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Post Info TOPIC: KIC 10449976
Blobrana


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RE: KIC 10449976
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Title: KIC 10449976: discovery of an extreme-helium subdwarf in the Kepler field
Authors: C.S. Jeffery (1), G. Ramsay (1), N. Naslim (1), R. Carrera (2,3), S. Greiss (4), T. Barclay (5,6), R. Karjalainen (7), A. Brooks (1,8), P. Hakala (9), ((1) Armagh Observatory, (2) IAC, (3) Universidad de La Laguna, (4) Warwick, (5) NASA Ames (6) Bay Area ERI, (7) ING (8) MSSL-UCL, (9) Finca)

Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature T=40000±300 K and surface gravity log g=5.3±0.1. Radial-velocity measurements over a five-day timescale show an upper variability limit of ~50±20 km/s. Kepler photometry of KIC 10449976 in both long and short cadence modes shows evidence for a periodic modulation on a timescale of ~3.9 days. We have examined the possibility that this modulation is not astrophysical but conclude it is most likely real. We discuss whether the modulation could be caused by a low-mass companion, by stellar pulsations, or by spots. The identification of any one of these as cause has important consequences for understanding the origin of helium-rich subdwarfs.

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Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: KIC 10449976: discovery of an extreme-helium subdwarf in the Kepler field
Authors: C.S. Jeffery, G. Ramsay, N. Naslim, R. Carrera, S. Greiss, T. Barclay, R. Karjalainen, A. Brooks, P. Hakala

Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature Teff = 40 000 ± 300 K and surface gravity log g = 5.3 ± 0.1. Radial-velocity measurements over a five-day timescale show an upper variability limit of \approx 50 ± 20 km s^-1. Kepler photometry of KIC 10449976 in both long and short cadence modes shows evidence for a periodic modulation on a timescale of \approx 3.9 days. We have examined the possibility that this modulation is not astrophysical but conclude it is most likely real. We discuss whether the modulation could be caused by a low-mass companion, by stellar pulsations, or by spots. The identification of any one of these as cause has important consequences for understanding the origin of helium-rich subdwarfs.

Read more (PDF)



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