Using GALEX-SDSS-PanSTARRS-HST-Gaia to understand post-AGB evolution

Bianchi, Luciana; Keller, Graziela R.; Bohlin, R. C.; Barstow, M. A.; Casewell, Sarah L.

doi:10.1007/s10509-018-3369-z

Cited by 7 publications

(4 citation statements)

References 24 publications

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“…Using the photometric criteria defined above, the Besanc˛on model does not predict a single such contaminant in either the LMC sample of BBSs, or in the combined M31/M33 data set. Our extensive spectroscopy in M31/M33 ) has actually found seven foreground white dwarfs (three of these meet the photometric criteria we are using), reinforcing the fact that the space density of white dwarfs is not particularly well known locally, although progress is being made in this area (see, e.g., Bianchi et al 2018). As for red stars, we have found that using proper motions was an effective tool to eliminate contamination of the LMC sample (see Neugent et al 2012b), while for M31 and M33 we have successfully employed two-color diagrams to separate foreground stars and RSGs (Massey 1998a;Drout et al 2012;Massey & Evans 2016).…”

Section: Removing Foreground Starssupporting

confidence: 55%

Shedding Light on the Isolation of Luminous Blue Variables

Aadland¹,

Massey²,

Neugent³

et al. 2018

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In the standard view of massive star evolution, luminous blue variables (LBVs) are transitional objects between the most massive O-type stars and Wolf-Rayet (WR) stars. With short lifetimes, these stars should all be found near one another. A recent study of LBVs in the Large Magellanic Cloud (LMC) found instead that LBVs are considerably more isolated than either O-type stars or WRs, with a distribution intermediate between that of the WRs and red supergiants (RSGs). A similar study, using a more restricted sample of LBVs, reached the opposite conclusion. Both studies relied upon the distance to the nearest spectroscopically identified O-type star to define the degree of isolation. However, our knowledge of the spectroscopic content of the LMC is quite spotty. Here we re-examine the issue using carefully defined photometric criteria to select the highest-mass unevolved stars ("bright blue stars," or BBSs), using spatially complete photometric catalogs of the LMC, M31, and M33. Our study finds that the LBVs are no more isolated than BBSs or WRs. This result holds no matter which sample of LBVs we employ. A statistical test shows that we can rule out the LBVs having the same distribution as the RSGs, which are about 2× more isolated. We demonstrate the robustness of our results using the second-closest neighbor. Furthermore, the majority of LBVs in the LMC are found in or near OB associations as are the BBS and WRs; the RSGs are not. We conclude that the spatial distribution of LBVs therefore is consistent with the standard picture of massive star evolution.

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Section: Removing Foreground Starssupporting

confidence: 55%

Shedding Light on the Isolation of Luminous Blue Variables

Aadland¹,

Massey²,

Neugent³

et al. 2018

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“…We also removed the sources with the saturated=1 (from IGAPS catalogue) which indicates a saturated source in one or more than one optical bands. Similarly, we only selected FUV and NUV with magnitudes fainter than 13.73 and 13.85 mag, respectively (see Bianchi et al 2018, for more information related to non-linearity limits). According to the work of Bianchi et al (2011) the FUV−NUV< −0.13 colour cut corresponds to stellar 𝑇 eff hotter than 18 000 K (exact value might vary with gravity).…”

Section: Wd Candidate Selectionmentioning

confidence: 99%

“…The combination of GALEX FUV and NUV, and IGAPS g r H𝛼 i, analysed with synthetic spectra, enable a preliminary characterisation of the WD and unresolved binary WD candidates (see e.g., Bianchi et al 2018). Figures A1 to B3 show the best fitted synthetic spectrum to the UV-optical photometry, as extracted from GaPHAS catalogue, for single and binary WD candidates, respectively.…”

Section: Physical Properties Of Wd Candidatesmentioning

confidence: 99%

Hot white dwarf candidates from the IGAPS-GALEX cross-match

Gómez-Muñoz,

Sabin,

Raddi

et al. 2022

Preprint

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White dwarf (WD) stars are often associated with the central stars of planetary nebulae (CSPNe) on their way to the cooling track. A large number of WD star candidates have been identified thanks to optical large-scale surveys such as Gaia DR2 and EDR3. However, hot-WD/CSPNe stars are quite elusive in optical bands due to their high temperatures and low optical luminosities. The Galaxy Evolution Explorer (GALEX) matched with the INT Galactic Plane Survey (IGAPS) allowed us to identify hot-WD candidates by combining the GALEX far-UV (FUV) and near-UV (NUV) with optical photometric bands (g, r, i and H𝛼). After accounting for source confusion and filtering bad photometric data, a total of 236 485 sources were found in the GALEX and IGAPS footprint (GaPHAS). A preliminary selection of hot stellar sources was made using the GALEX colour cut on FUV−NUV> −0.53, yielding 74 hot-WD candidates. We analysed their spectral energy distribution (SED) by developing a fitting program for single-and two-body SED using an MCMC algorithm; 41 are probably binary systems (a binary fraction of ∼55% was estimated). Additionally, we classified the WD star candidates using different infrared (IR) colours available for our sample obtaining similar results as in the SED analysis for the single and binary systems. This supports the strength of the fitting method and the advantages of the combination of GALEX UV with optical photometry. Ground-based time-series photometry and spectra are required in order to confirm the nature of the WD star candidates.

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“…The fundamental parameters of stars, including mass, radius, metallicity, and age are inferred by matching accurate stellar atmosphere models to precisely calibrated UV spectroscopic data from which the effective temperature, surface gravity, composition, and interstellar reddening are determined for all types of hot stellar objects, e.g. Bianchi & Garcia (2002; Bianchi (2012); Bianchi et al (2018b) and references therein: Herald & Bianchi (2007; Garcia & Bianchi (2004); Pala et al (2015); Joyce et al (2018). The set of >100,000 GALEX UV spectra with a homogeneous spectral range of ∼1300-3000 Å) and resolution of 8 Å in the far-ultraviolet (FUV) and 20 Å in the near-ultraviolet (NUV) is a resource with similar characterstics to the IUE spectral database but with about ten times larger sample and fainter fluxes.…”

Section: Introductionmentioning

confidence: 99%

A Correction for GALEX Spectroscopic UV Flux Distributions from Comparisons with CALSPEC and IUE

Bohlin

Bianchi

2019

Self Cite

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The CALSPEC database of absolute spectral energy distributions (SEDs) from the Hubble Space Telescope (HST) is based on pure hydrogen model atmosphere calculations for three unreddened white dwarf (WD) stars and represents the current UV flux calibration standard with a precision approaching 1% for well observed stars. Following our previous work to correct IUE fluxes, this paper provides an average correction for the GALEX spectral database that places GALEX fluxes on the current CALSPEC scale. Our correction is derived by comparing GALEX spectroscopic flux distributions with CALSPEC and corrected IUE SEDs. This re-calibration is relevant for any project based on GALEX archival spectroscopic data, e.g. UV or multi-wavelength analyses, correlating GALEX spectra with other existing or future databases, and planning of new observations. The re-calibration will be applied to our planned catalog of corrected GALEX SEDs.

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Using GALEX-SDSS-PanSTARRS-HST-Gaia to understand post-AGB evolution

Cited by 7 publications

References 24 publications

Shedding Light on the Isolation of Luminous Blue Variables

Shedding Light on the Isolation of Luminous Blue Variables

Hot white dwarf candidates from the IGAPS-GALEX cross-match

A Correction for GALEX Spectroscopic UV Flux Distributions from Comparisons with CALSPEC and IUE

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