side i’ve been mostly trying to chug out my analysis plots, namely the R and I band rotation period vs mass plot. Which I have produced! But let me not get ahead of myself. It could not have been done without some wrestling of lightcurves. I inspected the periods of each of the targets that I had masses from for the TESS input table and tried to weed out those that were in the noise if there was a peak of considerable amplitude at longer periods, and folded the data over that period to do a “chi-by-eye” goodness of fit assessment on the new period. If I liked what I saw I edited the period I had recorded. I did this seperatley for each band, not looking at the results from the other band so I could refrain from becoming bias and trying to match them up intentionally. This was the result I produced:

The blue points are indeed on the graph. The periods are just so similar the data are on top of one another. I prevented bias is every way I could. I in no way had the periods of the targets in my head of either band while doing the other. This was the result of my determination of the periods independently. I had reported last week that the best periods were different from one another, but since then the result has improved after I went through and determined the new best periods. Next steps for analysis is making this plot for the brown dwarf targets, and then making other calculations for analysis plots such as percentage amplitude change, which I think i will simply determine to be the amplitude of the LS model. I think this is the least expensive in terms of time and should be simple enough to put together. I’d also like to make a R-I vs. time plot for my targets, as well as compare my data with Cassidy and hopefully combine our data and make more comprehensive plots of what I’ve just discussed above.

I decided to take a closer look at the abstract and intro of this paper: https://arxiv.org/pdf/2002.09135.pdf

I’ve kind of been focused on this paper the whole semester because the author has a similar scientific motivation behind their data and their purpose for it. The methods are similar as they also use differential photometry and periodograms to measure periods. Some of my notes on the background that I’d like to remember for the presentaion are as follows:

• Young stars are born very active and thus variable. We look at object on their surface such as sunspots which is also an indicator of the stars variability as they arise from magnetic activity around the star.
• Skumanich 1972 find that Ca II H & K line intensities decay as t^1/2
• Photospheric activity has been able to be observed with a higher fidelidty since then with the Kepler K2 and TESS space telescope missions
• They take data from these missions to measure clusters of different ages to see how properties like rotation period depend on stellar lifetime
• The smoothed amplitude is a quantity derived from difference of the max and minimum of the phase-folded lightcurve (after a gaussian kernel is applied). –>We will use a quantity like this for our analysis.
• Morris 202 finds that stars become less variable as they get older. As well as targets in older fields have a longer rotation period on average.
• Must consider that a single lightcurve can be produced by a myriad of models. The group puts it nicely in their own words so I’ll quote them: ” (1) that stars of similar age, mass, and rotation period should have similar spot distributions; and (2) the inclination angles of stars are nearly randomly distributed as observed from Earth. If these assumptions are true, then an ensemble of light curves of stars in a young cluster can be used to constrain their spot distributions.” (we cannot make these assumptions of the TESS data.

In terms of the presentaion what i’ve been doing is trying to boil down our text blocks into digestable bullet points, and making it look aesthetically pleasing. This is what I have so far for the first section:

Motivation: 

• Detecting variable low-mass stars (masses) and brown dwarfs (masses) in the Praesepe field in order to characterize relationships between stellar mass, age, variability, and rotation period. 
• (things) like these have been explored in the past by groups such as BLAH, BLAH for objects in the intermediate (solar) and high mass regimes. It is still unclear weather these relationships extend down to the lower mass regime
• We explore (name) R and I band in order to measure variable targets in fields of differing ages: the Praesepe star forming region in the Beehive Cluster, and objects encompassed in the TESS BD-21 scan conducted in January/February of this year

It is difficult trying to pin down what should be on the poster and what shouldn’t. It is valuable real estate that we can’t really afford to be generous with. I’d also like to move away from the more traditional headers, so that the poster can be more digestable as a whole. The feedback was very thorough so I think chugging through that is a good gameplan for now.

Scratch that plot from the beginging, I was doing something silly. Here is prot v. m for I band m-dwarfs:

Although not completely disheartening it is still not as gorgeous as the result before. I was plotting it such that the data was sorted and it would naturally plot that way, now i have adjusted it. I am making fixes R-band now but I think my computer has been working hard for too long because Jupyter notebooks is getting confused.

Until next time.