MOA-192 b's mass revisited?

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OGLE 2007-BLG-192 b ... 1.4 M_e?

Post by Sirius_Alpha on 18th January 2009, 8:57 pm

Does anyone know anything about this?
http://www.newscientist.com/article/dn16439-smallest-known-planet-may-actually-be-earthmass.html

Or is the article optimistically speculating?

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Re: MOA-192 b's mass revisited?

Post by Stalker on 19th January 2009, 12:21 pm

MOA-2007-BLG-192 b, not OGLE-2007-BLG-192 b
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Re: MOA-192 b's mass revisited?

Post by Lazarus on 19th January 2009, 3:39 pm

I'd like to see something more substantial than a New Scientist story. If confirmed, its something of a pity... a super-Earth orbiting a brown dwarf would be neat


Last edited by Lazarus on 21st January 2009, 6:05 pm; edited 1 time in total
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Re: MOA-192 b's mass revisited?

Post by Stalker on 20th January 2009, 2:04 am

The star is in the border between brown dwarf and red dwarf. If it is a red dwarf it is much more luminous. if I do not make a mistake it is well the brightness of the star (which depends of course on its mass) which has an influence.
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Re: MOA-192 b's mass revisited?

Post by Michael Johne on 21st January 2009, 4:47 am

Hi!

Dear All,
The New Scientist and perhaps other media outlets are reporting that the mass of MOA-2007-BLG-192Lb has been revised down to 1.5 Earth masses, but these reports are in error. The reporter has been confused by a report of one of my colleagues regarding a revision in the mass estimate that would be possible if the host star was confirmed to be a ~0.09 solar mass M-dwarf instead of a brown dwarf. The correct mass estimate remains 3.3 ( +4.9 / - 1.8 ) Earth masses. This is currently the lowest mass estimate for an exoplanet except for PSR 1257+12 b, but the error bars have large overlap with a number of other planets detected by both radial velocities and microlensing.

- David Bennett, for the MOA, OGLE, and PLANET collaborations

link: http://listes.obs.ujf-grenoble.fr/wws/arc/exoplanets/2009-01/msg00008.html

Bye!
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MOA-192 b's mass revisited?

Post by Stalker on 2nd February 2010, 2:41 pm

ABSTRACT.
At present, microlensing light curves from different telescopes and filters are photometrically aligned by fitting them to a common model. We present a second method based on photometry of common field stars. If two spectral responses are similar (or the color of the source is known), then this technique can resolve important ambiguities that frequently arise when predicting the future course of the event, and that occasionally persist even when the event is over. Or, if the spectral responses are different, it can be used to derive the color of the source when that is unknown. We present the essential elements of this technique and apply it to the case of MOA-2007-BLG-192, an important planetary event for which the system may be a terrestrial planet orbiting a brown dwarf or very low mass star. The refined estimate of the source color that we derive here V I = 2.36 0.03 will aid in making the estimate of the lens mass more precise.

http://arxiv.org/abs/0910.1832
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Re: MOA-192 b's mass revisited?

Post by Sirius_Alpha on 2nd February 2010, 3:39 pm

Merged two threads about the same topic. Great to see the paper came out though! Nice find, Stalker.

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Re: MOA-192 b's mass revisited?

Post by Stalker on 2nd February 2010, 4:12 pm

I wrote an article about MOA-192 b when the link towards the paper was published on EPE.


I flew over the paper, it is not written which mass give new method for this planet.
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Re: MOA-192 b's mass revisited?

Post by Stalker on 2nd February 2010, 4:20 pm

The French magazine Ciel & Espace had answered one of my mails that according to a study not published the mass of the star was close to 0.09M_S.Their conclusion is that the mass of the planet is close to 1,4M_T.

But it is not a good source.
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Re: MOA-192 b's mass revisited?

Post by Stalker on 3rd February 2010, 10:29 am

http://fr.arxiv.org/abs/1002.0332

Gravitational microlensing occurs when a foreground star happens to pass very
close to our line of sight to a more distant background star. The foreground
star acts as a lens, splitting the light from the source star into two images,
which are typically unresolved. However, these images are also magnified, by an
amount that depends on the angular lens-source separation. The relative
lens-source motion results in a time-variable source magnification: a
microlensing event. If the foreground star happens to host a planet with
projected separation near the paths of these images, the planet will further
perturb the images, resulting in a characteristic, short-lived signature of the
planet. This chapter provides an introduction to the discovery and
characterization of exoplanets with gravitational microlensing. The theoretical
foundation of the method is reviewed, focusing on the phenomenology of
planetary perturbations. The strengths and weaknesses of the microlensing
technique are discussed, highlighting the fact that it is sensitive to low-mass
planets with separations just beyond the snow line, orbiting stars located
throughout the Galactic disk and foreground bulge. An overview of the practice
of microlensing planet searches is given, with a discussion of some of the
challenges with detecting and analyzing planetary perturbations. The chapter
concludes with a review of the results that have been obtained to date, and a
discussion of the near and long-term prospects for microlensing planet surveys.
Ultimately, microlensing is potentially sensitive to multiple-planet systems
containing analogs of all the solar system planets except Mercury, as well as
to free floating planets, and will provide a crucial test of planet formation
theories by determining the demographics of planets throughout the Galaxy.
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Re: MOA-192 b's mass revisited?

Post by Lazarus on 3rd February 2010, 3:53 pm

Nice review of exoplanet detection via microlensing there. Microlensing Planet Finder would definitely be an interesting mission.
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Re: MOA-192 b's mass revisited?

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