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Published February 2019 | Published + Accepted Version
Journal Article Open

On the isochronal age-mass discrepancy of young stars: SCExAO/CHARIS integral field spectroscopy of the HIP 79124 triple system


We present SCExAO/CHARIS 1.1–2.4 μm integral field direct spectroscopy of the young HIP 79124 triple system. HIP 79124 is a member of the Scorpius-Centaurus association, consisting of an A0V primary with two low-mass companions at a projected separation of < 1″. Thanks to the high quality wavefront corrections provided by SCExAO, both companions are decisively detected without the employment of any PSF-subtraction algorithm to eliminate quasi-static noise. The spectrum of the outer C object is very well matched by Upper Scorpius M4 ± 0.5 standard spectra, with a T_(eff) = 2945 ± 100 K and a mass of ∼350 M_(Jup). HIP 79124 B is detected at a separation of only 180 mas in a highly-correlated noise regime, and it falls in the spectral range M6 ± 0.5 with T_(eff) = 2840 ± 190 K and ∼100 M_(Jup). Previous studies of stellar populations in Sco-Cen have highlighted a discrepancy in isochronal ages between the lower-mass and higher-mass populations. This could be explained either by an age spread in the region, or by conventional isochronal models failing to reproduce the evolution of low-mass stars. The HIP 79124 system should be coeval, and therefore it provides an ideal laboratory to test these scenarios. We place the three components in a color–magnitude diagram and find that the models predict a younger age for the two low-mass companions (∼3 Myr) than for the primary star (∼6 Myr). These results imply that the omission of magnetic effects in conventional isochronal models inhibit them from reproducing early low-mass stellar evolution, which is further supported by the fact that new models that include such effects provide more consistent ages in the HIP 79124 system.

Additional Information

© 2019 ESO. Article published by EDP Sciences. Received 20 November 2018; Accepted 18 December 2018; Published online 24 January 2019. We thank Kevin Luhman, Eric Mamajek, and Mark Pecaut for helpful draft comments. We wish to emphasize the pivotal cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the privilege to conduct scientific observations from this mountain. R.A.-T. and M.J. gratefully acknowledge funding from the Knut and Alice Wallenberg foundation. S.D. acknowledges support from the "Progetti Premiali" funding scheme of the Italian Ministry of Education, University, and Research. E. A. is supported by MEXT/JSPS KAKENHI grant No. 17K05399. M.T. is supported by MEXT/JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005.M. H. is supported by the Grant-in-Aid for Scientific Research on Innovative Areas (2302, 23103002) under the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. This research has benefited from the Montreal Brown Dwarf and Exoplanet Spectral Library, maintained by Jonathan Gagne. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

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Accepted Version - 1811.10684.pdf

Published - aa34688-18.pdf


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August 19, 2023
August 19, 2023