Outburst of AQ CMi -- A new SU UMa-type dwarf nova

Beginning of the story

In vsnet-obs 2076, Jochen Pietz (also http://aibn55.astro.uni-bonn.de:8000/~jpietz) reports on a possible outburst of a suspected dwarf nova, AQ CMi, probably for the first time since its discovery.

He estimated the variable at mv=14.4 on 1996 Feb. 10.975 UT, with a possible uncertainty in identification. Immediate confirmation is most urgently needed.

AQ CMi was discovered as a possible dwarf nova, appearing only in one photographic plate (in an old volume of Astron. Nachricht. - sorry I have no memo on the author, volume and pages - T. Kato). Downes and Shara (1993) identifed AQ CMi with a very faint object of 19-20 mag. Recent spectroscopy by Zwitter et al. revealed the CV nature of this counterpart (based on a poster presented at Keele CV Conference, from my memo).

    071434.84  +084805.0    2000 AQ CMi     UG?          14.5-(16.5P
       (Downes & Shara 1993)

Independent detection of the outburst by Claudi

At UT 1996-02-9 21:45 I observed the CV AQ CMi with the 182 cm Telescope of Padova - Asiago Observatories equipped with the B&C spectrograph at a resolution of 2 Ang. in the H alfa region.

The star was in outburst with a magnitude of about 14.5 and it showed a featureless spectrum.

This seems to confirm the DN nature of the object.

dr. R.U Claudi
Osservatorio Astronomico di Padova
vicolo dell' osservatorio,5
I-35122 Padova

Detection of superhumps (Patterson)

(vsnet-obs 2105, Joe Patterson)

                    AQ CANIS MINORIS

V-band photoelectric photometry by A. Shambrook with the CTIO 1 m telescope shows superhumps in the light curve of this recently- erupted dwarf nova. Timings on February 12 and 13 indicate a period of 95.9+-0.3 minutes. The amplitude (0.17 mag peak-to- trough) and waveform (fast rise, slow decline) are normal for SU UMa stars in early decline from a superoutburst. On February 13 the star was at V=14.5.

CCD observers can perhaps follow this star as it gets considerably fainter, and look for the "echo" signature (after a sharp fading to near quiescence) that is often seen in this class of dwarf novae. That would be awfully interesting, as would its (certifiable) absence!

Joe Patterson
Dept of Astronomy, Columbia Univ.

Independent confirmation of superhumps

(vsnet-alert 328, Daisaku Nogami)

Dear colleagues,

We observed AQ CMi for 6 hours at Ouda Staion on Feb. 12, using 60-cm refl. + CCD + Johnson V filter. Our observation independently detected superhumps with an apmlitude of about 0.2 mag. A preliminary period analysis gives 0.06625 d (= 95.4 min) as the best estimated superhump period, which agrees with the one given by Patterson et al. (vsnet-obs 2105, vsnet-alert 327).

        mid-UT     V-C   S.D.   N
CMIAQ  960212.556  1.378 0.073  83 V

Comp. V=13.22 (VSNET chart)

Best reagrds,
Daisaku Nogami

CCD Image (Ouda Station)

taken by

AQ CMi eruption over?

(vsnet-obs 2179, Joe Patterson)


The following are mean V magnitudes of AQ CMi obtained by Anouk Shambrook on the CTIO 1-m telescope. Superhumps continued throughout February 12-19, with a mean period of 95.2+-0.2 min.

Feb 12.1     14.56
    13.1     14.71
    14.1     14.90
    16.1     14.96
    17.1     15.15
    18.1     15.24
    19.1     15.78
    20.1     17.5
    21.1     18.3
    22.1     18.3

So probably the dwarf nova has returned to near minimum. Continued vigilance is very desirable to see if the star "echoes" within a few days. Also, the star is so little-known that there is still no basic information about the recurrence time of normal and super-maxima, so observation over the next few months is quite important. The little fella might yet have a few tricks up his sleeve.

CCD image at Ouda on Feb. 23

(taken by D. Nogami)

Outburst CCD image

CMIAQ.GIF -- outburst image of AQ CMi

  observer    : Makoto Iida (VSOLJ)
  instruments : 20-cm refl. + ST-6 unfiltered
  date & time : 1996 Feb. 11  09h 58m UT
  exposure    : 120 s

VSNET charts

Wide-field chart based on GSC

Immediate surroundings

PostScript file

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