We report a significantly tighter trend between gaseous N/O and M*/Re (a proxy for gravitational potential) than has previously been reported between gaseous metallicity and M*/Re, for star-forming galaxies in the MaNGA survey. We argue this result to be a consequence of deeper potential wells conferring greater resistance to metal outflows while also being associated with earlier star-formation histories, combined with N/O being comparatively unaffected by metal-poor inflows. The potential–N/O relation thus appears to be both more resistant to short-timescale baryonic processes and also more reflective of a galaxy’s chemical evolution state, when compared to previously-considered relations.
{"title":"A tight N/O–potential relation in star-forming galaxies","authors":"N. Boardman, Vivienne Wild, N. V. Asari","doi":"10.1093/mnrasl/slae071","DOIUrl":"https://doi.org/10.1093/mnrasl/slae071","url":null,"abstract":"\u0000 We report a significantly tighter trend between gaseous N/O and M*/Re (a proxy for gravitational potential) than has previously been reported between gaseous metallicity and M*/Re, for star-forming galaxies in the MaNGA survey. We argue this result to be a consequence of deeper potential wells conferring greater resistance to metal outflows while also being associated with earlier star-formation histories, combined with N/O being comparatively unaffected by metal-poor inflows. The potential–N/O relation thus appears to be both more resistant to short-timescale baryonic processes and also more reflective of a galaxy’s chemical evolution state, when compared to previously-considered relations.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"42 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141805110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Sahu, B. Medina-Carrillo, D. I. P'aez-S'anchez, G. S'anchez-Col'on, Subhash Rajpoot
Gamma-ray burst (GRB), GRB 221009A, a long-duration GRB, was observed simultaneously by the Water Cherenkov Detector Array (WCDA) and the Kilometer Squared Array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO) during the prompt emission and the afterglow periods. Characteristic multi-TeV photons up to 13 TeV were observed in the afterglow phase. The observed very high-energy (VHE) gamma-ray spectra by WCDA and KM2A during different time intervals and in different energy ranges can be explained very well in the context of the photohadronic model with the inclusion of extragalactic background light models. In the photohadronic scenario, interaction of high-energy protons with the synchrotron self-Compton (SSC) photons in the forward shock region of the jet is assumed to be the source of these VHE photons. The observed VHE spectra from the afterglow of GRB 221009A are similar to the VHE gamma-ray spectra observed from the temporary extreme high-energy peaked BL Lac (EHBL), 1ES 2344+514 only during the 11th and the 12th of August, 2016. Such spectra are new and have been observed for the first time in a GRB.
大型高空气流淋浴天文台（LHAASO）的水切伦科夫探测器阵列（WCDA）和千米平方阵列（KM2A）同时观测了伽马射线暴（GRB）--GRB 221009A，这是一个持续时间很长的伽马射线暴。在余辉阶段观测到了高达 13 TeV 的特征性多 TeV 光子。WCDA和KM2A在不同时间间隔和不同能量范围内观测到的极高能伽马射线光谱，可以很好地用包含银河系外背景光模型的光电子模型来解释。在光电子模型中，高能质子与同步加速器自康普顿（SSC）光子的相互作用被假定为这些甚高频光子的来源。从GRB 221009A余辉中观测到的VHE光谱与2016年8月11日和12日从临时极高能峰BL Lac（EHBL）1ES 2344+514中观测到的VHE伽马射线光谱相似。这种光谱是首次在GRB中观测到的新光谱。
{"title":"TeV afterglow from GRB 221009A: photohadronic origin?","authors":"S. Sahu, B. Medina-Carrillo, D. I. P'aez-S'anchez, G. S'anchez-Col'on, Subhash Rajpoot","doi":"10.1093/mnrasl/slae063","DOIUrl":"https://doi.org/10.1093/mnrasl/slae063","url":null,"abstract":"\u0000 Gamma-ray burst (GRB), GRB 221009A, a long-duration GRB, was observed simultaneously by the Water Cherenkov Detector Array (WCDA) and the Kilometer Squared Array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO) during the prompt emission and the afterglow periods. Characteristic multi-TeV photons up to 13 TeV were observed in the afterglow phase. The observed very high-energy (VHE) gamma-ray spectra by WCDA and KM2A during different time intervals and in different energy ranges can be explained very well in the context of the photohadronic model with the inclusion of extragalactic background light models. In the photohadronic scenario, interaction of high-energy protons with the synchrotron self-Compton (SSC) photons in the forward shock region of the jet is assumed to be the source of these VHE photons. The observed VHE spectra from the afterglow of GRB 221009A are similar to the VHE gamma-ray spectra observed from the temporary extreme high-energy peaked BL Lac (EHBL), 1ES 2344+514 only during the 11th and the 12th of August, 2016. Such spectra are new and have been observed for the first time in a GRB.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"64 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141694672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding physical mechanisms relies on the accurate determination of fundamental constants, although inherent limitations in experimental techniques introduce uncertainties into these measurements. This paper explores the uncertainties associated with measuring the fine-structure constant (α) and the proton-to-electron mass ratio (μ) using observed fast radio bursts (FRBs). We select 50 localized FRBs to quantify the effects of varying this fundamental coupling on the relation between dispersion measure and redshift. By leveraging independent measurements of dispersion measures and redshifts of these FRBs, we constrain the uncertainties in α and μ approximately to Δα/α = 1.99 × 10−5 and Δμ/μ = −1.00 × 10−5 within the standard ΛCDM cosmological framework. Remarkably, these constraints improve nearly an order-of-magnitude when considering a dynamical dark energy model. This investigation not only yields one of the most stringent constraints on α and μ to date but also emphasizes the criticality of accounting for the energy scale of the system when formulating constraints on fundamental parameters.
