Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars

E. M. Green; G. Fontaine; M. D. Reed; K. Callerame; I. R. Seitenzahl; B. A. White; E. A. Hyde; R. Oestensen; O. Cordes; P. Brassard; S. Falter; E. J. Jeffery; S. Dreizler; S. L. Schuh; M. Giovanni; H. Edelmann; J. Rigby; A. Bronowska

arXiv · astro-ph/0210285

Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars

E. M. Green·G. Fontaine·M. D. Reed·K. Callerame·I. R. Seitenzahl·B. A. White·E. A. Hyde·R. Oestensen·O. Cordes·P. Brassard·S. Falter·E. J. Jeffery·S. Dreizler·S. L. Schuh·M. Giovanni·H. Edelmann·J. Rigby·A. Bronowska

View original source ↗Read source document ↗Export metadata ↓

Abstract

During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, we have serendipitously discovered a new class of low amplitude, multimode sdB pulsators with periods of the order of an hour. These periods are more than a factor of ten longer than those of previously known multimode sdB pulsators (EC 14026 stars), implying that they are due to gravity modes rather than pressure modes. The longer period pulsators are found only among cooler sdB stars, where they are surprisingly common. The iron opacity instability that drives the short period EC 14026 stars is effective only in hot sdB's, leaving the driving mechanism for the deeper gravity modes in cool sdB's currently unknown. We present the first observational results for our newly identified sdB variables, and discuss possible implications.

Explore related subjects

astro-ph

Keep this discovery

BibTeX RIS

E. M. Green, G. Fontaine, M. D. Reed, K. Callerame, I. R. Seitenzahl, B. A. White, E. A. Hyde, R. Oestensen, O. Cordes, P. Brassard, S. Falter, E. J. Jeffery, S. Dreizler, S. L. Schuh, M. Giovanni, H. Edelmann, J. Rigby, A. Bronowska. 2002-12-16. Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars. https://arxiv.org/abs/astro-ph/0210285

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2014

Interacting Phantom Energy and Avoidance of the Big Rip Singularity

Models of the universe with arbitrary (non gravitational) interaction between the components of the cosmic fluid: the phantom energy and the background, are investigated. A general form of the interaction that is inspired in scalar-tensor theories of gravity is considered. No specific model for the phantom fluid is assumed. We concentrate our investigation on solutions that are free of the coincidence problem. We found a wide region in the parameter space where the solutions are free of the big rip singularity also. Physical arguments, together with arguments based on the analysis of the observational evidence, suggest that phantom models without big rip singularity might be preferred by Nature.

astro-ph↗

arXiv2014

Exploring the Small Magellanic Cloud to the Faintest X-ray Fluxes: Source Catalog, Timing and Spectral Analysis

We present the results of a pair of 100 ksec Chandra observations in the Small Magellanic Cloud to survey high mass X-ray binaries (HMXBs), stars and LMXBs/CVs down to Lx = 4.3 x 10^32 erg/s The two SMC Deep Fields are located in the most active star forming region of the bar, with Deep Field-1 positioned at the most pulsar-rich location identified from previous surveys. Two new pulsars were discovered in outburst: CXOU J004929.7-731058 (P=892s), CXOU J005252.2-721715 (P=326s), and 3 new HMXB candidates were identified. Of 15 Be-pulsars now known in the field, 13 were detected, with pulsations seen in 9 of them. Ephemerides demonstrate that 6 of the 10 pulsars known to exhibit regular outbursts were seen outside their periastron phase, and quiescent X-ray emission at Lx=10^33 - 10^34 is shown to be common. Comparison with ROSAT, ASCA, XMM-Newton catalogs resulted in positive identification of several previously ambiguous sources. Bright optical counterparts exist for 40 of the X-ray sources, of which 33 are consistent with early-type stars Mv<-2, B-V<0.2), and are the subject of a companion paper. The results point to an underlying HMXB population-density up to double that of active systems. The full catalog of 394 point-sources is presented along with detailed analyses of timing and spectral properties.

astro-ph↗

arXiv2014

A Computer Program to Visualize Gravitational Lenses

Gravitational lenses are presently playing an important role in astrophysics. By means of these lenses the parameters of the deflector such as its mass, ellipticity, etc. and Hubble's constant can be determined. Using C, Xforms, Mesa and Imlib a computer program to visualize this lens effect has been developed. This program has been applied to generate sequences of images of a source object and its corresponding images. It has also been used to visually test different models of gravitational lenses.

astro-ph↗