Proposal #218
| Proposer | (43544) Nathan Kurth (nikurth04@gmail.com) obscode: KNAC |
|---|---|
| Assigned To | (3663) Dirk Terrell |
| Date Submitted | June 27, 2021 |
| Status | Allocated |
| Priority | Normal |
| Proposal | Photometric Ultra Low Resolution Transmission Spectrum of LTT 9779b Summary LTT 9779b is an ultra-hot neptune discovered in 2020. It orbits its V 9.76 G8V star once every 0.792070 days, and takes ~52 minutes to transit its star. The planet was found using TESS data. This proposal seeks to secure time on the OC61 telescope at MJUO, to observe at least 3 transits in the sloan g filter. The goal would be to produce an ultra low resolution transmission spectrum for simple atmospheric study by combining the transit depths in the g band and TESS band. Short Observation History and the Justification for New Observations The paper announcing its discovery was JS Jenkins 2020 (2020NatAs...4.1148J). Another study presented by D Dragomir 2020 (2020ApJ...903L...6D) used Spitzer observations to observe secondary eclipses, and concluded that there is CO absorption. Another study (2020ApJ...903L...7C) also using Spitzer observations measured the phase curve variations. JS Jenkins noted in the paper's abstract that “Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness”, and also noted in the paper that its properties “...makes LTT 9779 b an excellent target for future transmission spectroscopy, secondary eclipse studies, and phase variation analyses.” The g band data would help extend the transmission spectrum over a wider spectral range than what is currently available. Observation Requests Observations would use the g band filter on the OC61 telescope at MJUO. 3 full transit observations are requested, however it would also likely work to observe 3-4 partial transits. It is requested that observations start ~15 minutes before the start of a transit, and end ~15 minutes after the transit. Observations would ideally have a frequency of roughly 1 observation every ~2 minutes, however this can be adjusted as needed. Slight defocusing is also requested. Data Processing Light curves would be created using the AstroImageJ software. Resulting light curves would then be binned together to produce a higher SNR light curve. The binned light curve would then be fit with the Batman python package to calculate the transit depth. Transit depths from the g band observations as well as from TESS would then be fit using the pyrat bay package to perform a basic atmospheric retrieval. A list of upcoming transits visible from MJUO can be found at the link below: https://astro.swarthmore.edu/transits/print_transits.cgi?observatory_string=-43.986667%3B170.465%3BPacific%2FAuckland%3BMount%20John%20University%20Observatory%2C%20New%20Zealand&use_utc=0&single_object=0&observatory_latitude=-43.986667&observatory_longitude=170.465&timezone=Pacific/Auckland&days_to_print=90&days_in_past=0&target_string=LTT%209779%20b&minimum_start_elevation=30&and_vs_or=or&minimum_end_elevation=30&minimum_ha=-12&maximum_ha=12&baseline_hrs=2.1&show_unc=&minimum_priority=0&minimum_depth=0&print_html=1&twilight=-12 |
| Target | RA (H.HH) | Dec (D.DD) | Magnitude | Telescope | Observation Frequency | Expiration Date | Proprietary Term |
|---|---|---|---|---|---|---|---|
| CD-38 15670 / LTT 9779 | 23.911240 | -37.62818 | 9.79 | OC61 | — | Jan. 24, 2022 | 1 Year |
Comments
- (3663) Dirk Terrell — June 28, 2021, 5:30 p.m.
The TAC is skeptical that observations of sufficient precision can be achieved to measure a 0.002 mag transit depth. OC61 does not autoguide, so flatfielding errors will add to the problem. However we are willing to allocate time to see what precision can be achieved. We suggest waiting until after the camera is upgraded in late July.
- (4726) Kenneth Menzies — June 29, 2021, 2:07 p.m.
Nathan:
Good luck on this nearly impossible task! Observing the transit will be extremely difficult, let alone observing some atmospheric effect.
You will need to provide a table of three specific full transit intervals that you find feasible from OC61. That is your task as the proposer! I will then put the ACP imaging plan together.
Ken
- (43544) Nathan Kurth — July 7, 2021, 5:11 p.m.
Ken:
Here is a table of transit times in UTC. Let me know if there is anything that needs to be adjusted.