{"title":"Constraining fundamental constants with fast radio bursts: Unveiling the role of energy scale","authors":"Surajit Kalita","doi":"10.1093/mnrasl/slae062","DOIUrl":"https://doi.org/10.1093/mnrasl/slae062","url":null,"abstract":"\u0000 Understanding physical mechanisms relies on the accurate determination of fundamental constants, although inherent limitations in experimental techniques introduce uncertainties into these measurements. This paper explores the uncertainties associated with measuring the fine-structure constant (α) and the proton-to-electron mass ratio (μ) using observed fast radio bursts (FRBs). We select 50 localized FRBs to quantify the effects of varying this fundamental coupling on the relation between dispersion measure and redshift. By leveraging independent measurements of dispersion measures and redshifts of these FRBs, we constrain the uncertainties in α and μ approximately to Δα/α = 1.99 × 10−5 and Δμ/μ = −1.00 × 10−5 within the standard ΛCDM cosmological framework. Remarkably, these constraints improve nearly an order-of-magnitude when considering a dynamical dark energy model. This investigation not only yields one of the most stringent constraints on α and μ to date but also emphasizes the criticality of accounting for the energy scale of the system when formulating constraints on fundamental parameters.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"48 33","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141689705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present novel insights into the interplay between tidal forces and star formation in interacting galaxies before their first pericentre passage. We investigate seven close pair galaxies devoid of visible tidal disturbances, such as tails, bridges, and shells. Using integral field spectroscopy (IFS) data of extended Calar Alto Legacy Integral Field Area (eCALIFA), we unveil a previously unreported phenomenon: Hα emission, a proxy for recent star formation, exhibits a significant enhancement in regions facing the companion galaxy, reaching up to 1.9 times higher flux compared to opposite directions. Notably, fainter companions within pairs display a more pronounced one-sided Hα excess, exceeding the typical range observed in isolated galaxies with 2σ confidence level. Furthermore, the observed Hα excess in fainter companion galaxies exhibits a heightened prominence at the outer galactic regions. These findings suggest that tidal forces generated before the first pericentre passage exert a stronger influence on fainter galaxies due to their shallower potential wells by their brighter companions. This unveils a more intricate interplay between gravitational interactions and star formation history within interacting galaxies than previously understood, highlighting the need further to explore the early stages of interaction in galaxy evolution.
