### Possibly interesting papers from arXiv

29 Jun22

Title: The chemical signature of the Galactic spiral arms revealed by Gaia DR3
Authors: E. Poggio, A. Recio-Blanco, P. A. Palicio, P. Re Fiorentin, P. de Laverny, R. Drimmel, G. Kordopatis, M. G. Lattanzi, M. Schultheis, A. Spagna, E. Spitoni
https://arxiv.org/pdf/2206.14849 .pdf
Abstract: Taking advantage of the recent Gaia Data Release 3 (DR3), we map chemical inhomogeneities in the Milky Way's disc out to a distance of $\sim$ 4 kpc of the Sun, using different samples of bright giant stars (log($g$) < 1.5 dex, T$_{\rm{eff}}$ \sim 3500-5500 K). We detect remarkable inhomogeneities, which appear to be more prominent and structured for the sample containing stars with relatively hotter effective temperatures. For this sample, we identify three (possibly four) metal-rich elongated features in the Galactic plane, which are located in proximity of the spiral arms in the Galactic disc. When projected onto Galactic radius, those features manifest themselves as statistically significant bumps on top of the observed radial gradients, making the assumption of a linear radial decrease not applicable to this sample. In contrast, the sample containing cooler giants exhibits a relatively smooth decrease as a function of Galactic radius. Considering different slices in Galactic azimuth $\phi$, the slope of the measured radial metallicity gradient for the cool giants varies gradually from $\sim$-0.05 dex kpc$^{-1}$ at $\phi \sim -20^{\circ}$ to $\sim$ -0.03 dex kpc$^{-1}$ at $\phi \sim 20^{\circ}$. The strong correlation between the spiral structure of the Galaxy and the observed chemical pattern in the sample with relatively hotter effective temperatures indicates that the spiral arms might be at the origin for the detected chemical inhomogeneities. In this scenario, the spiral arms would leave in the hotter stars a strong signature, which progressively disappears when cooler giants stars are considered.

Title: Blanco DECam Bulge Survey (BDBS) IV: Metallicity Distributions and Bulge Structure from 2.6 Million Red Clump Stars
Authors: Christian I. Johnson, R. Michael Rich, Iulia T. Simion, Michael D. Young, William I. Clarkson, Catherine A. Pilachowski, Scott Michael, Tommaso Marchetti, Mario Soto, Andrea Kunder, Andreas J. Koch-Hansen, A. Katherina Vivas, Meridith Joyce, Juntai Shen, and Alexis Osmond
https://arxiv.org/pdf/2206.14851 .pdf
Abstract: We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity distribution functions appear at b < -5. We can discern a metal-poor ([Fe/H] ~ -0.3) and metal-rich ([Fe/H] ~ +0.2) abundance distribution that each show clear systematic trends with latitude, and may be best understood by changes in the bulge's star formation/enrichment processes. Both groups exhibit asymmetric tails, and as a result we argue that the proximity of a star to either peak in [Fe/H] space is not necessarily an affirmation of group membership. The metal-poor peak shifts to lower [Fe/H] values at larger distances from the plane while the metal-rich tail truncates. Close to the plane, the metal-rich tail appears broader along the minor axis than in off-axis fields. We also posit that the bulge has two metal-poor populations -- one that belongs to the metal-poor tail of the low latitude and predominantly metal-rich group, and another belonging to the metal-poor group that dominates in the outer bulge. We detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with [Fe/H] > -0.5. Stars with [Fe/H] < -0.5 may form a spheroidal or "thick bar" distribution while those with [Fe/H] > -0.1 are strongly concentrated near the plane.

Title: Non-solar abundance ratios trends of dEs in Fornax Cluster using newly defined high resolution indices
Authors: \c{S}eyda \c{S}en, Reynier F. Peletier, Alexandre Vazdekis
https://arxiv.org/pdf/2206.15214 .pdf
Abstract: We perform a detailed study of the stellar populations in a sample of massive Fornax dwarf galaxies using a set of newly defined line indices. Using data from the Integral field spectroscopic data, we study abundance ratios of eight dEs with stellar mass ranging from 10$^8$ to 10$^{9.5}$ M$_\odot$ in the Fornax cluster. We present the definitions of a new set of high-resolution Lick-style indices to be used for stellar population studies of unresolved small stellar systems. We identify 23 absorption features and continuum regions, mainly dominated by 12 elements (Na, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Ba and Nd) in the wavelength range 4700 - 5400 \r{A} and characterise them as a function of age, metallicity and alpha element abundance ratios. We analyse eight dEs and interpret the line strengths, measured in our new high resolution system of indices, with the aid of stellar population models with high enough spectral resolution. We obtain abundance ratio proxies for a number of elements that have never been studied before for dwarf ellipticals outside the Local Group. These proxies represent relative deviations from predicted index-strengths of base stellar population models built-up following the abundance pattern of The Galaxy. The abundance proxy trend results are compared to abundance ratios from resolved stars in the Local Group, and indices from integrated light of larger early-type galaxies. We find that all our dwarfs show a pattern of abundance ratios consistent with the disk of the Milky Way, indicative of slow formation in comparison to their high mass counterparts.

