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.