Gliese 892 / HD 219134 - six planets (at least one planet in transit)

See my breadit on the previous page.

Good to see the Geneva paper. Frankly, I'm mildly surprised it's taken this long for that program to reach their first result, considering they've been dedicating so much time on HARPS-N to it. Still, it is highly deserved.

At a declination of +57°, there's about 50% odds between the star being observed over one or two TESS pointings (there's probably some source that gives TESS' exact pointings, but odds are fun). That means the star will either have 1 or 2 months of photometry, if I understand the mission right. As the star is so very bright (roughly 1000 times brighter than a modest Kepler star), that photometry will probably be of ppm precision per point. That's… staggeringly exciting.

What a time to be alive, eh.

There's a fun diagram in the TESS overview paper (figure 11) that shows the expected cumulative yields of the mission per stellar magnitude. Looking at the <2 Rearth line, it looks like Gliese 892 is likely either the brightest or second-brightest star with a transiting planet. That's… well, something to chew on.

On ArXiv now.
http://arxiv.org/abs/1507.08532

If planet c will have the same inclination as b will not transit.Where is planet with 22.8 days period? What does it mean :
Note added in proof. During the refereeing process, we
learned about an independent detection by Vogt et al. (Laughlin,
private communication) reporting additional planets in the
system, based on long-term radial velocities obtained with the
Keck and APF telescopes.

We can bet that second planet is surely rocky with radius less than 1.55 earths, better would be to find transit of planet with 46 days period if transits

http://arxiv.org/abs/1509.07912

A Six-Planet System Orbiting HD 219134

We present new, high-precision Doppler radial velocity (RV) data sets for the nearby K3V star HD 219134. The data include 175 velocities obtained with the HIRES Spectrograph at the Keck I Telescope, and 101 velocities obtained with the Levy Spectrograph at the Automated Planet Finder Telescope (APF) at Lick Observatory. Our observations reveal six new planetary candidates, with orbital periods of P=3.1, 6.8, 22.8, 46.7, 94.2 and 2247 days, spanning masses of msini=3.8, 3.5, 8.9, 21.3, 10.8 and 108 M_earth respectively. Our analysis indicates that the outermost signal is unlikely to be an artifact induced by stellar activity. In addition, several years of precision photometry with the T10 0.8~m automatic photometric telescope (APT) at Fairborn Observatory demonstrated a lack of brightness variability to a limit of ~0.0002 mag, providing strong support for planetary-reflex motion as the source of the radial velocity variations. The HD 219134 system, with its bright (V=5.6) primary provides an excellent opportunity to obtain detailed orbital characterization (and potentially follow-up observations) of a planetary system that resembles many of the multiple-planet systems detected by Kepler, and which are expected to be detected by NASA's forthcoming TESS Mission and by ESA's forthcoming PLATO Mission.

Looks like some inconsistency over which planet is the d planet.

Well in my opinion in this case distance from the star should have priority

Sirius_Alpha wrote:

Looks like some inconsistency over which planet is the d planet.

Also a discrepancy about the period of the outer planet. Though HARPS gave period of 1190⁺³⁷⁹_-34 days, new period is 2247±43 days. So ~2.8σ_HARPS difference.

Would be interesting to try and do a model of the combined data set. Also, it seems that they aren't incorporating the possibility of correlated noise in the model, wonder what incorporating that would do.

The difference in periods is solely due to the HARPS-N data being, like, 3 seasons long (~1100 days). Their model prefers a considerable eccentricity, which is clearly strongly disfavoured by the data that actually covers multiple periods.

It's good to see such independent results reaching comparable solutions. That's not been possible for some time at the lowest RV semi-amplitudes, with HIRES and HARPS observing mostly mutually exclusive stars. Repeatable observations, and all that jazz. Though HARPS-N isn't being used in nearly the same way as HARPS or, indeed, HIRES, the co-operation is admirable.

