Recurrent outburst of IM Nor

(Liller's image)

(CCD image by Berto Monard)

(vsnet-alert 7004)

W. Liller reports:

Hola Everyone,

On a total of five photographs (85mm f/1.4 lens, Tech Pan film, orange filter) taken between Jan. 10.3432 and Jan 10.3595, a star, apparently the old nova IM Normae, was found at red magnitude 8.3. It was subsequently found at approximate magnitude 8.5 at the very edge of another pair of photographs taken on Jan. 3.3479 and Jan. 3.3493. Nothing was visible at the position of the star on Oct. 13 down to magnitude 11.5.

IM Nor was originally discovered by I.E. Woods at 9th magnitude on a blue-sensitive plate taken on July 7, 1920. J.L. Elliot and W. Liller later suggested that it was an X-ray source (ApJ 175, L69, 1972), and determined its light curve from old Harvard plates. No other outbursts were found.

Note that there has never been any spectroscopic verification. Because the star is an early morning object, it is can be followed -- and should be folllowed -- for much of the year. Its position is (2000) R.A. 15h 39m 29.9s, Dec. -52d 19' 20".

I will try to get an accurate position and a low-resolution sprectrum tonight although I see that there is a fog bank on the western horizon.

All the best to all, Bill Liller

Astrometry, spectroscopy

(vsnet-alert 7020)

Hola again -

Last night, Jan.12.330 UT, using a CCD and a 20cm f/1.5 Schmidt camera, I measured the position of the recurrent nova to be (2000) RA = 15h 39m 26.61s +/- 0.18s, Dec. -52d 19' 18.6" +/- 0.5". This agrees moderately well with the position for IM Normae measured from a Harvard MC plate: end figures: 26.26s, 21.4" (See Duerbeck, A Reference Catalogue and Atlas of Galactic Novae. Reidel, 1987).

The magnitude, measured from the same CCD frame and with a minus-red-and-IR filter -- I call it V(bv) = was 8.13 +/- 0.03. The comparison stars used were GSC 8308 511 and 8308 651.

A low-dispersion objective prism spectrum, taken Jan. 12.351 UT, shows H-alpha to be very strong and relatively narrow with FWHM = 950 km/sec +/-50. Other lines of the Balmer Series, the Fe II multiplets 42 and 74, and O I at 777.1 nm are also clearly present.

All the best to all, Bill Liller

Quiescent counterpart

(vsnet-alert 7021)

The nearest USNO stars is located at:

153926.298 -521918.85 (2000.0) 18.2 19.4

This figure is moderately outside Liller's error box. This star is one of two stars described to be possible quiescent counterpart. Would this mean the quiescence is below the plate limit (fainter than 20?) -- then what a surprize for a recurrent nova! But this seems to explain the observed lack of emission lines in the supposed quiescent counterpart.

Taichi Kato
(vsnet-alert 7026)

It seems from USNO_A1.0, which is

153926.378 -521918.66 (2000.0) 17.0 17.9

in USNO_A2.0.

Actually, on DSS2 I or R image, this "star" is composed of at least three stars, line-uping ENE-WSW. Liller's position is moderately coinsident with the most eastern star, whose rough position end figures are: 26s.42, 17".9.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan

(vsnet-alert 7029)

This possible identification seems to support a minimal outburst amplitude of 11.5 mag (Wyckoff and Wehinger (1979) PASP 91, 173). This value is quite unexpected for a slow recurrent nova! (as well as strong [O I] line, suggesting a fair amount of ejecta comparable to those of classical novae).

Similar (but with a lesser degree) of surprise has been found in CI Aql. It may be possible we are encountering a new era of discoveries of a new class of recurrent novae!

The faint quiescent counterpart could also be explained if the system was seen near edge-on. In such a case, we can expect that eclipse can emerge (as in U Sco and CI Aql) as the nova fades. Continuous photometry would be helpful in testing this possibility!

Taichi Kato

IM Nor and 2U 1536-52

(vsnet-alert 7028)

The proposed identification of IM Nor with 2U 1536-52 (as referred in IAUC 7789) has proven to be false. 2U 1536-52 is an high-mass X-ray binary QV Nor.

    QV Nor = 1A 1540-53 = 3A 1538-522 = 1H 1538-522 = 2S 1538-522
    = 2U 1536-52 = 3U 1538-52 = 4U 1538-52
The originally supposed identification of 2U 1536-52 with IM Nor was already questioned by Wyckoff and Wehinger (1979) PASP 91, 173. The optical candidate of this X-ray source was proposed by Cowley et al. (1977) ApJ 218, 3L; Parkes et al. (1978) MNRAS 184, 73P. See also IAUCs 3201, 3323.
Taichi Kato

Quiescent counterpart

(Likely counterpart, counterparts suggested in the past are marked on Downes et al.'s CV chart "Living Edition").


Chart by Japan Variable Stars Study Association

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