Title: Disentangling emission from star-forming regions in the Magellanic Clouds: Linking [OIII]88 micron and 24 micron
Authors: Antigone Lambert-Huyghe, Suzanne C. Madden, Vianney Lebouteiller, Fr\'ed\'eric Galliano, Nicholas P. Abel, Dangning Hu, Lise Ramambason, Fiorella L. Polles
https://arxiv.org/pdf/2206.15417 .pdf
Abstract: This study explores the link between the [OIII]88mu emission, a well-known tracer of HII regions, and 24mu continuum, often used to trace warm dust in the ionized phases of galaxies. We investigate the local conditions driving the relation between those tracers in the Magellanic Clouds, comparing observations with Cloudy models consisting of an HII region plus a photodissociation region (PDR) component, varying the stellar age, the initial density (at the illuminated edge of the cloud), and the ionization parameter. We introduce a new parameter, cPDR, to quantify the proportion of emission arising from PDRs and that with an origin in HII regions along each line of sight. We use the ratio ([CII]+[OI])/[OIII] as a proxy for the ratio of PDR versus HII region emission, and compare it to [OIII]/24mu. The use of [OIII]/24mu and [OIII]/70mu together allows us to constrain the models most efficiently. We find a correlation over at least 3 orders of magnitude in [OIII]88mu and 24mu continuum in spatially resolved maps of the Magellanic Cloud regions as well as unresolved galaxy-wide low metallicity galaxies of the Dwarf Galaxy Survey. Most of the regions have low proportions of PDRs along the lines of sight (< 12%), while a limited area of some of the mapped regions can reach 30 to 50%. For most lines of sight within the star-forming regions we have studied in the Magellanic Clouds, HII regions are the dominant phase. We propose the use of the correlation between the [OIII]88mu and 24mu continuum as a new predictive tool to estimate, for example, the [OIII]88mu emission when the 24mu continuum is available or inversely. This can be useful to prepare for ALMA observations of [OIII]88mu in high-z galaxies. This simple and novel method may also provide a way to disentangle different phases along the line of sight, when other 3D information is not available.

28 Jun22

Title: Discovery of a Short Period Pulsator from Istanbul University Observatory
Authors: Mustafa Turan Sa\u{g}lam, Meryem \c{C}\"ord\"uk, Sinan Ali\c{s}, G\"orkem \"Ozg\"ul, Olcaytu\u{g} \"Ozg\"ull\"u, Fatih Erkam G\"okt\"urk, Rahmi G\"und\"uz, S\"uleyman Fi\c{s}ek, F. Korhan Yelkenci, Ey\"up Kaan \"Ulgen, Tolga G\"uver
https://arxiv.org/pdf/2206.14632 .pdf
Abstract: We report the discovery of a new short period pulsating variable in the field of exoplanet host star XO-2. Variable has been identified while it was being used as a comparison star. In order to verify the variability of the candidate, a follow-up program was carried out. Period analysis of multi-band light curves revealed a very prominent and consistent pulsation periodicity of $P\sim0.95$ hours. Given the variability period, amplitude and the color index, the object is most likely a \emph{Delta Scuti} type variable. Absolute magnitude ($M_{v}$) and the color index $(B-V)_{0}$ of the star determined as $2.76$ and $0.22$, respectively. This $(B-V)_{0}$ of the star corresponds to A7 spectral type with an approximate effective temperature of 7725 K. Machine-learning analysis of the time-series data also revealed that the object is of variable type DSCT with a probability of 78\%.

27 Jun22

Title: Untangling the Galaxy. IV. Empirical Constraints on Angular Momentum Evolution and Gyrochronology for Young Stars in the Field
Authors: Marina Kounkel, Keivan G. Stassun, Luke G. Bouma, Kevin Covey, Lynne A. Hillenbrand, Jason Lee Curtis
https://arxiv.org/pdf/2206.13545 .pdf
Abstract: We present a catalog of ~100,000 periodic variable stars in TESS FFI data among members of widely distributed moving groups identified with Gaia in the previous papers in the series. By combining the periods from our catalog attributable to rotation with previously derived rotation periods for benchmark open clusters, we develop an empirical gyrochronology model of angular momentum evolution that is valid for stars with ages 10-1000 Myr. Excluding stars rotating faster than 2 days, which we find are predominantly binaries, we achieve a typical age precision of ~0.2-0.3 dex and improving at older ages. Importantly, these empirical relations apply to not only FGK-type stars but also M-type stars, due to the angular momentum distribution being much smoother, simpler, continuous and monotonic as compared to the rotation period distribution. As a result, we are also able to begin tracing in fine detail the nature of angular momentum loss in low-mass stars as functions of mass and age. We characterize the stellar variability amplitudes of the cool stars as functions of mass and age, which may correlate with the starspot covering fractions. We also identify pulsating variables among the hotter stars in the catalog, including $\delta$ Scuti, $\gamma$ Dor and SPB-type variables. These data represent an important step forward in being able to estimate precise ages of FGK- and M-type stars in the field, starting as early as the pre-main-sequence phase of evolution.

