adsabs/FOCAL huggingface dataset:
In order to explode as an ECSN, several ingredients need to be in place. Nomoto (1984) argued that stars with helium cores between 2.0 and 





 (which corresponds roughly to initial masses between 8 and 





) would explode as an ECSN. His models, however, did not develop a second dredge-up, which can significantly reduce the mass of the helium core and diminishes the predictive power of this criterion (see Podsiadlowski et al. 2004; Poelarends et al. 2008). Since then, several authors (Siess 2007; Poelarends et al. 2008; Doherty et al. 2010, 2015; Jones et al. 2013) have established precise initial mass ranges for ECSNe to occur, although these mass ranges are highly sensitive to the adopted convection criteria, overshooting, and mass-loss prescriptions (Poelarends et al. 2008; Doherty et al. 2010; Langer 2012). Jones et al. (2013) produced several detailed models, computed all the way to electron captures on 24Mg and 20Ne and found that CO cores with masses over 





 are able to reach densities high enough for this to occur (





 g cm−3). If the CO core is massive enough, neon will ignite off-center (Jones et al. 2013; Schwab et al. 2016), but Jones et al. (2014) also found that the upper boundary for ECSNe is affected by uncertainties regarding the progression or stalling of the neon flame. There seems to be consensus, however, that the mass of the CO core is a reliable indicator for the final fate of stars in this mass range. How this translates into the initial mass of the star depends on the adopted convection criterion, with the Schwarzschild criterion producing more massive cores than the Ledoux criterion for the same initial mass. Inclusion of overshooting will also lead to larger cores (see Siess 2007). However, although the initial mass range for ECSNe is therefore quite sensitive to the adopted convection criteria, this does not seem to be the case for the final MCO, as most authors find similar values for MCO at which neon ignites, even though they treat convection differently. In the context of binary evolution, this provides an additional reason to adopt MCO as an indicator for whether the star explodes as an ECSN or not, as the CO core is generally not eroded by mass transfer, in contrast to the He core.
Citation: Langer 2012
Citation function: Background; Background
Within the same scenario, Smith et al. (2004, 2005) have theoretically predicted that, when observed in polarized light, NLS1s should have a low polarization fraction, the polarization angle should change monotonically from one wing of the BELs to the other, and the BELs should be significantly broader than those observed in direct light (Smith et al. 2004, 2005). We assume that polarized BELs are scattered into the line of sight by material that is close to coplanar with the BLR (i.e. the torus). This prediction has been searched for in RQ-NLS1s, but many objects have not been detected in polarized light, and none of the detected show any significant broadening of the BELs (e.g. Goodrich 1989; Breeveld & Puchnarewicz 1998; Kay et al. 1999). On the other hand, only one RL-NLS1 (PKS 2004-447) has been the object of a spectropolarimetry study (Baldi et al. 2016), and the three predicted features have been observed that have a FWHM in the polarized Hα of ≈ 9000 km s−1. We propose for the first time a simple scenario that can resolve such apparent tension between the two classes of NLS1s. We speculate that in those NLS1s that are intrinsically without a jet (a fraction of the RQ-NLS1) a significant amount of polarized light could be due to polar scattering of the BELs, by material above the BLR, as observed for type II AGN (Antonucci 1983; Miller & Antonucci 1983; Antonucci & Miller 1985). A polar-scattered component could easily overwhelm the planar-scattering contribution, predicted to result in low polarization fractions for face-on objects because of the axi-symmetry of the scattering material. In RL-NLS1s, on the contrary, the jet could evacuate the intervening material, resulting in a lower degree of polarization in which only the broadened component of the BEL is left. The evacuation of the polar material by a jet closely aligned withthe line of sight has been already proposed by Ghisellini & Sbarrato (2016) to account for the lack of high-z blazar parent population. This simple speculative scenario can be tested through spectropolarimetry of a larger sample of RL-NLS1s.
Citation: Breeveld & Puchnarewicz 1998
Citation function: Compare/Contrast
