ADONIS high contrast infrared imaging of Sirius-B

Abstract

Sirius is the brightest star in the sky and a strong source of diffuse light for modern telescopes so that the immediate surroundings of the star are still poorly known. We study the close surroundings of the star (2 to 25 arcsec) by means of adaptive optics and coronographic device in the near-infrared, using the ESO/ADONIS system. The resulting high contrast images in the JHKs bands have a resolution of ~ 0.2 arcsec and limiting apparent magnitude ranging from mK = 9.5 at 3 arcsec, from Sirius-A to mK = 13.1 at 10 arcsec. These are the first and deepest images of the Sirius system in this infrared range. From these observations, accurate infrared photometry of the Sirius-B white dwarf companion is obtained. The JH magnitudes of Sirius-B are found to agree with expectations for a DA white dwarf of temperature (T=25000K) and gravity (log(g) = 8.5), consistent with the characteristics determined from optical observations. However, a small, significant excess is measurable for the K band, similar to that detected for "dusty" isolated white dwarfs harbouring suspected planetary debris. The possible existence of such circumstellar material around Sirius-B has still to be confirmed by further observations. These deep images allow us to search for small but yet undetected companions to Sirius. Apart from Sirius-B, no other source is detected within the total 25 arcsec field. The minimum detectable mass is around 10 MJup inside the planetary limit, indicating that an extrasolar planet at a projected distance of ~ 25 AU from Sirius would have been detected (abridged abstract).

Comments: 6 pages, 5 figures. Accepted for publication in A&A

References in corpus (11)

• Spectral Irradiance Calibration in the Infrared. XIV: the Absolute Calibration of 2MASS
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects of Temperature, Clouds, and Gravity
• L and T Dwarf Models and the L to T Transition
• A gaseous metal disk around a white dwarf
• Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs
• The Dust cloud around the White Dwarf G 29-38
• Spectral Irradiance Calibration in the Infrared. XIII. "Supertemplates" and On-Orbit Calibrators for SIRTF's Infrared Array Camera (IRAC)
• The New Class of Dusty DAZ White Dwarfs
• T Dwarfs and the Substellar Mass Function. I. Monte Carlo Simulations
• Hubble Space Telescope Spectroscopy of the Balmer lines in Sirius B
• A Search for Exozodiacal Dust and Faint Companions Near Sirius, Procyon, and Altair with the NICMOS Coronagraph

Cited by in corpus (7)

• Imaging Extrasolar Giant Planets
• High-contrast imaging of Sirius~A with VLT/SPHERE: Looking for giant planets down to one astronomical unit
• Sirius B Imaged in the Mid-Infrared: No Evidence for a Remnant Planetary System
• High contrast imaging at 10 microns, a search for exoplanets around: Eps Indi A, Eps Eri, Tau Ceti, Sirius A and Sirius B
• Piercing the Glare: Direct Imaging Search for Planets in the Sirius System
• An Imaging Search for Post-Main-Sequence Planets of Sirius B
• Galactic astronomy with AO: Nearby star clusters and moving groups