Monthly Archives: February 2009

‘606

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The primary transit of HD 80606b

After 10 days of no news, definitively flat news (Arizona) and tantalizing hints in my inbox, the HD 80606b transit story is resolving itself dramatically.

Earlier today, Stephen Fossey, Ingo Waldmann and David Kipping submitted their paper on the detection. I based the diagram on the results of their photometry, which points to a twelve hour transit, and a planetary radius just larger than Jupiter:

Fossey et al. photometry of the primary transit of HD 80606b

The Fossey et al observations were made using two small telescopes at the University College London’s observatory in Mill Hill, North London. (Co-author Ingo Waldmann is a final-year undergraduate project student.) It’s certainly been a long time since an observational astronomical discovery of this magnitude has made from within the London City Limits!

Also in my inbox this morning was an e-mail from Jose Manuel Almenara Villa, who made the definitive initial observation of HD 17156 (and made the initial announcement on the comment section of this weblog). He writes, I know it’s late, but here there are the data from Tenerife. The egress is fully there, fully present. Nice work!

Jose Manuel Almenara Villa Photometry for HD 80606

And then, no more than an hour ago, another dramatic update. In an e-mail to myself and Jean Schneider, Enrique Garcia-Melendo writes:

Dear Greg and Jean,

We observed the transit of HD80606b.

Please find attached the submitted paper to the ApJ. The manuscript will also appear at http://arXiv.org/abs/0902.4493

Best regards,
Enrique Garcia-Melendo

Title: Unconfirmed Detection of a Transit of HD 80606b
Authors: E. Garcia-Melendo and P. R. McCullough
Categories: astro-ph.EP
Comments: Submitted to ApJ, 11 pages, 4 figures.

We report a times series of B-band photometric observations initiated on the eve of Valentine’s day, February 14, 2009, at the anticipated time of a transit of the extrasolar planet HD 80606b. A transit model favored by the data has minimum light of 0.990 times the nominal brightness of HD 80606. The heliocentric Julian date (HJD) of the model’s minimum light is 2454876.33, which combined with the orbital period P = 111.4277 pm 0.0032 days, longitude of periastron, omega = 300.4977 pm 0.0045 degrees, and time of mid-secondary eclipse HJD 2454424.736 pm 0.003 (Laughlin et al. 2009), refines the eccentricity, e = 0.9337 +0.0012 -0.0004}, and the inclination, i = 89.26 +0.24 -0.04 degrees. The duration of the model transit is 0.47 days, and its four contacts occur at HJD 2454876 plus 0.10, 0.24, 0.42, and 0.57 days. We observed only the last two contacts, not the first two. We obtained “control” time series of HD 80606 on subsequent nights; as expected, the “controls” do not exhibit transit-like features. We caution that 1) the transit has not been confirmed independently [note: no longer true.]; 2) we did not observe the transit’s ingress; 3) consequently, we cannot reliably measure the relative sizes of the planet and its star in a model-independent manner, and 4) hence, the other values derived herein are also model dependent.

Now here’s the kicker — the Garcia-Melendo & McCullough paper was submitted on Feb. 23rd…

Update: I just heard from Shigeru Ida at Tokyo Institute of Technology, who has coordinated a number of photometric campaigns by amateur observers in Japan. It turns out that it was either rainy or totally cloudy on the night of the transit ingress (Feb. 13/14) for all of the observers. Bummer. The following night, the conditions were a little better, allowing several observers to get noisy baseline data.

HD 80606b transit detected

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I’m very pleased to be able to announce that HD 80606b is a transiting planet!

It looks like priority of discovery goes Claire Moutou and the French and Swiss team, who beat at least one other team to submission by a matter of hours. I’m attaching a draft of the French and Swiss Team’s paper that was just sent to me. Congratulations to Everyone involved!

Here’s the preprint.

Details to follow…

go

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Image Source: Mearth Live.

Update 4 : Feb. 14 2009, 07:12:00 UT

The first reports are coming in. Gregor Srdoc in Croatia got a lightcurve through most of the night for HD 80606 combined with HD 80607. No sign of a transit, but the data is relatively noisy due to imperfect weather.

Veli-Pekka Hentunen reports that weather conditions in Finland were bad generally, and were specifically bad in Varkaus.

At least four sets of observations from various locations in Arizona are currently underway, including both the 40” and the 1.3m at USNO Flagstaff under the able command of Paul Shankland.

Jonathan Irwin reports that data from Mearth through 5 UT shows no sign of an egress.

Ohio State Grad Student Jason Eastman reports on his remote Demonex observations (from the comments page):

Halfway through the night…

We started observing at UT 02:30 in the V band. No sign of an egress at the ~0.005 mag level.

http://www.astronomy.ohio-state.edu/~jdeast/demonex/HD80606b.R.2009-02-14.jpg

That link will be updated with the entire night’s data in the morning.

So it’s not looking particularly good for a transit, but I’m really happy that data is coming in. We’ll have a definitive answer sometime tomorrow.

Thanks to everyone who observed. It’s really cool how a planet 190 light years away can bring observers all over the globe into a common mission.

Update 3 : Feb. 13 2009, 23:29:00 UT

We’re now closing in on the moment of inferior conjunction, which hopefully will wind up being the midpoint of a central transit. The current weather in Europe looks like it’s clear for observers in Finland and Northern Italy, so it’s now quite likely that we’ll get a definitive answer from the campaign.

No word yet on whether an ingress was observed, but Jonathan Irwin did send a nice light curve from last night’s baseline run with Mearth. He writes:

Here’s our entire night of data (about 11 hours) from one telescope, using 80607 as the comparison star. Raw and binned x12 (about 5 minutes per bin). We are getting rms scatter of about 1.6 times Poisson with this fairly quick reduction.

There is usually a slight offset when the target crosses the meridian (data point 777) due to flat-fielding error, that I have not removed in this – over the ~20 arcsec separation of the pair it’s pretty small. There is also a bit of a blip there as my guide loop recovers its lock after crossing – still needs a little tuning :)

Fingers crossed for tonight!

Update: Clear Skies in Arizona. Dave Charbonneau writes:

http://mearth.sao.arizona.edu/live/

Clear skies. You can even watch the images in real time, and see how many
MEarth scopes are on ‘606…

Update 2 : Feb. 13 2009, 17:04:00 UT

It’s now the middle of the night in the Far East, and the transit window has opened. The weather in Japan looks a little spotty, but Southern China is in the clear.

Observers in Arizona reported good weather last night, but the forecast is a little iffy for tonight.

In addition, I just got an e-mail (UT 17:48) from Gregor Srdoc in Croatia, who is on the sky under quite good conditions just after nightfall…

Update 1 : Feb. 13 2009, 06:03:03 UT

There’s about a half-day left until the possible start of the ingress. On the map above, I’ve marked the locations of confirmed observers with small red dots. HD 80606b is 190 light years above the spot labeled with the orange circle.

Observers in the US are currently taking data of both HD 80606 and its binary companion, HD 80607. It’s always good to have an out-of-transit baseline photometric time series.

Dave Charbonneau checked in with a status report:

MEarth is ready. You can watch us in real time at
http://mearth.sao.arizona.edu/live/

If the roof is closed, it is cloudy.

The up-to-the-minute stop-action animations showing the disconcertingly reptilian movements of the telescopes are completely mesmerizing. Mearth (pronounced “mirth”) is located at the Fred Lawrence Whipple Observatory on Mt. Hopkins in Arizona, and spends most of its nights searching for potentially habitable terrestrial planets transiting nearby M dwarfs. The telescopes have a list of ~2000 nearby red dwarf stars. Each star is subjected to repeated visits of ~30-45 minute duration. The idea is to catch transiting planets in progress and to broadcast the information to larger telescopes that can obtain immediate real-time photometric confirmation of a discovery. (For a more detailed overview of Mearth, see Irwin, Charbonneau, Nutzmann & Falco 2008.)

Update 0 : Feb. 12 2009, 22:47:40 UT

I’ll be posting updates on the global HD 80606b transit campaign as I get them, with newer updates going to the top of this post.

A number of observers have indicated that they’ll be on the sky. Right now, it looks like telescopes are confirmed for Finland, Israel, Italy, Japan and the US. Given the vagaries of the weather, however, it would be great if we can get as much coverage as possible. As Vince Lombardi would have put it, “We’re looking at 15%, so if you can get 1%, get out there and give 110%!”

Everyone is encouraged to comment as the campaign progresses (click the number next to the post title to access the discussion page). I’ve lifted the restriction that only allows registered oklo users to comment, but all comments are now held for moderation, in order to keep the Viagra contingent off the air.

ready set…

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Even as I write, HD 80606b is closing in fast on its inferior conjunction. It’s basically a roll of a die, a roughly one in 6 chance, that the orbital alignment is good enough for a primary transit to be observable. (The odds are boosted from the a-priori geometric probability of 11% to ~15% by the fact that the secondary transit was fully consistent with an uninclined passage directly behind the star.)

Here’s the situation:

A central transit will last roughly 16 hours, with the ingress best suited for observers in the Far East, and the egress best suited for observers in North America. Europe is the place to be for transits that are closer to grazing. HD 80606 itself is favorably sited in Ursa Majoris, and is at low air mass for basically the entire night, especially at higher latitudes.

Good luck to everyone who’ll be observing!

What’s your angle?

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P. Diddy flossing his '606 pose.
Happy ‘606 day!

HD 80606b swung through periastron at about 01:40 UT this morning (Feb. 8, 2009) and will spend the balance of the week spinning out toward inferior conjunction, which will occur at 00:50 UT on Valentine’s day (Feb. 14th).

