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He II 4686 in eta Carinae: no significant changes between 2009.0 and 2014.6

ATel #6464; Mairan Teodoro (NASA/GSFC), Bernard Heathcote (SASER), Noel Richardson (U. of Montreal), Paul Luckas (SASER/Univ. Western Australia), Frederick Walter (Stony Brook Univ.), Rodrigo Prates (LNA), Gabriel Hickel (Univ. Federal de Itajuba), Adriano M. Coimbra (LNA), Felipe Navarete (IAG/USP), Malcolm Locke (SASER), Terry Bohlsen (SASER), Augusto Damineli (IAG/USP), Francisco Jablonski (DAS/INPE), William Henrique(Univ. Federal de Itajuba), Jonathan Powles (SASER), Julian West (SASER), Thiago A. Andrade (IAG/USP), Eduardo Fernandez-Lajus (Univ. Nacional de La Plata), Theodore Gull (NASA/GSFC), Michael F. Corcoran (NASA/GSFC-CRESST/USRA), Jose H. Groh (U. of Geneva), Kenji Hamaguchi (NASA/GSFC-CRESST/UMBC), Thomas Madura (NASA/GSFC/NPP), Lucas St-Jean (U. of Montreal), Gerd Weigelt (MPIfR)
on 12 Sep 2014; 20:52 UT
Credential Certification: Mairan Teodoro (mairan.teodoro@gmail.com)

Subjects: Optical, Binary, Star, Variables

We are conducting a multi-observatory campaign focused on the monitoring of He II 4686 emission across the periastron event of eta Carinae. The behavior of the equivalent width of the He II 4686 emission line across the 2014.6 event is similar to that observed in 2009.0. Our monitoring of the He II 4686 during the 2014 international campaign confirmed the presence of the same three local maxima observed in 2009: P1 and P2 (before the equivalent width minimum), and P3 (after the minimum).

We confirm the presence of a short-lived (< 5 days) increase in the He II 4686 equivalent width (as compared to 2009.0) near August 31 (as noted in ATEL #6448). Our monitoring data show that this increase reached a maximum on September 02, corresponding to twice the equivalent width seen at a slightly later phase in 2009. Nevertheless, the latest measurements show that the He II 4686 equivalent width is already back to the same intensity level as observed in 2009.0. Since we did not have frequent observations during the phase of this increase in the previous cycles, we cannot determine whether this additional emission on top of P3 is recurrent or not.

We note that the equivalent width of this emission line reached its minimum value at the predicted time, based on the ephemeris from Damineli et al. 2008 (MNRAS, 384(4), 1649-1656). Also, the duration of the minimum and the recovering phase followed the same trend for both 2009.0 and 2014.6 (as reported in ATEL #6380). In summary, judging from the timing, strength, and overall behavior of the equivalent width of the He II 4686, we can conclude that no significant changes have occurred between the 2009.0 and 2014.6 events, i.e., the two passages produced amazingly similar results.