{"title":"One-sided Hα excess before the first pericentre passage in galaxy Pairs","authors":"Jiwon Chung, J. Lee, Hyunjin Jeong","doi":"10.1093/mnrasl/slae053","DOIUrl":"https://doi.org/10.1093/mnrasl/slae053","url":null,"abstract":"\u0000 We present novel insights into the interplay between tidal forces and star formation in interacting galaxies before their first pericentre passage. We investigate seven close pair galaxies devoid of visible tidal disturbances, such as tails, bridges, and shells. Using integral field spectroscopy (IFS) data of extended Calar Alto Legacy Integral Field Area (eCALIFA), we unveil a previously unreported phenomenon: Hα emission, a proxy for recent star formation, exhibits a significant enhancement in regions facing the companion galaxy, reaching up to 1.9 times higher flux compared to opposite directions. Notably, fainter companions within pairs display a more pronounced one-sided Hα excess, exceeding the typical range observed in isolated galaxies with 2σ confidence level. Furthermore, the observed Hα excess in fainter companion galaxies exhibits a heightened prominence at the outer galactic regions. These findings suggest that tidal forces generated before the first pericentre passage exert a stronger influence on fainter galaxies due to their shallower potential wells by their brighter companions. This unveils a more intricate interplay between gravitational interactions and star formation history within interacting galaxies than previously understood, highlighting the need further to explore the early stages of interaction in galaxy evolution.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"31 46","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141354576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. Dors, G. C. Almeida, C B Oliveira, S. R. Flury, R. Riffel, R. Riffel, M. Cardaci, G. Hägele, G. S. Ilha, A. Krabbe, K. Arellano-Córdova, P C Santos, I. N. Morais
For the first time, a calibration between the He i$lambda 5876$/H $beta$ emission line ratio and the helium abundance y = 12 + log(He/H) for Narrow line regions of Seyfert 2 Active Galactic Nuclei is proposed. In this context, observational data (taken from the SDSS-DR15 and from the literature) and direct abundance estimates (via the $T_{rm e}$-method) for a sample of 65 local ($z : lt : 0.2$) Seyfert 2 nuclei are considered. The resulting calibration estimates the y abundance with an average uncertainty of 0.02 dex. Applying our calibration to spectroscopic data containing only strong emission lines, it yields a helium abundance distribution similar to that obtained via the $T_{rm e}$-method. Some cautions must be considered to apply our calibration for Seyfert 2 nuclei with high values of electron temperature (${gtrsim} 20, 000$ K) or ionization parameter ($log U gt {-}2.0$).
{"title":"Emirical calibration for helium abundance determinations in active galactic nuclei","authors":"O. Dors, G. C. Almeida, C B Oliveira, S. R. Flury, R. Riffel, R. Riffel, M. Cardaci, G. Hägele, G. S. Ilha, A. Krabbe, K. Arellano-Córdova, P C Santos, I. N. Morais","doi":"10.1093/mnrasl/slae052","DOIUrl":"https://doi.org/10.1093/mnrasl/slae052","url":null,"abstract":"\u0000 For the first time, a calibration between the He i$lambda 5876$/H $beta$ emission line ratio and the helium abundance y = 12 + log(He/H) for Narrow line regions of Seyfert 2 Active Galactic Nuclei is proposed. In this context, observational data (taken from the SDSS-DR15 and from the literature) and direct abundance estimates (via the $T_{rm e}$-method) for a sample of 65 local ($z : lt : 0.2$) Seyfert 2 nuclei are considered. The resulting calibration estimates the y abundance with an average uncertainty of 0.02 dex. Applying our calibration to spectroscopic data containing only strong emission lines, it yields a helium abundance distribution similar to that obtained via the $T_{rm e}$-method. Some cautions must be considered to apply our calibration for Seyfert 2 nuclei with high values of electron temperature (${gtrsim} 20, 000$ K) or ionization parameter ($log U gt {-}2.0$).","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"26 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141353690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Alpha Centauri system has two close stars Alpha and Beta (A & B) and one much further away: Proxima Centauri. All three stars are co-moving with similar chemistry, which implies they are bound, but the fast orbit of Proxima implies it is gravitationally unbound given the visible mass of A and B. This problem cannot be fixed with the addition of dark matter, which must be uniform on such scales, or adding mass to A and B (their mass is well constrained) or by MoND. A new model for inertia called Quantised Inertia (QI) has been proposed that solves the galaxy rotation problem by reducing the inertia of low-acceleration stars at the galaxies’ edge in a new way, thus keeping them bound without the need for dark matter. It is shown here that if quantised inertia is applied to Proxima Centauri in the same way, it predicts the observed orbital velocity, within the bounds of observational uncertainty, and binds Proxima, without the need for extra mass.