Title: Constraining the Planet Occurrence Rate around Halo Stars of Potentially Extragalactic Origin
Authors: Stephanie Yoshida, Samuel Grunblatt, and Adrian Price-Whelan
https://arxiv.org/pdf/2206.13556 .pdf
Abstract: The search for planets orbiting other stars has recently expanded to include stars from galaxies outside the Milky Way. With the TESS and Gaia surveys, photometric and kinematic information can be combined to identify transiting planet candidates of extragalactic origin. Here, 1,080 low-luminosity red giant branch stars observed by Gaia and TESS with kinematics suggesting a high likelihood of extragalactic origin were searched for planet transits. Transit injection-recovery tests were performed to measure the sensitivity of the TESS data and completeness of the transit search. Injected signals of planets larger than Jupiter with orbital periods of 10 days or less were recovered in $\approx$44% of cases. Although no planet transits were detected in this sample, we find an upper limit on planet occurrence of 0.52% for hot Jupiters, consistent with previous studies of planet occurrence around similar host stars. As stars in the halo tend to be lower metallicity, and short period giant planet occurrence tends to be strongly correlated with stellar metallicity, we predict that relative to the Galactic disk population, a smaller fraction of halo stars will host planets detectable by transit surveys. Thus, applying the known planet occurrence trends to potential planet detection around halo stars, we predict $\gtrsim$7,000 stars must be searched with similar cadence and precision as the stars studied here before a detection of a planet of extragalactic origin is likely. This may be possible with future data releases from the TESS and Gaia missions.

Title: Rotation measure structure functions with higher-order stencils as a probe of small-scale magnetic fluctuations and its application to the Small and Large Magellanic Clouds
Authors: Amit Seta, Christoph Federrath, Jack D. Livingston, and N. M. McClure-Griffiths
https://arxiv.org/pdf/2206.13798 .pdf
Abstract: Magnetic fields and turbulence are important components of the interstellar medium (ISM) of star-forming galaxies. It is challenging to measure the properties of the small-scale ISM magnetic fields (magnetic fields at scales smaller than the turbulence driving scale). Using numerical simulations, we demonstrate how the second-order rotation measure (RM, which depends on thermal electron density, $n_{\rm e}$, and magnetic field, $b$) structure function can probe the properties of small-scale $b$. We then apply our results to observations of the Small and Large Magellanic Clouds (SMC and LMC). First, using Gaussian random $b$, we show that the characteristic scale where the RM structure function flattens is approximately equal to the correlation length of $b$. We also show that computing the RM structure function with a higher-order stencil (more than the commonly-used two-point stencil) is necessary to accurately estimate the slope of the structure function. Then, using Gaussian random $b$ and lognormal $n_{\rm e}$ with known power spectra, we derive an empirical relationship between the slope of the power spectrum of $b$, $n_{\rm e}$, and RM. We apply these results to the SMC and LMC and estimate the following properties of small-scale $b$: correlation length ($160~\pm 21~{\rm pc}$ for the SMC and $87~\pm~17~{\rm pc}$ for the LMC), strength ($14~\pm 2~\mu{\rm G}$ for the SMC and $15~\pm 3~\mu{\rm G}$ for the LMC), and slope of the magnetic power spectrum ($-1.3~\pm~0.4$ for the SMC and $-1.6~\pm~0.1$ for the LMC). We also find that $n_{\rm e}$ is practically constant over the estimated $b$ correlation scales.

