Nova Oph 1998

(V-band CCD image taken at Osaka-Kyoiku University, courtesy by Ando et al.)

According to IAUC 6941 and Takamizawa, Kesao Takamizawa discovered a possible nova in Oph. The object was photographic mag 9.5 on June 15.561. The accurate position measured by R. and Y. Kushida is

   17h 31m 59s.82  (J2000.0)
   -19o 13' 57".0

T. Kato has pointed out that the object lies within the error circle of the ROSAT source 1RXS 173200.0-191349. More detailed infromation, charts, sequence, Web pages will be made available within hours.

Spectroscopic observations, multi-color photometry, examination of the possible identification with the ROSAT source are strongly encouraged.

When reporting to vsnet-obs in usual format, please use the designation OPHnova1998 (in VSNET format).

Congratulations to Mr. Takamizawa on his discovery!

Regards,
Taichi Kato

(vsnet-alert 1891)

POSSIBLE NOVA OPHIUCHI 1998

S. Nakano reports in IAUC 6941 that Kesao Takamizawa, Saku-machi, Nagano-ken, Japan has discovered a possible nova of mag. 9.5 on two exposures from 1998 June 15.561 UT. Takamizawa was using a 10-cm f/4.0 lens and T-Max 400 film. According to positions derived by the discoverer and R. and Y. Kushida (who confirmed the discovery with CCD) the possible nova is located at R.A. = 17h32m00s, Decl. = -19o13'.9 (2000.0). No object was present at this place on 48 previous patrol films from 1994 Feb 17 to 1998 May 19. T. Kato, Kyoto University, notes that this object lies within the error circle of the ROSAT source 1RXS 173200.0-191349. No spectral observations are available at present.

(vsnet-alert 1892)

On possible Nova Oph location

This object lies close to the edge of the dark cloud LDN195. If the object is indeed a nova, it may suffer from considerable reddening. Pure UBV(RI) photometry may distinguish several possibilities.

Regards,
Taichi Kato

Confirmation as a nova

(vsnet-alert 1899)

Nova Oph 1998

According to IAUC 6943, the possible nova discovered by Takamizawa has been spectroscopically confirmed to be a real nova. The measured expansion velocity suggests the noba to be a fast one.

The new astrometry by Hanzl (IAUC 6943)

  17h 31m 59s.79  (J2000.0)
  -19o 13' 56".0

Regards,
Taichi Kato

Disucussion

(vsnet-alert 1900)

On Nova Oph 1998

The new astrometry by Hanzl (IAUC 6943) brings the nova closer (~1 arcsec) to the nearest USNO star:

USNO0675.13305963 173159.788 -191355.04 (2000.0) 16.8 18.0
OPHnova1998       173159.79  -191356.0  (2000.0)

If the identification of the nova with this USNO star is proven, the outburst amplitude may be rather small for such a fast nova (of course, the value depending on the actual outburst maximum). Further assuming the association with the ROSAT source, the previous X-ray detection may be the result of earlier nuclear burning event, which may be explained by a recurrent nova phenomenon. An extensive search for plate archives would be meaningful.

Regards,
Taichi Kato

Hipparcos/Tycho sequence

(vsnet-alert 1893)

H/T sequence around possible Nova Oph

173408.7 -191029 (2000.0) V=8.677(-) b-y=0.312(-)
173409.1 -191029 (2000.0) 867H 0.50 HIP085965 plx=3.90(1.24) (0.02 0.02)

173040.6 -190650 (2000.0) V=8.619(-) b-y=0.430(-)
173040.7 -190654 (2000.0) 864 0.59 TYC6243.54.1 plx=15.5(9.6) (0.01 0.02)

173315.0 -192237 (2000.0) 952 0.23 TYC6243.337.1 plx=21.2(15.3) (0.03 0.04)
173407.5 -193348 (2000.0) 1035Vw 0.88 TYC6243.253.1 plx=-216.8(42.3) (0.07 0.10)
173351.9 -193003 (2000.0) 1049 0.61 TYC6243.11.1 plx=106.4(49.1) (0.07 0.08)
173324.3 -192822 (2000.0) 1069 1.15 TYC6243.27.1 plx=35.9(56.3) (0.11 0.23)
173228.6 -191913 (2000.0) 1071 0.89 TYC6243.435.1 plx=-95.4(65.1) (0.09 0.16)
173221.4 -190328 (2000.0) 1070 0.46 TYC6243.147.1 plx=-0.1(47.7) (0.09 0.12)
173229.2 -192312 (2000.0) 1074 0.87 TYC6243.255.1 plx=-46.0(53.4) (0.10 0.16)
173110.8 -190707 (2000.0) 1085 0.77 TYC6243.391.1 plx=-106.7(75.9) (0.14 0.19)