Fig. 6 displays the MLR for the investigated CCs whose intrinsic stellar parameters were derived from the best-fitting models listed in Table 1. These data are compared with the predicted canonical (no overshooting, no mass-loss) MLR (Bono et al. 2000; the solid lines) and with the relations obtained by increasing the zero-point of the canonical MLR by 0.25 dex (the dashed lines) and 0.5 dex (the dotted lines) to reproduce the effect of mild and full overshooting,5 respectively (see Chiosi et al. 1993; Bono et al. 1999, for details). Inclusion of mass-loss and/or rotation would produce a similar increase in the Cepheid luminosity level at fixed mass (see Neilson et al. 2012, for details). As the light curves of $OGLE\_CEP\_LMC\_2019$ are best reproduced adopting a different value of the helium content (see above), in Fig. 6 we also show the MLR for Y = 0.30, Z = 0.008 (the green lines). Note that this relation is slightly more luminous than those calculated for the standard LMC elemental composition (Y = 0.25, Z = 0.008). According to the location of the variables in the ML plane, the canonical MLR is not strictly satisfied, as the points are spread between the canonical and full overshooting predictions. Even if at this stage we cannot disentangle the role of overshooting, mass-loss, and rotation in producing the quoted excess luminosity, at fixed mass, the detected dispersion might indicate a combination of these different non-canonical phenomena. Indeed, if only overshooting were efficient, one would in principle expect the same amount of excess luminosity for all stellar masses (within small uncertainties). Rotation produces similar effects as overshooting because it implies a larger He burning core and a brighter luminosity at fixed mass (see e.g. Anderson et al. 2016) On the other hand, if the mass-loss process were efficient, this could be inferred from the predicted deviation of the best-fitting stellar mass from the value corresponding to the canonical MLR. Such a deviation is represented in Fig. 7 as a function of the canonical mass (top) and of the pulsation period (bottom) for the CCs in our sample. We note that the expected mass differences range from $0{{\ \rm per\ cent}}$ to almost $\sim 50{{\ \rm per\ cent}}$ and are not clearly correlated with the pulsation period or the stellar mass.
Citation: Neilson et al. 2012
Citation function: Uses; Uses
Leitzinger et al. (2014) briefly compared the mass estimates of stellar mass ejection events and the estimated X-ray energies of their associated flares with the solar scaling. We extend their comparison here. Specifically, we consider the events observed as blueshifted extra emissions in Balmer lines on the active M dwarfs AD Leo (Houdebine et al. 1990), AT Mic (Gunn et al. 1994), V374 Peg (Vida et al. 2016) and the pre-main-sequence star DZ Cha (Guenther & Emerson 1997). Published estimates of their minimum masses are 7.7 × 1017, ∼1015, ∼1016 and 1.4 × 1018…7.8 × 1019 g, respectively. Since no simultaneous X-ray observations of the associated flares are available, we estimate the corresponding X-ray flare energies based on the assumption that the published U-band energies are of comparable magnitude (cf. Hawley & Pettersen 1991). Doing so, we find EX ≈ EU ∼ 2 × 1032 erg for AD Leo (Rodono et al. 1985; Hawley & Pettersen 1991), 3 × 1031 erg for AT Mic (Gunn et al. 1994) and 1.2…2.5 × 1035 erg for DZ Cha (Guenther & Emerson 1997), respectively. The recently published event at V374 Peg has an Hγ flare energy of ∼4 × 1030 erg, which corresponds to ∼1032 erg in X-rays (Butler, Rodono & Foing 1988). We add two other events, which are, however, more uncertain in their interpretation as real CME events. Doyle et al. (1988) observed a strong increase in neutral hydrogen column density during a flare on the active M dwarf YZ CMi, which may be interpreted as a rising filament obscuring parts of the flare region. The estimated mass of this event is 3 × 1017 g and the estimated X-ray flare energy EX ≈ EU ∼ 8 × 1030 erg, since the observed X-ray flare emission was likely partly absorbed by the neutral material (Doyle et al. 1988). The second one is a long-decay flare on the young, active M dwarf AU Mic, which was interpreted as an eruptive event with a CME mass in the order of 1020 g by Cully et al. (1994). However, there is a different model of this strong flare (∼3 × 1035 erg) including post-eruptive energy release, which does not involve a CME (Katsova, Drake & Livshits 1999). Other studies that observed stellar CME events (cf. Section 1) did not provide mass estimates and had to be excluded.
Citation: Rodono et al. 1985
Citation function: Uses
In the expectation of a relationship between the observed IRX and the rest-frame UV slope there is the assumption that the stars and dust are well mixed, which leads to the coupling of any observed reddening in the UV to the FIR emission detected (e.g. Meurer et al. 1999; Charlot & Fall 2000; Calzetti 2001). If instead the galaxy consists of regions of significantly different obscuration, then the relationship will break down for the galaxy as a whole. Indeed, geometric effects have been put forward as an explanation of the discrepant results at z > 5 (Faisst et al. 2017; Popping, Somerville & Galametz 2017). In local starburst galaxies, the existence of an IRX–β relation and a clear morphological similarity, indicates that the rest-frame UV emission from young stars is being attenuated from dust that is tracing broadly the same star-forming regions of the galaxy (e.g. in the spiral arms; Kennicutt et al. 2003; Gil de Paz et al. 2007). In the high-redshift Universe, however, where