AAVSO: American Association of Variable Star Observers

Proposal #129

Proposer (18434) Guy Stringfellow (Guy.Stringfellow@colorado.edu) obscode: SGUA
Assigned To(3663) Dirk Terrell
Date SubmittedJan. 8, 2020

Accretion driven outbursts during the formation of young stars with disks still present are relatively rare events observationally, contrary to theoretical expectations that this may be the main mechanism of the final growth of low-mass stars as they approach the main-sequence with as much as half their final mass being accreted during this phase. Those events that are (serendipitously) caught are not well observed. Hence, we often know little about the duration of these events, the changes in the physical properties of the stars during these events, nor the frequency of the outbursts. One case in point pertains to 2MASS J07092139-1029344, a virtually unstudied star. This star experienced an outburst in early 2015 that lasted less than 150 days. Its lightcurve during the 2015 outburst is comprised of only 7 data points - two during the rapid rise and 5 clustered around peak. A second outburst was "observed" in 2018, with no data points observed during the rise and decline, but with a clustering around peak light (including Gaia). The duration of the second outburst lasted less than 100 days; the breadth of the events are actually defined by observations near quiescence on either side of the peak rather than a time-resolved light curve during outburst. The first outburst was roughly 2.5 mag above quiescence (peak R~16.5 mag) while the second outburst appeared somewhat brighter at R~15.8 mag.

During our late December 2019 run on the WIYN 0.9m at KPNO we obtained new observations of the star clearly showing the star to now be in outburst yet again, at R~14.5 - the brightest outburst yet. We propose to obtain time-resolved imaging in BVRI filters with cadence sufficient to fully characterize the subsequent evolution of the present outburst. We wish to determine what if any color changes occur as the star returns to quiescence, the duration of the outburst and whether it is a smooth transition of undergoing rapid and large variations during the event. We request 4-filter imaging every other day through the next 2 months. The star is observable from both SRO and MJUO over the next many months. If the star has not yet returned to quiescence after the initial 2-month campaign we will request an extention of the ongoing observations. The observations should cycle through IRVB filters with 3x180s exposures in each filter. These observations should be started immediately. My AAVSO observer code is sgua. Please let me know how to notify you if/when the exposure times need to be updated.

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
2MASS J07092139-1029344 7.155944 -10.49291 20.0–13.0 SRO July 20, 2020 1 Year


(3663) Dirk Terrell — Jan. 9, 2020, 3:45 p.m.

From Arne:

There are no technical problems with this program, except that OC61 only has BVgri. We usually use Sloan r,i as surrogates for Cousins R,I, as they can be transformed to that system for most stars. For monitoring with two telescopes, there may be an offset between the transformed Sloan filters in the south and the true Cousins filters in the north. If accepted, you should make Guy aware of this potential difficulty.

(18434) Guy Stringfellow — Jan. 9, 2020, 3:52 p.m.

Hi Arne & Dirk - now worries about the filters. I should ahve commented on that in the proposal. Looking primarily for major changes int he light curve. Thanks.

(4726) Kenneth Menzies — Jan. 10, 2020, 11:47 a.m.

Plan created and committed to SRO by MZK. Thanks for defining filter image duration!

(4726) Kenneth Menzies — Jan. 10, 2020, 11:53 a.m.

Plan also created and committed to OC61 by MZK. Filters changed to irVB from IRVB. Same durations as SRO (3 x 180s). There was a security certificate issue with acceptance at both SRO and OC61 so need to keep an eye on these plans. Also, since the target may not be listed in VSX yet (?) some fields in the plans could not be filled in automatically by SVN Validate, so again need to check?

(4726) Kenneth Menzies — Jan. 22, 2020, 2:30 p.m.

Entered plan manually on SRO. Report if you get on vphot account? Also look on FTP. I know you have 12 images??

(4726) Kenneth Menzies — Jan. 16, 2022, 11:58 p.m.

committed to TMO61

Comments on this proposal are closed.