That hole in the vicinity of 1 AU is notable. Though the detection probabilities in the area are probably not very high, it seems plausible that the relatively massive outer companion could have been disruptive, as with Jupiter and the region of the asteroid belt, or possibly not, as in a few systems. A planet detection (or null detection) in the ~200 - ~1000-day region would be interesting for understanding the system formation… and would, of course, be interesting for lying about the HZ…

A highly important system. This will be one with a lot of papers, in due course.

Well in solar system between Mars and Jupiter we have no planets it could be the case but I wonder whether possible is both 1190 and 2247 days periods can exist as planets or one exclude another?

On EPE i have noticed this system has 7 planets ? I found this :

17 Nov 2015: The names an characteristics of planets HD 219134 d, e, f, g and h raise two specific problems since there are two papers: Motalebi et al. 2015 and Vogt et al. 2015 with different sets of parameters. We adopt the following solution, at least provisionally:
- names: The standard rule is two give names NNN b, c, d etc by order of discovery, the criterion being the date of submission of a paper. The Motalebi et al paper has been submitted on June 24th 2015, the Vogt et al. paper on July 17th 2015. The four Motalebi planets are there fore named b, c, d and e and the new Vogt planets named f, g and h.
- parameter values: The Vogt et al. planet data are based on 276 observation points while the Motalebi et al data are based on 98 data points. We therefore adopt Vogt et al. values for all planet.
- remark: It is not impossible that more data will change this situation. In particular HD 219134 e and h may merge in a single object.

Quote :

In particular HD 219134 e and h may merge in a single object

Considering they're the same signal, I don't see why that hasn't been done already. Though, this is the EPE we're talking about…

EPE is making some mess lately.

I generally find EPE most useful for the bibliography section, rather than the data...

NASA Exoplanet Archive has also gone with a 7-planet representation.

The Automated Planet Finder's Detection of a 6-planet System Orbiting the Bright, Nearby Star HD219134
The Automated Planet Finder (APF) is the newest facility at Lick Observatory, comprised of a 2.4m telescope coupled with the high-resolution Levy echelle spectrograph. Purpose built for exoplanet detection and characterization, 80% of the telescope's observing time is dedicated to these science goals. The APF has demonstrated 1 m/s radial velocity precision on bright, RV standard stars and performs with the same speed-on-sky as Keck/HIRES when observing M-dwarfs. The APF has contributed to the detection of four planetary systems in its first two years of scientific operations. Our most recent detection is that of a 6-planet system around the bright (V=5.5), nearby (d=6.5pc), K3V star HD219134. The planets in this system have masses ranging from 3.5 to108 MEarth, with orbital periods from 3 to 2247 days. An independent detection of the inner 4 planets in this system by the HARPS-N team has shown that the 3d planet transits the star, making this system ideal for follow-up observations. I will discuss the APF's detections to date, highlighting HD219134, as well as the overall performance results of the telescope and our future observing strategy.

I found this recently announced but third planet transit not first? Mistake?

"3d planet" = "3-day planet"

Ok I really hoped for more transiting planets in this system 6.7 and 22.8 days

Pity though, a multi-transiting system at such close range would definitely be interesting!

One of the planet signals may actually be stellar activity.

A 12-Year Activity Cycle for HD 219134
http://arxiv.org/abs/1602.05200

twit from Davos (meeting july 4)

Hurrah indeed!

c's inclination appears to be 2.2 degrees lower than b's. If they were coplanar, c would not be transiting (impact parameter ~1.5). Sometimes non-coplanarity can be favourable, it seems.

That's incredible news! It looks like we're getting some particularly favourable targets for low-mass planet transmission spectroscopy ahead of JWST, even before TESS.

As far as I can tell, that radius is compatible with it being a terrestrial planet.

I hoped for transit planet c to happen and I am pleased now .Looks like c is slightly smaller and denser than b but both definitely rocky