Tag Archives: Featured

Peak-bagging in Helio- and Asteroseismology

We are pleased to announce the SpaceInn Group Meeting Workshop “Peak-bagging in Helio- and Asteroseismology” to be held in Tenerife on 11-13 March 2014. The aim of the workshop is to bring together active researches in these domains to contribute to define and to establish the proper methodology to achieve the goals associated with some of the deliverables of the “Global Helioseismology” work package of the Spaceinn Project.

The workshop will take place in the Sandos San Blas Hotel Reserva Ambiental, in the village of San Miguel de Abona, South of Tenerife.

The workshop webpage can be found at: http://www.iac.es/congreso/spaceinn-wp41/

On this webpage you can find more information on the scientific program, the venue, and how to register and make the hotel reservation. We hope to welcome many of you in Tenerife!

In case of questions, you can contact to us at spaceinn_wp41 (at) iac (dot) es

Important dates:

  • February 10, 2014: deadline for hotel reservation and registration
  • March 11-13, 2014: SpaceInn Workshop 4.1

Propagating Linear Waves in Convectively Unstable Stellar Models: A Perturbative Approach

Authors. Papini, E.; Gizon, L.; Birch, A. C.

Journal. Solar Physics, Volume 289, Issue 6, pp.1919-1929

Abstract. Linear time-domain simulations of acoustic oscillations are unstable in the stellar convection zone. To overcome this problem it is customary to compute the oscillations of a stabilized background stellar model. The stabilization affects the result, however. Here we propose to use a perturbative approach (running the simulation twice) to approximately recover the acoustic wave field while preserving seismic reciprocity. To test the method we considered a 1D standard solar model. We found that the mode frequencies of the (unstable) standard solar model are well approximated by the perturbative approach within 1 μHz for low-degree modes with frequencies near 3 mHz. We also show that the perturbative approach is appropriate for correcting rotational-frequency kernels. Finally, we comment that the method can be generalized to wave propagation in 3D magnetized stellar interiors because the magnetic fields have stabilizing effects on convection.

Links. Solar Physics, NASA ADS, arXiv

A search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy

Authors. Morel, T.; Briquet, M.; Auvergne, M.; Alecian, G.; Ghazaryan, S.; Niemczura, E.; Fossati, L.; Lehmann, H.; Hubrig, S.; Ulusoy, C.; Damerdji, Y.; Rainer, M.; Poretti, E.; Borsa, F.; Scardia, M.; Schmid, V. S.; Van Winckel, H.; De Smedt, K.; Papics, P. I.; Gameiro, J. F.; Waelkens, C.; Fagas, M.; Kaminski, K.; Dimitrov, W.; Baglin, A.; Michel, E.; Dumortier, L.; Fremat, Y.; Hensberge, H.; Jorissen, A.; Van Eck, S.

Journal. Astronomy & Astrophysics, Volume 561, id.A35, 14 pp.

Abstract. The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provides evidence of monoperiodic variations with a frequency of 0.7572 c/d and a peak-to-peak amplitude of ~2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g., Mn and Y). In contrast, lines of other elements do not show significant variations. As found in other HgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ~50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star.

Links. A&A , NASA ADS, arXiv