HAT-P-13: b probably well aligned, evidence for third companion?

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HAT-P-13: b probably well aligned, evidence for third companion?

Post by Sirius_Alpha on 24th March 2010, 8:28 pm

The HAT-P-13 Exoplanetary System: Evidence for Spin-Orbit Alignment and a Third Companion
http://arxiv.org/abs/1003.4512

Abstract wrote:We present new radial-velocity measurements of HAT-P-13, a star with two previously known companions: a transiting giant planet "b" with an orbital period of 3 days, and a more massive object "c" on a 1.2 yr, highly eccentric orbit. For this system, dynamical considerations would lead to constraints on planet b's interior structure, if it could be shown that the orbits are coplanar and apsidally locked. By modeling the Rossiter-McLaughlin effect, we show that planet b's orbital angular momentum vector and the stellar spin vector are well-aligned on the sky (lambda = -0.9 +/- 8.5 deg), suggesting that the planetary orbits are also well-aligned. The refined orbital solution favors a slightly eccentric orbit for planet b (e = 0.0142_{-0.0044}^{+0.0052}), although it is not clear whether it is apsidally locked with c's orbit (\Delta\omega = 48_{-38}^{+25} deg). We find a long-term trend in the star's radial velocity and interpret it as evidence for an additional body "d", which may be another planet or a low-mass star. The next inferior conjunction of c, when a transit may happen, is expected on JD 2,455,315.2 +/- 1.9 (centered on UT 17h 2010 April 28).

This is quickly becoming the best planetary system ever.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Sirius_Alpha on 25th March 2010, 7:01 pm

Relevant Oklo blog post.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Lazarus on 31st March 2010, 2:33 pm

The bad news with this new configuration is that all the fun with transit timing variations occurs when HAT-P-13 passes too close to a star which appears roughly a quadrillion times brighter.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Sirius_Alpha on 2nd February 2011, 9:25 pm

An interesting paper on TTVs at HAT-P-13.

Transit timing variations in the HAT-P-13 planetary system
http://arxiv.org/abs/1102.0525

In this Letter we present observations of recent HAT-P-13b transits. The combined analysis of published and newly obtained transit epochs shows evidence for significant transit timing variations since the last publicly available ephemerides. Variation of transit timings result in a sudden switch of transit times. The detected full range of TTV spans ~0.015 days, which is significantly more than the known TTV events exhibited by hot Jupiters. If we have detected a periodic process, its period should be at least ~3 years because there are no signs of variations in the previous observations. This argument makes unlikely that the measured TTV is due to perturbations by HAT-P-13c.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Sirius_Alpha on 24th May 2011, 9:08 pm

TASTE. II. A new observational study of transit time variations in HAT-P-13b
http://arxiv.org/abs/1105.4603

TASTE (The Asiago Search for Transit timing variations of Exoplanets) project is collecting high-precision, short-cadence light curves for a selected sample of transiting exoplanets. The hot jupiter HAT-P-13b has been claimed to have suddenly deviated from a linear ephemeris by ~20 min, suggesting the presence of a perturber in the system. Using five new transits, we discuss the plausibility of this transit time variation (TTV), and show that a periodic signal should not be excluded. More follow-up observations are required to constrain the mass and the orbit of the hypotetical perturber.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Lazarus on 26th May 2011, 1:57 am

That's quite neat - apparently HAT-P-13c cannot explain the TTV, maybe more evidence for the third companion?
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Re: HAT-P-13: b probably well aligned, evidence for third companion?

Post by Sirius_Alpha on 29th May 2011, 8:16 pm

Unless there's just no strong evidence for TTVs at HAT-P-13. Question

Long-Term Transit Timing Monitoring and Refined Light Curve Parameters of HAT-P-13b
http://arxiv.org/abs/1105.5599

We present 10 new transit light curves of the transiting hot Jupiter HAT-P-13b, obtained during two observational seasons by three different telescopes. When combined with 12 previously published light curves, we have a sample consisting of 22 transit light curves, spanning 1,041 days across 4 observational seasons. We use this sample to examine the recently observed large-amplitude transit timing variations (P\'al et al. 2011), and give refined system parameters. We find that the transit times are consistent with a linear ephemeris, with the exception of a single transit time, from UT 2009 Nov 5, for which the measured mid transit time significantly deviates from our linear ephemeris. The nature of this deviation is not clear, and the rest of the data does not show any significant transit timing variation.

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Re: HAT-P-13: b probably well aligned, evidence for third companion?

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