Nathan
Date UTC (m/d) | Obs start UTC | Obs mid UTC | Obs end UTC
8/02 | 11:53 | 12:34 | 12:49
8/09 | 14:58 | 15:39 | 16:20
8/13 | 14:01 | 14:42 | 15:33- (4726) Kenneth Menzies — July 8, 2021, 4:19 p.m.
I have not looked at the predicted duration of this transit but is 1-1.5 hours enough? Does it include some time before and after the transit to record baseline? Sounds short compared to most transit runs. Do these dates include full transits? If not, you are making it even more unlikely you will detect this small transit!
Ken
- (43544) Nathan Kurth — July 8, 2021, 5:48 p.m.
I made a few mistakes on the table. The end of observations (Obs end UTC) on 8/02 should be 13:15 not 12:49. It probably would have been better if I had Obs mid UTC say Transit mid UTC The dates provided cover full transits. The transit duration is roughly 52 minutes, so 1.5 hours would be enough. The start and end times should provide ~15 minutes before and after each transit. Let me know if there is anything else. Also is it known what precision has been achieved on OC61?
- (3663) Dirk Terrell — July 8, 2021, 8:07 p.m.
A new camera is to be installed later in the month and that will surely help things. One reason the TAC was supportive of this project was to see if such precisions could be achieved.
- (3000) Sebastián Otero — July 8, 2021, 8:23 p.m.
Accordint to the VSX ephemeris, the transit will happen between 12.09 and 13.13 on August 2, so I think you should be a little more generous with the times to take the period uncertainties into account.
- (43544) Nathan Kurth — July 8, 2021, 10:17 p.m.
Out of curiosity, what is the maximum time that I can request? I don't want to take up to much time but is it possible to extend from 1.5 hours to 2 hours?
- (4726) Kenneth Menzies — July 9, 2021, 2:41 p.m.
Nathan, you need to be thinking about what you need for your project to succeed. We will tell you if we think that is too much to ask for. There is no hard and fast rule! IMO, if you do not include at least 1/2-1 hour before and after the transit the quality of your AIJ analysis will degrade significantly. Additionally, there is no way to 'guarantee' that the ACP Scheduler algorithm will start the plan 'exactly' on time (+- 15 min). BTW, IMHO you can anticipate 0.01-0.02 mags as a typical random error. Yes, it is possible to get smaller errors (5 millimag/0.005?) by increasing the exposure to move the ADU count up to the top of the linear range. I will do that BUT I can only note that most AAVSONet scopes do not routinely achieve that level. That does not mean you will not 'see' transits that are smaller than 0.01. Statistics are amazing at pulling trends out of the noise. BUT, can you trust what the black box says? Statistics actually says no! In this case, the additional problem is the shortness of the transit (52 min). In order to get many data points you need fast cadence, e.g., <1 minute. Unfortunately, that makes it harder to get high ADU/SNR. This makes it harder to succeed! As the TAC stated, you can try.
Please update your three desired transit run times in a table.
- (43544) Nathan Kurth — July 9, 2021, 4:59 p.m.
I will work on the transit table and give it early next week. I would like to thank everyone for providing their comments. Is there anything else that I will need to provide?
- (43544) Nathan Kurth — July 14, 2021, 1:25 a.m.
Here is an updated table of transit times. Let me know if there is anything that needs to be changed.
date (UTC) | start | end
8/9 | 14:30 |16:45
8/13 | 13:30 | 15:35
9/1 | 13:50 | 15:50- (4726) Kenneth Menzies — July 15, 2021, 11:57 p.m.
Nathan:
What is your observer code? Are you an AAVSO member?
- (4726) Kenneth Menzies — July 16, 2021, 12:16 a.m.
Committed to OC61, check test image you receive for exposure.
- (43544) Nathan Kurth — July 16, 2021, 6:19 p.m.
My obscode is KNAC.
- (4726) Kenneth Menzies — July 28, 2021, 9:19 p.m.
Did you see any test images yet?
- (43544) Nathan Kurth — Aug. 3, 2021, 1:29 a.m.
I have not seen a test image yet.
Comments on this proposal are closed.