scholarly journals NIR counterparts to ULXs (III): completing the photometric survey and selected spectroscopic results★

2020 ◽  
Vol 497 (1) ◽  
pp. 917-932 ◽  
Author(s):  
K M López ◽  
M Heida ◽  
P G Jonker ◽  
M A P Torres ◽  
T P Roberts ◽  
...  
Keyword(s):  
Binary Systems ◽  
Near Infrared ◽  
Absolute Magnitude ◽  
Stellar Clusters ◽  
Stellar Spectra ◽  
Stellar Cluster ◽  
Cluster Candidate ◽  
Spatially Extended ◽  
Binary Evolution

ABSTRACT We present results from the remaining sources in our search for near-infrared (NIR) candidate counterparts to ultraluminous X-ray sources (ULXs) within ≃10 Mpc. We observed 23 ULXs in 15 galaxies and detected NIR candidate counterparts to 6 of them. Two of these have an absolute magnitude consistent with a single red supergiant (RSG). Three counterparts are too bright for an RSG and spatially extended, and thus we classify them as stellar clusters. The other candidate is too faint for an RSG. Additionally, we present the results of our NIR spectroscopic follow-up of five sources: four originally classified as RSG and one as a stellar cluster on the basis of previous photometry. The stellar cluster candidate is actually a nebula. Of the four RSG candidates, one source has a broad H α emission line redshifted by ∼z = 1, making it a background active galactic nucleus (AGN). Two other sources show stellar spectra consistent with them being RSGs. The final RSG candidate is too faint to classify, but does not show strong (nebular) emission lines in its spectrum. After our search for NIR counterparts to 113 ULXs, where we detected a candidate counterpart for 38 ULXs, we have spectroscopically confirmed the nature of 12: 5 sources are nebulae, 1 source is not classified, 1 source is an AGN, and 5 are RSGs. These possible five ULX–RSG binary systems would constitute ${\simeq} (4 \pm 2){{\ \rm per\ cent}}$ of the observed ULXs, a fraction almost four times larger than what was predicted by binary evolution simulations.

scholarly journals Comparing ALMA, VLT, and HST data for Massive, Young Clusters in Grand-Design Spirals

2015 ◽  
Vol 12 (S316) ◽  
pp. 141-142
Author(s):  
Preben Grosbøl ◽  
Horacio Dottori
Keyword(s):  
Near Infrared ◽  
Detailed Comparison ◽  
Stellar Clusters ◽  
Giant Molecular Clouds ◽  
Cluster Complexes ◽  
Stellar Cluster ◽  
Grand Design ◽  
Nearby Galaxies ◽  
Massive Clusters ◽  
Co Emission

AbstractA population of young, massive stellar cluster complexes with near-infrared (NIR) colors indicating high extinction (i.e. Av ~ 7m) was identified on HAWK-I/VLT images of several nearby, grand-design spiral galaxies. Models suggest that they are very young cluster complexes still embedded in a dust/gas envelope which will be expelled after 5-7 Myr. This type of very young, embedded clusters are not seen in optical studies using HST data.A detailed comparison of HST and HAWK-I images was done to better understand the discrepancy between the optical and NIR detection of stellar clusters in nearby galaxies. More than 70% of the NIR clusters are located close to dust lanes which would make an optical detection difficult. A comparison of the ALMA CO(1-0)-map of NGC 4321 and the young, massive clusters shows that 60% of them have CO emission within 2“ indicating a correlation between giant molecular clouds and formation of massive clusters.

scholarly journals massclean (MASSive CLuster Evolution and ANalysis Package): description, tests, and results

2009 ◽  
Vol 5 (S266) ◽  
pp. 511-515
Author(s):  
Bogdan Popescu ◽  
M. M. Hanson
Keyword(s):  
Monte Carlo ◽  
Near Infrared ◽  
Age Determination ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Cluster Evolution ◽  
Analysis Package ◽  
Determination Methods ◽  
Mass Dependent ◽  
Massive Cluster

Abstractmassclean is a new, sophisticated and robust stellar cluster image and photometry simulation package. This package can create color–magnitude diagrams and standard FITS images in any of the traditional optical and near-infrared bands based on cluster characteristics input by the user, including but not limited to distance, age, mass, radius and extinction. At the limit of very distant, unresolved clusters, we have checked the integrated colors created in massclean against those from other simple stellar population models, with consistent results. Because the algorithm populates the cluster with a discrete number of tenable stars, it can be used as part of a Monte Carlo method to derive the probabilistic range of characteristics (integrated colors, for example) consistent with a given cluster mass and age. We present the first ever mass-dependent integrated colors as a function of age, derived from over 100 000 Monte Carlo runs, which can be used to improve the current age-determination methods for stellar clusters.

scholarly journals The evolution of luminous red nova AT 2017jfs in NGC 4470

2019 ◽  
Vol 625 ◽  
pp. L8 ◽  
Author(s):  
A. Pastorello ◽  
T.-W. Chen ◽  
Y.-Z. Cai ◽  
A. Morales-Garoffolo ◽  
Z. Cano ◽  
...  
Keyword(s):  
Near Infrared ◽  
Absolute Magnitude ◽  
Emission Lines ◽  
Late Time ◽  
Absorption Bands ◽  
Common Envelope ◽  
Bolometric Luminosity ◽  
Link Type ◽  
Second Peak

