In a recent paper in New Astronomy, Koen et al. (2004, New Astron. 9, 565) announced the discovery of two new short period pulsating sdB (EC14026) stars. One of them, PG 0048+091, showed a rich spectrum with at least 7 pulsation frequencies, with periods ranging from 140 to 190 seconds. The amplitudes of these modes range from 1.4 to 4.1 mma. Intriguingly, there are several frequency separations between the modes of multipes of about 60 uHz - suggesting that it is a rapidly rotating star -- on the inside, at least. As a result of this preliminary work, PG 0048 is another interesting candidate to test theoretical models of differential rotation within subdwarf B stars. With extended coverage as a tertiary target during a WET run, PG 0048 can provide a comparison with PG 0014 and address similar science issues. See the scientific justification for PG 0014 for further detail about these.
PG 0048+091 is relatively bright (V=14.3) putting it within easy range of all telescopes in the WET network. Given that the discovery paper shows results based on 25.5 hours of photometry spread over nearly a full year, we can expect to get significantly denser data with a far better duty cycle during Xcov24. Even with imperfect phase coverage, our results should yield secure measurements of the principal pulsation frequencies in PG 0048+091 - allowing us to test the initial suggestion by Koen et al. (2004) that it shows evidence of rapid rotation. This would complement the science goals of the primary target for Xcov24, PG 0014+067.
From a logistical standpoint, PG 0048 is in a part of the sky accessible to all sites (North and South). Sites that are unable to produce data on PG 0014 because of its faintness can therefore observe PG 0048 and obtain 3 or more hours of data after RX J2117.1, the secondary target, has set.
RA = 0h 51m 27s
Dec = +9:21:33
Epoch = J2000
V Magnitude 14.3
Koen, C., O'Donoghue, D.O., Kilkenny, D., and Pollacco, D.L.
2004, New Astronomy 9, 565
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