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 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 Okayama Astrophysical Observatory Wide-Field Camera

2019 ◽  
Vol 71 (6) ◽  
Author(s):  
Kenshi Yanagisawa ◽  
Yasuhiro Shimizu ◽  
Kiichi Okita ◽  
Daisuke Kuroda ◽  
Hironori Tsutsui ◽  
...  
Keyword(s):  
Focal Plane ◽  
Near Infrared ◽  
Galactic Plane ◽  
Focal Plane Array ◽  
Variable Stars ◽  
Field Of View ◽  
Wide Field

Abstract We report on the development of a wide-field near-infrared (0.9–2.5$\, \mu$m) camera built as a renewal of the existing classical Cassegrain 0.91 m telescope at Okayama Astrophysical Observatory. The optics system was replaced with fast hybrid optics (f/2.5) composed of forward Cassegrain optics and quasi-Schmidt optics, which results in an effective image circle of 52 mm diameter on the focal plane. The new camera, called the Okayama Astrophysical Observatory Wide-Field Camera (OAOWFC), has imaging capabilities in the $Y$, $J$, $H$, and $K_{\rm s}$ bands over a field of view of $0.^{\!\!\!\circ }47 \times 0.^{\!\!\!\circ }47$ with a HAWAII-1 HgCdTe PACE focal plane array. The primary purpose of OAOWFC is to search for variability in the Galactic plane in the $K_{\rm s}$ band and to promptly follow up transients. We have demonstrated a photometric repeatability of 2% in the densest field in the northern Galactic plane and successfully discovered previously unreported variable stars. The observations of OAOWFC are fully autonomous, and we started scientific operations in 2015 April.

scholarly journals The Fleming Survey: High-cadence Survey for Variable Stars in the Northern Galactic Plane

2021 ◽  
Vol 5 (10) ◽  
pp. 245
Author(s):  
Aleks Scholz ◽  
Ben Warwick ◽  
Thomas van Aalten
Keyword(s):  
Galactic Plane ◽  
Variable Stars ◽  
High Cadence

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

A large-scale variability survey for the northern Galactic plane: KISOGP

2017 ◽  
Vol 13 (S334) ◽  
pp. 335-336
Author(s):  
Noriyuki Matsunaga ◽  
Keyword(s):  
Data Analysis ◽  
Initial Data ◽  
Large Scale ◽  
Galactic Plane ◽  
Variable Stars ◽  
Wide Field ◽  
Schmidt Telescope ◽  
Large Scale Survey

AbstractWe have conducted a large-scale survey of variable stars in the northern Galactic plane, about 320 square degrees using Kiso Wide Field Camera attached to the 105-cm Schmidt telescope at Kiso observatory. In the KISOGP (KWFC Intensive Survey of the Galactic Plane), we collected 40–100 epoch I-band images between 2012 and 2017. In our survey region roughly 5 million stars exist down to the limiting magnitude of ~16.5 mag in I. In the initial data analysis, we detected a couple of thousands of variable stars including approximately 100 Cepheids and more than 700 Miras. More than 80 percents of them were not previously reported as variable stars, indicating that there are still many relatively bright variables to be found in the Galactic plane.

scholarly journals The HST Key Project galaxies NGC 1326A, NGC 1425, and NGC 4548: New variable stars and massive star population

2019 ◽  
Vol 629 ◽  
pp. A3 ◽  
Author(s):  
Z. T. Spetsieri ◽  
A. Z. Bonanos ◽  
M. Yang ◽  
M. Kourniotis ◽  
D. Hatzidimitriou
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Absolute Magnitude ◽  
Variable Stars ◽  
Star Formation History ◽  
Wide Field ◽  
Absolute Deviation ◽  
Solar Metallicity ◽  
Red Supergiants ◽  
Candidate Variable

Studies of the massive star population in galaxies beyond the Local Group are the key to understanding the link between their numbers and modes of star formation in different environments. We present the analysis of the massive star population of the galaxies NGC 1326A, NGC 1425, and NGC 4548 using archival images obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 in the F555W and F814W filters. Through high-precision point spread function fitting photometry for all sources in the three fields, we identified 7640 candidate blue supergiants, 2314 candidate yellow supergiants, and 4270 candidate red supergiants. We provide an estimate of the ratio of blue to red supergiants for each field as a function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) at solar metallicity, we defined the luminosity function and estimated the star formation history of each galaxy. We carried out a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von Neumann ratio. This analysis yielded 243 new variable candidates with absolute magnitudes ranging from MV = −4 to −10 mag. We classified the variable stars based on their absolute magnitude and their position on the color–magnitude diagram using the MESA evolutionary tracks at solar metallicity. Our analysis yielded 8 candidate variable blue supergiants, 12 candidate variable yellow supergiants, 21 candidate variable red supergiants, and 4 candidate periodic variables.

scholarly journals Processing GOTO data with the Rubin Observatory LSST Science Pipelines I: Production of coadded frames

