Wednesday, August 10, 2011

Finally was able to put together and show my data in a more effective way.
I reorganized my code so that for all the samples that I considered to be active, four plots will be created, 1) Ha equivalent widths vs. time of exposure, 2) Ha equivalent widths vs. adjusted dM radial velocity, 3) adjusted dM radial velocity vs. time of exposure, and 4) spectra for each exposure in Ha emission region.


I like this one because it illustrates the benefits of having multiple exposures. You can also see the hint of periodic motion. I was pleased that most of the samples that I have singled out have had periodic motion. I didn't have a lot of time to prepare before group meeting, so I quickly just printed out a few of the ones at the beginning of my file.

With just a couple more days at the office, there are a few important things that MUST get done:

- create read me file (and put code that is useful/important in one directory that is easily accessible)
- go through important codes and more thoroughly comment on it
- put all calculated data into a structure
- finish latex document (so far it looks good - just need to write up about the last few weeks)
- pull out nice plots that I would want to use in my poster for the KINSC symposium
- write up summary for KINSC Summer Stipend and submit it
- write up abstract for KINSC Research Symposium and submit it

Had our last group meeting today. Andrew mentioned about a paper he just read that looked at a sample that is similar to Dylan's with multiple exposure spectra and analyzed "fractional variability" of Ha emission over time (apparently it's pretty much the same across early and late types). They determined that around 6 hours or so is enough time to determine the variability of the Ha emission for these stars. Pretty interesting considering that our spectra is taken over about an hour or so. Anyways, I'm glad I had some plots to show, but wish I had more time to pick some cool ones.

Monday, August 8, 2011

I spent the past couple of days reworking my code so that I would be able to more easily sort out the active binaries in my sample.

From West, et al (2011), active is defined as where:
- equivalent width is greater than .75 Angstroms
- s/n is greater than 3
- height of spectral line is greater than 3x noise

One of the great things about the data set that I'm working with, is that is has a time component; for fast binaries, from exposure to exposure, we can see a difference in the Ha emissions for the M dwarfs.

To illustrate this, I went through the spectra of the samples that had been categorized as active, and if they had velocity shifts of about 30 km/s over the course of their exposures, I would then make two plots. 1) equivalent width vs. time difference b/w exposures, and 2) equivalent width vs. dM radial velocity.


It's been pretty slow going, but I think I'm finally getting somewhere.

I ran into a little problem with the the time listed for some of my exposures. A few of the times listed for each exposure have been rounded, causing small errors in the time exposure of each sample. I think I have it figured out, but will finish fixing it up tomorrow.

I also have to start wrapping up my work. This week is my last week here in Boston at the West lab.

Things that MUST get done by the end of the week:
-short summary for KINSC
-poster for symposium
-write-up for records
-categorize/organize directories

Wednesday, August 3, 2011

very productive day!

I feel like I accomplished so much today (finally!)

I started out the morning working on my error calculation for my equivalent widths. After writing out a long code, I realized that I didn't need to do this by hand and that I could just use TSUM with my flux error array and go from there. After that it wasn't too difficult, and my values look pretty reasonable.

I moved on to recreate a plot that Dylan has for his sample. It's a plot of activity vs. separation as seen in log-log space, with activity being measured through Lbol/LHa. In order to do this, I needed to calculate Lbol/LHa, and go back and fix my pesky separation calculation.

Also team West dinner at Andrew's tonight. So excited!

Tuesday, August 2, 2011

It's been a while since I last posted, so I'm going to have to recap.

My equivalent widths are finally figured out. I made a lot of plots last week that are currently kind of wonky, but once I update them with my new equivalent widths, I think we'll see some really cool plots. I also reformatted my code to now take into account the s/n ratios for both continuum A and B and to take into account the 3x noise level that is necessary to be considered active. Dylan helped me out this afternoon (issues with some of my splining with the redder ends of my spectra) and now my spectra have clearer H alpha regions. YES!

Cool trick I learned: If you want to just click through multiple plots, put this in you plotting code:
cursor, x, y, /down

On a super cool note, I may be writing up something for Dylan's upcoming paper. So exciting!

Monday, July 25, 2011

Equivalent Widths -- Error calculations and more!

