Open AccessNew observations of the PZ Tel system, its substellar companion and debris disc
Author(s) -
Mugrauer M.,
Röll T.,
Ginski C.,
Vogt N.,
Neuhäuser R.,
Schmidt T. O. B.
Publication year - 2012
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2012.21216.x
Subject(s) - physics , photometry (optics) , proper motion , astrophysics , orbital motion , astronomy , stellar classification , orbital inclination , binary number , stars , angular momentum , arithmetic , mathematics , quantum mechanics
We present follow‐up high‐contrast imaging data of PZ Tel B, the substellar companion of a solar analogue pre‐main‐sequence star and member of the approximately 12‐Myr‐old β Pic moving group. Between 2010 October and 2011 June, we observed PZ Tel in three observing epochs with NACO/ESO‐VLT, which proves the companionship of PZ Tel B on a very high significance level and shows that the photometry of the PZ Tel system is stable on the 10 per cent level. The orbital motion of PZ Tel B relative to its primary is clearly detected between all observing epochs, and we even find evidence for deceleration of its orbital motion, as expected for an object on a Keplerian orbit moving towards its apastron. We also present new photometric measurements of PZ Tel just recently obtained by WISE , which clearly confirm that there is no excess emission in the spectral energy distribution (SED) of the star up to 24 μ m, while a prominent excess is detected at 70 μm with MIPS/ Spitzer . To quantify the orbit elements of the PZ Tel system, we applied a least‐squares Monte Carlo (LSMC) fit on all astrometric measures taken with NACO. The results of the performed LSMC fit are that one cannot yet determine a single ‘best'‐fitting orbital solution, due to the poor astrometric coverage of the orbit. However, the obtained good LSMC solutions ( χ red 2 ≤ 2 ) give an overview of the distributions and correlations of all orbit elements. According to our LSMC fit, PZ Tel is an eccentric binary ( e ≳ 0.6), and the orbit elements degenerate with growing eccentricity. For e < 0.95, the PZ Tel system is seen nearly edge‐on (92° ≲ i ≲ 110°), has a longitude of the ascending node of 50° ≲ Ω ≲ 65°, an argument of periastron 170° ≲ ω ≲ 290° and exhibits a semimajor axis a larger than about 20 au, with the highest peak in the a ‐histogram located at about 25 au (or about 110 yr of orbital period), up to a few tens of au, as orbital solutions with a significantly larger semimajor axis would not be able to harbour a circumbinary disc which excites the observed excess in the SED of PZ Tel A.