Get Ready - A Brightening Luminous Blue Variable Awaits
Attention Southern Hemisphere observers! This is a big deal for the actual observers. It’s time to get out your equipment as take a closer look in the Large Magellanic Cloud.
The luminous blue variable (LBV) HDE 269006 = R71 is now reaching a visual magnitude of 8.3. Using the AAVSO International Database, recordings from 1987 show HDE 269006 to have a visual magnitude of 10.8 until 2006 when it began to get brighter. In the late half of 2009 it had increased to magnitude 8.5, but declined to magnitude 9 over the next three years. It hasn’t changed since 2012… but it is now!
“All observations of this LBV are welcome. In particular, VBRI photometry would be very valuable in the coming seasons to correlate with the spectra being obtained now and multiwavelength observations sure to be obtained in the future, and to document the optical behavior of HDE 269006 at this time in its history.” says the AAVSO. Coordinates are: 05 02 07.39 -71 20 13.1 (2000.0)
According to IAU Central Bureau Electronic Telegram 3192 (Daniel W. E. Green, Ed.), “R. Gamen, Instituto de Astrofisica de La Plata, CONICET, Universidad Nacional de la Plata; N. Walborn, Space Telescope Science Institute; N. Morrell, Las Campanas Observatory, Carnegie Observatories; R. Barba, Instituto de Ciencias Astronomicas y de la Tierra, CONICET, San Juan; and E. Fernandez Lajus, Instituto de Astrofisica de La Plata, CONICET, Universidad Nacional de la Plata, write that the luminous blue variable HDE 269006 (= R71) in the Large Magellanic Cloud continues to brighten in the visual since their last report in 2009 (IAUC 9082), when it was at magnitude V = 9. Differential photometry from images obtained in Apr. 2012 shows that R71 has brightened by 0.6 mag in V since Apr. 2010 and is currently at V approximately 8.3.
This unprecedented rise in its light curve is accompanied by spectacular variations in its optical spectrum. In August 2009, it resembled a (peculiar) early-F supergiant, while currently R71 displays early-G supergiant characteristics, on the basis of ionization ratios of absorption lines such as Fe I/Fe II as well as the strength and width of the Ca II H and K absorption lines.
Concurrently, H-alpha has transformed from a P-Cyg profile into a centrally reversed, symmetrical broad emission (alternatively, an absorption line with symmetrical emission wings), while the Ca II infrared triplet (849.8-, 854.2-, and 866.2-nm) emission has declined and strong forbidden [Ca II] 729.1- and 732.4-nm emission lines have appeared — along with weaker ones of [O I-II], [N II], and [S II].
This is the first report of [Ca II] emission in an apparent S Dor event to their knowledge and suggests comparison with the red transients (Humphreys et al. 2011, Ap.J. 743, 118). R71 is previously known to have an unusually strong dust signature in the infrared (Bonanos et al. 2009, A.J. 138, 1003, and references therein). Further monitoring is indicated to determine the nature and outcome of the current event.” [extensive quotation from CBET 3192 by permission of D. Green]
Please report your observations to the AAVSO International Datbase as HD 269006. Report: Tammy Plotner for Astro Space News