Scholz's Star B or b?

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Scholz's Star B or b?

Post by Edasich on 24th November 2015, 10:05 am

Extrasolar Planet Encyclopaedia is listing WISE J072003.20-084651.2 (also known as Scholz's Star) as hosting a planetary(?) substellar companion with 62 times the mass of Jupiter 1.3 AUs away.

http://exoplanet.eu/catalog/wise_j0720-0846/

Upper limit of planetary domain is broadening day by day. Are brown dwarfs and planets going to merge in a single category? Suspect

Paper cited:

Radio Emission and Orbital Motion from the Close-Encounter Star-Brown Dwarf Binary WISE J072003.20-084651.2

We report the detection of radio emission and orbital motion from the nearby star-brown dwarf binary WISE J072003.20-084651.2AB. Radio observations across the 4.5-6.5 GHz band with the Very Large Array identify at the position of the system quiescent emission with a flux density of 153 μJy, and a highly-polarized radio source that underwent a 2-3 min burst with peak flux density 30090 μJy. The latter emission is likely a low-level magnetic flare similar to optical flares previously observed for this source. No outbursts were detected in separate narrow-band Hα monitoring observations. We report new high-resolution imaging and spectroscopic observations that confirm the presence of a co-moving T5.5 secondary and provide the first indications of three-dimensional orbital motion. We used these data to revise our estimates for the orbital period (4.1+2.7−1.3 yr) and tightly constrain the orbital inclination to be nearly edge-on (93.6\deg+1.6deg−1.4deg), although robust measures of the component and system masses will require further monitoring. The inferred orbital motion does not change the high likelihood that this radio-emitting very low-mass binary made a close pass to the Sun in the past 100 kyr.
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Re: Scholz's Star B or b?

Post by Daniel on 24th November 2015, 2:39 pm

Well I stop use the EPE as exoplanet reference long time ago...
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Re: Scholz's Star B or b?

Post by Stalker on 24th November 2015, 4:22 pm

Interestingly it is in the "brown dwarf desert"

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Re: Scholz's Star B or b?

Post by Lazarus on 24th November 2015, 7:00 pm

I guess that fits with the Hatzes and Rauer (2015) mass-density relationship criterion for distinguishing brown dwarfs and giant planets, which puts the transition at 60 Jupiter masses. EPE's readme document says they have adopted 30 Jupiter masses to 1-sigma as the cutoff.

The mass value for WISE J0720-0846B on the EPE page is a bit weird, the source goes with 0.062+0.009-0.011 solar masses (table 4), while EPE gives 62+0.09-0.11 Jupiter masses, i.e. using 1 solar mass = 1000 Jupiter masses - although the errors would then be +9-11 Jupiter masses.

Using Google's values for the jovian and solar masses and rounding to the nearest integer values, I get 65+9-12 Jupiter masses. Both conversions put the 1-sigma error bar below 60 Jupiter masses.

So it looks like EPE is now using the 60 Jupiter masses cutoff but haven't updated their readme, and their mass conversion for this object is somewhat off.


Last edited by Lazarus on 30th November 2015, 5:37 pm; edited 1 time in total (Reason for editing : fix formatting)
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Re: Scholz's Star B or b?

Post by Edasich on 25th November 2015, 4:33 am

Does this mean many substellar objects previously classed as "brown dwarfs" are going to be listed in planet count sooner or later, disproven planets characterized by astrometry as brown dwarfs included (to say HD 137510 b and HD 190228 b)?
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