Title: The Galactic Nova Rate: Estimates from the ASAS-SN and Gaia Surveys
Authors: A. Kawash, L. Chomiuk, J. Strader, K. V. Sokolovsky, E. Aydi, C. S. Kochanek, K. Z. Stanek, Z. Kostrzewa-Rutkowska, S. T. Hodgkin, K. Mukai, B. Shappee, T. Jayasinghe, M. Rizzo Smith, T. W.-S. Holoien, J. L. Prieto, T. A. Thompson
https://arxiv.org/pdf/2206.14132 .pdf
Abstract: We present the first estimate of the Galactic nova rate based on optical transient surveys covering the entire sky. Using data from the All-Sky Automated Survey for Supernovae (ASAS-SN) and \textit{Gaia} -- the only two all-sky surveys to report classical nova candidates -- we find 39 confirmed Galactic novae and 7 additional unconfirmed candidates discovered from 2019--2021, yielding a nova discovery rate of $\approx 14$ yr$^{-1}$. Using accurate Galactic stellar mass models, three-dimensional dust maps, and incorporating realistic nova light curves, we have built a sophisticated Galactic nova model that allows an estimate of the recovery fraction of Galactic novae from these surveys over this time period. The observing capabilities of each survey are distinct: the high cadence of ASAS-SN makes it sensitive to fast novae, while the broad observing filter and high spatial resolution of \textit{Gaia} make it more sensitive to highly reddened novae across the entire Galactic plane and bulge. Despite these differences, we find that ASAS-SN and \textit{Gaia} give consistent Galactic nova rates, with a final joint nova rate of $26 \pm 5$ yr$^{-1}$. This inferred nova rate is substantially lower than found by many other recent studies. Critically assessing the systematic uncertainties in the Galactic nova rate, we argue that the role of faint fast-fading novae has likely been overestimated, but that subtle details in the operation of transient alert pipelines can have large, sometimes unappreciated effects on transient recovery efficiency. Our predicted nova rate can be directly tested with forthcoming red/near-infrared transient surveys in the southern hemisphere.

24 Jun22

Title: Blanco DECam Bulge Survey (BDBS) V. Cleaning the foreground populations from Galactic bulge colour-magnitude diagrams using Gaia EDR3
Authors: Tommaso Marchetti, Christian I. Johnson, Meridith Joyce, R. Michael Rich, Iulia Simion, Michael D. Young, William I. Clarkson, Catherine A. Pilachowski, Scott Michael, Andrea Kunder, Andreas J. Koch-Hansen
https://arxiv.org/pdf/2206.12817 .pdf
Abstract: The Blanco DECam Bulge Survey (BDBS) has imaged more than 200 square degrees of the southern Galactic bulge, providing photometry in the ugrizy filters for $\sim 250$ million unique stars. The presence of a strong foreground disk population, along with complex reddening and extreme image crowding, has made it difficult to constrain the presence of young and intermediate age stars in the bulge population. We employed an accurate cross-match of BDBS with the latest data release (EDR3) from the Gaia mission, matching more than 140 million sources with BDBS photometry and Gaia EDR3 photometry and astrometry. We relied on Gaia EDR3 astrometry, without any photometric selection, to produce clean BDBS bulge colour-magnitude diagrams (CMDs). Gaia parallaxes were used to filter out bright foreground sources, and a Gaussian mixture model fit to Galactic proper motions could identify stars kinematically consistent with bulge membership. We applied this method to 127 different bulge fields of $1$ deg$^2$ each, with $|\ell| \leq 9.5^\circ$ and $-9.5^\circ \leq b \leq -2.5^\circ$. The astrometric cleaning procedure removes the majority of blue stars in each field, especially near the Galactic plane, where the ratio of blue to red stars is $\lesssim 10\%$, increasing to values $\sim 20\%$ at higher Galactic latitudes. We rule out the presence of a widespread population of stars younger than 2 Gyr. The vast majority of blue stars brighter than the turnoff belong to the foreground population, according to their measured astrometry. We introduce the distance between the observed red giant branch bump and the red clump as a simple age proxy for the dominant population in the field, and we confirm the picture of a predominantly old bulge. Further work is needed to apply the method to estimate ages to fields at higher latitudes, and to model the complex morphology of the Galactic bulge.

Title: The evolutionary state of the chemically peculiar members of the open cluster NGC2516
Authors: N.V. Kharchenko, A.E. Piskunov, S. Hubrig, M. Sch\"oller
https://arxiv.org/pdf/2206.12824 .pdf
Abstract: We aim at establishing safe membership and evolutionary status of 11 chemically peculiar (CP) stars that are residing in the domain of the open cluster NGC2516 and are frequently referred to as cluster members. We queried the Gaia EDR3 catalogue in an area with a radius of 1deg and selected 37508 stars brighter than G=19mag. The cluster membership was determined in parallax-proper motion-space and 719 probable and 764 possible members were found. The obtained average astrometric and photometric parameters of the cluster are in good agreement with the most recent literature data. The evolutionary status of the target stars was determined with respect to Padova isochrones. After minor adjustments including the metallicity, the reddening, and the transformation scale variation, a perfect fit of the model to the observations over the whole observed magnitude range was achieved. Only 5 of the 11 considered CP stars could be classified as highly probable cluster members. Among the Ap/Bp stars with previously detected magnetic fields HD65987 and HD65712 have a high membership probability and the magnetic star CPD-60 944B is a possible cluster member. Further we discuss the blue straggler nature of HD66194 and the magnetic star HD65987. To our knowledge, HD65987 is currently the only known blue straggler, with a field of the order of a few hundred Gauss. The most striking result of our study is that the strongly magnetic A0p star HD66318 with previously reported very low fractional age does not belong to the NGC2516 cluster at a high level of confidence.

