An M-dwarf star in the transition disk of Herbig HD 142527

This is the final version of the article. Available from the publisher via the DOI in this record.Aims. HD 142527A is one of the most studied Herbig Ae/Be stars with a transitional disk, as it has the largest imaged gap in any protoplanetary
disk: the gas is cleared from 30 to 90 AU. The HD 142527 system is also unique in that it has a stellar companion with a small mass compared to
the mass of the primary star. This factor of ≈ 20 in mass ratio between the two objects makes this binary system different from any other YSO.
The HD142527 system could therefore provide a valuable test bed for understanding the impact of a lower mass companion on disk structure. This
low-mass stellar object may be responsible for both the gap and dust trapping observed by ALMA at longer distances.
Methods. We observed this system with the NACO and GPI instruments using the aperture masking technique. Aperture masking is ideal for
providing high dynamic range even at very small angular separations. We present the spectral energy distribution (SED) for HD 142527A and B.
Brightness of the companion is now known from the R band up to the M0 band. We also followed the orbital motion of HD 142527B over a period
of more than two years.
Results. The SED of the companion is compatible with a T = 3000 ± 100 K object in addition to a 1700 K blackbody environment (likely a
circum-secondary disk). From evolution models, we find that it is compatible with an object of mass 0.13 ± 0.03 M , radius 0.90 ± 0.15 R ,
and age 1.0
+1.0
−0.75 Myr. This age is significantly younger than the age previously estimated for HD142527A. Computations to constrain the orbital
parameters found a semimajor axis of 140+120
−70 mas, an eccentricity of 0.5 ± 0.2, an inclination of 125 ± 15 degrees, and a position angle of the right
ascending node of −5 ± 40 degrees. Inclination and position angle of the ascending node are in agreement with an orbit coplanar with the inner
disk, not coplanar with the outer disk. Despite its high eccentricity, it is unlikely that HD142527B is responsible for truncating the inner edge of
the outer diskSL acknowledges fruitful discussions with S. Casassus
 about the existence of HD142527B and the inner disk of HD142527A. This
 research made use of Astropy, a community-developed core Python package
 for Astronomy (Astropy Collaboration et al. 2013). This work was supported
 by the French National Agency for Research (ANR-13-JS05-0005)
 and the European Research Council (ERC-STG-639248). AG and AS acknowledge support from NSF Graduate Research Fellowship grant no. DGE-
 1232825 and NASA grant NNX11AF74G. JO acknowledges support from the
 Millennium Nucleus RC130007 (Chilean Ministry of Economy). IB acknowledges
 the European Research Council through grant ERC-AdG No. 320478-
 TOFU. Based on observations collected at the European Southern Observatory
 (ESO) during runs 088.C-0691(A), 090.C-0649(A), 091.C-0572(A), and 094.C-
 0608(A). Also based on observations obtained at the Gemini Observatory (programs
 GS-2014A-SV-406 and GS-ENG-GPI-COM), which is operated by the
 Association of Universities for Research in Astronomy, Inc., under a cooperative
 agreement with the NSF on behalf of the Gemini partnership: the National
 Science Foundation (United States), the National Research Council (Canada),
 CONICYT (Chile), the Australian Research Council (Australia), Ministerio da ´
 Ciencia, Tecnologia e Inovac¸ ˆ ao (Brazil) and Ministerio de Ciencia, Tecnolog ˜ ´ıa e
 Innovacion Productiva (Argentina)