SEARCHING FOR Be STARS IN THE OPEN CLUSTER NGC 663

Yu, Po-Chieh; Lin, C. C.; Chen, Wen-Ping; Lee, Chien-De; Ip, Wing-Huen; Ngeow, Chow-Choong; Laher, Russ R.; Surace, J.; Kulkarni, S. R.

doi:10.1088/0004-6256/149/2/43

Cited by 6 publications

(6 citation statements)

References 23 publications

(35 reference statements)

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“…NGC 6830, located at a distance of 1.8 kpc (Kharchenko et al 2013) in the constellation Vulpecula (Barkhatova 1957), has a fairly loose structure. In contrast to our previous work (NGC 663 with an age of ∼31 Myr, Yu et al 2015), the age of NGC 6830 is about 125 Myr (Kharchenko et al 2013) and only one Be star has been reported in this cluster (Hoag & Applequist 1965) prior to our work. Using the relation of effective temperature and age, Peña et al (2011) determined that the age of NGC 6830 is log(age)=7.69 years (48.9 Myr) with the hottest star (17,000 K) in the membership of 19 stars.…”

Section: Introductioncontrasting

confidence: 96%

“…The methodology of searching for Be star candidates and identifying membership has been presented in our pilot project. Further details can be found in Yu et al (2015) and will not be repeated here. Briefly, procedures that we followed in this study are summarized below.…”

Section: Identification Of Be Candidates and Membershipmentioning

confidence: 99%

“…Nevertheless, the sample of Be stars in open clusters is far from complete due to a couple of difficulties: (1) a comprehensive spectroscopic survey is time consuming and (2) spectroscopic surveys are often limited to bright stars. Therefore, with the wide field of view (7.3 square degree) of the 48-inch Samuel Oschin Telescope, the Palomar Transient Factory (PTF; Law et al 2009) project provides an efficient way to search for emission-line candidates in open clusters using Hα imaging photometry (Yu et al 2015). Furthermore, a new instrument called the spectral energy distribution-machine (SED-machine; Ben-Ami et al 2012;Ngeow et al 2013;Ritter et al 2014) provides a possible solution for the fast and efficient follow-up spectroscopic observations for the emissionline candidates found in PTF, because the highly efficient SEDmachine is designed to classify transient events rapidly with a low-resolution (λ/δλ∼100) integrated field unit (IFU) spectrograph that covers a large wavelength range (370-920 nm).…”

Section: Introductionmentioning

confidence: 99%

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Be STARS IN THE OPEN CLUSTER NGC 6830

Lin

et al. 2016

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We report the discovery of two new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven Hα emitters were discovered using the Hα imaging photometry of the Palomar Transient Factory Survey. Stellar membership of the candidates was verified with photometric and kinematic information using 2MASS data and proper motions. The spectroscopic confirmation was carried out by using the Shane 3 m telescope at the Lick observatory. Based on their spectral types, three Hα emitters were confirmed as Be stars with Hα equivalent widths greater than −10 Å. Two objects were also observed by the new spectrograph spectral energy distribution-machine (SED-machine) on the Palomar 60-inch Telescope. The SED-machine results show strong Hα emission lines, which are consistent with the results of the Lick observations. The high efficiency of the SED-machine can provide rapid observations for Be stars in a comprehensive survey in the future.

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Section: Introductioncontrasting

confidence: 96%

Section: Identification Of Be Candidates and Membershipmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Be STARS IN THE OPEN CLUSTER NGC 6830

Lin

et al. 2016

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“…The PTF/iPTF project employed various camera filters (some have yet to be documented), including broadband filters for the g, R, and i bands, and narrow-band filters for Hα 6563 Å(on), and Hα 6630 Å(off), and, more recently, for Hα 6720 Å and Hα 6810 Å. The wide field of the PTF/iPTF Hα images allow us to conduct a program to search for Be star candidates in open clusters of different ages (Yu et al 2015(Yu et al , 2016. In the first of a series (Paper I), we present the cluster sample and their basic properties in Section 2.…”

