New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92–125723.9 b

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: zakhozhay@mpia.de
² Main Astronomical Observatory, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
³ Centro de Astrobiología, CSIC-INTA, Crta. Ajalvir km 4, 28850 Torrejon de Ardoz, Madrid, Spain
⁴ Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁵ Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
⁶ Departament d’Astronomia i Astrofísica, Universitat de Valencia, C. Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
⁷ Observatori Astronomic, Universitat de Valencia, Parc Científic, C. Catedrático José Beltrán 2, 46980 Paterna, Valencia, Spain
⁸ Universidad Internacional de Valencia (VIU), C/ Pintor Sorolla 21, 46002 Valencia, Spain
⁹ Janusz Gil Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65–265 Zielona Góra, Poland
¹⁰ Department of Chemistry, Ludwig Maximilian University, Butenandtstr. 5–13, 81377 Munich, Germany
¹¹ Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹² Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
¹³ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
¹⁴ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France

Received: 18 January 2023
Accepted: 13 March 2023

Abstract

Context. The existence of warm (protoplanetary) disks around very young isolated planetary and brown dwarf mass objects is known based on near- and mid-infrared flux excesses and millimeter observations. These disks may later evolve into debris disks or rings, although none have been observed or confirmed so far. Little is known about circum(sub)stellar and debris disks around substellar objects.

Aims. We aim to investigate the presence of debris disks around two of the closest (~20 pc), young substellar companions, namely G196-3 B and VHS J125601.92–125723.9 b (VHS J1256–1257 b), whose masses straddle the borderline between planets and brown dwarfs. Both are companions at wide orbits (≥100 au) of M-type dwarfs and their ages (50–100 Myr and 150–300 Myr, respectively) are thought to be adequate for the detection of second-generation disks.

Methods. We obtained deep images of G196-3 B and VHS J1256–1257 b with the NOrthern Extended Millimeter Array (NOEMA) at 1.3 mm. These data were combined with recently published Atacama Large Millimeter Array (ALMA) and Very Large Array (VLA) data of VHS J1256–1257 b at 0.87 mm and 0.9 cm, respectively.

Results. Neither G196-3 B nor VHS J1256–1257 b were detected in the NOEMA, ALMA, and VLA data. At 1.3 mm, we imposed flux upper limits of 0.108 mJy (G196-3 B) and 0.153 mJy (VHS J1256–1257 b) with a 3-σ confidence. Using the flux upper limits at the millimeter and radio wavelength regimes, we derived maximum values of 1.38×10⁻² M_Earth and 5.46 × 10⁻³ M_Earth for the mass of any cold dust that might be surrounding G196-3 B and VHS J1256–1257 b, respectively.

Conclusions. We put our results in the context of other deep millimeter observations of free-floating and companion objects with substellar masses smaller than 20 M_Jup and ages between approximately one and a few hundred million years. Only two very young (2–5.4 Myr) objects are detected out of a few tens of them. This implies that the disks around these very low-mass objects must have small masses, and possibly reduced sizes, in agreement with findings by other groups. If debris disks around substellar objects scale down (in mass and size) in a similar manner as protoplanetary disks do, millimeter observations of moderately young brown dwarfs and planets must be at least two orders of magnitude deeper to be able to detect and characterize their surrounding debris disks.