Jennifer-Medina AAS 30x40 poster · 2020. 2. 23. · Title: Jennifer-Medina_AAS_30x40_poster...
1
Calculating Vsin(i) of Young Planet-hosting Stars Jennifer Medina 1,2 , Andrew Mann 3 1. Florida International University, 2. TAURUS Program, 3. University of Texas, Austin The spin-orbit alignment of extra-solar planets in young systems can provide insight on their migratory history: An aligned system might indicate that the exoplanet formed through interactions with the disk. We can obtain a transiting system's spin-orbit relation by calculating the Vsin(i) of the host star. Acknowledgements During our data analysis, we noticed the accuracy of our Vsin(i) values decreased as we observed stars with a slower radial velocity: Our values would tend to have larger uncertainties as we fit our model to spectra with less rotational broadening in these spectral lines. Using Spectroscopy to find our Vsin(i) Background Results and Conclusions Telluric Reduction The Vsin(i) of a star is its rotational velocity at the equator multiplied by the sine of the inclination. As you can see, the Vsin(i) will always be less than the equatorial velocity. A diagram of the physical representation of a star’s Vsin(i) A physical representation of a spin-orbit misalignment Source: http://web.gps.caltech.edu/ We can use spectroscopy as a tool to determine the Vsin(i) of a star through the rotational broadening on its spectral lines. The rotational broadening observed in a star’s spectral lines is due to the rotational velocity of the star with respect to our plane of vision. As the star spins on its axis, half of the star will be rotating towards us while the other half rotates away from us. This leads to an emission (or absorption) line that is not perfectly straight, but slightly broadened. Objectives Absorption lines in the IGRINS spectral range Source: Dr. Andrew Mann Spectral line-broadening as a result of the star’s rotational velocity • Develop a program that fits a model’s spectral lines onto the star’s broadened spectral lines • Have our program produce a Vsin(i) value of the star, using our optimized model • Extract an inclination value from our Vsin(i) • Compare the calculated inclination of the star with respect to the exoplanet’s orbital inclination (which is around 85°-90° because it is a transiting system) The TAURUS Program in the University of Texas for providing the opportunity to complete this research, as well as the Cox Endowment Fund and the Keck PI Data Award for supporting the program. Telluric Model Fitting Model Fitting The Data: We used stellar spectra taken from the Immersion GRating INfrared Spectrometer (IGRINS) in the McDonald Observatory. Targets were observed in the NIR H and K bands. The Standard: Our standard was an A0 star that was observed under the same airmass as our target star. The Results: The raw data was divided by our A0 standard which eliminated most of the telluric lines. We developed a program with correction parameters that would fit the model spectra onto our target spectra. This program would then produce a Vsin(i) value close to the Vsini(i) of our target star, which we can use to determine the inclination of the star relative to our point of view. References 1.55 1.60 1.65 1.70 1.75 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Normalized Flux Wavelength ( m) 2.10 2.15 2.20 2.25 2.30 2.35 2.40 2.45 1.7080 1.7103 1.7127 1.7150 Wavelength ( m) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.114 2.116 2.118 2.120 Wavelength ( m) 0.5 0.6 0.7 0.8 0.9 1.0 2.2056 2.2071 2.2085 2.2100 Wavelength ( m) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Tellurics are a result of light scattering off of molecules in the earth’s atmosphere and creating noise on the incoming data. To remove the tellurics, we used a relatively featureless hot, rapidly rotating star as our standard star. We divided the spectrum of the target star by our standard to eliminate as many of the tellurics as possible to produce a new set of telluric-reduced data. Target name: V830 Tau Calculated Vsin(i): 30.1 km⋅s −1 ± 3.4 Literature Vsin(i): 30.5 km⋅s −1 ± 0.5 Target name: EPIC 211990866 Calculated Vsin(i): 15.7 km⋅s −1 ± 2.1 Calculated inclination: ≥ 78.0° [1] Mann, A., et al., 18, Aug. 2016, AJ, Published. [2] Mann, A., et al., 11, Jan. 2017, AJ, Published. [3] Mann, A., et al., 08, Feb. 2016, ApJ, Published. [4] Donati, J.F., et al., 09, Sep. 2015, MNRAS, Published. • Improves noise-reduction from tellurics • Standard star no longer required • Air mass under which data was taken does not matter Source: http://glentner.github.io/SLiPy/ IGRINS spectrum plotted against our unoptimized model IGRINS spectrum plotted against our model after applying the optimization parameters
Transcript of Jennifer-Medina AAS 30x40 poster · 2020. 2. 23. · Title: Jennifer-Medina_AAS_30x40_poster...
