scholarly journals Blue large-amplitude pulsators as a new class of variable stars

2017 ◽  
Vol 1 (8) ◽  
Author(s):  
Paweł Pietrukowicz ◽  
Wojciech A. Dziembowski ◽  
Marilyn Latour ◽  
Rodolfo Angeloni ◽  
Radosław Poleski ◽  
...  
Keyword(s):  
Large Amplitude ◽  
Variable Stars ◽  
New Class

scholarly journals Confirmation of monoperiodicity above 20 s for two blue large-amplitude pulsators

2020 ◽  
Vol 496 (2) ◽  
pp. 1105-1114 ◽  
Author(s):  
Paul Ross McWhirter ◽  
Marco C Lam ◽  
Iain A Steele
Keyword(s):  
Gravitational Lensing ◽  
Large Amplitude ◽  
Variable Stars ◽  
Light Curves ◽  
Driving Mechanism ◽  
New Class ◽  
Pulsating Variable Stars ◽  
Short Period ◽  
Filter Frequency ◽  
High Cadence

ABSTRACT Blue large-amplitude pulsators (BLAPs) are a new class of pulsating variable stars. They are located close to the hot subdwarf branch in the Hertzsprung–Russell diagram and have spectral classes of late O or early B. Stellar evolution models indicate that these stars are likely radially pulsating, driven by iron group opacity in their interiors. A number of variable stars with a similar driving mechanism exist near the hot subdwarf branch with multiperiodic oscillations caused by either pressure (p) or gravity (g) modes. No multiperiodic signals were detected in the OGLE (Optical Gravitational Lensing Experiment) discovery light curves since it would be difficult to detect short-period signals associated with higher order p modes with the OGLE cadence. Using the RISE instrument on the Liverpool Telescope, we produced high-cadence light curves of two BLAPs, OGLE-BLAP-009 (mv = 15.65 mag) and OGLE-BLAP-014 (mv = 16.79 mag), using a 720 nm longpass filter. Frequency analysis of these light curves identifies a primary oscillation with a period of 31.935 ± 0.0098 min and an amplitude from a Fourier series fit of 0.236 mag for BLAP-009. The analysis of BLAP-014 identifies a period of 33.625 ± 0.0214 min and an amplitude of 0.225 mag. Analysis of the residual light curves reveals no additional short-period variability down to an amplitude of 15.20 ± 0.26 mmag for BLAP-009 and 58.60 ± 3.44 mmag for BLAP-014 for minimum periods of 20 and 60 s, respectively. These results further confirm that the BLAPs are monoperiodic.

scholarly journals Identifying blue large-amplitude pulsators in the Galactic plane using Gaia DR2: a case study

2018 ◽  
Vol 620 ◽  
pp. L9 ◽  
Author(s):  
G. Ramsay
Keyword(s):  
Large Amplitude ◽  
Galactic Plane ◽  
Absolute Magnitude ◽  
High Amplitude ◽  
Variable Stars ◽  
Wide Field ◽  
New Class ◽  
Moderate Resolution ◽  
High Cadence

Blue large-amplitude pulsators (BLAPs) are blue stars emitting high-amplitude (> 0.2 mag) pulsations on a timescale of a few tens of minutes. Recently discovered using OGLE data, they form a new class of variable star and have inspired a number of investigations searching for the origin of their pulsations. This short study presents the Gaia DR2 data for ten BLAPs for which parallax measurements are available. We have dereddened their colours using Gaia DR2 data from the stars in their immediate field and find that six show absolute magnitude and intrinsic colour consistent with expectations, whilst four stars have a less certain classification. This work highlights the extra information that Gaia DR2 data can provide to help classify those variable stars for which moderate-resolution optical spectra are not currently available. We also show how Gaia DR2 can make searches for BLAPs in wide-field high-cadence surveys more systematic and robust.

scholarly journals The Secret Lives of Cepheids:δCep—The Prototype of a New Class of Pulsating X-Ray Variable Stars*

2017 ◽  
Vol 838 (1) ◽  
pp. 67 ◽  
Author(s):  
Scott G. Engle ◽  
Edward F. Guinan ◽  
Graham M. Harper ◽  
Manfred Cuntz ◽  
Nancy Remage Evans ◽  
...  
Keyword(s):  
Variable Stars ◽  
X Ray ◽  
New Class

scholarly journals The Puzzling K and Early-M Giants: A Summary of Precise Radial Velocity Results for 15 Stars

