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Published May 2020 | Accepted Version + Published
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Accretion Properties of PDS 70b with MUSE

Abstract

We report a new evaluation of the accretion properties of PDS 70b obtained with the Very Large Telescope/Multi Unit Spectroscopic Explorer. The main difference from the previous studies of Haffert et al. and Aoyama & Ikoma is in the mass accretion rate. Simultaneous multiple line observations, such as Hα and Hβ, can better constrain the physical properties of an accreting planet. While we clearly detected Hα emissions from PDS 70b, no Hβ emissions were detected. We estimate the line flux of Hβ with a 3σ upper limit to be 2.3 × 10⁻¹⁶ erg s⁻¹ cm⁻². The flux ratio F_(Hβ) /F_(Hα) for PDS 70b is <0.28. Numerical investigations by Aoyama et al. suggest that F_(Hβ) /F_(Hα) should be close to unity if the extinction is negligible. We attribute the reduction of the flux ratio to the extinction, and estimate the extinction of Hα (A_(Hα) ) for PDS 70b to be >2.0 mag using the interstellar extinction value. By combining with the Hα linewidth and the dereddening line luminosity of Hα, we derive the PDS 70b mass accretion rate to be ≳5 × 10⁻⁷ M_(Jup) yr⁻¹. The PDS 70b mass accretion rate is an order of magnitude larger than that of PDS 70. We found that the filling factor f_f (the fractional area of the planetary surface emitting Hα) is ≳0.01, which is similar to the typical stellar value. The small value of f_f indicates that the Hα emitting areas are localized at the surface of PDS 70b.

Additional Information

© 2020 The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 February 5; revised 2020 March 11; accepted 2020 March 17; published 2020 April 22. Based on data collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO program 60.A-9100(K). We thank the anonymous referee for a helpful review of the manuscript. We are grateful to K. Kanagawa and Y. Hasegawa for their contributions. This work was supported by JSPS KAKENHI grant Nos. 19H00703, 19H05089, 19K03932, 18K13579, and 15H02065.

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Published - Hashimoto_2020_AJ_159_222.pdf

Accepted Version - 2003.07922.pdf

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Created:
August 22, 2023
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October 20, 2023