[vsnet-ip 68] Re: HT Cam super-ultra-bright outburst!

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Re: HT Cam super-ultra-bright outburst!

   Further useful information previously posted to VSNET:
   (In addition to them, there have been a number of postings related
to previous very short outbursts).

[vsnet-chat 662]

  According to "Astronomical Time Series" (ed Maoz et al. 1997, Kluwer
Academic Press) p.195, Tovmassian et al. identified the ROSAT source
RX J0757.0+6306 (=1RXS J075700.5+630602) as a new, ultrashort-period
cataclysmic variable.  The orbital period is 75+/-1.4 min.  The optical
spectrum shows strong hydrogen emission lines, resembling that of WZ Sge.
Tovmassian et al. discussed in this paper the possibility of a DQ Her type.
This star may be worth monitoring for possible future outbursts.

  The paper did not mention the accurate coordinates, but watching at
the ROSAT position (07h 57m 00s.5, +63o 06' 02" 2000.0) might be sufficient.

Regards,
Taichi Kato

[vsnet-chat 663]

Dear VSNET fans,

I'm readily support Taichi's call for monitoring
RX J0757+6306. Indeed this system has all chances to
turn into another WZ Sge system or proof to be
the shortest period Intermediate Polar.
Briefly what we know about this system:
a. It is X-ray source, not much known about spectra or variability in X-rays.
b. Optical Spectroscopy indicates CV nature with prominent accretion disk
        and hot spot.
c. Period derived from the S-wave radial velocity variations is
        most probably 81 minutes (+/- 5 min are not excluded).
d. The limitted photometry shows no eclipsing, high amplitude flickering
        light curves. On 4 ocassions out of 5, significant signal was recorded
        at frequency corresponding to 8.5 min  oscillations.
e. No outburst history is available at the moment.

The POSS measurments of coordinates and magnitude are as follows:
RA 07h57m01.3s  DEC +63d06m01s   2000.0   16.06 (red)

The identification chart is posted to VSNET separately.
The system was reported by Tovmassian et al. in  Proceedings of
Symp. dedicated to 25th aniversary of Wise observatory
"Astronomical Time Series" (ed Maoz et al. 1997, Kluwer Academic
Press) p.195
and 13th NorthAmerican Workshop on Cataclysmic Variables,
in press.

Regards, Gaghik Tovmassian
 OAN, IAUNAM, Mexico

[vsnet-alert 1387] by John Thorstensen

Hello VSNetters,

Gaghik Tovmassian (UNAM) recently called attention to
RX J0757.0+6306, for which he quoted a most likely orbital
period of 81 +- 5 minutes (vsnet-chat number 663).
The object has very strong H emission and he noted
the similarities with WZ Sge (another very short-period,
strong-lined cataclysmic).  In addition the object
showed 8.5-minute oscillations in its light curve on
several occasions, suggesting the possibility of a DQ
Her classification.

I obtained spectra of this remarkable object on
December 18 and 19 UT, using the MDM 2.4-m telescope
and modular spectrograph, at 3 A FWHM resolution
from 4000 to 7500 Angstroms.  The hydrogen lines are indeed
extremely strong, with H-alpha having an equivalent
width of about 200 Angstroms.  HeII 4686 is not unusually
strong, with an equivalent width of 13 A, about 1/10 the strength
of H-beta.  The strong H lines made it possible
to measure good radial velocities in this object, for
which I guesstimate a magnitude well fainter than 17
(see Bob Fried's observations reported below).
Discarding a few weakly-exposed spectra taken
through moonlit clouds left 67 exposures of 6
minutes each.  The spectra covered a 6.79 hour range
of hour angle.

The radial velocities of the emission lines define
an unambiguous period

        0.05982 +- 0.00013 days,

or
        86.14 +- 0.19 minutes.

[...]

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