ER Uma and RZ Lmi: Observations requested.

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  • #584179
    Graeme Coates
    Participant

    Forecast looks OK for me this evening – I’ll have a go if OK. 

    #584180
    Stewart John Bean
    Participant

    Continues to look like a superoutburst. Stewart

    #584182
    Graeme Coates
    Participant

    Currently 13.0-13.1CV (21:40-22:20UT on 6th May 2021). Answers on a postcard for this intruder…

    #584183
    Graeme Coates
    Participant

    Appears to show superhumps with period similar to the published 91.67min (going from the minima). Data in BAA VSS database for analysis. Got hindered by next door’s greengage tree, and software hang at the end…

    (Clear filter with V comparison stars used. 40sec each, ST2000XM+350mm Newt @ f4.52)

    #584184
    Stewart John Bean
    Participant

    They look good to me. Variation of about 0.15 mag is about right for superhumps, i think. So it all fits.

    Thanks , Stewart

    #584185
    Maxim Usatov
    Participant

    ER UMa May 7.2837 2021 V = 13.08 ± 0.03

    #584386
    Stewart John Bean
    Participant

    ER Uma was at quite dim last night at 15.0 V mag. It is also approaching time for the next superoutburst as the last one started around JD 2459338. With a super outburst period of 55 +_ 5 days, this minimum may be the last before a normal outburst triggers the superoutburst. A few extra observations in the next 5 days could capture the event nicely.

    Thanks in advance.

    Stewart

    #584387
    Graeme Coates
    Participant

    ER UMa appears in outburst this evening:

    Jun 23.907UT – 12.83CV

    #584389
    Tim Haymes
    Participant

    I also find the variable bright at r 12.88 +/-0.05 (Unfiltered CCD, GaiaDR2/Astrometrica). Poor conditions of drifting high cloud in Moonlight  Measurement were from start, mid and end of a frame sequence at 5s intervals for 20min.

    #584393
    Stewart John Bean
    Participant

    Definitely in outburst and possibly this will trigger the superoutburst. The last superoutburst was recorded, at its brightest at 12.2 visual, by OJR (AAVSO) on 2459339. So we are ~50 days later right now. Could well brighten over the next day or two.

    Stewart 

    #584401
    Stewart John Bean
    Participant

    Its a difficult target right now!

    #584404
    Stewart John Bean
    Participant

    I used iTEL 18 last night to get a time series. VPhot reports the V filter magnitude dropping from 13.15 to 13.3 over 13 minutes. The variation may be related to the orbital period of 90 min or the change in skyglow in the dusk sky. Going to repeat tonight but starting a bit later. Stewart

    #584406
    Stewart John Bean
    Participant

    The present superoutburst seems to have been recorded first by Graeme Coates and Tim Haymes on the evening of the 23rd June. This translates to a superoutburst period of 51 +-1 day which is right in the middle of the range of values from 45 to 55 days discussed in VSSC188. 

    Thanks again to Graeme and Tim and all other contributors.

    This target is now really difficult and June has previously marked the end of the observing season. In October the whole cycle begins again with a possible superoutburst around Oct 1. Can this one be observed?

    Stewart

    #584695
    Stewart John Bean
    Participant

    AAVSOnet telescopes in New Mexico have made two observations of ER UMa this week marking the start of this star’s observing season.  As noted above, the next superoutburst may be around Oct 1 but could be later by a week or so as ER Uma does appear to vary its super cycle period between 45 and 55 days.

    For UK observers, the star is very low in the north by north west sky in the evening. In the unsociable early morning, it does rise about 30 degrees above the horizon before dawn.

    More details on ER UMa  were presented in VSS Circular 188.

    #584947
    Stewart John Bean
    Participant

    As mentioned by Jeremy in VSSC 190 (the latest) several ER UMa stars are due a superoutburst before the year end. With a disclaimer on the accuracy of the dates, I copy below my expectations for four stars.

                       Superoutburst period (d)           Next superoutburst (give or take a few days)

    RZ LMi                    25                                  Dec 11          Late evenings

    V1159 Ori                ~50                                Dec 22       A late evening target

    IX Dra                      60                                  Dec 30       An early evening target

    ER Uma                   50-55                             Dec 30 – Jan 2        Late evening target

    Stewart

    #584952
    Jeremy Shears
    Participant

    Looks like a busy December, Stewart!

    #585016
    Stewart John Bean
    Participant

    My prediction was one day early, but that is consistent with the superoutburst period very gradually getting larger. The last period was 26 days as I judge it.

    Actually, this seasons light curve has good coverage as Sjoerd Dufoer (BE) has made 52 observations. Gary Poyner and Raymond Pearce have contributions as well. Thanks to all three.

    Stewart

    #585049
    Stewart John Bean
    Participant

    Measured ER UMa at 12.9 CV on 2021/12/28 03:08:50 using SLOOH in the Canaries. Hopefully some more results will arrive to refine the timing of what appears to be a superoutburst.

    This is only ~45 days after the start of the last one. Most periods lie in the range 45 to 60 days – so quite short.  See  VSSC188 for a full graph of super cycle period over the last 200 or so cycles for context.

    Stewart

    #610260
    Stewart John Bean
    Participant

    ER UMa is likely to go into superoutburst in the next few days. The last superoutburst started at 2459660. The superoutburst period varies between 45- 55 days. It is now 50 days since the last outburst.

    Further observations this week would be timely.

    Stewart

    #610298
    Richard Sargent
    Participant

    Attachment shows measurements of ER UMa from a 2 hour period starting at approximately 22.00 hours UT last night. Each point is a block average of 6 ten second images.

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