New Blue and Red Variable Stars in NGC 247

Abstract

Images recorded with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South are combined with archival images from other facilities to search for variable stars in the southern portion of the nearby disk galaxy NGC 247. Fifteen new periodic and non-periodic variables are identified. These include three Cepheids with periods < 25 days, four semi-regular variables, one of which shows light variations similar to those of R CrB stars, five variables with intrinsic visible/red brightnesses and colors that are similar to those of luminous blue variables (LBVs), and three fainter blue variables, one of which may be a non-eclipsing close binary system. The S Doradus instability strip defines the upper envelope of a distinct sequence of objects on the (i', g'-i') color-magnitude diagram (CMD) of NGC 247. The frequency of variability with an amplitude > 0.1 magnitude in the part of the CMD that contains LBVs over the seven month period when the GMOS images were recorded is ~ 0.2. The light curve of the B[e] supergiant J004702.18--204739.9, which is among the brightest stars in NGC 247, is also examined. Low amplitude variations on day-to-day timescales are found, coupled with a systematic trend in mean brightness over a six month time interval.

Accepted for publication in the Astronomical Journal

References in corpus (14)

• Binary interaction dominates the evolution of massive stars
• The ACS Nearby Galaxy Survey Treasury
• Luminous Blue Variables are Antisocial: Their Isolation Implies that they are Kicked Mass Gainers in Binary Evolution
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
• Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, and the B[e] Supergiants; How to Tell Them Apart
• The Araucaria Project. The Distance to the Sculptor Galaxy NGC 247 from Near-Infrared Photometry of Cepheid Variables
• The Disk and Extraplanar Environment of NGC 247
• Candidate LBV stars in galaxy NGC 7793 found via HST photometry + MUSE spectroscopy
• The young stellar population in NGC 247 Main properties and hierarchical clustering
• The Araucaria Project: The Distance to the Sculptor Group Galaxy NGC 247 from Cepheid Variables Discovered in a Wide-Field
• New luminous blue variable candidates in the NGC 247 galaxy
• Multi-Epoch BVRI Photometry of Luminous Stars in M31 and M33
• The Lop-sided Spiral Galaxy NGC 247: Clues to a Possible Interaction with NGC 253