Title: Asteroseismology of RR Lyrae stars with non-radial modes
Authors: H. Netzel, R. Smolec
https://arxiv.org/pdf/2206.12853 .pdf
Abstract: The additional signals observed in the frequency spectra of the first-overtone RR Lyrae stars, that form a period ratio around 0.61 with the period of the first overtone, are a common phenomenon for RRc and RRd stars, as well as for first-overtone classical Cepheids. The recently proposed model explains these signals as harmonics of non-radial modes of degrees 8 or 9 in the case of RR Lyrae stars and 7, 8, or 9 in the case of classical Cepheids. We selected at least triple-mode RR Lyrae stars pulsating in radial and non-radial modes for asteroseismic modeling. We assume the identification of the non-radial modes as predicted by the model. We calculated a dense grid of models for RR Lyrae stars using envelope pulsation code. By matching first overtone period and period ratios we obtained physical parameters for the selected sample of triple-mode stars. It is the very first attempt of modeling RR Lyrae stars with non-radial modes. We compared our results with predictions of stellar evolution theory, which resulted in a mass discrepancy more noticeable for long-period stars: pulsation masses seem higher than evolutionary masses. We compared metallicity estimates for RRc stars from modeled sample with metallicities determined spectroscopically for a sample of RRc stars in the solar neighbourhood: both distributions are consistent.

Title: Luminosity distribution of Type II supernova progenitors
Authors: \'Osmar Rodr\'iguez
https://arxiv.org/pdf/2206.12974 .pdf
Abstract: I present progenitor luminosities ($L$) for a sample of 112 Type II supernovae (SNe II), computed directly from progenitor photometry and the bolometric correction technique, or indirectly from empirical correlations between progenitor luminosity and [OI] $\lambda\lambda$6300, 6364 line luminosity at 350 d since explosion, $^{56}$Ni mass, or absolute $V$-band magnitude at 50 d since explosion. To calibrate these correlations, I use twelve SNe II with progenitor luminosities measured from progenitor photometry. I find that the correlations mentioned above are strong and statistically significant, and allow to estimate progenitor luminosities to a precision between 20 and 24 per cent. I correct the SN sample for selection bias and define a subsample of 112 SNe II with progenitor luminosities between $\log(L/L_{\odot})=4.6$ dex, corresponding to the completeness limit of the corrected sample, and the maximum observed progenitor luminosity of $\log(L/L_{\odot})=5.091$ dex. The luminosity distribution for this subsample is statistically consistent with those for red supergiants (RSGs) in LMC, SMC, M31, and M33 with $4.6\leq\log(L/L_{\odot})\leq5.091$. This supports that SN II progenitors correspond to RSGs. The conspicuous absence of SN II progenitors with $\log(L/L_{\odot})>5.1$ dex with respect to what is observed in RSG luminosity distributions, known as the RSG problem, is significant at a $5.2\pm0.5\,\sigma$ level.

Title: Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5$-$101002.3
Authors: N. Lodieu (1,2), M. R. Zapatero Osorio (3), E. L. Martin (1,2,4), R. Rebolo Lopez (1,2,4), B. Gauza (5,6)
https://arxiv.org/pdf/2206.13097 .pdf
Abstract: Our goal is to characterise the physical properties of the metal-poor brown dwarf population. In particular, we focus on the recently discovered peculiar dwarf WISE J1810055$-$1010023. We collected optical iz and near-infrared J-band imaging on multiple occasions over 1.5 years to derive accurate trigonometric parallax and proper motion of the metal-depleted ultra-cool dwarf candidate WISE1810. We also acquired low-resolution optical spectroscopy (0.6$-$1.0 $\mu$m) and new infrared (0.9$-$1.3 $\mu$m) spectra of WISE1810 that were combined with our photometry, other existing data from the literature and our trigonometric distance to determine the object's luminosity from the integration of the observed spectral energy distribution covering from 0.6 through 16$\mu$m. We compared the full optical and infrared spectrum with state-of-the-art atmosphere models to further constrain its effective temperature, surface gravity and metallicity. WISE1810 is detected in the $iz$ bands with AB magnitudes of $i$=23.871$\pm$0.104 and $z$=20.147$\pm$0.083 mag in the PanSTARRS system. It does not show any obvious photometric variability beyond 0.1$-$0.2 mag in any of the $z$- and $J$-band filters. The very red $z-J \approx 2.9$ mag colour is compatible with an ultra-cool dwarf nature. Fitting for parallax and proper motion, we measure a trigonometric parallax of 112.5$^{+8.1}_{-8.0}$ mas for WISE1810, placing the object at only 8.9$^{+0.7}_{-0.6}$ pc, about three times closer than previously thought. We employed Monte Carlo methods to estimate the error on the parallax and proper motion. The object's luminosity was determined at log$L/L_\odot$=$-$5.78$\pm$0.11 dex. From the comparison to atmospheric models, we infer a likely metallicity of [Fe/H] $\approx -1.5$ and an effective temperature cooler than 1000K. Abridged

