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Blue Large-Amplitude Pulsators (BLAPs) are rare short-period ($\lesssim$80 min) pulsating variable stars exhibiting large-amplitude brightness variations (typically between 0.1 and 0.4 mag). As a recently discovered class of radial-mode…

Pulsars are often lauded for their (relative) rotational and radio emission stability over long time scales. However, long-term observing programmes are identifying an increasing number of pulsars that deviate from this preconceived notion.…

High Energy Astrophysical Phenomena · Physics 2025-03-13 M. E. Lower , A. Karastergiou , S. Johnston , P. R. Brook , S. Dai , M. Kerr , R. N. Manchester , L. S. Oswald , R. M. Shannon , C. Sobey , P. Weltevrede

The surface rotations of some red giants are so fast that they must have been spun up by tidal interaction with a close companion, either another star, a brown dwarf, or a planet. We focus here on the case of red giants that are spun up by…

Solar and Stellar Astrophysics · Physics 2017-06-28 Georges Meynet , Patrick Eggenberger , Giovanni Privitera , Cyril Georgy , Sylvia Ekstroem , Yann Alibert , Christophe Lovis

Despite the large number of studies focused on the characterisation of Li-rich stars and understanding the mechanisms leading to such enrichment, their origin remains a mystery. Magnetic activity, particularly the phenomena usually…

Solar and Stellar Astrophysics · Physics 2024-08-13 Inês Rolo , Elisa Delgado Mena , Maria Tsantaki , João Gomes da Silva

30$\%$--50$\%$ of the luminous pulsating red-giant stars show light variations of a longer period than the pulsation periods. Those periods are called long secondary periods (LSP). There has been debated for many years but the origin of the…

Solar and Stellar Astrophysics · Physics 2024-01-08 Masaki Takayama

We have measured the times of onset of recent fadings in four R CrB stars -- V854 Cen, RY Sgr, R CrB, and S Aps. These times continue to be locked to the stars' pulsation periods, though with some scatter. In RY Sgr, the onsets of fading…

Solar and Stellar Astrophysics · Physics 2018-09-20 John R. Percy , Kevin H. Dembski

Based on the data from the ''Pi of the Sky'' project we made a catalog of the variable stars with periods from 0.1 to 10 days. We used data collected during a period of two years (2004 and 2005) and classified 725 variable stars. Most of…

Long secondary periods (LSPs), observed in a third of pulsating red giant stars, are the only unexplained type of large-amplitude stellar variability known at this time. Here we show that this phenomenon is a manifestation of a substellar…

The period-luminosity sequences and the multiple periods of luminous red giant stars are examined using the OGLE III catalogue of long-period variables in the Large Magellanic Cloud. It is shown that the period ratios in individual…

Solar and Stellar Astrophysics · Physics 2015-06-23 P. R. Wood

Red supergiants (RSGs) are important for our understanding of supernova progenitors, stellar populations, stellar evolution, mass loss and dust production. Extragalactic surveys of RSGs have a long history in the Local Group, but few…

The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to non-classical atmosphere models to interpret these regions.…

We have used the unique low frequency sensitivity of the Large Phased Array radio telescope of Pushchino Radio Astronomy Observatory to collect dataset of the single pulse observations of second period pulsars of the Northern hemisphere.…

High Energy Astrophysical Phenomena · Physics 2018-02-19 Kazantsev A. N. , Potapov V. A

Excitation of radial oscillations in population I (X=0.7, Z=0.02) red supergiants is investigated using the solution of the equations of radiation hydrodynamics and turbulent convection. The core helium burning stars with masses 8M_odot <=…

Solar and Stellar Astrophysics · Physics 2015-06-03 Yuri A. Fadeyev

Context. The advent of space-borne missions such as CoRoT or Kepler providing photometric data has brought new possibilities for asteroseismology across the H-R diagram. Solar-like oscillations are now observed in many stars, including red…

Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the HR diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after…

We present the results of time-series photometric analysis of 15106 A-K type stars observed by the Kepler space mission. We identified 513 new rotational variables and measured their starspot rotation periods as a function of spectral type…

Solar and Stellar Astrophysics · Physics 2018-12-10 Sowgata Chowdhury , Santosh Joshi , Chris A. Engelbrecht , Peter De Cat , Yogesh. C. Joshi , K. T. Paul

Red giants are evolved stars which exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red-giant stars were targets of spectroscopic asteroseismic observing projects. We…

Thanks to their large angular dimension and brightness, red giants and supergiants are privileged targets for optical long-baseline interferometers. Sixteen red giants and supergiants have been observed with the VLTI/AMBER facility over a…

Solar and Stellar Astrophysics · Physics 2015-06-16 P. Cruzalèbes , A. Jorissen , Y. Rabbia , S. Sacuto , A. Chiavassa , E. Pasquato , B. Plez , K. Eriksson , A. Spang , O. Chesneau

Observations from the Heliospheric Imagers (HI-1) on both the STEREO spacecraft have been analysed to search for very long period large amplitude stellar variability, finding 6 new candidates. A total of 85 objects, mostly previously known…

Solar and Stellar Astrophysics · Physics 2015-06-05 K. T. Wraight , D. Bewsher , Glenn J. White , W. Nowotny , A. J. Norton , C. Paladini

Oscillating stars in binary systems are among the most interesting stellar laboratories, as these can provide information on the stellar parameters and stellar internal structures. Here we present a red giant with solar-like oscillations in…

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