galaxies become more turbulent and irregular (e.g. Förster Schreiber et al. 2011; Buitrago et al. 2013; Guo et al. 2015) the expected morphology of the dust relative to the observed UV emission is not clear. Evidence for offset dust continuum emission relative to the rest-UV has been identified in several high-redshift Lyman-break galaxies (LBGs; Koprowski et al. 2016; Faisst et al. 2017; Laporte et al. 2017; Bowler et al. 2018), and similar trends have been found when comparing the [C ii] FIR line and the rest-UV continuum (e.g. Maiolino et al. 2015; Carniani et al. 2017). Although some of these offsets have been attributed to astrometric systematics (e.g. Dunlop et al. 2017) there is a growing consensus that FIR continuum and line emission are frequently physically offset as compared to the observed rest-UV emission (see Carniani et al. 2018). Whether high-redshift galaxies show large and distinct regions of obscured and unobscured star formation has implications for the use of the IRX–β relation in deriving the cosmic SFR density (e.g. Bouwens et al. 2016b), as the assumed energy balance will break down (Buat et al. 2019) and the global β measurement will not be representative of the full source.
Citation: Faisst et al. 2017
Citation function: Compare/Contrast
Observations by a single coronagraph allow us to obtain CME 2D images projected on the plane of the sky. Using the image sequences of CME expansions, we can determine CME 2D parameters such as speed and angular width. Such observations do have some limitations, mostly the projection effect. Kwon et al. (2015) showed that the apparent width of CMEs does not represent an accurate measure of the CME ejecta size. In previous studies, geometrical models based on the assumption of different cone shapes were developed to obtain CME 3D parameters from single spacecraft observations (Xie et al. 2004; Xue et al. 2005; Michalek 2006). Na et al. (2013) compared the 3D parameters of halo CMEs obtained from the cone shapes (elliptical-cone, ice-cream-cone, and asymmetric-cone models) and found that their 3D speeds are comparable to one another but their angular widths and inclination angles are quite different. We note that stereoscopic observations by twin spacecraft STEREO make it possible to obtain the CME 3D parameters using geometrical triangulation methods (Mierla et al. 2008, 2009; Liewer et al. 2009; Temmer et al. 2009; Liu et al. 2010a, 2010b) and a flux rope method (Chen et al. 2000; Thernisien et al. 2009). Recently, the STEREO CME Analysis Tool (StereoCAT), based on a triangulation method from multiple spacecraft observations, was developed by the Community Coordinated Modeling Center (CCMC) for real-time CME analysis carried out by the CCMC/SWRC forecasting team. CME 3D parameters can be determined by selecting two coronagraphs from SOHO/LASCO C3 and STEREO/SECCHI COR2 images using the model. The triangulation algorithm and the performance of the CME measurements from StereoCAT are described in Sections 3.1 and 3.2 of Mays et al. (2015). Lee et al. (2015) showed, using 44 halo CMEs from 2010 to 2011, that the CME 3D parameters (speed, angular width, and source location) obtained from StereoCAT are similar to those obtained from the graduated cylindrical shape flux rope model (Thernisien et al. 2009; Thernisien 2011). Jang et al. (2016) showed, using 306 LASCO front-side halo CMEs from 2009 to 2013, that around 20% of the CME 2D speeds in the LASCO CME catalog are underestimated compared with the 3D ones obtained from StereoCAT.
Citation: Xie et al. 2004
Citation function: Background
Pair-instability supernovae (PI SNe) are the most energetic thermonuclear explosions known and can be detected near the edge of the observable universe. They have now been studied by several groups for their potential to probe the properties of the first stars and galaxies (Greif et al. 2008, 2010, 2011, 2012; Johnson et al. 2009, 2014; Turk et al. 2009; Stacy et al. 2010, 2012; Clark et al. 2011; Hosokawa et al. 2011; Smith et al. 2011; Glover 2013; Jeon et al. 2012; Susa 2013; Pawlik et al. 2011, 2013; Wise et al. 2012; Whalen 2013; Hirano et al. 2014). They can also shed light on the origins of supermassive black holes and early cosmological reionization and chemical enrichment (Mackey et al. 2003; Whalen et al. 2004, 2008a, 2010; Abel et al. 2007; Smith & Sigurdsson 2007; Wise & Abel 2008; Alvarez et al. 2009; Tanaka & Haiman 2009; Smith et al. 2009; Park & Ricotti 2011, 2012, 2013; Volonteri 2012; Agarwal et al. 2012; Ritter et al. 2012; Whalen & Fryer 2012; Choi et al. 2013; Latif et al. 2013a, 2013b; Reisswig et al. 2013; Schleicher et al. 2013; Johnson et al. 2014; Chiaki et al. 2013; Safranek-Shrader et al. 2014). For example, detections of both PI and core-collapse (CC) SNe at high redshift could be roughly binned by mass, thereby building up a simple Pop III IMF over time as enough events are discovered (de Souza et al. 2013, 2014). If the Pop III initial mass function (IMF) proves to be top heavy, this could account for the origins of SMBHs because enough 200–300 