Title: Solenoidal turbulent modes and star formation efficiency in Galactic-plane molecular clouds
Authors: Raffaele Rani, Toby J. T. Moore, David J. Eden, Andrew J. Rigby
https://arxiv.org/pdf/2206.13442 .pdf
Abstract: It is speculated that the high star-formation efficiency observed in spiral-arm molecular clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be the main cause of the low star-formation efficiency that characterises clouds in the Central Molecular Zone. Similarly, analysis of the Orion B molecular cloud has confirmed that, although turbulent modes vary locally and at different scales within the cloud, the dominant solenoidal turbulence is compatible with its low star formation rate. This evidence points to inter-and intra-cloud fluctuations of the solenoidal modes being an agent for the variability of star formation efficiency. We present a quantitative estimation of the relative fractions of momentum density in the solenoidal modes of turbulence in a large sample of plane molecular clouds in the \ce{^{13}CO}/\ce{C^{18}O} ($J=3\rightarrow 2$) Heterodyne Inner Milky Way Plane Survey (CHIMPS). We find a negative correlation between the solenoidal fraction and star-formation efficiency. This feature is consistent with the hypothesis that solenoidal modes prevent or slow down the collapse of dense cores. In addition, the relative power in the solenoidal modes of turbulence (solenoidal fraction) appears to be higher in the Inner Galaxy declining with a shallow gradient with increasing Galactocentric distance. Outside the Inner Galaxy, the slowly, monotonically declining values suggest that the solenoidal fraction is unaffected by the spiral arms.

23 Jun22

Title: The Properties of Fast Yellow Pulsating Supergiants: FYPS Point the Way to Missing Red Supergiants
Authors: Trevor Z. Dorn-Wallenstein, Emily M. Levesque, James R. A. Davenport, Kathryn F. Neugent, Brett M. Morris, and K. Azalee Bostroem
https://arxiv.org/pdf/2206.11917 .pdf
Abstract: Fast yellow pulsating supergiants (FYPS) are a recently-discovered class of evolved massive pulsator. As candidate post-red supergiant objects, and one of the few classes of pulsating evolved massive stars, these objects have incredible potential to change our understanding of the structure and evolution of massive stars. Here we examine the lightcurves of a sample of 126 cool supergiants in the Magellanic Clouds observed by the Transiting Exoplanet Survey Satellite (TESS) in order to identify pulsating stars. After making quality cuts and filtering out contaminant objects, we examine the distribution of pulsating stars in the Hertzprung-Russel (HR) diagram, and find that FYPS occupy a region above $\log L/L_\odot \gtrsim 5.0$. This luminosity boundary corresponds to stars with initial masses of $\sim$18-20 $M_\odot$, consistent with the most massive red supergiant progenitors of supernovae (SNe) II-P, as well as the observed properties of SNe IIb progenitors. This threshold is in agreement with the picture that FYPS are post-RSG stars. Finally, we characterize the behavior of FYPS pulsations as a function of their location in the HR diagram. We find low frequency pulsations at higher effective temperatures, higher frequency pulsations at lower temperatures, with a transition between the two behaviors at intermediate temperatures. The observed properties of FYPS make them fascinating objects for future theoretical study.

22 Jun22

Title: Probable Dormant Neutron Star in a Short-Period Binary System
Authors: Tsevi Mazeh, Simchon Faigler, Dolev Bashi, Sahar Shahaf, Niv Davidson, Matthew Green, Roy Gomel, Dan Maoz, Amitay Sussholz, Subo Dong, Haotong Zhang, Jifeng Liu, Song Wang, Ali Luo, Zheng Zheng, Na'ama Hallakoun, Volker Perdelwitz, David W. Latham, Ignasi Ribas, David Baroch, Juan Carlos Morales, Evangelos Nagel, Nuno C. Santos, David R. Ciardi, Jessie L. Christiansen, Michael B. Lund, Joshua N. Winn
https://arxiv.org/pdf/2206.11270 .pdf
Abstract: We have identified 2XMM J125556.57+565846.4, at a distance of 600 pc, as a binary system consisting of a normal star and a probable dormant neutron star. Optical spectra exhibit a slightly evolved F-type single star, displaying periodic Doppler shifts with a 2.76-day Keplerian circular orbit, with no indication of light from a secondary component. Optical and UV photometry reveal ellipsoidal variations with half the orbital period, due to the tidal deformation of the F star. The mass of the unseen companion is constrained to the range $1.1$--$2.1\, M_{\odot}$ at $3\sigma$ confidence, with the median of the mass distribution at $1.4\, M_{\odot}$, the typical mass of known neutron stars. A main-sequence star cannot masquerade as the dark companion. The distribution of possible companion masses still allows for the possibility of a very massive white dwarf. The companion itself could also be a close pair consisting of a white dwarf and an M star, or two white dwarfs, although the binary evolution that would lead to such a close triple system is unlikely. Similar ambiguities regarding the certain identification of a dormant neutron star are bound to affect most future discoveries of this type of non-interacting system. If the system indeed contains a dormant neutron star, it will become, in the future, a bright X-ray source and might even host a millisecond pulsar.

