Accretion rates of 42 nova-like stars with IUE and Gaia data

被引：0

作者：

Gilmozzi, Roberto ^{[1
]}

Selvelli, Pierluigi ^{[2
]}

机构：

[1] European Southern Observatory, Karl Schwarzschild-Str. 2, Garching,85748, Germany

[2] INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, Trieste,34143, Italy

来源：

Astronomy and Astrophysics | 2024年 / 681卷

关键词：

This work is based on INES data from the IUE satellite ( http://sdc.cab.inta-csic.es/ines/ ) and on data from the European Space Agency (ESA) mission Gaia ( https://www.cosmos.esa.int/gaia ); processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national institutions; in particular the institutions participating in the Gaia Multilateral Agreement. We wish to thank and commend the AAVSO for their excellent photometric work on variable stars: their results have been of invaluable help to us in this paper. We thank Elena Mason and Antonio Bianchini for fruitful discussions; and the anonymous referee for helpful and meticulous comments and suggestions;

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摘要：

We analyzed more than 700 ultraviolet spectra of 45 nova-like stars (NLs) observed with the International Ultraviolet Explorer (IUE) satellite, obtaining reliable data for 42 of them. Combining these with the distances from the Gaia Early Data Release 3 (EDR3) and with results from the literature, for each object we determined the reddening EB−V, the disk spectral energy distribution (SED), the reference (i.e., inclination-corrected) absolute magnitude and disk luminosity (MVref, Ldiskref ), and the mass accretion rate (M ), all with propagated errors. The de-reddened UV continuum of NLs in a high state is well approximated by a power-law distribution with index α in the range −2.4 ≤ α ≤ −0.2. The agreement between the power-law extrapolation to the V band and the observed V magnitude is outstanding and implies that for NLs in a high state, the disk continuum dominates not only in the UV but also in the optical, with other possible contributions (white dwarf, M dwarf, and hot spot) being minor. We note that the accretion rate correlates with the period, power-law index, and MVref, making them convenient proxies for M . The strongest correlation (pH0 −6) is log M = −0.57 ± 0.06 MVref − 5.98 ± 0.29. Nine of the 42 NLs fall within the period gap but all have M very similar to that of the objects above the gap, contrary to theory expectations but in agreement with other observational work, and indicating that − at least for NLs − the theoretical assumptions of the standard model of the evolution of CVs need substantial revision. Medians and weighted means of log M (≈ −8.5) are very similar among NL classes, and also to those of old novae, dispelling the prejudice that stars belonging to the SW Sex class of NLs have exceptionally high M compared to other NLs (and old novae). In fact, it is one of the most interesting results of this study that NLs and old novae are indistinguishable in terms of M and its correlation with MVref. Two NLs (V1315 Aql and BZ Cam) have shells around them, a likely fingerprint of a past nova eruption, but the suggested association with guest stars of ancient Chinese chronicles is questionable. c The Authors 2024.

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