1999 ◽  
Vol 170 ◽  
pp. 193-203 ◽  
Author(s):  
Ana M. Larson ◽  
Stephenson L. S. Yang ◽  
Gordon A. H. Walker
Keyword(s):  
Radial Velocity ◽  
Physical Mechanism ◽  
Variable Stars ◽  
Published Data ◽  
Iodine Cell ◽  
New Class ◽  
Type K ◽  
Low Amplitude ◽  
Term Monitoring

AbstractNearly a decade ago, “yellow giants” were introduced as a new class of low-amplitude radial-velocity variable stars. In this report we discuss new results for 12 spectral type K and early-M giants based on long-term monitoring using both the hydrogen-fluoride and iodine-cell techniques. We compare these results with those of published data for 3 additional stars (ϒ Cephei, β Geminorum, and β Ophiuchi), and discuss possible implications for the underlying physical mechanism(s).

The interaction of large amplitude shallow-water waves with an ambient shear flow: non-critical flows

1972 ◽  
Vol 56 (2) ◽  
pp. 241-255 ◽  
Author(s):  
P. A. Blythe ◽  
Y. Kazakia ◽  
E. Varley
Keyword(s):  
Gravity Waves ◽  
Water Waves ◽  
Large Amplitude ◽  
Vertical Direction ◽  
Shallow Water Waves ◽  
Flow Equations ◽  
Hydraulic Flow ◽  
New Class ◽  
Simple Waves ◽  
The Waves

This paper describes the behaviour of large amplitude, long gravity waves as they move over a horizontal bed into a region where the flow is steady but sheared in a vertical direction. A new class of exact solutions to the nonlinear hydraulic flow equations is derived. These solutions describe progressing waves and are sufficiently general to allow both the shape of the free surface at any instant and the shear profile of the undisturbed flow to be specified. The waves are examples of neutrally stable disturbances in the sense that they neither grow nor decay in amplitude, although, like simple waves on an unsheared flow, they can break.

K Giants in 47 Tucanae: Detection of a New Class of Variable Stars

1996 ◽  
Vol 464 (2) ◽  
pp. L157-L160 ◽  
Author(s):  
Peter D. Edmonds ◽  
Ronald L. Gilliland
Keyword(s):  
Variable Stars ◽  
New Class ◽  
K Giants

scholarly journals Long Period Variable Stars in the Hipparcos Observing Program

1992 ◽  
Vol 9 ◽  
pp. 422-422
Author(s):  
D. Barthes ◽  
H. Boughaleb ◽  
F. Figueras ◽  
E. G. Foster ◽  
J. A. Mattei ◽  
...  
Keyword(s):  
Real Time ◽  
Large Amplitude ◽  
World Wide ◽  
Variable Stars ◽  
Satellite Observations ◽  
Long Period ◽  
Pulsating Variable Stars ◽  
Period Variable ◽  
Symbolic Methods ◽  
Statistical Results

AbstractAmong the long period variable stars included in the Hipparcos observing program, 245 large-amplitude ones require brightness predictions during the mission in order to allocate the necessary observing time. We present the computation of the light ephemerides with numeric and symbolic methods using AAVSO’s 75-year data on maxima and minima dates and magnitudes and 20 years of individuai observations; the evaluation and revision of the ephemerides using ground-based observations compiled monthly by the AAVSO from observers world-wide and real-time monitoring of ephemerides stars from satellite observations performed at ESOC; the statistical results derived from one-and-a-half years of simultaneous ground-based and Hipparcos observations. We show the usefulness of all this work in understanding the physics of these pulsating variable stars.

scholarly journals The puzzling new class of variable stars in NGC 3766: old friend pulsators?

2014 ◽  
Vol 569 ◽  
pp. A18 ◽  
Author(s):  
S. J. A. J. Salmon ◽  
J. Montalbán ◽  
D. R. Reese ◽  
M.-A. Dupret ◽  
P. Eggenberger
Keyword(s):  
Variable Stars ◽  
New Class
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