I worked on my equivalent width errors -- still really high, but consulted with Jan Marie who had a similar issue. I redid the calculation and they look much better. I went back to my equivalent widths and widened my area around the H alpha emission region to be 10 Angstroms. Plotted the spectra from 6500-6000 Angstroms and then overplotted the selected range around the H alpha region. At first it looked a little wonky (hence enlarging the region). But now it looks really good, and even for the spectra that look like they have a strong H alpha region, the calculation still seems to underestimate the EW. Currently fixing that problem.

After I fix that, on to plotting the the equivalent widths vs. spectral type. There are two plots that I hope to make by Wednesday afternoon. 1) Mean EW per spectral type vs. spectral type, and 2) fraction of active binaries vs. spectral type. In order to do this second plot (and also for just good measure), I need to determine sigma for my equivalent widths (...and then make a histogram and calculate sigma). I was having trouble with the plothist procedure -- it says that one of the called procedures doesn't exist in my library. I downloaded it and put it in the right folder, but it still isn't working so well. I'll check further into it by tomorrow.

BUT this means that I need to get my EW calculation figured out.

Red Sox game tonight!

Friday, July 22, 2011

review of the day

-Worked on error calculation for equivalent widths -- currently have it written up, and in the middle of implementing it into my code. Need to check on error calculation when dividing by constants.
-Fixed equivalent widths -- took into account dM radial velocity and thereby shifted H alpha region over
-Worked on separation calculation - check with Dylan on monday

Thursday, July 21, 2011

...and I made possibly the most stupid mistake I've made in a very long time.

Binary separation should be the same for each pair (duh). My calculation does not show that. Not quite sure how this went by me at first, but it did.

I also corrected my equivalent width calculation.

Here are some plots that I made that show a possible correlation between equivalent width along with the velocities at each exposure.

Wednesday, July 20, 2011

separation and H alpha calculations

I worked on a separation calculation for the binaries today. In order to make sure that I was getting reasonable answers, I pulled out the separation values that Dylan calculated. I spent a while making sure that my values were reasonable - this included attempting to make a histogram. Because some of dylan's values were put in as INF, I ran into some issues, so I ended up just looking at medians of each. Median of calculated separation values = .28 AU, median of dylan's =.49 AU and median difference between Dylan and my calculation separation= .0037 in AU.

Also worked on calculating equivalent widths for H alpha. I chose to look at flux values between 6560 and 6565 Angstroms. Instead of calculating my own area underneath the spectra, I decided to go for the simpler option and use tsum. Looks a little high, but I don't have a real sense of high and low values. Looking through old West papers to get a better idea. Added equivalent width to my huge table.

Tuesday, July 19, 2011

I started the morning by reworking my system velocity calculation. Redid it and checked in with Dylan to see what he thought. He said it looked good, so I went on to make lots of plots.

The rest of the day was spent going through Dylan's sample and making plots of interesting looking binaries. Usually this included plotting up dM velocity-system velocity vs. WD velocity-system velocity and also time vs. both corrected velocities. Looking for fast samples, and good sig-to-noise ratios. Also re-ran sample to have a better formatted output table.


Monday, July 18, 2011

So I adjusted my velocity plots in order to take into account the system velocity. They look TOO good, so things that I have to do next:

-consult how Dylan calculate his system velocities
-plot time vs. M dwarf velocity
-check out spec types (earlier M dwarf types should be closer)

Friday, July 15, 2011

Great end to the week

Recap of this week:

-Calculated the radial velocities of the WDs in the first sample of dM+WD binaries
-Calculated system velocity of these binaries, and made sure that it was reasonable (after going back and being a little more stringent on my boundaries for signal-to-noise ratios and velocity limits, sigma ends up being a little less than 20 km/s)

-Applied this code to new sample of binaries from Dylan. I now have a file that has plate, mjd, fiber, dM rv, WD rv, system v, # expos, sig-to-noise and time (days/hours/min/sec).

Excited to go through the sample and have a closer look at some interesting pairs, especially considering that this sample has a much higher average number of exposures for each pair. I'd especially like to analyze some very fast binaries and plot out their radial velocities to see if we can get an idea of their orbits.

I started going through the data at the end of the day. Things I looked for: lots of exposures, good quality spectra (higher stns), relatively okay sounding velocities. I then plotted some up just for fun. Here's an example:

I wish I had more time in the day (have to catch a train in an hour), but really excited about continuing with this. What a wonderful way to end the week!