  seed black holes might be formed at 





 20 for a few to reach 109





  by 





 7. If not, alternatives for SMBH seeds must be found, such as BHs forming by direct collapse in atomically cooled halos at slightly later epochs, z ∼ 10–15 (Johnson et al. 2012, 2013b). PI SN candidates such as SN 2007bi (Gal-Yam et al. 2009; Kozyreva et al. 2014) and SN 2213–1745 (Cooke et al. 2012) have now been discovered at z = 0.126 and 2.05, respectively.
Citation: Tanaka & Haiman 2009
Citation function: Motivation
In the standard AGN unification theory, the anisotropic radio emission produced by relativistic jets points to a description where properties like radio morphology and radio spectral index depend on orientation. Two widely used orientation indicators in the radio regime are the (a) core-to-lobe flux density ratio (R), which is the ratio of the flux densities of the core and lobe in radio wavelengths, and (b) radio-to-optical ratio of the quasar core (RI), which is the ratio of flux densities of the core in radio and optical wavelengths (See equation 5 and 6 for the exact definition of R and RI parameters). A high R-value suggests a small viewing angle to the jet axis, while a low R-value indicates more of an edge-on view to the quasar (Kapahi & Saikia 1982; Orr & Browne 1982; Morisawa & Takahara 1987; Morganti et al. 1997). Studies have shown that R correlates with core radio luminosity (Hardcastle & Worrall 2000) as well with the core optical luminosity (Kharb & Shastri 2004). Factors like age and environment are believed to introduce the scatter in the correlation involving the R parameter suggesting that R might not be the best measure for orientation. The R parameter depends on both the core’s radio flux as well as the radio flux of the lobes arising from the quasar jets. These jets are suggested to be affected by environmental factors. Wills & Brotherton (1995) and Kharb, Lister & Cooper (2010) showed that the radio-to-optical ratio (RI) of the quasar core might be a better measure of studying the orientation. The RI parameter measures the core-boosting factor by normalizing the core’s radio flux by the core’s optical flux. Although with some scatter in the correlation, Kimball et al. (2011) demonstrated a strong correlation between R and RI parameter suggesting that the two parameters are good indicators of quasar orientation. The scatter in the correlation supports the idea that other factors like age, size, environment, and luminosity also influence these two measurements.
Citation: Orr & Browne 1982
Citation function: Background
Armstrong et al. (2020) recently announced the discovery of TOI-849b, a planet having a size comparable to the one of Neptune (




R
pl

=
3
.

45

−
0.12


+
0.16




R
⊕



$ R_{\mathrm{pl}} = 3.45^{+0.16}_{-0.12}\,R_{\oplus} $


), but an anomalously larger mass (




M
pl

=
40
.

8

−
2.5


+
2.4




M
⊕



$ M_{\mathrm{pl}} = 40.8^{+2.4}_{-2.5}\,M_{\oplus} $


) and a density similar to the one of the Earth (ρ = 5.5 ± 0.8 g cm−3). This is the densest Neptune-sized planet discovered to date. Interior structure models suggest that for this kind of planet, any H/He envelope would consist of no more than 3.9% of the total mass (Armstrong et al. 2020). TOI-849b orbits around a late G-type star, with an orbital period of P = 18.4 h. Its equilibrium temperature is Teq = 1800 K (for a Bond Albedo 0.3). With such properties, TOI-849b represents one of the few planets populating the hot Neptune desert, a region on the radius-orbital distance plane characterised by a surprising deficit of Neptune-sized planets on very short orbits (e.g. Lecavelier Des Etangs 2007; Beaugé & Nesvorný 2013; Mazeh et al. 2016). Growing evidence suggests that the evaporation of hot Neptunes due to stellar irradiation represents a major process in shaping the desert (Owen 2019). Some of the planets within the desert or at its lower-radius border could thus be the remnant cores of larger gas-rich progenitors that lost most of their atmosphere (e.g. Lecavelier des Etangs et al. 2004). Alternatively, orbital migration may have also played a part in sculpting the desert, with different classes of planets forming differently (e.g. Batygin et al. 2016), or following different dynamical tracks (e.g. Matsakos & Königl 2016). Even so, the origin of this key feature in the demographics of close-in planets remains debated (Zahnle & Catling 2017; Owen & Lai 2018), and investigating the past history of planets such as TOI-849b contributes to the global effort towards disentangling the important mechanisms at the root of the desert. Since the mass of the planet is larger than the threshold value for runaway gas accretion (roughly 10 − 20 M⊕, Mizuno et al. 1978; Rafikov 2006; Piso et al. 2015), TOI-849b might have been a gas giant before undergoing extreme mass loss via thermal self-disruption, collisions with other giant planets, or it was prevented from accreting gas because of gap openings in the protoplanetary disc, or because of late formation (Armstrong et al. 2020). In their work, Armstrong et al. (2020) found that their estimated photoevaporation rates cannot provide the mass-loss rates needed to remove a roughly 280 M⊕ envelope from a Jupiter-like gas giant. Nevertheless, in their estimations the planetary atmosphere is not self-consistently monitored, and neither is the luminosity emitted by the host star relative to its rotational history. This is critical, considering how recent works emphasise the interplay between all these elements in driving the evolution of close-in worlds (e.g. Owen & Alvarez 2016; Kubyshkina et al. 2018; King & Wheatley 2021; Pezzotti et al. 2021).
Citation: Beaugé & Nesvorný 2013
Citation function: Background
Carbon-enhanced metal-poor (CEMP) stars form an important class of metal-poor giants, sub-giants, and dwarfs, with a large fraction of them showing enhanced abundances of heavy elements (see Beers & Christlieb 2005; Frebel 2018 for a general review). Among the different types of CEMP stars, the CEMP-s stars are enriched with products of s-process nucleosynthesis, the CEMP-r stars are enriched with the products of r-process nucleosynthesis, and CEMP-r/s stars are enriched with products of i-process nucleosynthesis. Understanding the diverse abundance patterns exhibited by different groups of CEMP stars that are believed to be associated with different formation mechanisms has been a challenge. In Goswami et al. (2021), we present a detailed analysis and discussion on the classification criteria of CEMP stars, as well as the formation scenarios of CEMP stars put forward by different authors (Cowan & Rose 1977; Hill et al. 2000; Qian & Wasserburg 2003; Cohen et al. 2003; Jonsell et al. 2006; Campbell & Lattanzio 2008; Campbell et al. 2010; Stancliffe et al. 2011; Herwig et al. 2011; Doherty et al. 2015; Abate et al. 2016; Jones et al. 2016; Banerjee et al. 2018; Clarkson et al. 2018; Denissenkov et al. 2017; Côté et al. 2018). In this paper, we report an extremely metal-poor carbon-enhanced star, HE 1005–1439, whose surface chemical composition is found to be enriched with both s-process and i-process nucleosynthesis that forms a new class of object with a distinct abundance pattern. The peculiar abundance pattern, observed for the first time in a CEMP star, was investigated based on a parametric-model-based analysis that revealed almost equal contributions from both the s-process and the i-process to its surface chemical composition. We examined various production mechanisms and formation scenarios for this object. A formation scenario involving effective proton ingestion episodes (PIEs) triggering i-process nucleosynthesis followed by s-process asymptotic giant branch (AGB) nucleosynthesis with limited third-dredge-up (TDU) episodes seems to be most promising for this type of object.
Citation: Qian & Wasserburg 2003
Citation function: Background