Nova Scorpii 2007 (V1280 Sco)
An IAU Circular on February 06 announced the discovery of Nova Scorpii 2007 which was around 10th magnitude when it was first seen by a Japanese astronomer, Yuji Nakamura. It was independently discovered by countryman Yukio Sakurai – who found it on images taken with a Fuji FinePix S2 digital camera and a Nikon 180-mm f/2.8 lens!
The nova is located at RA 16h 57m 41s, Dec. -32°20.5'. The photo above, taken 2007.02.19 at 03:30 SAST shows Scorpius, with Jupiter left of centre, rising over my neighbour's trees. The nova is clearly visible near the centre of the image, to the bottom-left of epsilon Scorpii. The highlighted block is shown below.
From this morning's observation, 2007 February 19.05, it is certainly brighter than V=5.0 (as the image above confirms; HR 6316 has V=5.0). Using HR 6143 (V=4.2; from AAVSO chart) as second comparison star, I estimate the nova at V=4.4 (the red dot in the light curve below).
After yesterday morning's cloud, I was keen to see what the nova was up to (arrowed in today's photo, below). Interestingly it has a reddish tinge, though not as prominent as nearby HR 6288 (V=5.5, B-V=+1.6).
From CBET No 852 I later learnt that Munari and colleagues carried out photometry of the nova on Feb 20.2, finding B=5.90, V=4.83 giving a vaguely reddish B-V = +1.07.
On IAU Circular 8810, a second nova eruption in the Scorpion was announced. How about that! More details and images here.
Yesterday's cold front passed over leaving the skies beautifully clear this morning, and Nova Scorpii 20070 was still plainly visible.
I estimated its magnitude as V=5.1 (2007 Feb 23 @ 03:01 UT, using AAVSO chart 070217 and comparison stars 50 and 55; green dot in the light curve below).
Remarkably, it doesn't look so red this morning; I would estimate the B-V = +0.1. It certainly didn't look as red as HR 6288 nearby (see Wednesday's remarks).
IAUC 8812, issued yesterday by the Central Bureau for Astronomical Telegrams, briefly reports CCD photometry of V1280 Sco carried out on Feb 21.483 by J.D. West (Kansas, USA), who found V=4.73±0.01. I've indicated this measurement with a yellow dot on the light-curve below.
West also did near-infared photometry, finding H=2.87±0.06, showing the star to be very bright in the infra-red.
I'm holding thumbs that the cloudy weather this weekend will clear up and give open skies on Monday morning...
The skies were mostly clear this morning, and I could see V1280 still going strong at just a bit fainter than 5th magnitude.
V1280 seems happy at V=5.5 this morning (2007.02.27, 02:21 UT); with 11x80 binoculars I compared it to nearby HD 156098 (V=5.5) and HD 155450 (V=6.0).
Colour-wise, I estimate its B-V as redder than +0.3 but not as far as +0.8; I'd be happy with B-V=+0.6.
This morning (2007.02.28, 04:20 SAST), using 11x80 binocs, V1280 looked convincingly fainter than V=5.5 but not quite down to V=6.0.
Its fading in the infra-red too; on Feb 27.5 it was at H=3.79 (measured by J.D. West), a one-magnitude drop since Feb 21.5.
The light curve below, compiled from IAU Circular data and recent AAVSO records, shows the sudden increase in brightness and on-going fading.
It is still brighter than 6th magnitude so remains a naked-eye object from dark skies, and easy in binoculars.
Spectroscopic observations on Feb 5.9 at Nishi-Harima Astronomical Observatory (reported on IAUC 8803, Feb 6) suggest that it is a classical nova caught near maximum light.
Follow-up spectroscopy, made on Feb. 14.86, shows a much bluer continuum than reported earlier. "The new spectra resemble the spectrum of an F-type star," IAU Circular 8807 reports. "Balmer lines (relatively weaker than in the Feb. 5 spectrum) show clear P-Cyg profiles (expansion velocity about 500 km/s), along with other weak lines."
Feb 19 @16:14 Feb 19 @22:20 Feb 21 @22:50 Feb 22 @19:00 Feb 23 @07:12 Feb 23 @13:40 Feb 25 @22:20 Feb 27 @05:57 Feb 28 @07:29.
nothing more to see. please move along.