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Special Notice #153: Outbursting system in Libra [V364 Lib]

AAVSO Special Notice #153

Outbursting system in Libra
April 27, 2009

Pojmanski et al. (CBET 1774, D.W.E. Green, editor) formally reported that an outbursting source, ASAS J150946-2147.7 [V364 Lib], first discovered by ASAS in July 2003, is now in outburst again.  The current outburst was first reported by Pojmanski via VSNET (vsnet-alert 11167) on 2009 April 6, and subsequent observations by A. Henden (vsnet-alert 11172) and H. Bond (vsnet-alert 11173) identified the source as the relatively bright star 2MASS J15094657-2147462 (V=11.0).  Photometry by Henden indicated the star had brightened to V=10.40, and become bluer, with (B-V)=0.22. Subsequent spectroscopy by K. Kinagusa et al (CBET 1774, and vsnet-alert 11177, reported by T. Kato) indicate the presence of both high-ionization emission lines with strongly red- and blue-shifted components suggesting accretion around a black hole.  They also note a possible similarity between this system and the galactic microquasar V4641 Sgr, and note that the latter's jet outbursts were preceeded by optical outbursts.  J. Greaves (vsnet-alert 11214) notes that ASAS3 photometry shows variability with a timescale of about 0.35 days and full amplitude of about 0.2 magnitudes in V; he notes that the spectrum exhibits several peaks, and thus the period may be an alias.

This is an interesting source, and futher time-series is encouraged. Since the source is bright, short exposures should still yield good signal to noise. If possible, transformed multicolor photometry would be very useful to track the color evolution of the source.  B. Skiff notes that because this star is a bright source (CPD-21 5892), it likely appears on any and all patrol and survey plates of the region, and a search of archival photometry is also strongly encouraged.

ASAS J150946-2147.7 is located at the following (J2000) coordinates:

RA: 15 09 46.58 , Dec: -21 47 46.3

Charts for this object may be plotted using AAVSO VSP: http://www.aavso.org/observing/charts/vsp/index.html?pickname=ASAS%20150946-2147.7

Please submit data promptly to the AAVSO using the name "ASAS J150946-2147.7" (AUID 000-BJP-099).  

This AAVSO Special Notice was prepared by M. Templeton.

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