We present the results of our photometric and spectroscopic follow-up of the intermediate-luminosity optical transient AT 2017jfs. At peak, the object reaches an absolute magnitude of Mg = −15.46 ± 0.15 mag and a bolometric luminosity of 5.5 × 1041 erg s−1. Its light curve has the double-peak shape typical of luminous red novae (LRNe), with a narrow first peak bright in the blue bands, while the second peak is longer-lasting and more luminous in the red and near-infrared (NIR) bands. During the first peak, the spectrum shows a blue continuum with narrow emission lines of H and Fe II. During the second peak, the spectrum becomes cooler, resembling that of a K-type star, and the emission lines are replaced by a forest of narrow lines in absorption. About 5 months later, while the optical light curves are characterized by a fast linear decline, the NIR ones show a moderate rebrightening, observed until the transient disappears in solar conjunction. At these late epochs, the spectrum becomes reminiscent of that of M-type stars, with prominent molecular absorption bands. The late-time properties suggest the formation of some dust in the expanding common envelope or an IR echo from foreground pre-existing dust. We propose that the object is a common-envelope transient, possibly the outcome of a merging event in a massive binary, similar to NGC 4490−2011OT1.

scholarly journals A New Galactic Wolf-Rayet Star in Centaurus

2011 ◽  
Vol 2011 ◽  
pp. 1-6
Author(s):  
A. Roman-Lopes
Keyword(s):  
Near Infrared ◽  
Galactic Center ◽  
Absolute Magnitude ◽  
Infrared Emission ◽  
Point Sources ◽  
Cluster Candidate ◽  
Colour Distribution ◽  
Band Spectra ◽  
Rayet Star ◽  
Extended Emission

I communicate the detection of a new Galactic Wolf-Rayet star (WR60a) in Centaurus. The H- and K-band spectra of WR60a show strong carbon near-infrared emission lines, characteristic of Wolf-Rayet stars of the WC5-7 subtype. Adopting mean absolute magnitude MK and mean intrinsic (J-KS) and (H-KS) colours, it was found that WR60a suffers a mean visual extinction of 3.8±1.3 magnitudes, being located at a probable heliocentric distance of 5.2±0.8 Kpc, which for the related Galactic longitude (l=312) puts this star probably in the Carina-Sagittarius arm at about 5.9 kpc from the Galactic center. I searched for clusters in the vicinity of WR60a and in principle found no previously known clusters in a search radius region of several tens arcminutes. The detection of a well-isolated WR star induced us to seek for some still unknown cluster, somewhere in the vicinity of WR60a. From inspection of 5.8 μm and 8.0 μm Spitzer/IRAC GLIMPSE images of the region around the new WR star, strong mid-infrared extended emission at about 13.5 arcmin south-west of WR60a was found. The study of the H-KS colour distribution of point sources associated with the extended emission reveals the presence of a new Galactic cluster candidate probably formed by at least 85 stars.

scholarly journals SN 2019muj – a well-observed Type Iax supernova that bridges the luminosity gap of the class

2020 ◽  
Vol 501 (1) ◽  
pp. 1078-1099
Author(s):  
Barnabás Barna ◽  
Tamás Szalai ◽  
Saurabh W Jha ◽  
Yssavo Camacho-Neves ◽  
Lindsey Kwok ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectroscopic Data ◽  
Near Infrared ◽  
Early Time ◽  
Absolute Magnitude ◽  
Good Match ◽  
Chemical Abundance ◽  
Synthetic Spectra ◽  
Short Rise Time

ABSTRACT We present early-time (t < +50 d) observations of SN 2019muj (=ASASSN-19tr), one of the best-observed members of the peculiar SN Iax class. Ultraviolet and optical photometric and optical and near-infrared spectroscopic follow-up started from ∼5 d before maximum light [tmax(B) on $58707.8$ MJD] and covers the photospheric phase. The early observations allow us to estimate the physical properties of the ejecta and characterize the possible divergence from a uniform chemical abundance structure. The estimated bolometric light-curve peaks at 1.05 × 1042 erg s−1 and indicates that only 0.031 M⊙ of 56Ni was produced, making SN 2019muj a moderate luminosity object in the Iax class with peak absolute magnitude of $M_\rm {V} = -16.4$ mag. The estimated date of explosion is t0 = $58698.2$ MJD and implies a short rise time of trise = 9.6 d in B band. We fit of the spectroscopic data by synthetic spectra, calculated via the radiative transfer code tardis. Adopting the partially stratified abundance template based on brighter SNe Iax provides a good match with SN 2019muj. However, without earlier spectra, the need for stratification cannot be stated in most of the elements, except carbon, which is allowed to appear in the outer layers only. SN 2019muj provides a unique opportunity to link extremely low-luminosity SNe Iax to well-studied, brighter SNe Iax.