While I was waiting for the sample to run, I was reading Astrobites and and saw this quote by Ed Salpeter about finding the type of research that fits you best:

"For my scientific temperament I needed a field that was more controversial, more open-ended and new, where quick was useful and sloppy did not matter too much because it would all change soon anyway"

I think this is a really nice quote. One of the major reasons I was drawn to astronomy is that sense of urgency behind it all; right now we're at the time where our technology and scientific methods are catching up to each other, and that's extremely exciting place to be. It was nice to read this quote and see that sentiment reflected in someone who has experienced so much in astronomy.

All in all, a great way to end the week.

Thursday, July 14, 2011

It's been a slightly upsetting afternoon. I've been working on applying my code to Dylan's new sample of binaries, but I keep running into issues. I carefully mimicked my previous code in order to avoid obvious errors (i.e. different file names, etc.) but I've having some more serious issues, such as reading some of my fits files. Dylan had to go through my program yesterday in order to update it - hopefully this isn't the source of my problems, but it is something I have to more closely investigate. I also just feel like I'm not moving through this as efficiently as I should be. I was hoping to get this done by early afternoon so I could move onto looking at interesting objects (i.e. fast binaries), but it looks like I will spend the rest of the afternoon debugging. Ah well.

Wednesday, July 13, 2011

After toying around with my histogram a little bit more, I went ahead and calculated sigma. Assuming that it was (relatively) gaussian, I was able to use the FWHM in order to calculate sigma. FWHM roughly equals 2.356 sigma, giving me a sigma of roughly 10.187. Which is reasonable!

Tuesday, July 12, 2011

I've spent the entire day working on this histogram. It looked pretty funky at first, with a lot of outliers. I've designed it so that I can easily put in different constraints. At the moment, I've been getting rid of spectra that have a signal-to-noise ratio that is smaller than 10, and if either the velocity of the white dwarf or M dwarf is above an absolute value of 600 km/s (also another indicator of crappy data). So far it has been kind of frustrating. Hopefully by the end of the day, my histogram will look a little better.

Monday, July 11, 2011

on to system velocities

After calculating my WD radial velocities, I moved on to calculating the system velocities of each of the binaries. The values seemed to range from reasonable for some of the binaries, to super weird for others. I compared my values to the ones that Dylan worked with, and some of them seem to be an average of the system velocities for the multiple exposures. In order to better gauge my error, I'm going to make a histogram of the differences of the system velocities between each exposure.

Friday, July 8, 2011

velocity shifts calculated for WDs!

Rather than using the system velocity that Dylan has already calculated, I instead applied the velocity shift calculation that I used for the M dwarfs to the white dwarfs in the binaries.

When I first approached this, I said to myself "This will be easy! I already did this for the M dwarfs." But reading in a different type of spectra file, and dealing with my bazillion indices in order for everything to align properly, along with formatting everything into a neat table caused it to ta
ke the better part of the day. It also took me a little to get back into the coding mindset -- but considering I was away for a couple of weeks, it was pretty easy getting back to it.

Applying my code to the WDs also got me prepared to apply it to new samples that Dylan will have for me shortly.

Here is a sample of the shift calculation
using the same binary as the one previously posted. The shift isn't as accurate as for the M dwarf, but this might just be on account of the accuracy of the WDs in general.

Goal for next week: Calculate the system's velocity. Hopefully I will have it in time for group meetings.

It feels so good to be back in the lab!

back to work!

After a wonderful holiday, it's time to get back to the lab! Things to do today:

-read back over orbital velocity calculation steps
-calculate orbital velocity!

It's been a while since I've looked at code. Hopefully all will go well.

Friday, June 17, 2011

Summary of Work So Far:


May 28-June 17

My research so far has focused on calculating the velocities of single M dwarfs and M dwarfs in binary pairs.

This summer I am researching the velocities of close binary pairs. From SDSS, we have spectral data on these binaries for multiple exposures. Because the binary pairs that we’re examining are so close together and moving so quickly, in each exposure taken (which can be over a couple of hours), the binaries may have moved causing its spectrum to be redshifted.Using these SDSS exposures and previously compiled templates for each spectral type, we can actually calculate the velocity of these binary pairs. At this point in my research, I have calculated the velocities of over 4,000 M dwarfs that are in M dwarf and white dwarf binary pairs.