半人马座阿尔法星系有两颗距离很近的恒星阿尔法星和贝塔星（A 和 B），还有一颗距离更远：半人马座比邻星。所有这三颗恒星都以相似的化学性质共同运动，这意味着它们是结合在一起的，但由于 A 和 B 的可见质量，比邻星的快速轨道意味着它在引力上是非结合的。这个问题无法通过增加暗物质（在这样的尺度上暗物质必须是均匀的）或增加 A 和 B 的质量（它们的质量受到很好的约束）或 MoND 来解决。我们提出了一个新的惯性模型，叫做 "量化惯性（QI）"，它通过以一种新的方式减少星系边缘低速恒星的惯性来解决星系旋转问题，从而使星系保持约束而不需要暗物质。本文表明，如果将量化惯性以同样的方式应用于半人马座比邻星，它就能在观测不确定性的范围内预测出观测到的轨道速度，并在不需要额外质量的情况下束缚比邻星。
{"title":"Testing quantised inertia on proxima centauri","authors":"M. E. McCulloch","doi":"10.1093/mnrasl/slae047","DOIUrl":"https://doi.org/10.1093/mnrasl/slae047","url":null,"abstract":"\u0000 The Alpha Centauri system has two close stars Alpha and Beta (A & B) and one much further away: Proxima Centauri. All three stars are co-moving with similar chemistry, which implies they are bound, but the fast orbit of Proxima implies it is gravitationally unbound given the visible mass of A and B. This problem cannot be fixed with the addition of dark matter, which must be uniform on such scales, or adding mass to A and B (their mass is well constrained) or by MoND. A new model for inertia called Quantised Inertia (QI) has been proposed that solves the galaxy rotation problem by reducing the inertia of low-acceleration stars at the galaxies’ edge in a new way, thus keeping them bound without the need for dark matter. It is shown here that if quantised inertia is applied to Proxima Centauri in the same way, it predicts the observed orbital velocity, within the bounds of observational uncertainty, and binds Proxima, without the need for extra mass.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"14 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141098212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Kocifaj, P. Markoš, F. Kundracik, J. C. Barentine, S. Wallner
Most measurements of the diffuse light of the night sky to date consider only the intensity of the light field, and current models can successfully reproduce these measurements. However, this approach is incomplete as it overlooks the polarization state of the light. Few measurements (and no successful models) of night-sky polarimetry appear in the literature. We present a new model of night-sky polarization that successfully reproduces observations in a heterogeneous environment and for a real distribution of finite-sized light sources over the intermediate region surrounding the observer. The model compares favourably with field measurements made in Slovakia in May 2021. The results described herein help advance understanding the angular distributions of artificial light at night from ground sources and the relative contributions of sources to the overall brightness of the night sky.
{"title":"An accurate and realistic polarization model for night-sky brightness","authors":"M. Kocifaj, P. Markoš, F. Kundracik, J. C. Barentine, S. Wallner","doi":"10.1093/mnrasl/slae048","DOIUrl":"https://doi.org/10.1093/mnrasl/slae048","url":null,"abstract":"\u0000 Most measurements of the diffuse light of the night sky to date consider only the intensity of the light field, and current models can successfully reproduce these measurements. However, this approach is incomplete as it overlooks the polarization state of the light. Few measurements (and no successful models) of night-sky polarimetry appear in the literature. We present a new model of night-sky polarization that successfully reproduces observations in a heterogeneous environment and for a real distribution of finite-sized light sources over the intermediate region surrounding the observer. The model compares favourably with field measurements made in Slovakia in May 2021. The results described herein help advance understanding the angular distributions of artificial light at night from ground sources and the relative contributions of sources to the overall brightness of the night sky.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141098844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elena Hoemann, Andrea Socci, Stefan Heigl, Andreas Burkert, Alvaro Hacar
We suggest that filaments in star-forming regions undergo frequent mergers. As stellar nurseries, filaments play a vital role in understanding star formation and mergers could pave the way for understanding the formation of more complex filamentary systems, such as networks and hubs. We compare the physical properties derived from hydrodynamic RAMSES simulations of merging filaments to those obtained from ALMA observations towards the LDN 1641-North region in Orion. We find similarities in the distributions of line-mass, column density and velocity dispersion. Such common features support the hypothesis of filament mergers shaping the structure of the interstellar medium.
我们认为恒星形成区的丝状体经常发生合并。作为恒星的苗圃，长丝在了解恒星形成方面起着至关重要的作用，而合并可以为了解更复杂的长丝系统（如网络和枢纽）的形成铺平道路。我们将 RAMSES 对合并长丝的流体力学模拟得出的物理性质与 ALMA 对猎户座 LDN 1641-North 区域的观测结果进行了比较。我们发现两者在线质量、柱密度和速度色散的分布上有相似之处。这些共同特征支持了星丝合并塑造星际介质结构的假说。
{"title":"Merging filaments II: The origin of the tuning fork","authors":"Elena Hoemann, Andrea Socci, Stefan Heigl, Andreas Burkert, Alvaro Hacar","doi":"10.1093/mnrasl/slae045","DOIUrl":"https://doi.org/10.1093/mnrasl/slae045","url":null,"abstract":"\u0000 We suggest that filaments in star-forming regions undergo frequent mergers. As stellar nurseries, filaments play a vital role in understanding star formation and mergers could pave the way for understanding the formation of more complex filamentary systems, such as networks and hubs. We compare the physical properties derived from hydrodynamic RAMSES simulations of merging filaments to those obtained from ALMA observations towards the LDN 1641-North region in Orion. We find similarities in the distributions of line-mass, column density and velocity dispersion. Such common features support the hypothesis of filament mergers shaping the structure of the interstellar medium.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"61 28","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141110360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The detection of a Keplerian rotation is rare among Class 0 protostellar systems. We have investigated the high-density tracer HCN as a probe of the inner disk in a Class 0 proto-brown dwarf candidate. Our ALMA high angular resolution observations show the peak in the HCN (3-2) line emission arises from a compact component near the proto-brown dwarf with a small bar-like structure and a deconvolved size of ∼50 au. Radiative transfer modelling indicates that this HCN feature is tracing the innermost, dense regions in the proto-brown dwarf where a small Keplerian disk is expected to be present. The limited velocity resolution of the observations, however, makes it difficult to confirm the rotational kinematics of this feature. A brightening in the HCN emission towards the core center suggests that HCN can survive in the gas phase in the inner, dense regions of the proto-brown dwarf. In contrast, modelling of the HCO+ (3-2) line emission indicates that it originates from the outer pseudo-disk/envelope region and is centrally depleted. HCN line emission can reveal the small-scale structures and can be an efficient observational tool to study the inner disk properties in such faint compact objects where spatially resolving the disk is nearly impossible.
{"title":"HCN as a probe of the inner disk in a candidate proto-brown dwarf","authors":"B. Riaz, W.-F. Thi, M. Machida","doi":"10.1093/mnrasl/slae044","DOIUrl":"https://doi.org/10.1093/mnrasl/slae044","url":null,"abstract":"\u0000 The detection of a Keplerian rotation is rare among Class 0 protostellar systems. We have investigated the high-density tracer HCN as a probe of the inner disk in a Class 0 proto-brown dwarf candidate. Our ALMA high angular resolution observations show the peak in the HCN (3-2) line emission arises from a compact component near the proto-brown dwarf with a small bar-like structure and a deconvolved size of ∼50 au. Radiative transfer modelling indicates that this HCN feature is tracing the innermost, dense regions in the proto-brown dwarf where a small Keplerian disk is expected to be present. The limited velocity resolution of the observations, however, makes it difficult to confirm the rotational kinematics of this feature. A brightening in the HCN emission towards the core center suggests that HCN can survive in the gas phase in the inner, dense regions of the proto-brown dwarf. In contrast, modelling of the HCO+ (3-2) line emission indicates that it originates from the outer pseudo-disk/envelope region and is centrally depleted. HCN line emission can reveal the small-scale structures and can be an efficient observational tool to study the inner disk properties in such faint compact objects where spatially resolving the disk is nearly impossible.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"104 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141124867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The linear relationship between pulsar micro-pulse widths and rotation period is consistent with the existence of a physical length L on the neutron-star surface and seen on the observer arc of transit across the polar cap. Within the ion-proton model it is the width of the minimum area of surface that can support the critical growth rate of the unstable two-beam Langmuir mode that is the source of the radio emission.
脉冲星微脉冲宽度与自转周期之间的线性关系与中子星表面存在的物理长度 L 以及观测者穿越极冠的弧线是一致的。在离子-质子模型中，能够支持不稳定的双束朗缪尔模式临界增长率的最小表面区域的宽度就是无线电发射源。
{"title":"On the origin of the quasi-periodic micro-pulses observed in the radio-frequency emission of some neutron stars","authors":"P. B. Jones","doi":"10.1093/mnrasl/slae041","DOIUrl":"https://doi.org/10.1093/mnrasl/slae041","url":null,"abstract":"\u0000 The linear relationship between pulsar micro-pulse widths and rotation period is consistent with the existence of a physical length L on the neutron-star surface and seen on the observer arc of transit across the polar cap. Within the ion-proton model it is the width of the minimum area of surface that can support the critical growth rate of the unstable two-beam Langmuir mode that is the source of the radio emission.","PeriodicalId":18951,"journal":{"name":"Monthly Notices of the Royal Astronomical Society: Letters","volume":"51 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140978755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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