Section: Introductionmentioning

confidence: 99%

Searching for Be Stars in the Open Clusters with PTF/iPTF. I. Cluster Sample and Be Star Candidates

Lee

et al. 2018

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We conducted a search for Be star candidates in open clusters using Hα imaging photometry of the Palomar Transient Factory Survey to investigate some connections among Be star phenomena, cluster environments, and ages. Stellar members of clusters were identified by spatial distributions, near-infrared magnitudes and colors, and by proper motions. Among 104 open clusters, we identified 96 Be star candidates in 32 clusters; 11 of our candidates have been reported in previous studies. We found that the clusters with age 7.5 < log(t(year))  8.5 tend to have more Be star candidates; there is about a 40% occurrence rate within this age bin. The clusters in this age bin also tend to have a higher Be fraction N(Be)/N(Be+B-type). These results suggest that the environments of young and intermediate clusters are favorable to the formation of Be phenomena. Spatial distribution of Be star candidates with different ages implies that they do not form preferentially in the central regions. Furthermore, we showed that the mid-infrared (MIR) colors of the Be star candidates are similar to known Be stars, which could be caused by free-free emission or bound-free emission. Some Be star candidates might have no circumstellar dust according to their MIR colors. Finally, among 96 Be candidates, we discovered that one Be star candidate FSR 0904-1 exhibits long-term variability on the timescale of ∼2000 days with an amplitude of 0.2-0.3 mag, indicating a long timescale of disk evolution.

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“…Be phenomena are the photometric and spectroscopic variability seen in the main-sequence luminous rapid rotators, known as Be stars, with a luminosity class III−V. In recent years, we have studied the evolutionary effect on the formation of Be stars in open clusters (Yu et al 2015(Yu et al , 2016(Yu et al , 2018 using the Palomar Transient Factory (Law et al 2009) and the intermediate Palomar Transient Factory (iPTF; Kulkarni 2013). The Zwicky Transient Facility (ZTF; Bellm et al 2019;Graham et al 2019;Masci et al 2019) came after iPTF, and its improved data can extend our investigation on the variability of Be stars (Ngeow et al 2019), especially for the Be stars and Be-star candidates at the faint end (m > 13 mag), which were largely excluded from previous works (e.g., in Labadie- Bartz et al 2017).…”

Section: Introductionmentioning

confidence: 99%

HO Puppis: Not a Be Star, but a Newly Confirmed IW And-type Star

Lee

et al. 2021

ApJ

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HO Puppis (HO Pup) was considered as a Be-star candidate based on its γ Cassiopeiae-type light curve, but lacked spectroscopic confirmation. Using distance measured from Gaia Data Release 2 and the spectral-energydistribution fit on broadband photometry, the Be-star nature of HO Pup is ruled out. Furthermore, based on the 28,700 photometric data points collected from various time-domain surveys and dedicated intensive-monitoring observations, the light curves of HO Pup closely resemble those of IW And-type stars (as pointed out by Kimura et al.), exhibiting characteristics such as a quasi-standstill phase, brightening, and dips. The light curve of HO Pup displays various variability timescales, including brightening cycles ranging from 23 to 61 days, variations with periods between 3.9 days and 50 minutes during the quasi-standstill phase, and a semiregular ∼14 day period for the dip events. We have also collected time-series spectra (with various spectral resolutions), in which Balmer emission lines and other spectral lines expected for an IW And-type star were detected (even though some of these lines were also expected to be present for Be stars). We detect Bowen fluorescence near the brightening phase, and that can be used to discriminate between IW And-type stars and Be stars. Finally, despite only observing for four nights, the polarization variation was detected, indicating that HO Pup has significant intrinsic polarization.

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SEARCHING FOR Be STARS IN THE OPEN CLUSTER NGC 663

Cited by 6 publications

References 23 publications

Be STARS IN THE OPEN CLUSTER NGC 6830

Be STARS IN THE OPEN CLUSTER NGC 6830

Searching for Be Stars in the Open Clusters with PTF/iPTF. I. Cluster Sample and Be Star Candidates

HO Puppis: Not a Be Star, but a Newly Confirmed IW And-type Star

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