Getting Background Information

For some background information, I read and took notes on Silverstri et al (2005), West et al (2008), West et al (2011), and Hilton et al (2010). Also read the chapter “Stellar Activity” in the Textbook New Light on Dark Stars: Red Dwarfs, Low-Mass stars, Brown Dwarfs by Reid and Hawley. After doing this, I worked on some calculations on deriving velocity from wavelength change (Doppler shifts), and also the relationship between mass, separation, and velocity of binaries.

Calculating the velocities of M dwarfs in DR7 Catalogue

The first velocity calculation included calculating the velocities for the M dwarfs listed in AAW’s DR7 Catalogue. Using Doppler shifting techniques, we are able to calculate the velocities of M dwarfs from their spectra. Each binary is catalogued by plate, mjd, and fiber.Plate is the plug plate used, mjd is the mean julian time, which records the time that the exposure was taken, and fiber is the fiber number. In order to calculate a velocity of one of these dwarfs, we had to match spectral templates to the DR7 spectra. In order to normalize them, we zoomed into a flat area of the spectrum between 7300 and 8800 Angstrom and took the average over that region. We then divided the total flux by that average in order to normalize the spectrum. We did the same for the template spectra. Because there aren’t the same number of data points in the template and the DR7 spectra, we had to use the spline function in order to interpolate points in the DR7 spectra. Because we were going to apply this same process to the binary pairs, we zoomed in on the redder end of the spectrum, between 7300 and 8800 Angstroms. This range was determined to be the optimum range that focused on the redder range without giving up too much data accuracy in the spline process. Using the xcorl function, we were able to calculate the pixel shift between the template and the spectra.In order to convert pixel shift into velocity in units of km/s we multiplied the shift by 69.1.

Calculating the velocities of M dwarfs in dM-WD binaries

The same process was used with calculating the velocities of M dwarfs in M dwarf and white dwarf binary pairs. We first read in Dylan’s file, wddm_goods2.dat in order to get plate, mjd, fiber and template used (and therefore spectral type) for each of the M dwarfs in the binaries.We then matched the spectral types to each of the exposures. Depending on the binary, there were 3-9 exposures of each binary. Using the process described above, we calculated the velocities of the M dwarfs for each exposure. From these calculated velocities, we were able to calculate the expected spectrum Doppler shift; by plotting the image below, we can see how the expected shift (represented by dashed lines), corresponds with the movement in the corresponding exposure.

Estimating the separation between the binaries

The next step was to estimate the separation between the binaries. Using a two-body setup, we are able to calculate the separation, but we have to take into account the fact that the radial velocity of the entire system is also measured in our velocity calculation. To take this into consideration, we have to calculate what the radial velocity of the system is. See equations below:

wrapping up a bit

Things I've done:
- finished write-up
- backed up important files
- figured out velocity calculation so that it takes into account the radial velocity of the entire system.
- replied to summer stipend newletter entry/press release
- said goodbye for a couple weeks!

until then!

Thursday, June 16, 2011

separation calculation

Today I worked on a separation calculation for the binaries. Now that we have their velocities, based on spectral type, and making assumptions about their masses, we can estimate the separation between the M dwarf and the WD.

I have a hard time determining what is a reasonable separation between binaries. The only limit that puts it into perspective is Saurav's binaries which are extremely far apart, which means more than 10^13 meters, as given in one of his papers. So if we're smaller than that, we're okay? We'll see.

I toyed around with my first sample before writing out a more automated code. IDL's inability to work with big numbers makes me miss mathematica a little. Ah well.

I've included the SDSS site on the binary I was looking, just to get an idea of 1) how cool the site is (just plug in plate, mjd, fiber and voila!), and 2) see what the spectrum and actual picture looks like.

Super cool!

Dylan reminded me that when looking at spectra to make sure to note if wavelength is in air wavelength -- good reminder, that actually might make the plot I posted yesterday look a little bit better.

Also worked on writing up some quick summaries about my work for KINSC stuff. It's been difficult knowing how much detail I need to put into explaining astronomy jargon and whatnot, but it's been fun. With a little down time today, I read up a little on astrobites, explored astrobetter and read quite a few articles that warned students from entering grad school in astronomy. Let's gooo.

Wednesday, June 15, 2011

....and it was accurate enough!

