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ADONIS high contrast infrared imaging of Sirius-B | | Jean-Marc Bonnet-Bidaud
; Eric Pantin
; | | Date: |
28 Sep 2008 | | 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). | | Source: | arXiv, 0809.4871 | | Services: | Forum | Review | PDF | Favorites | |
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