The Panchromatic Hubble Andromeda Treasury. Xv. The Beast: Bayesian Extinction and Stellar Tool*

Gordon, K. D.; Fouesneau, M.; Arab, H.; Tchernyshyov, Kirill; Weisz, Daniel R.; Dalcanton, Julianne J.; Williams, Benjamin F.; Bell, Eric F.; Bianchi, Luciana; Boyer, Martha L.; Choi, Yumi; Dolphin, Andrew E.; Girardi, L.; Hogg, David W.; Kalirai, Jason; Kapala, Maria; Lewis, Alexia R.; Rix, Hans─Walter; Sandström, Karin; Skillman, Evan D.

doi:10.3847/0004-637x/826/2/104

Cited by 58 publications

(83 citation statements)

References 67 publications

(105 reference statements)

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“…We note that there is a unique HST blue source in the 0 4 region (the open blue star in Figure 6). Fitting the 4-band spectral energy distribution (SED) using the Bayesian Extinction and Stellar Tool (Gordon et al 2016) suggests that it is not consistent with any model of stable evolutionary phases, suggesting that it is a post-AGB and/or the X-ray source is contaminating the UV and optical flux. We examined the F275W-F336W color and magnitude of this blue source and found that it is likely a hot post-horizontal branch star at the distance of M31 as studied in Rosenfield et al (2012).…”

Section: Uv and Optical Counterpartsmentioning

confidence: 99%

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Yukita

Ptak

Hornschemeier

et al. 2017

ApJ

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We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E<10 keV observations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT ∼ 0.2 keV) plus a hard spectrum with a power law of 1 G~and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST images exclude high-mass (>3 M  ) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (<3 M  ) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.

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Section: Uv and Optical Counterpartsmentioning

confidence: 99%

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Yukita

Ptak

Hornschemeier

et al. 2017

ApJ

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“…However, it is possible that these have spatial variation, and this could lead to scatter in the flux ratios. Robust SED fitters, such as the BEAST (Gordon et al 2016) may be able to measure such region-to-region variation. Additionally, scattering of light by dust (Section 4.4) may alter the effective attenuation curve in a given region, producing extra flux that does not originate in that region and giving the attenuation curve a shape that is different from that of a perfectly known extinction curve.…”

Section: Dust Modelsmentioning

confidence: 99%

“…Such fitting, though, ideally produces the star's full spectrum, both reddened and intrinsic, which can then be used to infer the flux at wavelengths that were not observed. The PHAT survey motivated the development of the Bayesian Extinction and Stellar Tool (BEAST; Gordon et al 2016), an SED fitter thatcould be used to provide anindependent check of the results presented in this paper. SED fitting will, however, miss any stars below the detection limit, because it requires that they be detected in multiple filters.…”

Section: Introductionmentioning

confidence: 99%

The Panchromatic Hubble Andromeda Treasury. Xvii. Examining Obscured Star Formation With Synthetic Ultraviolet Flux Maps in M31*

Lewis

Simones

Johnson

et al. 2017

ApJ

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We present synthetic far-and near-ultraviolet (FUV and NUV) maps of M31, both with and without dust reddening. These maps were constructed from spatially resolved star formation histories (SFHs) derived from optical Hubble Space Telescope imaging of resolved stars, taken as part of the Panchromatic Hubble Andromeda Treasury program. We use stellar population synthesis modeling to generate synthetic UV maps with a spatial resolution of ∼100 pc (∼24 arcsec), projected. When reddening is included, these maps reproduce all of the main morphological features in the GALEX imaging, including rings and large star-forming complexes. The predicted UV flux also agrees well with the observed flux, with median ratios between the modeled and observed flux of in the FUV and NUV, respectively. This agreement is particularly impressive given that we used only optical photometry to construct these UV maps. Having verified the synthetic reddened maps, we use the dust-free maps to examine properties of obscured flux and star formation. We compare our dust-free and reddened maps of FUV flux with the observed GALEX FUV flux and FUV + 24 μm flux to examine the fraction of obscured flux. We find that the maps of synthetic flux require that ∼90% of the FUV flux in M31 is obscured by dust, while the GALEX -based methods suggest that ∼70% of the FUV flux is absorbed by dust. This 30% increase in the estimate of the obscured flux is driven by significant differences between the dust-free synthetic FUV flux and that derived when correcting the observed FUV flux for dust absorption with 24 μm emission observations. The difference is further illustrated when we compare the SFRs derived from the FUV + 24 μm flux with the 100 Myr average SFR from the CMD-based SFHs. We find that the 24 μm corrected FUV flux underestimates the SFR by a factor of 2.3-2.5, depending on the chosen calibration. This discrepancy could be reduced by allowing for variability in the weight applied to the 24 μm data, as has been recently suggested in the literature.

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“…Our analysis showed that our broadband exposures covered a short enough portion of the orbit that the thermal expansion and contraction of the optics caused a significant offset between the orbit-averaged PSF used by DOLPHOT and that of the F625W images across epochs, which introduced a systematic error that we further discuss in Appendix A. Next, our source catalog was enhanced by adding the output of the Bayesian Extinction And Stellar Tool (BEAST; Gordon et al 2016a) on the PHAT catalog data, which added T e f f , log g, and age information for each source. Gordon et al (2016a) developed the BEAST to model the observed broad spectral energy distribution (SED) of an individual star by considering the full observational uncertainties.…”

Section: Data Reductionmentioning

confidence: 99%

The Hubble Space Telescope Advanced Camera for Surveys Emission Line Survey of Andromeda. I. Classical Be Stars

Peters¹,

Wisniewski²,

Williams³

et al. 2020

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We present results from a 2-epoch HST Hα emission line survey of the Andromeda Galaxy that overlaps the footprint of the Panchromatic Hubble Andromeda Treasury (PHAT) survey. We find 552 (542) classical Be stars and 8429 (8556) normal B-type stars in epoch # 1 (epoch # 2), yielding an overall fractional Be content of 6.15% ±0.26% (5.96% ±0.25%). The fractional Be content decreased with spectral sub-type from ∼23.6% ±2.0% (∼23.9% ±2.0%) for B0-type stars to ∼3.1% ±0.34% (∼3.4% ±0.35%) for B8-type stars in epoch # 1 (epoch # 2). We observe a clear population of cluster Be stars at early fractional main sequence lifetimes, indicating that a subset of Be stars emerge onto the ZAMS as rapid rotators. Be stars are 2.8x rarer in M31 for the earliest sub-types compared to the SMC, confirming that the fractional Be content decreases in significantly more metal rich environments (like the Milky Way and M31). However, M31 does not follow a clear trend of Be fraction decreasing with metallicity compared to the Milky Way, which may reflect that the Be phenomenon is enhanced with evolutionary age. The rate of disk-loss or disk-regeneration episodes we observe, 22% ± 2% yr −1 , is similar to that observed for seven other Galactic clusters reported in the literature, assuming these latter transient fractions scale by a linear rate. The similar number of disk-loss events (57) as disk-renewal events (43) was unexpected since disk dissipation time-scales can be ∼2x the typical time-scales for disk build-up phases.

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The Panchromatic Hubble Andromeda Treasury. Xv. The Beast: Bayesian Extinction and Stellar Tool*

Cited by 58 publications

References 67 publications

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

The Panchromatic Hubble Andromeda Treasury. Xvii. Examining Obscured Star Formation With Synthetic Ultraviolet Flux Maps in M31*

The Hubble Space Telescope Advanced Camera for Surveys Emission Line Survey of Andromeda. I. Classical Be Stars

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