Title: Is there a nearby microlensing stellar remnant hiding in Gaia DR3 astrometry?
Authors: Maja Jab{\l}o\'nska, {\L}ukasz Wyrzykowski, Krzysztof A. Rybicki, Katarzyna Kruszy\'nska, Zofia Kaczmarek, and Zephyr Penoyre
https://arxiv.org/pdf/2206.11342 .pdf
Abstract: Galactic massive lenses with large Einstein Radius should cause a measurable astrometric microlensing effect, i.e. the light centroid shift due to motion of two images. Such shift in the position of a background star due to microlensing was not included in the $Gaia$ astrometric model, therefore significant deviation should cause $Gaia$ astrometric parameters to be determined incorrectly. Here we studied one of the photometric microlensing events reported in the $Gaia$ DR3, GaiaDR3-ULENS-001, for which $Gaia$ poor goodness of fit and erroneous parallax could indicate presence of the astrometric microlensing signal. Based on the photometric microlensing model, we simulated $Gaia$ astrometric time-series with astrometric microlensing effect added. We found that including microlensing with the angular Einstein Radius of $\theta_{\rm E}$ from 2.23-2.81 mas reproduces well the astrometric quantities reported by $Gaia$. We estimate the mass of the lens to within 0.57-1.23 $M_\odot$ and its distance within 0.60-1.04 kpc, proposing the lens could be a nearby isolated white dwarf.

21 Jun22

Title: SpinSpotter: An Automated Algorithm for Identifying Stellar Rotation Periods With Autocorrelation Analysis
Authors: Rae J. Holcomb, Paul Robertson, Patrick Hartigan, Ryan J. Oelkers, Caleb Robinson
https://arxiv.org/pdf/2206.10629 .pdf
Abstract: Spinspotter is a robust and automated algorithm designed to extract stellar rotation periods from large photometric datasets with minimal supervision. Our approach uses the autocorrelation function (ACF) to identify stellar rotation periods up to one-third the observational baseline of the data. Our algorithm also provides a suite of diagnostics that describe the features in the ACF, which allows the user to fine-tune the tolerance with which to accept a period detection. We apply it to approximately 130,000 main-sequence stars observed by the Transiting Exoplanet Survey Satellite (TESS) at 2-minute cadence during Sectors 1-26, and identify rotation periods for 13,504 stars ranging from 0.4 to 14 days. We demonstrate good agreement between our sample and known values from the literature and note key differences between our population of rotators and those previously identified in the Kepler field, most notably a large population of fast-rotating M dwarfs. Our sample of rotating stars provides a data set with coverage of nearly the entire sky that can be used as a basis for future gyrochronological studies, and, when combined with proper motions and distances from Gaia, to search for regions with high densities of young stars, thus identifying areas of recent star formation and undiscovered moving group members. Our algorithm is publicly available for download and use on GitHub.

Title: Moving Groups Across Galactocentric Radius with Gaia DR3
Authors: Scott Lucchini, Emil Pellett, Elena D'Onghia, J. Alfonso L. Aguerri
https://arxiv.org/pdf/2206.10633 .pdf
Abstract: The kinematic plane of stars near the Sun has proven an indispensable tool for untangling the complexities of the structure of our Milky Way (MW). With ever improving data, numerous kinematic "moving groups" of stars have been better characterized and new ones continue to be discovered. Here we present an improved method for detecting these groups using MGwave, a new open-source 2D wavelet transformation code that we have developed. Our code implements similar techniques to previous wavelet software

