The Second [ITAL]EXTREME ULTRAVIOLET EXPLORER[/ITAL][ITAL]Extreme Ultraviolet Explorer[/ITAL] Right Angle Program Catalog

Christian, D. J.; Craig, N.; Cahill, W. D.; Roberts, Bryce; Malina, Roger F.

doi:10.1086/300847

Cited by 24 publications

(26 citation statements)

References 33 publications

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“…Christian et al (1999) showed light curves of GD 394 obtained during EUV E RAP observations which appear, at least in one case, similar to the DS light curve observed in 1995 October. We veriÐed that measured periods are in agreement with the period of the 1995 October light curve.…”

Section: Morphology and Periodogramsupporting

confidence: 77%

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Adding More Mysteries to the DA White Dwarf GD 394

Dupuis

Chayer

Vennes

et al. 2000

ApJ

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We present spectroscopic and timing analyses of the hot DA white dwarf GD 394 showing abundance inhomogeneities across its surface. Lick Hamilton echelle, International Ultraviolet Explorer (IUE), HST GHRS, and Hopkins Ultraviolet Telescope (HUT) spectra show dominant Si III and Si IV features, while Extreme Ultraviolet Explorer (EUV E) spectra show evidence of a host of trace element opacities. We report the detection of Si III j4552 triplet with a measured radial velocity of 27 km s~1 in agreement with far ultraviolet (FUV) line velocities, but indicating a silicon abundance (Si/H \ 2 ] 10~5) a factor of 10 larger than measured in the FUV range [Si/H \ (2È7) ] 10~6]. E †ective temperature measurements based on Lyman continuum (EUV E) and Lyman line series (HUT) are systematically cooler (*T D [4000 K) than measurements based on medium-dispersion Balmer line spectroscopy, an e †ect attributed to yet unidentiÐed opacities. A timing analysis of EUV E deep-survey and scanner time series, as well as spectrometer data, shows GD 394 to be variable in the extreme ultraviolet (EUV) with an amplitude of 25% and a period of 1.150^0.003 days. The EUV variability suggests abundance inhomogeneities in the atmosphere, and we explore di †erent models to explain its origin.

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Section: Morphology and Periodogramsupporting

confidence: 77%

“…Note that He II was not detected by IUE as would have been expected for a DO. The possibility that GD 394 may be variable resurfaced in Christian et al (1999) catalog of sources detected by EUV E scanners during right-angle pointed (RAP) observations.…”

Section: Discussionmentioning

confidence: 99%

Adding More Mysteries to the DA White Dwarf GD 394

Dupuis

Chayer

Vennes

et al. 2000

ApJ

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“…We note that it does appear as a far-UV emitter in the EUVE catalogue (Christian et al 1999) due to a stellar flare. The GALEX near-UV flux of 20.1 ± 2.4 µJy results in an F NUV /F J ratio of 7.1× 10 −5 or an F NUV /F Ks ratio of 7.7 × 10 −5 .…”

Section: The Age Of 2mass J0213+3648 Abmentioning

confidence: 82%

2MASS 0213+3648 C: A wide T3 benchmark companion to an an active, old M dwarf binary

Deacon

Magnier

Liu

et al. 2017

Mon. Not. R. Astron. Soc.

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We present the discovery of a 360 AU separation T3 companion to the tight (3.1 AU) M4.5+M6.5 binary 2MASS J02132062+3648506. This companion was identified using Pan-STARRS 1 data and, despite its relative proximity to the Sun (22.2 +6.4 −4.0 pc; Pan-STARRS 1 parallax) and brightness (J=15.3), appears to have been missed by previous studies due to its position near a diffraction spike in 2MASS. The close M dwarf binary has active X-ray and Hα emission and shows evidence for UV flares. The binary's weak GALEX UV emission and strong Na I 8200 Å Na absorption leads us to an age range of ∼1-10 Gyr. Applying this age range to evolutionary models implies the wide companion has a mass of 0.063±0.009 M ⊙ . 2MASS J02132+3648 C provides a relatively old benchmark close to the L/T transition and acts as a key, older comparison to the much younger early-T companions HN Peg B and GU Psc b.

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“…However, the detected X-ray luminosity is only 0.3 dex smaller than that of Cas, which has been suspected of having a compact companion (Mason, White, & Sanford 1976), and it may also be variable. Aqr was one of only a few Be stars detected by the Extreme Ultraviolet Explorer (EUVE; Christian et al 1999), which might imply the presence of flux in excess of the photospheric contribution in this wavelength region. Such an excess might be attributed to chromospheric activity of the secondary.…”

Section: Discussionmentioning

confidence: 99%

A Study of π Aquarii during a Quasi‐normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity

Bjorkman

Мирошниченко

McDavid

et al. 2002

ApJ

125

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We present the results of recent multicolor photometric and high-resolution spectroscopic observations of the bright Be star Aqr. Observational data collected from the literature were used to study the star's variations over the last four decades. The star is identified with the IR sources F22227+0107 in the IRAS Faint Point Source Catalog and MSX5 G066.0066À44.7392 in the MSX Catalog. The variations in near-IR brightness of Aqr are found to be among the largest reported for Be stars. Since 1996, the star has shown only weak signs of circumstellar emission, which has allowed us to refine the fundamental stellar parameters: A V ¼ 0:15 mag, T eff ¼ 24;000 K, log g ¼ 3:9, and M V ¼ À2:95 mag. A weak emission component of the H line has been detected during the recent quasi-normal star phase. From analysis of the H line profiles, we find antiphased radial velocity variations of the emission component and the photospheric absorption, with a period of 84.1 days and semiamplitudes of 101.4 and 16.7 km s À1 , respectively. This result suggests that Aqr may be a binary system consisting of stars with masses of M 1 sin 3 i ¼ 12:4 M , M 2 sin 3 i ¼ 2:0 M . We also estimate the orbital inclination angle to be between 50 and 75 . We suggest that the photometric, spectroscopic, and polarimetric variations observed during the second half of the 20th century may be due to variable mass transfer between the binary components.

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The Second [ITAL]EXTREME ULTRAVIOLET EXPLORER[/ITAL][ITAL]Extreme Ultraviolet Explorer[/ITAL] Right Angle Program Catalog

Cited by 24 publications

References 33 publications

Adding More Mysteries to the DA White Dwarf GD 394

Adding More Mysteries to the DA White Dwarf GD 394

2MASS 0213+3648 C: A wide T3 benchmark companion to an an active, old M dwarf binary

A Study of π Aquarii during a Quasi‐normal Star Phase: Refined Fundamental Parameters and Evidence for Binarity

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