2021 ◽  
Vol 38 ◽  
Author(s):  
J. R. Mullaney ◽  
L. Makrygianni ◽  
V. Dhillon ◽  
S. Littlefair ◽  
K. Ackley ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Time Domain ◽  
Wide Area ◽  
Wide Field ◽  
Process Data ◽  
Data Production ◽  
The Time Domain ◽  
Further Development ◽  
High Cadence

Abstract The past few decades have seen the burgeoning of wide-field, high-cadence surveys, the most formidable of which will be the Legacy Survey of Space and Time (LSST) to be conducted by the Vera C. Rubin Observatory. So new is the field of systematic time-domain survey astronomy; however, that major scientific insights will continue to be obtained using smaller, more flexible systems than the LSST. One such example is the Gravitational-wave Optical Transient Observer (GOTO) whose primary science objective is the optical follow-up of gravitational wave events. The amount and rate of data production by GOTO and other wide-area, high-cadence surveys presents a significant challenge to data processing pipelines which need to operate in near-real time to fully exploit the time domain. In this study, we adapt the Rubin Observatory LSST Science Pipelines to process GOTO data, thereby exploring the feasibility of using this ‘off-the-shelf’ pipeline to process data from other wide-area, high-cadence surveys. In this paper, we describe how we use the LSST Science Pipelines to process raw GOTO frames to ultimately produce calibrated coadded images and photometric source catalogues. After comparing the measured astrometry and photometry to those of matched sources from PanSTARRS DR1, we find that measured source positions are typically accurate to subpixel levels, and that measured L-band photometries are accurate to $\sim50$ mmag at $m_L\sim16$ and $\sim200$ mmag at $m_L\sim18$ . These values compare favourably to those obtained using GOTO’s primary, in-house pipeline, gotophoto, in spite of both pipelines having undergone further development and improvement beyond the implementations used in this study. Finally, we release a generic ‘obs package’ that others can build upon, should they wish to use the LSST Science Pipelines to process data from other facilities.

scholarly journals A Compact Muon Tracker for Dynamic Tomography of Density Based on a Thin Time Projection Chamber with Micromegas Readout

Particles ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 333-342
Author(s):  
Ignacio Lázaro Roche
Keyword(s):  
Time Projection Chamber ◽  
Wide Field ◽  
Track Reconstruction ◽  
Long Term Stability ◽  
Societal Issues ◽  
Primary Signal ◽  
And Performance ◽  
Time Projection

Tomography based on cosmic muon absorption is a rising technique because of its versatility and its consolidation as a geophysics tool over the past decade. It allows us to address major societal issues such as long-term stability of natural and man-made large infrastructures or sustainable underwater management. Traditionally, muon trackers consist of hodoscopes or multilayer detectors. For applications with challenging available volumes or the wide field of view required, a thin time projection chamber (TPC) associated with a Micromegas readout plane can provide a good tradeoff between compactness and performance. This paper details the design of such a TPC aiming at maximizing primary signal and minimizing track reconstruction artifacts. The results of the measurements performed during a case study addressing the aforementioned applications are discussed. The current works lines and perspectives of the project are also presented.

scholarly journals Global and regional evaluation of over-land spectral aerosol optical depth retrievals from SeaWiFS

2012 ◽  
Vol 5 (2) ◽  
pp. 2169-2220 ◽  
Author(s):  
A. M. Sayer ◽  
N. C. Hsu ◽  
C. Bettenhausen ◽  
M.-J. Jeong ◽  
B. N. Holben ◽  
...  
Keyword(s):  
North America ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Field Of View ◽  
Wide Field ◽  
Imaging Spectrometer ◽  
Wide Field Of View ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Multiangle Imaging

Abstract. This study evaluates a new spectral aerosol optical depth (AOD) dataset derived from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) measurements over land. First, the data are validated against Aerosol Robotic Network (AERONET) direct-sun AOD measurements, and found to compare well on a global basis. If only data with the highest quality flag are used, the correlation is 0.86 and 72% of matchups fall within an expected absolute uncertainty of 0.05 + 20% (for the wavelength of 550 nm). The quality is similar at other wavelengths and stable over the 13-yr (1997–2010) mission length. Performance tends to be better over vegetated, low-lying terrain with typical AOD of 0.3 or less, such as found over much of North America and Eurasia. Performance tends to be poorer for low-AOD conditions near backscattering geometries, where SeaWiFS overestimates AOD, or optically-thick cases of absorbing aerosol, where SeaWiFS tends to underestimate AOD. Second, the SeaWiFS data are compared with midvisible AOD derived from the Moderate Resolution Imaging Spectrometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR). All instruments show similar spatial and seasonal distributions of AOD, although there are regional and seasonal offsets between them. At locations where AERONET data are available, these offsets are largely consistent with the known validation characteristics of each dataset. With the results of this study in mind, the SeaWiFS over-land AOD record is suitable for quantitative scientific use.

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