(CCD image by the Okayama U. of Sci. team)
DM Dra: most likely superoutburst
According to Pavol A. Dubovsky (vsnet-outburst 5305), the SU UMa-type dwarf nova DM Dra is in bright outburst (mag 14.4), which is presumably a superoutburst.
The last reported outburst (2001 November) was a superoutburst. (see IBVS 5284, Kato et al. 2002). The best superhump period was 0.07561(3) d, although there was no thorough coverage of a superoutburst. Observations of DM Dra is strongly recommended in the morning sky, but its northern declination may enable full-night coverage from northern latitudes.
Regards, Taichi Kato VSNET Collaboration team(vsnet-campaign-dn 3526)
We have received from Maehara-san a successful run of DM Dra. The data clearly indicate the presence of 0.3-mag superhumps. The present outburst is thus confirmed to be a superoutburst! We have also received a successful report from Torii-san (RIKEN).
Regards, Taichi Kato VSNET Collaboration team(vsnet-campaign-dn 3531)
Dear Colleagues,
We have received additional nightly long time-series data of DM Dra from Torii-san (RIKEN). We have partly analyzed the available data. The superhumps are prominently seen on all observed nights, with a typical amplitude of 0.20 mag. Since DM Dra apparently showed almost disappearance of the superhumps during the late stage of a past superoutburst (cf. Kato et al. (2002) IBVS No. 5284), further continuous observations are strongly recommended.
Based on March 7-9 data (including Maehara-san's data), the best period has been determined to be 0.07571(6) d. Although the period can vary during the course of the superoutburst, the present period determination provides additional support to the previous period identification (Kato et al. 2002). The overall quality of the data have already surpassed that of the 2001 observation.
The superhump profile up to now is posted at:
Regards, Taichi Kato VSNET Collaboration team
DM Dra rare? outburst
Timo Kinnunen reports a possible rare outburst of the poorly known dwarf nova DM Dra. Confirmatory observations, potential time-resolved CCD photometry, accurate outburst astrometry are all important. No previous outburst had been reported to VSNET.
YYMMDD(UT) mag observer 980817.990 <156 (T. Kinnunen) 980819.850 <156 (T. Kinnunen) 980824.840 <156 (T. Kinnunen) 980826.860 <156 (T. Kinnunen) 980902.830 <156 (T. Kinnunen) 980903.819 <156 (T. Kinnunen) 980924.750 <156 (T. Kinnunen) 980925.750 160: (T. Kinnunen)DM Dra was discovered by Stepanyan as SVS 2426. The low resolution spectrum taken during the outburst revealed the OB-type (consistent with the dwarf nova classification). Stepanyan reports the object is visible on POSS at mag 20. Magnitude reports by Stepanyan:
JD mpg
2441119 <19.5
43608 <19.5
43613 <19.5
43670 <19.5
43965 15.5 spectroscopic observation done
44054 <19.5
44067 <19.5
44071 <19.5
44075 <19.5
Quiescent CCD photometry by Howell et al. (PASP 102, 758) suggested the
presence of a 125-min period. The object was V=20.8 at the time of this
observation.
Regards, Taichi Kato(vsnet-alert 5338)
DM DRACONIS (UGSU:)
CCD magnitudes obtained by P. Schmeer, Bischmisheim, Germany: DRADM 20000522.289 <175C Scp DRADM 20001017.078 144C Scp DRADM 20001018.081 141C Scp DRADM 20001026.085 154C Scp Sequence: USNO-A2.0 (red magnitudes) Instrument: IRO (0.5-m RCT + AP-8)The current rare outburst may well be a supermaximum. Time-resolved photometry during its final stage is very urgently required.
Clear skies, Patrick(Posted on 2001 Oct. 26)
A short break in the clouds has allowed me to get a few unfiltered CCD images of DM Dra, using a 0.35-m f/6.3 telescope. They show the object to be still 'bright' (see below), making it an interesting target for continued CCD photometry. Since virtually nothing is known about this object, long time-series photometry spread over geographically well-dispersed observatories is highly recommended.
20001026.760 151C (T. Vanmunster) Best regards, Tonny Vanmunster CBA Belgium Observatory(vsnet-alert 5345)
There is now strong evidence that DM Dra went into (super)outburst on Oct. 16, so we should expect the rapid fading to begin on Oct. 30 +/- 1 day.
Regards, Patrick(vsnet-alert 6878)
Observer Timo Kinnunen
Espoo, Finland
Instr. 44.5 cm f/4.5 refl.