Proposals for GO-6, the first general observing cycle of the forthcoming Spitzer Warm Mission, were due on Friday. Jonathan and Drake and I worked right down to the 5 PM PST wire, polishing our request to complement the Nov. 2007 8-micron periastron observations with a pair of additional photometric time series at 4.5 microns (Warm Spitzer’s longest IR wavelength). Two HD 80606b events are observable during GO-6; the first at the very start of the warm mission on May 30, 2009, and the second on Jan 08, 2010. We’re keen to watch the planet ring down from its maximum brightness, so we’ve proposed for a window that runs from 10 hours before periastron to 30 hours after periastron. In the 4.5 micron bandpass, we’re predicting a maximum planet-to-star flux ratio of a bit more than one part in a thousand — easily within Spitzer’s sensitivity.

Here’s a diagram showing the portion of the orbit that we’re proposing to observe. Even though the orbital period is 111.43 days, our forty-hour proposed observation encompasses more than 200 degrees of true anomaly. A planet with e=0.932 is quite truly anomalous.

In the near term, though, I’m very eager to see what shows up in my inbox on Valentine’s day, when observers across the Northern Hemisphere will be monitoring HD 80606 to ascertain whether a primary transit for the planet can be observed.

Here’s the geometric situation. If HD 80606’s orbit were inclined only negligibly to the sky plane, then Earth’s view of the system would be a simple reflection of the standard diagram. At inferior conjunction, six days after periastron, the planet is heading away from the star and slightly toward Earth:

The occurrence of the secondary transit tells us, however, that the orbital inclination relative to the sky plane is in reality close to 90 degrees. Using the Illustrator scale tool to compress along the north-south direction, we can see the result of increasing the inclination.


“Sooner can a camel thread the eye of a needle…”

CoRoT-7b

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From a cell phone picture transmitted by an oklo.org agent

The photo above is grainy, but what’s truly remarkable is that the depth of the dip is only 0.03%. Earth transiting in front of the Sun as seen from afar blocks roughly 0.01% of the Sun’s light. Look at the signal-to-noise of the bottom composite-average curve.

I can sure empathize with the CoRoT team. Their symposium date was set up long ago. Kepler is launching in a few weeks. The results of the Doppler surveys are suggesting that super-Earths with orbital periods of 50 days or less (with correspondingly high transit probabilities) are present around 30% of solar-type stars. Ground-based photometry is pushing below 0.5 millimagnitudes at 1-minute cadence. The pressure is on. And there’s an absolutely fascinating candidate planet that isn’t quite yet out of the oven, due to a paucity of high-precision radial velocities that would pin down the mass. What do you do?

I agree! You go ahead and announce.

Everything about CoRoT-7b reemphasizes the fact that planets are wont to turn up in every corner of parameter space to which observations are sensitive. In this case, a V=11 K0V star in the direction of the galactic anti-center displays 176 individual 1.5-hour 0.3 mmag photometric dips with a strict 0.854 day periodicity. These measurements suggest a 1.7 Earth-radii planet with a 20-hour year — a world that makes 51 Peg b look like Fargo North Dakota.

The abstract for Daniel Rouan’s talk at the meeting (transcribed from the cell phone photograph) describes the procedures that the CoRoT team has implemented to rule out the various false positives that can plague transit surveys. This gives a sense of the amount of follow-up work that needs to be done in order to secure a planet as small as this one (also, see comments section for this post, for many additional details):

To qualify/falsify the interpretation of the observed transits, we have considered different alternative interpretations: (1) transit of a main sequence star in front of a giant star — rejected by the measured log(g) of the target; (2) a grazing eclipse by a stellar companion — rejected by the radial velocity measurements (3) a weak Background Eclipsing Binary that would be inside the target mask — partially rejected by on/off transit photometric observations performed from the ground at angular distance from the target larger than 2 arcsec, and by high-resolution imaging at distances larger than 0.3 arcsec. (4) a triple system made of the target star (K0V) and a faint star (M5V) eclipsed by a giant planet or a dark stellar companion — rejected by the study of the transit colours which are the same as those of the main target.

Exoplanet.eu is quoting a significantly uncertain mass of 0.035 Jupiter masses (11 Mearth) for the planet, a figure that could have been arrived at via assumptions about the density and/or limits on the radial velocity detection. An 11 Earth-mass planet would induce an eminently detectable K=8 m/s RV signal, so it’s a bit odd that a firmer estimate of the mass isn’t available yet. The CoRoT “galactic anticenter” field is located in Monoceros, at RA~06h 45m, DEC~+0d, meaning that the candidate star is currently visible to HARPS (at air mass <2) all through the first half of the night. Exoplanet.eu also states an age of 1.1 Gyr for the star, so youth, with its attendant stellar activity, could possibly be making it tough to get good velocity precision.

In any case, it’s a remarkable detection, and will be hugely influential as soon as the mass is confirmed. The planet is orbiting at only four stellar radii — with the star filling nearly a thousand square degrees of sky…