Superoutburst of PU CMa in 2003 May

(CCD image by Peter Nelson)

(PU CMa in outburst; CCD image by K. Nakajima taken during the 2003 February normal outburst)

The 2003 May outburst

(vsnet-outburst 5544)

PU CMa outburst, recent data

[SU UMa-type candidate. Normal outburst?]

  YYYYMMDD(UT)   mag  observer
  20030416.394  <132  (Rod Stubbings)
  20030417.456  <130  (Rod Stubbings)
  20030418.387  <140  (Rod Stubbings)
  20030419.385  <144  (Rod Stubbings)
  20030420.424  <144  (Rod Stubbings)
  20030422.387  <144  (Rod Stubbings)
  20030423.437  <144  (Rod Stubbings)
  20030424.382  <144  (Rod Stubbings)
  20030425.410  <148  (Rod Stubbings)
  20030426.394  <144  (Rod Stubbings)
  20030428.390  <140  (Rod Stubbings)
  20030429.401  <144  (Rod Stubbings)
  20030504.378  <144  (Rod Stubbings)
  20030510.408  <130  (Rod Stubbings)
  20030518.353   118  (Rod Stubbings)

(vsnet-outburst 5571)

PU CMa superoutburst?

The short-period (candidate) SU UMa-type dwarf nova PU CMa is undergoing a possible superoutburst. Although the seasonal condition is already poor, a search for superhumps with time-series CCD photometry would be helpful, if the object is observable for (at least) 2 hours.

  YYYYMMDD(UT)   mag  observer
  20030504.378  <144  (Rod Stubbings)
  20030510.408  <130  (Rod Stubbings)
  20030518.353   118  (Rod Stubbings)
  20030524.360   120  (Rod Stubbings)

Taichi Kato

(vsnet-alert 7740)

PU CMa: first clear superhump detection!

Dear Colleagues,

We have received a run from Berto Monard, which clearly shows the presence of superhumps! This observation finally (most probably) confirms the SU UMa-type nature of PU CMa. Although this single run was not yet sufficient to determine the superhump period, runs on different nights or at different longitudes will certainly be able to pin down the true superhump period, now that we have the precise orbital period. The present superoutburst is thus most promising among the recent outbursts of PU CMa! Please observe as long as possible!

Taichi Kato
VSNET Collaboration team

(vsnet-alert 7741)

Dear Colleagues,

We have received new data from Peter Nelson. The data also clearly recorded superhumps. Combined with Monard's data, we have yielded a superhump period of 0.05832(5) d. This period is 2.9% longer than the orbital period. Because of the short visibilty in the evening sky, the period identification still needs to be confirmed by additional nights' observation. If this is the true superhump period, the fractional superhump excess of 2.9% is somewhat large for this period.

The full amplitude is smaller than long-period SU UMa-type dwar novae. This may be a result of systematic decrease of the superhump amplitudes in shorter period systems, or the observations may have covered the epoch when the superhumps had started to decay. In any case, further observations (hopefully 2hr continuous run each night) are strongly encouraged!

Taichi Kato
VSNET Collaboration team

Background Information

(vsnet-alert 3956)

RX J0640-24 (UG:)

RXJ0640-24  20000104.302  154C  Scp
RXJ0640-24  20000106.348  115C  Scp
Sequence:   USNO-A2.0 (red magnitudes) 
Instrument: IRO (0.5-m RCT + AP-8)
A minor brightening was observed with the same instrument on 1999 Dec. 14. The only previously known outburst was recorded on an ESO B plate (mag about 11).

This cataclysmic variable is also known as 1RXS J064047.8-242305 and RE J0640-24.

USNO-A2.0 data: 06:40:47.723 -24:23:14.50 (2000.0) r= 14.7, b= 16.3

Robert Fried (Braeside Observatory) confirms the outburst and reports an instrumental unfiltered magnitude of 11.8 for Jan. 7.185 UT.

Time-resolved photometry during the current bright outburst is strongly recommended.


(vsnet-alert 3959)

RX J0640-24 outburst confirmed and observation start

We confirmed RX J0640-24 outburst (about 12 mag) as mentioned by Mr. Schmeer in [vsnet-alert 3956], and started time-resolved CCD photometry at 16:45 (UT) at Kyoto. About 2-hour run will be possible.

More observation is strongly encouraged.

Makoto Uemura and Taichi Kato

(vsnet-alert 3968)

RX J0640-24 possible superhump?

Dear Colleagues,

From a 1.3-hour continuous run (vsnet-alert 3959), we have detected a modulation with an amplitude of ~0.3 mag, which might be attributed to a superhump. However, the large air-mass may be responsible. Longer observations at other longitudes (contributions from the southern hemisphere are extremely welcomed!) are strongly encouarged to clarify the nature of the object. Collaborating observations should be sent (as usual) to

Weather permitting, we will try to make a longer run tonight.