scholarly journals Secular dynamics of binaries in stellar clusters – I. General formulation and dependence on cluster potential

2019 ◽  
Vol 488 (4) ◽  
pp. 5489-5511 ◽  
Author(s):  
Chris Hamilton ◽  
Roman R Rafikov
Keyword(s):  
Binary Systems ◽  
Dynamical Evolution ◽  
Compact Object ◽  
Companion Paper ◽  
Orbital Evolution ◽  
Oort Cloud ◽  
Stellar Clusters ◽  
Dimensional Parameter ◽  
Stellar Cluster ◽  
Secular Dynamics

AbstractOrbital evolution of binary systems in dense stellar clusters is important in a variety of contexts: origin of blue stragglers, progenitors of compact object mergers, millisecond pulsars, and so on. Here we consider the general problem of secular evolution of the orbital elements of a binary system driven by the smooth tidal field of an axisymmetric stellar cluster (globular, nuclear, etc.) in which the binary orbits. We derive a secular Hamiltonian (averaged over both the inner Keplerian orbit of the binary and its outer orbit within the cluster) valid to quadrupole order for an arbitrary cluster potential and explore its characteristics. This doubly averaged ‘tidal’ Hamiltonian depends on just two parameters, which fully absorb the information about the background cluster potential and the binary’s orbit within it: a dimensional parameter A setting the secular time-scale, and a dimensionless parameter Γ which determines the phase portrait of the binary’s inner orbital evolution. We examine the dependence of A and Γ on cluster potential (both spherical and axisymmetric) and on the binary orbit within the cluster. Our theory reproduces known secular results – such as Lidov–Kozai evolution and the effect of the Galactic tide on Oort Cloud comets – in appropriate limits, but is more general. It provides a universal framework for understanding dynamical evolution of various types of binaries driven by the smooth tidal field of any axisymmetric potential. In a companion paper we provide a detailed exploration of the resulting orbital dynamics.

scholarly journals Deducing the Milky Way's Massive Cluster Population

2009 ◽  
Vol 5 (H15) ◽  
pp. 794-794
Author(s):  
M. M. Hanson ◽  
B. Popescu ◽  
S. S. Larsen ◽  
V. D. Ivanov
Keyword(s):  
Near Infrared ◽  
Galactic Plane ◽  
Mass Function ◽  
False Negatives ◽  
Stellar Cluster ◽  
Daunting Task ◽  
Imaging Simulation ◽  
Infrared Surveys ◽  
Massive Cluster

AbstractRecent near-infrared surveys of the galactic plane have been used to identify new massive cluster candidates. Follow up study indicates about half are not true, gravitationally-bound clusters. These false positives are created by high density fields of unassociated stars, often due to a sight-line of reduced extinction. What is not so easy to estimate is the number of false negatives, clusters which exist but are not currently being detected by our surveys. In order to derive critical characteristics of the Milky Way's massive cluster population, such as cluster mass function and cluster lifetimes, one must be able to estimate the characteristics of these false negatives. Our group has taken on the daunting task of attempting such an estimate by first creating the stellar cluster imaging simulation program, MASSCLEAN. I will present our preliminary models and methods for deriving the biases of current searches.

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

scholarly journals Formation of supermassive black holes in galactic nuclei – I. Delivering seed intermediate-mass black holes in massive stellar clusters

2021 ◽  
Vol 502 (2) ◽  
pp. 2682-2700
Author(s):  
Abbas Askar ◽  
Melvyn B Davies ◽  
Ross P Church
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Stellar Clusters ◽  
Orbital Eccentricity ◽  
Intermediate Mass ◽  
Stellar Cluster ◽  
Wave Emission ◽  
Gas Accretion ◽  
Intermediate Mass Black Holes

ABSTRACT Supermassive black holes (SMBHs) are found in most galactic nuclei. A significant fraction of these nuclei also contains a nuclear stellar cluster (NSC) surrounding the SMBH. In this paper, we consider the idea that the NSC forms first, from the merger of several stellar clusters that may contain intermediate-mass black holes (IMBHs). These IMBHs can subsequently grow in the NSC and form an SMBH. We carry out N-body simulations of the simultaneous merger of three stellar clusters to form an NSC, and investigate the outcome of simulated runs containing zero, one, two, and three IMBHs. We find that IMBHs can efficiently sink to the centre of the merged cluster. If multiple merging clusters contain an IMBH, we find that an IMBH binary is likely to form and subsequently merge by gravitational wave emission. We show that these mergers are catalyzed by dynamical interactions with surrounding stars, which systematically harden the binary and increase its orbital eccentricity. The seed SMBH will be ejected from the NSC by the recoil kick produced when two IMBHs merge, if their mass ratio q ≳ 0.15. If the seed is ejected then no SMBH will form in the NSC. This is a natural pathway to explain those galactic nuclei that contain an NSC but apparently lack an SMBH, such as M33. However, if an IMBH is retained then it can seed the growth of an SMBH through gas accretion and tidal disruption of stars.

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