Run the entire program for the 4,274 binaries. Ran into a little holdup as I had to reindex some of my lists (had some issues with printf at index 4219), and with some help from Dylan (accidentally deleted original file paths...thought I ruined my whole code, whatevs), I've managed to put it all into a neat file that will not be written over if I decide to run my code again.

I've also outlined what I've done so far this summer, so that I can have it all written down and accounted for. Will work on writing some of that up before I head out.

spectral shifts - check!

This morning, I plotted up a couple of exposures of the same binary to make sure that we can actually see the shift we calculated.

The white spectrum is the 1st exposure of a binary, and the red spectrum is the 3rd exposure of the binary. The time between the two exposures is about 36 minutes! The space between the white and red dotted lines show the calculated shift given our calculated radial velocities. They're a little off, but a shift is definitely there! This means that in half an hour or so between exposures, the binaries were moving quickly enough to cause their spectra to be noticeably shifted.

Waiting to hear Andrew's feedback. Fingers crossed that this is accurate enough...

Tuesday, June 14, 2011

goals for today:
-convert TAI into something more relatable
-add signal-to-noise ratio to output table
-clean up code and add more comments
-write-up past couple of weeks (at least lay it out)

Monday, June 13, 2011

Went through and finished formatting my code -- it now additionally outputs, # of exposures and exposure time. Changed my range to 7300 to 8800 A, and this allowed me to lower my shift range to 10. Next up, calc signal-to-noise ratio in the flat part of my curve to make sure my velocities aren't too out of whack. Also hope to write up my work for the last couple of weeks in LaTeX (note to self: remember how to do that).

Still haven't run through the entire sample with my velocity calculation code, but I'll do that tomorrow (I think), once I'm sure the kinks are all out.

you have 30 seconds to sum up your research so far...go!

For group meeting today, I'm supposed to have a brief summary of what I'm doing this summer (think elevator pitch to astro-related folks). Here is what I'm thinking for mine:

This summer, I'm researching the velocities of close binary pairs. From SDSS, we have spectral data on these binaries for multiple exposures. Because the binary pairs that we're examining are so close together and moving so quickly, in each exposure taken (which can be over a couple of hours), the binaries may have moved causing the spectrum to be redshifted. Using these SDSS exposures and previously compiled templates for each spectral type, we can actually calculate the velocity of these binary pairs. At this point in my research, I have calculated the velocities of ~5,000 white dwarf and M dwarf binaries.

Okay, so it needs a little work, and the last line won't be true for a couple of hours, but all in all a good start.

Friday, June 10, 2011

just got to fix that count format

As of now, I have an almost fully written automated code that will go through all the spectra for each exposure and then spit out a list with plate, mjd, fiber, template, and radial velocity. I've written the count function so that counts the number of exposures for each spectrum, but I just have to finish formatting it properly and it will be complete!

Wednesday, June 8, 2011

onto automating the binary spectra velocity code

Currently in the process of automating the binary spectra velocity code.

As of now, I've created a list of the binary spectra I'm reading in, separated it by weird time thing, and it successfully registers in my code. Next up, figure out a way to count the number of exposures and add it to the list. Then onto the radial velocity calculation. In order to do the RV calc, I need to FOR loop my code, but before (ha!) I do that, I want to make sure that all my code is indexed in the proper fashion. 'Til tomorrow.

I don't usually post in the middle of the day, but my code is finally successful!
My flux values for the binary spectra will now be fixed if there is errors on account of cosmic rays!
This will currently work if there are a max of 4 pixels in a row with mask =1. I might increase this later, but otherwise we're good.

Tuesday, June 7, 2011

oh, cosmic rays

I never thought cosmic rays would ever give me such trouble.

Before I can actually put templates to the M dwarf and white dwarf binary spectra, I have to get rid of the effects of cosmic rays. For about 20 or so pixels out of 3000 for any given spectrum, there is cosmic ray interference, causing the flux values at these wavelengths to be extremely large. In order to have a proper fit with the templates, these flux values need to seem normal for the given dwarf. Luckily there is a category titled 'mask' in the spectra files; if mask =1, then there is cosmic ray interference, if mask = 0, then flux isn't tampered with.

But because we're using templates that need to match the binary spectra, we can't just set the flux to 0 at these points; we need to have it somewhat match the rest of the spectra. To do this, we should be able to take the average of the flux values on either side of the pixel with mask =1 EXCEPT for the fact that there may be two or three pixels in a row with mask =1.

