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Alert Notice 694: Spectroscopy of gamma Cas requested

January 31, 2020

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports: https://www.aavso.org/gam-cas-campaign
- Spectroscopy: https://www.aavso.org/gam-cas-campaign-01

Ernst Pollmann (International Working Group ASPA (Active Spectroscopy in Astronomy)) has requested AAVSO observers' assistance in obtaining spectra of the very bright Be star gam Cas (HD 5394, 1.6-3V) in support of a long term study underway of HeI 6678 V/R periodicity in this star.

Pollmann writes that he is "reactivating a long-term study of HeI 6678 V/R periodicity in gamma Cas. Stee et al. (1998) proposed that the He excitation and ionization region, responsible for the emission in the HeI 6678 line, extends to 2.3 stellar radii. Thus, the HeI 6678 line has an important diagnostic value of activity close to the stellar surface.

"The time-dependent mass loss from the primary component of the gamma Cas binary system assumes that both photospheric and disk density variations lead to the double peak profile variations of HeI 6678.

"The analysis of the V/R periodicity (448 day) of the Hel 6678 double-peak emission for the period August 2009 to September 2019, cannot confirm the period, published [in] IBVS 6103 (2014), probably because of the few data available until 2014.

"The 448 day period found today, is based on a much longer monitoring time and a three times larger data set, from the data bases BAA, BeSS, and my own spectra."

CCD spectra with spectral resolution of at least 10000 (or better) should cover at least the wavelength section from 6650 to 6700 Angströms. One spectrum per week is requested.

The campaign is running already and should last at least through 2024.

Coordinates: R.A. 00 56 42.53  Dec. +60 43 00.3 (2000.0)

AAVSO finder charts for gam Cas may be generated using the AAVSO Variable Star Plotter (VSP).

Spectra should be sent directly to Ernst Pollmann <ernst-pollmann@t-online.de> and also submitted to the AAVSO Spectroscopy Database (AVSpec, https://www.aavso.org/apps/avspec/), as well as to any other sites the observer chooses.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Ernst Pollmann.
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