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Title: VI-band follow-up observations of ultra-long-period Cepheid candidates in M31

Abstract

The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ≈80 days. The intrinsic brightness of ULPCs are ∼1 to ∼3 mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color–magnitude diagram and the Period–Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be μ{sub M31,ULPC}=24.30±0.76 mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period–Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs asmore » standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.« less

Authors:
; ; ; ; ; ; ;  [1];  [2];  [3]
  1. Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China)
  2. Max Planck Institute for Extraterrestrial Physics, D-85748 Garching (Germany)
  3. Department of Physics, SUNY Oswego, Oswego, NY 13126 (United States)
Publication Date:
OSTI Identifier:
22342123
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 149; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; CEPHEIDS; COLOR; DISPERSIONS; DISTANCE; GALAXIES; PULSATIONS; TRANSIENTS; VISIBLE RADIATION

Citation Formats

Ngeow, Chow-Choong, Yang, Michael Ting-Chang, Lin, Chi-Sheng, Hsiao, Hsiang-Yao, Cheng, Yu-Chi, Lin, Zhong-Yi, Lin, I-Ling, Ip, Wing-Huen, Lee, Chien-Hsiu, and Kanbur, Shashi M. VI-band follow-up observations of ultra-long-period Cepheid candidates in M31. United States: N. p., 2015. Web. doi:10.1088/0004-6256/149/2/66.
Ngeow, Chow-Choong, Yang, Michael Ting-Chang, Lin, Chi-Sheng, Hsiao, Hsiang-Yao, Cheng, Yu-Chi, Lin, Zhong-Yi, Lin, I-Ling, Ip, Wing-Huen, Lee, Chien-Hsiu, & Kanbur, Shashi M. VI-band follow-up observations of ultra-long-period Cepheid candidates in M31. United States. https://doi.org/10.1088/0004-6256/149/2/66
Ngeow, Chow-Choong, Yang, Michael Ting-Chang, Lin, Chi-Sheng, Hsiao, Hsiang-Yao, Cheng, Yu-Chi, Lin, Zhong-Yi, Lin, I-Ling, Ip, Wing-Huen, Lee, Chien-Hsiu, and Kanbur, Shashi M. 2015. "VI-band follow-up observations of ultra-long-period Cepheid candidates in M31". United States. https://doi.org/10.1088/0004-6256/149/2/66.
@article{osti_22342123,
title = {VI-band follow-up observations of ultra-long-period Cepheid candidates in M31},
author = {Ngeow, Chow-Choong and Yang, Michael Ting-Chang and Lin, Chi-Sheng and Hsiao, Hsiang-Yao and Cheng, Yu-Chi and Lin, Zhong-Yi and Lin, I-Ling and Ip, Wing-Huen and Lee, Chien-Hsiu and Kanbur, Shashi M.},
abstractNote = {The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ≈80 days. The intrinsic brightness of ULPCs are ∼1 to ∼3 mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color–magnitude diagram and the Period–Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be μ{sub M31,ULPC}=24.30±0.76 mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period–Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.},
doi = {10.1088/0004-6256/149/2/66},
url = {https://www.osti.gov/biblio/22342123}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 2,
volume = 149,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 2015},
month = {Sun Feb 01 00:00:00 EST 2015}
}