Special Notice #35: Eclipse of HD74057

February 24, 2007

Don Davies discovered a 7th magnitude eclipsing binary (GSC 02484-00592, HD74057, VSX J084246.2+315145) in May, 2005, announced on our discussion group (posting 5/27/2005), and subsequently published in Peremennye Zvezdy:

The coordinates are
08:42:45.900 +31:51:41.00 J2000
and the approximate magnitude is V=7.18, with (B-V) = 0.56

By Davies' predictions, this star should undergo an eclipse on March 3 UT, well-placed for northern hemisphere observers. The period is about 31 days, and the eclipse length is about 5 hours. The eclipse is centered at JD 2454162.7165 (about 05:11 UT on March 3).

This is an interesting system, containing two main-sequence F/G stars, widely separated so that they are evolving separately, yet very nearby (about 48 parsec), with a highly eccentric orbit. It is also an X-ray source.

We request that PEP and CCD observers monitor this object through its eclipse, obtaining data for a night or two prior to the event, dense coverage during the eclipse, and a few datapoints on nights after the eclipse. The eclipse depth is small enough (about 0.5mag) that visual observations are not recommended.

We have added this new variable to the Variable Star Plotter as VSX0842+31:
http://www.aavso.org/observing/charts/vsp/ where any chart with 15arcmin or larger dimension will show the two comparison stars towards the south. The two comparison stars are:
Star RA (J2000) Dec V B-V
89 GSC 02484-00532 08:42:51.94 +31:43:19.4 8.86 0.69
96 GSC 02484-01314 08:43:00.88 +31:46:22.7 9.61 1.06

2016 link: https://www.aavso.org/vsp

Use 0532 as the comparison and 1314 as the check star for CCD and PEP work. BVRcIc observations are welcome. This star is bright enough and the eclipse long enough that you can take BVRI sets rather than having to stay in one filter through the entire eclipse if you have multi-filter capability. We will let you know as soon as we have better BVRcIc calibration for the comparison stars.

Arne Henden


Information on submitting observations to the AAVSO may be found at:


A Special Notice archive is available at the following URL:

Subscribing and Unsubscribing may be done at the following URL:


Please support the AAVSO and its mission -- Join or donate today: