UNSPECIFIED. (2005) SDSS J124058.03-015919.2: a new AM CVn star with a 37-min orbital period. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 361 (2). pp. 487-494. ISSN 0035-8711

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Abstract

We present high time-resolution spectroscopy with the Very Large Telescope of SDSS J124058.03-015919.2, anew helium-transferring binary star identified in the Sloan Digital Sky Survey. We measure an orbital period of 37.355 +/- 0.002 min, confirming the AM CVn nature of the system. From the velocity amplitudes of the accretor and the accretion stream-disc impact, we derive amass ratio q = 0.039 +/- 0.010. Our spectral coverage extends from lambda 3700-9500 angstrom and shows the presence of helium, nitrogen, silicon and iron in the accretion disc, plus the redshifted, low-velocity 'central spikes' in the helium lines, known from the low-state AM CVn stars GP Com and CE 315. Doppler tomography of the helium and silicon emission lines reveals an unusual pattern of two bright emission sites in the tomograms, instead of the usual one emission site identified with the impact of the mass stream into the accretion disc. One of the two is preferred as the conventional stream-disc impact point in velocity space, at the 3a confidence level. We speculate briefly on the origin of the second.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Journal or Publication Title:	MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Publisher:	BLACKWELL PUBLISHING
ISSN:	0035-8711
Date:	1 August 2005
Volume:	361
Number:	2
Number of Pages:	8
Page Range:	pp. 487-494
Identification Number:	10.1111/j.1365-2966.2005.09186.x
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/6736

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