Photometry log #2: 6 weeks of observations

It has been six weeks since we started the photometric follow-up campaign and here there are some updates and exciting plots from observatories involved:

SPACE Observatory
Check a strong flare caught in action! It was detected in Ross 154 during the night of July, 12th using the ASH2 telescope at SPACE Observatory in Chile. Figure 1 shows the luminosity variations in V and R filters as magnitude differences relative to the main check stars. For comparison, the light curves corresponding to the nights 11/Jul and 13/Jul are also displayed. As can be seen, the night of July 12th was very active for Ross 154, the luminosity level being larger than during the other two nights. We can also see that the energy released during the flare is much larger in the V band (ΔV=0.84 mag) than in R (ΔR=0.45 mag). The rising branch is also much faster than the decreasing one (5 min versus more than 40 min). The figure also shows some humps (plotted as black arrows) which occurred during the descending light curve.

Figure 1. Differential light curves taken at ASH2, of Ross 154 (also known as GJ 729) in V and R filters. A large flare of 0.84 mag in V and 0.45 mag in R was caught the night of July 12th. The precedent and following nights are shown for comparison.

Montsec Astronomical Observatory (OAdM)
The Joan Oró telescope (TJO) has obtained and processed more than 500 images of Barnard’s star and  Ross 154 during the first 6 weeks of the Red Dots campaign, producing the first multi-colour light curves for both M dwarfs.

As the TJO is in charge of a low time-cadence photometric monitoring, a mean of one measurement per night in each filter is obtained for each star. We decided to use the combination of 5 images for each photometric measurement, so a total of 28 and 29 measurements were already produced for Barnard’s star in I and R filters, respectively. For Ross 154 star, only 17, 18 and 11 could be obtained with filters I, R, V, respectively. This is because some observations were lost at the beginning due to saturated images, and also a number of bad weather nights (mainly thin clouds) occurred during the last two weeks.

Despite these issues, the TJO multi-colour light curves, shown in Figure 2, already show a significant variability in both targets. Quite unexpectedly for Barnard’s star, it increases its brightness about 4%, while Ross 128 is showing irregular variability (probably due to activity) with ~2% variations.

Figure 2. Differential light curves of Barnard’s star in I, R filters and Ross 154 in I, R, V filters. Montsec Astronomical Observatory
Figure 3. Differential folded light curves of Ross 154 taken with LCO in B (top), V (middle) and i (bottom) filters. The light curves are folded to the periods shown.

Las Cumbres Observatory (LCO)
LCO was allocated 14 hours of observations of Ross 154 with a moderate and high time-cadence, of which 10.3 hours have already been used. Figure 3 shows the light curves in B (top) and V (middle) filters folded to a period of ~ 2.9 days, consistent with the suspected rotation period. Observations with the i’ Sloan filter (bottom) are noisier, most likely due to internal errors of the filter and comparison stars being fainter at redder wavelengths and as a result they do not recover the rotation period.

4 Comments

  1. Hi, I can confirm the flare in GJ729 (V1216 Sgr) as I have observed during the same night from the asme location.
    Data for this and V2500 Oph and V0645 Cen are with the AAVSO under user HMB.

    Josch

  2. Hi, there was a flare in Proxima Centauri on July 5 of about 0.4 mag followed by a smaller hump on about 0.05 mag. I probably did not really catch the maximum of the large flare as the first image was already 0,4 mag brighter than the baseline. There is also some longer term periodicity observed of about 15 days or so.
    Josch

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