So while this should be an easy task: write a little code that searches for the closest pixel with mask value =0, and take the average, it is proving slightly more difficult.

Maybe it's because I'm having an off day (being sick is the worst), but for the life of me, I can't figure out the way to do this properly. I've ended up kind of screwing around with for, if, while statements in order to get the right code. At the moment, I have it just automated to do the average on each side of the pixel with mask =1. Hopefully tomorrow morning I'll be able to focus more and just quickly get this done.

Monday, June 6, 2011

M dwarf velocity code automated!

So I fixed my if/else statements, debugged here and there, and my code is now automated!

The program takes selected M dwarfs from Andrew's DR7 file, pulls the corresponding spectra from SDSS, matches it up with the appropriate template (based on spectral type), and calculates the shifts in spectra. This means that using this program, you can choose any set of M dwarfs from Andrew's DR7 file, and calculate their radial velocities (and compare them to the catalogued radial velocities).

So now that I've done this for individual M dwarfs, we can apply this same process to analyzing M dwarf and white dwarf binaries. Because the WD will take up the bluer end of the spectrum, I've written the code so that the velocity shifts are calculated using only the redder end of the spectrum (between 7200-8800 Angstroms), so as not to interfere with the WD.

Because there are multiple exposures from SDSS data, for close WD-Md pairs (which are moving very fast), we can calculate the velocity from the changes between exposures.

Tomorrow, I will focus on reading in the spectrum of a single WD-Md pair, and doing a similar process for the binary pair, then once that looks good, automating it. Andrew pointed out that I have to be careful as there is cosmic ray interference with some of the spectra I will be using. (It sounds really cool, but will be kind of a pain to deal with).

We had our first group meeting this afternoon -- It was great hearing about what everyone is working on.

Friday, June 3, 2011

(I've decided to do a little bit more on making this blog accessible. While it does serve as my lab notebook at times, I think it would be nice to have the blog written as clearly as possible.)

Looking back, I've done quite a few things today.

I came in needing to fix my spline procedure in order to coordinate my sample spectrum and template. From that I could use the xcorl procedure to return a shift value, which when converted to km/s from pixels (multiply by 69.1), returns the change in velocity.

Below, you can see the finished plot of a sample dM5 spectrum along with its template (blue = sample, black = template).

At the moment I am trying to automate my velocity calculation process so that you can just change the initial indexing number for the first fits file (indicating which SDSS spectrum you are selecting), and then end up with a velocity calculation.

This currently includes the task of automating my file names so that after getting the spectra from SDSS, the corresponding wavelength and flux data can be pulled. As the wavelength and flux data is categorized by file names that directly pertain to the fiber, mjd, and plate numbers, using an automated system that inserts the numbers and gets out the correct file name would quickly and efficiently continue the process. But alas, not all the fiber, mjd, and plate numbers have the same number of digits, so the troubling process of if statements and the like currently ensues.

plate: 3-4 digits
mjd: 5 digits
fiber: 1-3 digits
I thought I had my code fixed --- everything is in and is looped so you don't even have to input an index or anything. But something is still funny, as 1) some of the radial velocities are very off, and 2) running into problems with my IF and ELSE statements.

Thursday, June 2, 2011

So today the computer crashed -- aka, things that I've been working on are (temporarily?) gone.
But no worries! Data has been downloaded to this machine, and it took surprisingly little time to rewrite the codes I've worked on.

Progress report:
So yesterday I was working on downloaded SDSS spectrum.
At the end of today, I have avg flux calculations for my spectrum (neatly-ish graphed) and corresponding template. I've written the spline code out, and need to work on debugging it.

^ KEEP READING OVER SPLINE STUFF ON IDL LIBRARY! maybe it's supposed to be fitting star spectrum to template instead of the other way around?