Title: Important stellar perturbers found during the StePPeD database update based on Gaia EDR3 data
Authors: Piotr A. Dybczy\'nski, Filip Berski, Jakub Tokarek, Edyta Podlewska-Gaca, Krzysztof Langner, and Przemys{\l}aw Bartczak
https://arxiv.org/pdf/2206.11047 .pdf
Abstract: Context. In 2020, the initial version of the Stellar Potential Perturbers Database (StePPeD) was presented with the aim to deliver up-to-date information on the stars and stellar systems that may perturb a long-period comet motion. We used the minimal distance between a star and the Sun as a selecting tool when compiling a list of interesting objects with close encounters with the Solar System, and our selection for that study was based on Gaia DR2 data. Aims. When the Gaia EDR3 data release was published, it became necessary to update this database. Additionally, we performed Monte Carlo simulations to obtain uncertainties on the parameters of the closest approach to the Sun of each object. Methods. We recalculated the close approach parameters of all stars in the previous StePPeD release, which resulted in removing approximately one-third of the total. Then we searched for new candidates in the whole Gaia EDR3 catalogue. We also take into account the duplicity of the found stars and additionally searched for double stars passing near the Sun which had been overlooked in previous papers. We also found the necessary mass estimates for new objects and updated this information for previously selected stars. Results. After a careful checking of all the collected data, we composed a new list of 155 potential stellar perturbers of the long-period comet motion. We applied a new threshold of 2 pc for the minimum star-Sun distance. This list consists of 146 single stars and nine multiple systems. For each object, we also estimated the uncertainty of the parameters of their closest approach to the Sun. Among these stars, we found a new potential strong past perturber, HD 7977, and confirmed the plausibility of a similar action on the part of Gliese 710 in the future.

Title: An updated metal-dependent theoretical scenario for Classical Cepheids
Authors: Giulia De Somma, Marcella Marconi, Roberto Molinaro, Vincenzo Ripepi, Silvio Leccia, Ilaria Musella
https://arxiv.org/pdf/2206.11154 .pdf
Abstract: To properly quantify possible residual systematic errors affecting the Classical Cepheid distance scale, a detailed theoretical scenario is recommended. By extending the set of nonlinear convective pulsation models published for $Z=0.02$ \citep[][]{Desomma2020a} to $Z=0.004$, $Z=0.008$ and $Z=0.03$, we provide a detailed homogeneous nonlinear model grid taking into account simultaneous variations of the mass-luminosity relation, the efficiency of super-adiabatic convection and the chemical composition. The dependence of the inferred Period-Radius, Period-Mass-Radius, and Period-Mass-Luminosity-Temperature relations on the input parameters is discussed for both the Fundamental and First Overtone modes. The trend of the instability strip getting redder as the metallicity increases is confirmed for the additional ML assumptions and mixing length values. From the obtained multi-filter light curves, we derive mean magnitudes and colors and in turn Period-Luminosity-Color and Period-Wesenheit relations for each assumed chemical composition, mass-luminosity relation and efficiency of super-adiabatic convection. Application to a well-studied sample of Cepheids in the Large Magellanic Cloud allows us to constrain the dependence of the inferred distance modulus on the assumed mass-luminosity relation, and the inclusion of the metallicity term in the derivation of Period-Wesenheit relations allows us, for each assumed mass-luminosity relation, to predict the metallicity dependence of the Cepheid distance scale. The obtained metal-dependent Period-Wesenheit relations are compared with recent results in the literature and applied to a sample of Gaia Early Data Release 3 Galactic Cepheids with known metal abundances to derive individual parallaxes. The comparison of these predictions with Gaia results is finally discussed.

Title: Structural and Dynamical Analysis of the Quiescent Molecular Ridge in the Large Magellanic Cloud
Authors: Molly K. Finn, Remy Indebetouw, Kelsey E. Johnson, Allison H. Costa, C.-H. Rosie Chen, Akiko Kawamura, Toshikazu Onishi, J\"urgen Ott, Marta Sewi{\l}o, Kazuki Tokuda, Tony Wong, and Sarolta Zahorecz
https://arxiv.org/pdf/2206.11242 .pdf
Abstract: We present a comparison of low-J 13CO and CS observations of four different regions in the LMC -- the quiescent Molecular Ridge, 30 Doradus, N159, and N113, all at a resolution of $\sim3$ pc. The regions 30 Dor, N159, and N113 are actively forming massive stars, while the Molecular Ridge is forming almost no massive stars, despite its large reservoir of molecular gas and proximity to N159 and 30 Dor. We segment the emission from each region into hierarchical structures using dendrograms and analyze the sizes, masses, and linewidths of these structures. We find that the Ridge has significantly lower kinetic energy at a given size scale and also lower surface densities than the other regions, resulting in higher virial parameters. This suggests that the Ridge is not forming massive stars as actively as the other regions because it has less dense gas and not because collapse is suppressed by excess kinetic energy. We also find that these physical conditions and energy balance vary significantly within the Ridge and that this variation appears only weakly correlated with distance from sites of massive star formation such as R136 in 30 Dor, which is $\sim1$ kpc away. These variations also show only a weak correlation with local star formation activity within the clouds.

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