Affiliation
American Association of Variable Star Observers (AAVSO)
Fri, 01/24/2020 - 23:27
AAVSO Alert Notice 693 announces a campaign on the YSO V582 Mon (KH 15D). Please see the notice for details and observing instructions.
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
Hi Elizabeth, just checking but the submission name to the AAVSO says V694 Mon - is this a typo and it should read V582 Mon?
cheers, Merv
Hi Marv,
Yes, this was a typo on my part and it should be V582 Mon - on the day I wrote the Alert Notice for V582 Mon I had also been working on one on V694 Mon (MWC 560), and the Alert Notice numbers were 692 and 693. I confused myself! Thanks for catching it -
Good observing,
Elizabeth
The near-IR spectroscopy scheduled for this star is underway. Although the star has been faint and difficult to measure, some additional I-band photometry would be helpful in asessing the state of the system ust now. I have obtained V and I data in the past two weeks, but it is now cloudy locally (Arizona), so cannot follow the star during the spectroscopic observations.
\Brian
It is probably worth noting here that because of the virus shutdowns, the planned spectral observations of KH 15D with Gemini did not happen. The observing season will be ending in the coming weeks. In the last few days the star has gone into the deep double minimum of its variation cycle, down around mag 19 in V. AAVSO observations in the last couple months have shown this pattern very clearly. Because of the crowding and faintness, it is OK to get only I filter data: the variation pattern is well-known, so just knowing the state of things is sufficient. I will follow it until it is somewhat below 3 airmasses at Sun elevation -10 degrees.
\Brian
Hi all, I'm working with Bill Herbst on organizing observations of KH 15D for this upcoming season. We thought it would be worth presenting a few suggestions for observing based on our experience with it, given the star's rather challenging location about an arcminute to the north of HD 47887, which is around magnitude 7.5 in the I band, compared to 14th magnitude for KH 15D at its brightest, and 17th magnitude at its dimmest.
We have had success in taking sets of 5 consecutive 60 second exposures which are later average-combined. This strategy generally gets us just enough signal from KH 15D that our photometry software can detect it even when it's in an eclipse, but doesn't cause blooming issues on HD 47887. Take a look at the ephemeris. If the system is going into an eclipse, you'll want to push for as much signal as you can possibly get without blooming taking place. Of course, you may need to adjust your integration time depending on the speed of your telescope, camera gain, etc.
We have been using star apertures that are 1.5 times the FWHM of KH 15D, as opposed to the 3-4 times the average FWHM for all stars in the field recommended in the AAVSO CCD Photometry Guide. We then use rather narrow sizes for the gap and annulus (we used 5 pixels for both, for at a scale of 0.37"/pixel), which mitigates the incursion of a diffraction spike coming off of HD 47887. Diffraction spikes may, of course, not be as big of a concern given your specific setup, but it's worth watching out for them. If there's a chance the diffraction spike is poking through your sky annulus, it is helpful to use a median of the pixel values in the annulus, rather than a mean. We also don't recommend the common technique of defocusing the telescope because of the potential for photometric blending.
Speaking of scale, given the small apertures we are forced to use, a larger field of view is not advantageous for this target. If you're working with a larger FOV, be careful about your apertures getting too small in order to prevent blending with HD 47887 (or its diffraction spike).
Echoing Brian Skiff's post, I-band observations are the most important right now. V and R are nice, but not a priority.
Thanks to all who are working on this project. We're excited to see what this system will do next, and AAVSO observations will be extremely important for monitoring it going forwards!
Hi again, folks. We are expecting this system to be at a local maximum (a "central return to brightness," when star A "peeks out" at perihelion) on or around this Wednesday, November 18th. Getting multiple, relatively high-cadence data points around this time would be very, very useful in refining when the maximum actually occurs, and we would be greatly appreciative of anyone who is able to observe KH 15D on Wednesday. Thank you all!
Hello Kevin--observed the past 2 nights. Good results 2 nights ago, thru clouds last night (tuesday night) Plan to observe tonight (Wednesday). Any idea what time to look? Have a robotic scope, so need to share time with others and cannot observe all night.
Its faded to about 17 from 15 over the past week in I. Any interest in following it to minimum? That is listed at 21.5.