Makoto Uemura and Taichi Kato

(vsnet-alert 3970)

RX J0640-24 rapid fading

We started the second night's observation on RX J0640-24 at 14:45 (UT). Although our CCD image on display is hazy, the current magnitude seems to be 14mag, which indicates RX J0640-24 shows rapid fading. It is possible that we see a precursor of superoutburst or an outburst of IPs. The follow-up observation is very encouraged to clarify the nature of this outburst.

Makoto Uemura and Taichi Kato

(vsnet-alert 3980)

RXJ0640-24 outburst update

Dear Colleagues,

As notified by Uemura-san, RX J0640-24 is apparently quickly fading from outburst. The possible superhump-like feature observed in the Jan. 7 data seems to have decayed on Jan. 8 data. However, there looks like some evidence of modulations with a likely period less than an hour. During the 3.4-hour run, the object showed little trend of the continuing rapid fading. This precludes the possible explanation of the Jan. 7 variation as the effect of extinction. The rapid rate of decline (~1 mag/day between Jan. 6 and 8) suggests that the object can be a short-period system (e.g. SU UMa stars). It is not surprizing such a system may show transient superhump activities during a short outburst, or a precursor to a superoutburst (the good example is the superoutburst of SU UMa in 1998 December). Observers are strongly requested to continue monitoring the activity of the object for short-term variations on coming nights, and to look for a possible (immediate or future) superoutburst. The campaign is still ongoing, and please keep us in touch.

Taichi Kato and Makoto Uemura

(vsnet-alert 4255)

RX J0640-24 outburst

The ROSAT-selected cataclysmic variable (very likley a dwarf nova), RX J0640-24 is again reported to undergo an outburst. The first-ever outburst since the discovery was reported by Patrick Schmeer (vsnet-alert 3956), during which hump-like modulation was found by CCD photometry by Makoto Uemura and Taichi Kato (vsnet-alert 3968). The subsequent rapid fading (vsnet-alert 3969, 3970) suggests that the system may have a short orbital period. A photometric campaign has been conducted by Uemura (vsnet-alert 3968).

  YYYYMMDD(UT)   mag  observer
  20000129.819  <145  (B. Monard)
  20000130.819  <144  (B. Monard)
  20000201.780  <144  (B. Monard)
  20000202.493   148  (R. Stubbings)
  20000202.742  <144  (B. Monard)
  20000204.799  <145  (B. Monard)
  20000205.498   151  (R. Stubbings)
  20000206.490   151  (R. Stubbings)
  20000218.465  <120  (R. Stubbings)
  20000222.459   120  (R. Stubbings)
(vsnet-alert 7639)

[From Kato et al., MNRAS in press (astro-ph/0210674)]

Up to now, three three long outbursts (likely superoutbursts) [JD 2451677 (2000 May), 2452056 (2001 June), 2452418 (2002 May)] were detected.

Although definitive classification requires further time-resolved photometry, we propose that PU CMa to be an excellent candidate for an SU UMa-type dwarf nova. This indication is also strengthened by the recently reported orbital period of 0.05669(4) d (Thorstenesen and Fenton 2002). This period is one of the shortest periods among the known SU UMa-type dwarf novae (Thorstensen et al. 2002). Most of the systems with similar orbital periods show significant deviations (either related to WZ Sge-type dwarf novae or ER UMa-type dwarf novae) from normal SU UMa-type dwarf novae. PU CMa, with its outburst properties strongly resembling a normal SU UMa-type dwarf nova may be the first object filling the gap between the extreme WZ Sge-type and ER UMa-type systems.

Urgent time-series photometric observations are undoubtedly most needed! The Kyoto team (obervser Ishioka-san) magaged to take time-series observation last night, which will be soon analyzed. Please turn your telescope to this unusual and bright (11th mag) dwarf nova in outburst!

(vsnet-outburst 5223)

PU CMa: superhump-like variations in post-outburst state?

Dear Colleagues,

We have received additional data from Lew Cook and Nakajima-san. The object has been also observed by the Kyoto team, Torii-san (RIKEN), and Okayama U. of Sci. team (and presumably by Kiyota-san).

A preliminary analysis of the Feb. 16 data (object at 14-15 mag) is rather surprising. The light curve was dominated by large-amplitude variations (~0.3 mag). A preliminary period analysis has yielded a most likely period of 0.061+/-0.001 d, which is not inconsistent with the superhump-type variation. The phase-folded light curve shows a single-peaked profile (mean amplitude 0.3 mag), which is also reminiscient of superhumps. There also existed variations with shorter time scales, but they looked more aperiodic or quasi-periodic. Further observations are still encouraged to study the period structure of this ultrashort period bright dwarf nova.

Taichi Kato
VSNET Collaboration team

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