Also, while the computer was down, I read over the template paper, and read more up about how SDSS works. Very cool.

rememeber: my average for my template seems to be a little off -- while it would make sense for the graph of the wave vs. flux/avg flux to hover between more than and less than 0, it is edging on the side of being more than 0. There's a drop at the most left-hand side of the graph that would account for this, but no matter how narrower I make my xrange, it still includes that drop. For sake of continuing with the process, i'll leave that for now and continue on.

note to self: organize this blog better

Wednesday, June 1, 2011

So far today:
-read in fits file of Andrew's DR7 spectroscopic sample
-put into fits binary table
-picked out some arbitrary values for plate, fiver, and mjd
-used to pull out corresponding spectra from sdss
-used to return wavelength and flux information

Voila, my first spectra plot!
(plate = 53789, mjd = 2212, fiber = 356)

Then I looked at a relatively flat section, in order to calculate its velocity
Also learned that putting $ before my commands allows me to go back to my directory/files from within idl. Very useful trick.

So next up is to write a program that connects the spectra to templates. Dylan helped me out and downloaded the templates for me. First off, I need to figure out which templates correspond to which star spectra. To do this, I need to use a chi-squared fit. From there, I'll need to use the spline function in order to shift the template and star's spectra so that the wavelength values for each occupy the same bin number. From there I can start to connect the spectra to templates with the xcorl procedure.

Notes to self:

Spline function:
result=spline(x,y,t, sig)
where x is star wavelength, y is star flux, t is template flux --> should return adjusted wavelength so in same bin?

result = xcorl, star, temp, range

(-->not sure about how to use adjusted wavelength in the xcorl procedure; I think the input is should be adjusted flux, and that spline returns adjusted wavelength, which would make the spline procedure useless for I definitely need to check that out)

Not quite sure about what function will make the best fit graph using a chi-squared distribution. From what I can gather, I can use the curvefit command, but definitely need to discuss with Andrew.

On another note, I also created a document that will serve as a reference list for all the codes/procedures I make. Last summer I learned the hard way that two months of coding adds up to a lot of files that you forget the purpose of. Hopefully this will help avoid this.

I couldn't have done any of this without help from Bertie, Saurav, and Dylan (and Andrew, of course)! It's great to have such wonderful resources.

things to do tomorrow morning:
-look at red part of m dwarfs (larger than 7000 A), pick a section that is relatively flat, calculate mean value --> from this, divide both template and spectra by this, and compare using where command
-look at .rv in sdss spectra -- calculate velocity change and compare to see if it is the same (Andrew's catalog says v = 18.3088?)

Tuesday, May 31, 2011

binary stars and beyond!

First couple of days at BU under my belt!

My project this summer includes analyzing the different spectra of (close) binaries. The spectra of these binaries are made up of several different exposures from 9-25 min in length. By looking at the individual spectra that these were composed of, we can possibly see position changes of binaries through the shifts in their absorption and emission lines, and thereby calculate velocities. More to come once I'm further along.

I spent last Friday doing some background reading. Read and took notes on Silvestri et al (2005), West et al (2008), West et al (2011), and Hilton et al (2010). Also did some quick calculations on deriving velocity from wavelength change, and also the relationship between mass, separation, and velocity of binaries.

Things to further read up on:
-how to determine signal-to-noise ratio in spectra
-using the L Halpha/L bol ratio

This afternoon, I read through the chapter on stellar activity in the textbook New Light on Dark Stars: Red Dwarfs, Low-Mass stars, Brown Dwarfs (Reid and Hawley). We also set up the new computers in the lab. I also put together a quick little reminder list of useful idl tricks to have on my desktop. Tomorrow: spectra! (I think)

Thursday, May 26, 2011

New Summer, New Research

Oh hey blog, long time no see.

I haven't exactly decided if I'm going to keep this research journal going for the next few months or if I should open up a new one (I kind of feel like it would be nice to keep this one for a little).

A lot has happened since I last posted. Astro-related, I finished up my poster for the KINSC Research Symposium in Sept 2010. It was a lot of fun to talk about my summer work, but since then I haven't really looked at stealth galaxies. I did get through sophomore-level astro and physics classes -- success! All in all, it has been a great year.

But it is time to get back to research!

This summer, I will be working with Prof. Andrew West (HC '99) at Boston University, focusing on characterizing and identifying a new sample of binary stars. What this fully entails, I have yet to find out!

I had the wonderful opportunity to spend this past week at the AAS meeting in Boston. SO MUCH ASTRO (in the best way!). I went to lectures on a wide range of topics, heard both Beth and Andrew speak, met some great astronomers, and picked up some great Astro stickers and silly bands.

Tomorrow is my first day of work at BU. Can't wait!