The discrepancy between dynamical and theoretical mass in the triplet-system 2MASS J10364483+1521394

We combine new Lucky Imaging astrometry from New Technology Telescope /AstraLux Sur with already published astrometry from the AstraLux Large M-dwarf Multiplicity Survey to compute orbital elements and individual masses of the 2MASS J10364483 + 1521394 triple system belonging to the Ursa-Major moving group. The system consists of one primary low-mass M-dwarf orbited by two less massive companions, for which we determine a combined dynamical mass of MB+C = 0 : 48 +/- 0 : 14 M-circle dot. We show from the companions' relative motions that they are of equal mass (with a mass ratio of 1 : 00 +/- 0 : 03), thus 0 : 24 +/- 0 : 07 M-circle dot individually, with a separation of 3 : 2 +/- 0 : 3 AU, and we conclude that these masses are significantly higher (30%) than what is predicted by theoretical stellar evolutionary models. The biggest uncertainty remains the distance to the system, here adopted as 20 : 1 +/- 2 : 0 pc based on trigonometric parallax, whose ambiguity has a major impact on the result. With the new observational data we are able to conclude that the orbital period of the BC pair is 8.4(-0.021)(+0.04) yr.

Janson, MarkusStockholms universitet,Institutionen för astronomi(Swepub:su)mjanso (author)
Koehler, Rainer (author)
Durkan, Stephen (author)
Hippler, Stefan (author)
Dai, Xiaolin (author)
Brandner, Wolfgang (author)
Schlieder, Joshua (author)
Henning, Thomas (author)
Stockholms universitetInstitutionen för astronomi (creator_code:org_t)

By the author/editor: Calissendorff, P ...; Janson, Markus; Koehler, Rainer; Durkan, Stephen; Hippler, Stefan; Dai, Xiaolin; show more...; Brandner, Wolfga ...; Schlieder, Joshu ...; Henning, Thomas; show less...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

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