Nami Mowlavi

Astrophysicist
University of Geneva, Switzerland

Welcome CV Research Publications Data

-----------------------------------------------------------

Long-period variables Main-sequence pulsators Transients
 Eclipsing binarie
Long-period variables

Introduction -  Long-period variables (LPVs) are red giant stars that pulsate with periods from about a month to several years, and with amplitudes up to several magnitudes in the visual. All stars with masses up to about eight times the solar mass are predicted to become red giants after they have consumed hydrogen in their core (they then reach the so-called red giant branch, or RGB), and again after they have consumed helium in their core (they then reach the so-called asymptotic giant branch, or AGB).
They are very luminous, and hence detectable very far, beyond our Galaxy in extragalactic systems. Obeying period-luminosity relations, they are potential standard candles to measure distances in the Universe.

First all-sky Gaia catalog of LPVs -  In April 2018, we published the first Gaia catalog of LPVs, within Gaia Data Release 2 (DR2). It comprises 151’761 candidates with variability amplitudes larger than 0.2 magnitudes in the visual. This doubles the number of such objects known at the time of the release. The sky distribution of Gaia DR2 LPVs is shown in Figure 1. About one fifth of them are miras, with amplitudes larger than 1 magnitude.
The interested reader is referred to Mowlavi et al. (2018) for more details.

Figure 1. Sky distribution of Gaia DR2 long-period variable candidates. The color of each point is related to the Gaia G_BP - G_RP color of each star according to the color-scale shown on the right of the figure. From Figure 3 of Mowlavi et al. (2018).

N. Mowlavi, I. Lecoeur-Taïbi, T. Lebzelter, et al. (2018)

Astronomy & Astrophysics 618, A58

figAllSky_GaiaDR2_LPVs
Sub-classification of AGB stars using Gaia optical and 2MASS infrared data -  Red giants on the AGB undergo significant changes in their surface chemical abundances. In particular, their carbon abundance can increase above their oxygen abundance, leading to a totally different circum-stellar molecular chemistry. Intermediate-mass and massive AGB stars, on the other hand, have nucleosynthesis occurring at the base of the convective envelope (the convective envelope in red giants extends from the stellar surface to deep in their interior). 
Based on this Gaia catalog of LPVs, we found a new method to identify these subclasses among AGB stars using Gaia and 2MASS photometry. In particular, we were able to discriminate between O- and C-rich objects, and to identify low-mass, intermediate-mass, and massive O-rich red giants, as well as extreme C-rich stars. The application to the Gaia LPVs of the Large Magellanic Cloud, a satellite galaxy of our Milky Way, is shown in Figure 2.
The interested reader is referred to Lebzelter et al. (2018) for more details.

Figure 2. (W_RP, BP−RP − W_Ks,J−Ks ) vs. Ks diagram of Gaia DR2 LPVs in the Large Magellanic Cloud. The markers are colored with G_BP − G_RP according to the color-scale shown on the right of the figure. The solid line delineates O-rich (left of the line) and C-rich (right of the line) stars, and dashed lines delineate sub-groups as indicated in the figure. From Figure 1 of Lebzelter et al. (2018).

T. Lebzelter, N. Mowlavi, P. Marigo, et al. (2018)

Astronomy & Astrophysics 616, L13

figLMC_WRPminusWK_versus_K

https://obswww.unige.ch/~mowlavi


Page updated 15/11/2018

-----------------------------------------------------------

‌

Offline Website Builder