In the morning I wrote up a detailed summary of how I found the possible companion stars using Topcat. I also went through the process myself, using the mean proper motions, so I can have the exact results of what you get using them. I've already checked to make sure that the new stars that show up using the mean proper motions aren't emitting x-rays, but I wanted to have the correct lists on file anyways.
Today was the last day I could attend coffee time :( Starting tomorrow, I won't be able to come to work until around four because of double sessions of soccer try-outs. But the strawberry-smoothie I got today was amazing!
In the afternoon, Joel clarified a few background questions I had about companion stars and why they chose V4046 Sgr, MP Mus, T Cha, and TW Hya to study. It is because these stars are around 10 million years old and still have gas in their circumstellar disk, but are just starting to form planets. Usually, stars form planets and lose the gas in their circumstellar disks by 2 to 3 million years old. Therefore, there is a theory that these widely separated companion stars (like TWA 28) were once very close to, in this case, TW Hya, and prevented it from forming planets until now. I made a slide for this info in my powerpoint.
Things are looking good for 2M1155-79, the possible companion for T Cha. Rudy continues to analyze the spectrum and he found a small absorption which is good because that means the star doesn't have a disk (most companions don't). Joel is going to ask his friend in Australia if he will extract the spectrum using his telescope, so we can see if it has Li absorption (indication of a young star).
Thursday, August 18, 2011
Wednesday, August 17, 2011
Day 31
Today in the morning I used Topcat again and re-did the search for companion stars to T Cha, and V4046 sgr, because their simbad PM's are significantly different from the mean of their PM's. This time, I matched the PPMXL and UCAC3 lists and then made two more columns on the matched table for the mean pmRA and pmDE. Then, I matched this with the 2mass catalog and limited the stars so that only stars with the mean of their PM's within 15 mas/yr of the binary star's mean PM. I didn't come up with any new star coordinates for T Cha, but I came up with a few for v4046 sgr. However, none are emitting x-rays . . .but it was worth going back to just check and make sure. Also, I finished putting the vectors to represent proper motions on the ds9 x-ray image of MP Mus and it's possible companions. For lunch we had free pizza and watched a movie about entrepreneurs.
In the afternoon, I began by going through Joel's email about how he calculated the bolometric luminosity of our unknown star, which we nicknamed 2M1155-79 (from its 2mass coordinates). The ratio of its x-ray luminosity to its bolometric luminosity is a little large, but not unreasonable, but Joel suspected that this was because the x-ray luminosity (from the spectral fit) was a bit too large. So Rudy re-did the spectral fit and found another x-ray luminosity that is smaller and more reasonable. Now we have officially discarded the RXJ star as a possible companion star and the only one we are still considering is this 2M1155-79. Joel said he might try and get someone to calculate proper motion themselves of T Cha and 2M1155-79 (by comparing recent images with images taken a long time ago). Meanwhile, my job is to write up a detailed summary of how I obtained the data (using Topcat) so that Joel can write a paper on this if he decides to. Also I need try and keep my powerpoint up to date, and decide if I want to present what I did with the planetary nebulae in the beginning of the summer or not . . so much to do, so little time!
In the afternoon, I began by going through Joel's email about how he calculated the bolometric luminosity of our unknown star, which we nicknamed 2M1155-79 (from its 2mass coordinates). The ratio of its x-ray luminosity to its bolometric luminosity is a little large, but not unreasonable, but Joel suspected that this was because the x-ray luminosity (from the spectral fit) was a bit too large. So Rudy re-did the spectral fit and found another x-ray luminosity that is smaller and more reasonable. Now we have officially discarded the RXJ star as a possible companion star and the only one we are still considering is this 2M1155-79. Joel said he might try and get someone to calculate proper motion themselves of T Cha and 2M1155-79 (by comparing recent images with images taken a long time ago). Meanwhile, my job is to write up a detailed summary of how I obtained the data (using Topcat) so that Joel can write a paper on this if he decides to. Also I need try and keep my powerpoint up to date, and decide if I want to present what I did with the planetary nebulae in the beginning of the summer or not . . so much to do, so little time!
Tuesday, August 16, 2011
Day 30
Today I got an email from Joel explaining that according to the Pre-MS catalog he found, T Cha and RX J1158.5-7913 (its possible companion) do not have similar proper motions. This was confusing because when I used Topcat to find the possible companions stars, I limited the results so that only stars with a proper motion of within 15 mas/yr of T Cha would be present. At first, I thought I had made a mistake using Topcat and this whole process of investigating RX J1158.5-7913 was a waste of time. But after doing a little investigating, I realized the problem is that some of the proper motions listed in the PPMXL, UCAC3, and Pre-MS catalogs as well as in Simbad are different! So now, we don't really know what source to trust. Instead, I am taking the mean of the PM's found for each star, regardless if it is emitting x-rays or not, and plotting them as vectors on the x-ray images using ds9. This way, we can visually compare the magnitude and angle of the proper motion vectors and decide which could be companion stars. Unfortunately, RX J1158.5-7913's mean PM is about half that of T-Cha's, which probably means that it is in the chamaeleon cloud . . .around 80 parsecs (one parsec= 3.26 light-years) behind T-Cha, and therefore is not a companion star. However, our 'unnamed' star is still in the running to be a companion, so the next step is to calculate the bolometric luminosity and compare that to the x-ray luminosity!
