Arcminute Field Research Articles

Bias versus variance when fitting multi-species molecular lines with a non-LTE radiative transfer model

Context. Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines. Aims. We study several hypotheses that enable robust estimations of the column densities and physical conditions when fitting one or two transitions per molecular species. We study the extent to which simplifying assumptions aimed at reducing the complexity of the problem introduce estimation biases and how to detect them. Methods. We focus on the CO and HCO+ isotopologues and analyze maps of a 50 square arcminutes field. We used the RADEX escape probability model to solve the statistical equilibrium equations and compute the emerging line profiles, assuming that all species coexist. Depending on the considered set of species, we also fixed the abundance ratio between some species and explored different values. We proposed a maximum likelihood estimator to infer the physical conditions and considered the effect of both the thermal noise and calibration uncertainty. We analyzed any potential biases induced by model misspecifications by comparing the results on the actual data for several sets of species and confirmed with Monte Carlo simulations. The variance of the estimations and the efficiency of the estimator were studied based on the Cramér-Rao lower bound. Results. Column densities can be estimated with 30% accuracy, while the best estimations of the volume density are found to be within a factor of two. Under the chosen model framework, the peak 12CO (1 – 0) is useful for constraining the kinetic temperature. The thermal pressure is better and more robustly estimated than the volume density and kinetic temperature separately. Analyzing CO and HCO+ isotopologues and fitting the full line profile are recommended practices with respect to detecting possible biases. Conclusions. Combining a non-local thermodynamic equilibrium model with a rigorous analysis of the accuracy allows us to obtain an efficient estimator and identify where the model is misspecified. We note that other combinations of molecular lines could be studied in the future.

Twin High-Resolution, High-Speed Imagers for the Gemini Telescopes: Instrument Description and Science Verification Results

Two new imaging instruments, ‘Alopeke and Zorro, were designed, built, and commissioned at the Gemini-North and Gemini-South telescopes in 2018 and 2019, respectively. Here we describe them and present the results from over a year of operation. The two identical instruments are based on the legacy of the DSSI (Differential Speckle Survey Instrument) instrument, successfully used for years at the WIYN and the Gemini telescopes in Hawaii and Chile. ‘Alopeke and Zorro are dual-channel imagers having both speckle (6.7″) and “wide-field” (∼1 arcminute) field-of-view options. They were built to primarily perform speckle interferometry providing diffraction-limited imagery at optical wavebands, yielding pixel scale uncertainties of ±0.21 mas, position angle uncertainties of ±0.7◦, and photometric uncertainties of Δm ± 0.02–0.04 magnitudes (for the blue and red channels, respectively) when run through the standard data reduction pipeline. One of their main scientific roles is the validation and characterization of exoplanets and their host stars as discovered by transit surveys such as the NASA Kepler, K2, and TESS missions. The limiting magnitude for speckle observations at Gemini can be quite faint (r ∼18 in good observing conditions) but typically the observed targets are brighter. The instruments can also function as conventional CCD imagers providing a 1 arc-minute field of view and allowing simultaneous two-color, high-speed time-series operation. These resident visitor instruments are remotely operable and are available for use by the community via the peer-reviewed proposal process.

WALOP-South: a four-camera one-shot imaging polarimeter for PASIPHAE survey. Paper I—optical design

The WALOP-South instrument will be mounted on the 1 m SAAO telescope in South Africa as part of the PASIPHAE program to carry out a linear imaging polarization survey of the Galactic polar regions in the optical band. Designed to achieve polarimetric sensitivity of $0.05~\%$ across a $35\times35$ arcminute field of view, it will be capable of measuring the Stokes parameters I, q and u in a single exposure in the SDSS-r broadband and narrowband filters between $0.5~{\mu}m - 0.7~{\mu}m$. For each measurement, four images of the full field corresponding to linear polarization angles of 0 deg, 45 deg, 90 deg and 135 deg in the instrument coordinate system will be created on four detectors from which the Stokes parameters can be found using differential photometry. In designing the optical system, major challenges included correcting for the dispersion introduced by large split angle Wollaston Prisms used as analysers as well as other aberrations from the entire field to obtain imaging quality PSF at the detector. We present the optical design of the WALOP-South instrument which overcomes these challenges and delivers near seeing limited PSFs for the entire field of view.

