A search for accreting young companions embedded in circumstellar disks: High-Contrast Hαlpha imaging with VLT/SPHERE.

​​G. Cugno (1), S. P. Quanz (1), S. Hunziker (1), T. Stolker (1), H. M. Schmid (1), H. Avenhaus (2), P. Baudoz (3), A. J. Bohn (4), M. Bonnefoy (5), E. Buenzli (1), G. Chauvin (5 and 6), A. Cheetham (7), S. Desidera (8), C. Dominik (9), P. Feautrier (5), M. Feldt (2), C. Ginski (4), J. H. Girard (10), R. Gratton (8), J. Hagelberg (1), E. Hugot (11), M. Janson (12), A.-M. Lagrange (5), M. Langlois (11 and 13), Y. Magnard (5), A.-L. Maire (2), F. Menard (5 and 14), M. Meyer (15 and 1), J. Milli (10), C. Mordasini (16), C. Pinte (17 and 5), J. Pragt (18), R. Roelfsema (18), F. Rigal (18), J. Szulágyi (19), R. van Boekel (2), G. van der Plas (5), A. Vigan (11), Z. Wahhaj (10), A. Zurlo (11 and 20) ((1) ETH Zürich, (2) Max Planck Institute Heidelberg, (3) LESIA, (4) Leiden Observatory, (5) Univ. Grenoble, (6) Universidad de Chile, (7) Geneva Observatory, (8) Osservatorio Astronomico di Padova, (9) University of Amsterdam, (10) ESO Santiago de Chile, (11) Marseille Université, (12) Stockholm University, (13) CNRS Lyon, (14) CNRS Grenoble, (15) University of Michigan, (16) Universität Bern, (17) Monash University, (18) NOVA, (19) University of Zürich, (20) Universidad Diego Portales)
http://arxiv.org/abs/1812.06993
Aims: We want to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. Methods: We analyzed observations of 6 young stars (age 3.5−103.5−10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the VLT in the Hαα filter (656 nm) and a nearby continuum filter (644.9 nm). Results: We re-detect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both Hαα and the continuum. We derive new astrometry (r=62.8+2.1−2.7r=62.8−2.7+2.1 mas and PA=(98.7±1.8)∘PA=(98.7±1.8)∘) and photometry (ΔΔN_Ha=6.3+0.2−0.36.3−0.3+0.2 mag, ΔΔB_Ha=6.7±0.26.7±0.2 mag and ΔΔCnt_Ha=7.3+0.3−0.27.3−0.2+0.3 mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (M˙≈1−2×10−10M⊙ yr−1M˙≈1−2×10−10M⊙ yr−1). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142 and MWC758 and calculate that processes involving Hαα fluxes larger than ∼8×10−14−10−15erg/s/cm2∼8×10−14−10−15erg/s/cm2 (M˙>10−10−10−12M⊙ yr−1M˙>10−10−10−12M⊙ yr−1) can be excluded. Furthermore, flux upper limits of ∼10−14−10−15erg/s/cm2∼10−14−10−15erg/s/cm2 (M˙<10−11−10−12M⊙ yr−1M˙<10−11−10−12M⊙ yr−1) are estimated within the gaps identified in the disks surrounding HD135344B and TW Hya.

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