Possible superoutburst of DM Dra:
DRADM 011114.176 14.6 KNN
regards,
Timo Kinnunen
(vsnet-alert 6881)
About 2.5 hours ago (Nov 14/15, 2001), I started an unfiltered CCD run on DM Dra, using the 0.35-m f/6.3 telescope at CBA Belgium Observatory and ST-7 CCD. The intermediate light curve already clearly shows the presence of superhumps (amplitude about 0.35 - 0.4 mag). It's too early to make an estimate of the superhump period, but I will continue to observe the object as long as possible. Weather over Belgium is very stable now (extremely clear skies).
I will report further analysis results in a few hours (before heading off to Flagstaff, Arizona to observe the Leonids).
Best regards
Tonny Vanmunster CBA Belgium Observatory(vsnet-alert 6882)
Dear colleagues,
I have just concluded the observing session of DM Dra, and herewith provide some further details about my findings. Thanks also to Timo Kinnunen for his timely visual detection of this outburst !
- Observing time : 2001, November 14/15 - Duration : 4.1 hours - Equipment : 0.35-m f/6.3 telescope and unfiltered ST-7 CCD - Data points : 269The light curve shows genuine (single-peaked) superhumps with an amplitude of 0.36 mag and a period of 0.0734 +/- 0.0030 d (PDM technique). This value substantially differs from CCD photometry in quiescence by Howell et al. (PASP 102, 758), which suggested a possible periodicity in the system of 125 minutes, and a potential eclipse (0.4 mag in 5 minutes). The latter is not present in my observations neither.
The above observations firmly establish DM Dra as a new SU UMa type dwarf nova. To further refine the superhump period (longer baseline) and to study the evolution of the outburst development, I would recommend this object to receive sufficient attention from other observers worldwide. Unfortunately (?), I will not be able myself to follow up the DM Dra outburst in the next days, because of my Leonids expedition.
I have published the light curves, an outbursting image and additional details on DM Dra on my web site. Have a look !
Kind regards, Tonny Vanmunster CBA Belgium Observatory http://www.lunarpages.com/cbabelgium email : Tonny.Vanmunster@advalvas.be(vsnet-alert 6884)
Dear Colleagues,
We have partly finished the analysis of the Kyoto Nov. 14 run of DM Dra. The light curve clearly shows 0.3-mag superhump feature, perfectly consistent with Vanmunster's finding.
The Kyoto team observed this star on 2000 Oct. 27 (see vsnet-campaign-dn 243). The object was by about 0.6 mag brighter last night than on 2000 Oct. 27. Although the 2000 Oct. 27 observation covered 0.091 d, the upper limit of superhump-type variation was 0.1 mag (vsnet-campaign-dn 243). The conclusion is confirmed to be unchanged after another inspection of the past data. This suggests that the amplitude of superhumps can quickly decay in this system; early observations are very important.
The VSNET Collaboration team will continue observing this star in order to refine the superhump period, and to follow the time-evolution of hump features. Since the seasonal condition is not best for this object, we encourage further observations at different longitudes.
Regards, Taichi Kato VSNET Collaboration team(vsnet-alert 6892)
Dear Colleagues,
Based on preliminary analysis of 4 night observations, we have selected the two periods of 0.0733 d or 0.0750 d as the most likley superhump period. The determination suffers from the short visibility. Nevertheless, the superhump modulation is still clear. We hope we can further refine the period after receiving the full data set from Okayama Univ. of Science (T. Tanabe et al.) team.
Further observations are encouraged.
Regards, Taichi Kato VSNET Collaboration team(vsnet-campaign-dn 1925)
Dear Colleagues,
We have finished the analysis of Kyoto DM Dra runs up to Nov. 19. The latest run (Nov. 20) is being processed. On Nov. 19, the superhump signal was still clear, keeping the approximately similar amplitude as on Nov. 14. The best estimated of the period is 0.07572(4) d. The quoated error is just a nominal one; there is still possibility of other periods. We will be able to inform a more accurate value after receiving the final data from T. Tanabe-san (Okayama Univ. of Sci.), who has been keeping early evening runs.
Regards, Taichi Kato VSNET Collaboration team(vsnet-campaign-dn 1948)
Dear Colleagues,
We have partly analyzed DM Dra observations obtained by Tanabe-san, Okayama Univ. of Sci. We have also analyzed Kyoto observations (observers U. Uemura and R. Ishioka). The rapid fading reported regarding the Nov. 23 observation was actually not very striking, though the increased rate of the fading was confirmed. Superhumps became less apparent on Nov. 21-22, which is in agreement with our previous finding during the late stage of the 2000 October superoutburst.
The refined superhump period is 0.07556(4) d, which is still subject to small correction as new data will become available. We have also put a mean profile of superhumps at the following URL. The superhump profile is quite normal for a long-period SU UMa-type dwarf nova.
Regards, Taichi Kato VSNET Collaboration team
Return to Daisaku Nogami's page
Return to HomePage