The First Radio Spectrum of a Rapidly Rotating A-type Star

Sat, 01 May 2021 00:00:00 +0000

MESAS Meets KINICH-PAKAL: Measure and Modeling Main Sequence Stellar Atmospheres

Thu, 07 Jan 2021 00:00:00 +0000

The dominant emission mechanisms at millimeter/submillimeter remain largely unknown for most spectral types other than Solar analogues. This is due in part to the lack of data to inform stellar atmosphere models. In this work, we present a new methodology to fit the observed and synthetic spectrum of main-sequence stars through semiempirical models¹. We use the Levenberg-Marquardt algorithm as a Nonlinear method, PakalMPI² as the semiempirical model and the observations that are part of an ongoing observational campaign entitled Measuring the Emission of Stellar Atmospheres at Submillimeter/ Millimeter wavelengths³. Our results show that we can use semiempirical models as an input model to reproduce and constrain the observed spectrum of main-sequence stars⁴. In addition to a better understanding of stellar processes, these models are also essential for determining the stellar contribution to unresolved circumstellar disks at submillimeter/millimeter wavelengths⁵.

Today I'm going to present a project that @Jacob_White26 and I have been working on at the #AAS237 meeting. The talk is titled "MESAS Meets KINICH-PAKAL: Measure and Modeling Main Sequence Stellar Atmospheres" 1/n
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

This work has an observational and theoretical basis. MESAS is an ongoing observational campaign that seeks to obtain a broad spectral sub-mm/cm coverage of a range of spectral types to build a more complete catalog of stellar emission. 2/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

Nowadays, the spectrum of stars in this range remains poorly constrained due to a lack of data for most spectral types. This situation is due in part to the technical limitations of these wavelengths. 3/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

The development of more sensitive detectors has made it possible to observe for the first time, stars of main-sequence at sub-mm / mm wavelengths. The Stars with no known circumstellar material to provide valuable information about the physical conditions of the atmosphere. 4/n
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

This information is useful to characterize the emission and use it as a template for several studies in many areas such as: stellar atmospheres, debris disks, space weather, stellar evolution, and long term stellar variability studies. 5/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

As an example, we have the case of Sirius A an A1Vm star. Due to its proximity (2.64 pc), it was a good starting point to start studying the emission of A stars. The results can be found in White et al. (2019) https://t.co/WPWzt6y31t . 6/n #AAS237 pic.twitter.com/8PqaUaCf5s
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

For the theoretical part, we have Kinich-Pakal (KP). KP is a new methodology developed by @victor_delaluz and me, to fit the observed and synthetic spectrum of solar-like stars from the centimeter to infrared wavelengths through semiempirical models. 7/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

KP uses the Levenberg-Marquardt algorithm to minimize the differences between synthetic and observed spectrum by running PakalMPI (De la Luz et al., 2010) https://t.co/dIKB1QU21j to hydrostatically equilibrate the atmosphere and to compute their synthetic spectrum. 8/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

KP is capable of finding the physical conditions such as pressure, density, and temperature in function of the altitude. As an example, we have the model of Alpha Centauri A (Tapia-Vázquez & De la Luz, 2020) https://t.co/swRBqlKAFG . 9/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

Alpha Centauri A and B were the first stellar system resolved in the submillimeter wavelength by ALMA (Liseau et al. 2015). Thanks to these observations and the sun-like properties of alpha Centauri, we could calibrate the model. 10/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

As a result, we obtain a semi-empirical model that allows us to reproduce the observed spectrum more closely. This model shows similarities between Alpha Centauri A and our Sun, such as a low temperature, a flattening of the temperature in the high chromosphere. 11/n #AAS237 pic.twitter.com/swXi2l6434
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

But, in a broad stellar context, both MESAS and KINICH-PAKAL works as a compliment. MESAS provides an observational framework that constrains the stellar emission, and KP uses this information to model the atmosphere. 12/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

Using both, we have been able to characterize the emission in stars of spectral type F from the radio to the infrared wavelengths such as Gamma Vir A/B (F0V) and Gamma Lep (F6V) (White et al. 2020) https://t.co/oB5ELqvXzQ . 13/n #AAS237 pic.twitter.com/vBFPhDA0pp
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

As future work, we are going to expand the use of this framework with the help of more observations that will come primarily from the #VLA, @almaobs, #Noema, and the @gtmlmt_oficial. 14/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

The complete keynote can be found at https://t.co/R8sfncEuua :) Thanks to @Jacob_White26, @victor_delaluz, and Luis Zapata for the comments and the help! 15/n #AAS237
— Francisco Tapia 📡 (@ftapia_va) January 11, 2021

References

Tapia-Vázquez, F., & De la Luz, V. 2020, ApJS, 246, 5 Doi ↩︎
De la Luz, V., Lara, A., Mendoza-Torres, J. E., et al. 2010, ApJS, 188, 437 Doi ↩︎
White, J.A., Aufdenberg, J., Boley, A.C., 2018, ApJ,859(2), p.102. Doi ↩︎
White, J. A., Tapia-Vázquez, F., Hughes, A. G., et al. 2020, ApJ, 894, 76 Doi ↩︎
White, J. A., Aufdenberg, J., Boley, A. C., et al. 2019, ApJ, 875, 55 Doi ↩︎

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Thu, 07 May 2020 00:00:00 +0000

Nonlinear Convergence of Solar-like Stars Chromospheres Using Millimeter, Submillimeter, and Infrared Observations

Tue, 07 Jan 2020 00:00:00 +0000

The MESAS Project: Long-wavelength Follow-up Observations of Sirius A

Sun, 07 Apr 2019 00:00:00 +0000

ALMA's view of the nearest neighbors to the Sun. The submm/mm SEDs of the α Centauri binary and a new source

Fri, 07 Oct 2016 00:00:00 +0000

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