J/MNRAS/502/818 Periods and classifications of RR Lyrae in M15 (Hoffman+, 2021)
Periods and classifications of RR Lyrae stars in the globular cluster M15.
Hoffman A.M., Murakami Y.S., Zheng W., Stahl B.E., Filippenko A.V.
<Mon. Not. R. Astron. Soc., 502, 818-835 (2021)>
=2021MNRAS.502..818H 2021MNRAS.502..818H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Clusters, globular ; Optical
Keywords: methods: data analysis - techniques: photometric - stars: evolution -
stars: variables: RR Lyrae - globular clusters: individual: M15
Abstract:
We present measurements of the periods, amplitudes, and types of 74 RR
Lyrae stars in the globular cluster M15 derived from Nickel 1m
telescope observations conducted at Lick Observatory in 2019 and 2020.
Of these RR Lyrae stars, two were previously reported but without a
determination of the period. In addition, we identify five Type II
Cepheid variable stars for which we report three novel period
determinations, and a further 34 stars with uncertain classifications
and periods. We discuss the development and subsequent application to
our data of a new PYTHON package, Period-determination and
Identification Pipeline Suite (PIPS), based on a new adaptive
free-form fitting technique to detect the periods of variable stars
with a clear treatment of uncertainties.
Description:
Over approximately 1yr, we obtained 691 images of M15 on 46 nights
using the Nickel 1-m telescope, located at Lick Observatory (Mt.
Hamilton, CA). We observed M15 for an average of 20min per night, on
nights devoted mainly to supernova photometry, with a typical time
between observations of roughly 7d. As RR Lyrae stars generally have
oscillation periods of 0.2-0.9d (Corwin et al. 2008AJ....135.1459C 2008AJ....135.1459C,
Cat. J/AJ/135/1459), our observing cadence produces widely scattered
data when compared to the pulsation period. Ideally, fast pulsators
such as RR Lyrae stars should be observed as often as possible to
capture the full range of behaviour (VanderPlas 2018ApJS..236...16V 2018ApJS..236...16V).
With widely scattered data, period determination becomes difficult, as
does avoiding aliasing.
Our analysis led to confident period classifications for 74 RR Lyrae
stars in M15, 2 of which do not have a value listed in the reference
literature. Of these 74 stars, the majority (67) are single-mode
pulsators, which are classified as RRab and RRc stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 82 118 Results
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Star name (VNNNa)
7- 14 F8.4 deg RAdeg Right ascension (J2000)
16- 22 F7.4 deg DEdeg Declination (J2000)
24- 34 F11.9 d P Best-fitting period of the fundamental mode
36- 42 E7.2 d e_P ? Error on P
44- 51 F8.6 d P2 ? Best-fitting period of the secondary pulsation
mode
53- 59 E7.2 d e_P2 ? Error on P2
61- 64 F4.2 mag A1 Amplitude of the fundamental mode
66- 69 F4.2 mag A2 ? Amplitude of the secondary pulsation mode
71- 75 F5.2 mag Vmag ? Mean V-band magnitude
77- 82 A6 --- Type Star classification
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 26-Oct-2023