Day 29
The insight lab is now nearly empty because all of the REU students are gone. And there was no coffee-time :( I spent the morning working on my powerpoint and applying what I learned from the undergrad presentations last Friday to my own powerpoint. I went through what I've done with my presentation so far with Evelyn and she helped me identify what I need to improve on. For lunch, Bethany took us out to cross-roads with a prospective student who she was giving a tour too.
In the afternoon, I made of table of information (That Rudy got from the extracted spectra) about T Cha and it's two possible companions. It includes the extinction, temp in keV and MK, confidence range, observed flux, actual flux, distance in kpc and cm, and x-ray luminosity. Basically, we want the x-ray luminosity to be around 10^29 to 10^30 erg/s, because that means the star is more likely to be young. Using the spectra, we found that T-Cha's x-ray luminosity is 10^30 erg/s, RX J1158.5-7913's is 10^31 erg/s, and the unknown star's is 10^29 erg/s. T-Cha's and RXJ's higher luminosities could be due to flares which are common in young stars. To determine this, Rudy extracted the light curves of the stars. It seems as though T Cha and RXJ are showing some flaring, but it is not totally clear. The unknown star's light curve is pretty flat. He is going to try to extract a more clear light curve. I would post a pic of the light curves on here but it is a pdf and I'm not really sure how . . .you will have to wait until my presentation!
In the afternoon, I made of table of information (That Rudy got from the extracted spectra) about T Cha and it's two possible companions. It includes the extinction, temp in keV and MK, confidence range, observed flux, actual flux, distance in kpc and cm, and x-ray luminosity. Basically, we want the x-ray luminosity to be around 10^29 to 10^30 erg/s, because that means the star is more likely to be young. Using the spectra, we found that T-Cha's x-ray luminosity is 10^30 erg/s, RX J1158.5-7913's is 10^31 erg/s, and the unknown star's is 10^29 erg/s. T-Cha's and RXJ's higher luminosities could be due to flares which are common in young stars. To determine this, Rudy extracted the light curves of the stars. It seems as though T Cha and RXJ are showing some flaring, but it is not totally clear. The unknown star's light curve is pretty flat. He is going to try to extract a more clear light curve. I would post a pic of the light curves on here but it is a pdf and I'm not really sure how . . .you will have to wait until my presentation!
Friday, August 12, 2011
Day 28
Today was the last day for research undergrad students, and they all had to give presentations about what they've done over the summer. In the morning, Evelyn and I went to a few presentations. I took notes about things I liked/disliked about the presentations so that I can apply them to my own! For lunch we got to have free Chinese food which was awesome. I even ate with chopsticks! Afterwards, a few of us interns went to another presentation about using PTM images to diagnose medical problems. Then, we decided to explore the roof and helped out with a remote sensing experiment that was going on up there. It was a very fun day!
Day 27
Today we went on a field trip to CVI Melles Griot. It was this really small lens-making company and the tour was shorter than we expected. The lunch afterwards was really good though, we went to a sub shop. Afterwards I finished the excel sheet of the observations of MP Mus and T Cha. Then I spent the rest of the afternoon reading a paper about color-color diagrams and their correlation with a star's circumstellar disk. The infrared color-color diagrams that I will be working with are J-K vs. H-K. Using this graph I believe we can find out if any of the T-Cha or MP Mus candidates are brown dwarfs or not.
Thursday, August 11, 2011
Day 26
Today I finished comparing the 2mass magnitudes and colors of the regions in T-Cha and MP Mus to the brown dwarf TWA 28. We plotted a graph of J-K vs. H-K to try and see if any of the regions could be brown dwarfs but apparently this method won't work unless I am sure that the stars are young stars. So instead, I started to record fluxes found at different microns for the coordinates of the regions, using HEASARC. I searched for observations made of these coordinates in the Rosat, Akari, Iras, Galex, Usno B1, and 2mass missions. Then I recorded the fluxes for the results that had an offset of >1 arcmin from one of the coordinates. In addition, I also recorded the observation #, offset, count rate, and count rate error of observations that were returned without any recorded fluxes. In the end, the hope is to make a spectra graph that will show where the regions in MP Mus and T Cha peak. This will tell us more about what kind of star it is and what its temperature is. Also Rudy gave me an 11 page paper to read! Better get started on that . . .
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