Science Commissioning of NIHTS: The Near-infrared High Throughput Spectrograph on the Lowell Discovery Telescope

The Near-Infrared High Throughput Spectrograph (NIHTS) is in operation on the 4.3 m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. NIHTS is a low-resolution spectrograph (R ∼ 200) that operates from 0.86 to 2.45 microns. NIHTS is fed by a custom dichroic mirror which reflects near-infrared wavelengths to the spectrograph and transmits the visible to enable simultaneous imaging with the Large Monolithic Imager (LMI), an independent visible wavelength camera. The combination of premier tracking and acquisition capabilities of the LDT, a several arcminutes field of view on LMI, and high spectral throughput on NIHTS enables novel studies of a number of astrophysical and planetary objects including Kuiper Belt Objects, asteroids, comets, low mass stars, and exoplanet hosts stars. We present a summary of NIHTS operations, commissioning, data reduction procedures with two approaches for the correction of telluric absorption features, and an overview of select science cases that will be pursued by Lowell Observatory, Northern Arizona University, and LDT partners.

Habitable-Zone Exoplanet Observatory baseline 4-m telescope: systems-engineering design process and predicted structural thermal optical performance

The Habitable-Zone Exoplanet Observatory Mission (HabEx) is one of four large missions under review for the 2020 astrophysics decadal survey. Its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby Sun-like stars. In addition, HabEx will perform a broad range of general astrophysics science enabled by a 115- to 1700-nm spectral range and 3 × 3 arcminute field of view. Critical to achieving its science goals, HabEx requires a large, ultrastable UV/optical/near-IR telescope. Using science-driven systems engineering, HabEx specified its baseline telescope to be a 4-m off-axis, unobscured three-mirror anastigmatic architecture with diffraction-limited performance at 400 nm, and wavefront stability on the order of a few tens of picometers. We summarize the systems-engineering approach to the baseline telescope assembly’s optomechanical design, including a discussion of how science requirements drive the telescope’s specifications. We also present structural thermal optical performance analysis showing that the baseline telescope structure meets its specified tolerances. We report new and updated analysis that is not in the HabEx final report.

Noise performance of the multiwavelength sub/millimeter inductance camera (MUSIC) detectors

MUSIC is a multi-band imaging camera that employs 2304 Microwave Kinetic Inductance Detectors (MKIDs) in 576 spatial pixels to cover a 14 arc-minute field of view, with each pixel simultaneously sensitive to 4 bands centered at 0.87, 1.04, 1.33, and 1.98 mm. In April 2012 the MUSIC instrument was commissioned at the Caltech Submillimeter Observatory with a subset of the full focal plane. We examine the noise present in the detector timestreams during observations taken in the first year of operation. We find that fluctuations in atmospheric emission dominate at long timescales (< 0.5 Hz), and fluctuations in the amplitude and phase of the probe signal due to readout electronics contribute significant 1/f-type noise at shorter timescales. We describe a method to remove the amplitude, phase, and atmospheric noise using the fact that they are correlated among carrier tones. After removal, the complex signal is decomposed, or projected, into dissipation and frequency components. White noise from the cryogenic HEMT amplifier dominates in the dissipation component. An excess noise is observed in the frequency component that is likely due to fluctuations in two-level system (TLS) defects in the device substrate. We compare the amplitude of the TLS noise with previous measurements.