Calculating Vsin(i) of Young Planet-hosting Stars Jennifer Medina1,2, Andrew Mann3
1. Florida International University, 2. TAURUS Program, 3. University of Texas, Austin
The spin-orbit alignment of extra-solar planets in young systems can provide insight on their migratory history: An aligned system might indicate that the exoplanet formed through interactions with the disk. We can obtain a transiting system's spin-orbit relation by calculating the Vsin(i) of the host star.
Acknowledgements
During our data analysis, we noticed the accuracy of our Vsin(i) values decreased as we observed stars with a slower radial velocity: Our values would tend to have larger uncertainties as we fit our model to spectra with less rotational broadening in these spectral lines.
Using Spectroscopy to find our Vsin(i)
Background Results and ConclusionsTelluric Reduction
The Vsin(i) of a star is its rotational velocity at the equator multiplied by the sine of the inclination. As you can see, the Vsin(i) will always be less than the equatorial velocity.
A diagram of the physical representation of a star’s Vsin(i)
A physical representation of a spin-orbit misalignment Source: http://web.gps.caltech.edu/
We can use spectroscopy as a tool to determine the Vsin(i) of a star through the rotational broadening on its spectral lines. The rotational broadening observed in a star’s spectral lines is due to the rotational velocity of the star with respect to our plane of vision.
As the star spins on its axis, half of the star will be rotating towards us while the other half rotates away from us. This leads to an emission (or absorption) line that is not perfectly straight, but slightly broadened.
Objectives
Absorption lines in the IGRINS spectral range Source: Dr. Andrew Mann
Spectral line-broadening as a result of the star’s rotational velocity
• Develop a program that fits a model’s spectral lines onto the star’s broadened spectral lines
• Have our program produce a Vsin(i) value of the star, using our optimized model
• Extract an inclination value from our Vsin(i) • Compare the calculated inclination of the star with respect to the
exoplanet’s orbital inclination (which is around 85°-90° because it is a transiting system)
The TAURUS Program in the University of Texas for providing the opportunity to complete this research, as well as the Cox Endowment Fund and the Keck PI Data Award for supporting the program.
Telluric Model Fitting
Model Fitting
The Data: We used stellar spectra taken from the Immersion GRating INfrared Spectrometer (IGRINS) in the McDonald Observatory. Targets were observed in the NIR H and K bands.
The Standard: Our standard was an A0 star that was observed under the same airmass as our target star.
The Results: The raw data was divided by our A0 standard which eliminated most of the telluric lines.
We developed a program with correction parameters that would fit the model spectra onto our target spectra. This program would then produce a Vsin(i) value close to the Vsini(i) of our target star, which we can use to determine the inclination of the star relative to our point of view.
References
1.55 1.60 1.65 1.70 1.750.40.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Flu
x
Wavelength ( m)2.10 2.15 2.20 2.25 2.30 2.35 2.40 2.45
1.7080 1.7103 1.7127 1.7150Wavelength ( m)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
2.114 2.116 2.118 2.120Wavelength ( m)
0.5
0.6
0.7
0.8
0.9
1.0
2.2056 2.2071 2.2085 2.2100Wavelength ( m)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Tellurics are a result of light scattering off of molecules in the earth’s atmosphere and creating noise on the incoming data. To remove the tellurics, we used a relatively featureless hot, rapidly rotating star as our standard star. We divided the spectrum of the target star by our standard to eliminate as many of the tellurics as possible to produce a new set of telluric-reduced data.
Target name: V830 Tau Calculated Vsin(i): 30.1 km⋅s−1 ± 3.4 Literature Vsin(i): 30.5 km⋅s−1 ± 0.5
Target name: EPIC 211990866 Calculated Vsin(i): 15.7 km⋅s−1 ± 2.1 Calculated inclination: ≥ 78.0°
[1] Mann, A., et al., 18, Aug. 2016, AJ, Published. [2] Mann, A., et al., 11, Jan. 2017, AJ, Published. [3] Mann, A., et al., 08, Feb. 2016, ApJ, Published. [4] Donati, J.F., et al., 09, Sep. 2015, MNRAS, Published.
• Improves noise-reduction from tellurics
• Standard star no longer required
• Air mass under which data was taken does not matter
Source: http://glentner.github.io/SLiPy/
IGRINS spectrum plotted against our unoptimized model IGRINS spectrum plotted against our model after applying the optimization parameters