Physical and chemical differentiation of the luminous star-forming region W49A

The massive and luminous star-forming region W49A is a well known Galactic candidate to probe the physical conditions and chemistry similar to those expected in external starburst galaxies. We aim to probe the physical and chemical structure of W49A on a spatial scale of ~0.8 pc based on the JCMT Spectral Legacy Survey, which covers the frequency range between 330 and 373 GHz. The wide 2x2 arcminutes field and the high spectral resolution of the HARP instrument on JCMT provides information on the spatial structure and kinematics of the cloud. For species where multiple transitions are available, we estimate excitation temperatures and column densities. We detected 255 transitions corresponding to 60 species in the 330-373 GHz range at the center position of W49A. Excitation conditions can be probed for 16 molecules. The chemical composition suggests the importance of shock-, PDR-, and hot core chemistry. Many molecular lines show a significant spatial extent across the maps including high density tracers (e.g. HCN, HNC, CS, HCO+) and tracers of UV-irradiation (e.g. CN and C2H). Large variations are seen between the sub-regions with mostly blue-shifted emission toward the Eastern tail, mostly red-shifted emission toward the Northern clump, and emission peaking around the expected source velocity toward the South-west clump. A comparison of column density ratios of characteristic species observed toward W49A to Galactic PDRs suggests that while the chemistry toward the W49A center is driven by a combination of UV-irradiation and shocks, UV-irradiation dominates for the Northern Clump, Eastern tail, and South-west clump regions. A comparison to a starburst galaxy and an AGN suggests similar C2H, CN, and H2CO abundances (with respect to the dense gas tracer 34CS) between the ~0.8 pc scale probed for W49A and the >1 kpc regions in external galaxies with global star-formation.

Astrometric performance of the Gemini multiconjugate adaptive optics system in crowded fields

The Gemini Multi-conjugate adaptive optics System (GeMS) is a facility instrument for the Gemini-South telescope. It delivers uniform, near-diffraction-limited image quality at near-infrared wavelengths over a 2 arcminute field of view. Together with the Gemini South Adaptive Optics Imager (GSAOI), a near-infrared wide field camera, GeMS/GSAOI's combination of high spatial resolution and a large field of view will make it a premier facility for precision astrometry. Potential astrometric science cases cover a broad range of topics including exo-planets, star formation, stellar evolution, star clusters, nearby galaxies, black holes and neutron stars, and the Galactic center. In this paper, we assess the astrometric performance and limitations of GeMS/GSAOI. In particular, we analyze deep, mono-epoch images, multi-epoch data and distortion calibration. We find that for single-epoch, un-dithered data, an astrometric error below 0.2 mas can be achieved for exposure times exceeding one minute, provided enough stars are available to remove high-order distortions. We show however that such performance is not reproducible for multi-epoch observations, and an additional systematic error of ~0.4 mas is evidenced. This systematic multi-epoch error is the dominant error term in the GeMS/GSAOI astrometric error budget, and it is thought to be due to time-variable distortion induced by gravity flexure.

Astrometric orbit of a low-mass companion to an ultracool dwarf

Little is known about the existence of extrasolar planets around ultracool dwarfs. Furthermore, binary stars with Sun-like primaries and very low-mass binaries composed of ultracool dwarfs show differences in the distributions of mass ratio and orbital separation that can be indicative of distinct formation mechanisms. Using FORS2/VLT optical imaging for high precision astrometry we are searching for planets and substellar objects around ultracool dwarfs to investigate their multiplicity properties for very low companion masses. Here we report astrometric measurements with an accuracy of two tenths of a milli-arcsecond over two years that reveal orbital motion of the nearby L1.5 dwarf DENIS-P J082303.1-491201 located at 20.77 +/- 0.08 pc caused by an unseen companion that revolves about its host on an eccentric orbit in 246.4 +/- 1.4 days. We estimate the L1.5 dwarf to have 7.5 +/- 0.7 % of the Sun's mass that implies a companion mass of 28 +/- 2 Jupiter masses. This new system has the smallest mass ratio (0.36 +/- 0.02) of known very low-mass binaries with characterised orbits. With this discovery we demonstrate 200 micro-arcsecond astrometry over an arc-minute field and over several years that is sufficient to discover sub-Jupiter mass planets around ultracool dwarfs. We also show that the achieved parallax accuracy of < 0.4 % makes it possible to remove distance as a dominant source of uncertainty in the modelling of ultracool dwarfs.

THE FILLING FACTOR-RADIUS RELATION FOR 58 H II REGIONS ACROSS THE DISK OF NGC 6946

Using the OSIRIS tunable narrow band imager on the 10.4m GTC (La Palma) we have mapped the SAB(rs)cd galaxy NGC 6946 over a 7.3x7.5 square arcminutes field in the emission lines of the [SII]\lambda\lambda, 6717, 6731 doublet, and in H\alpha. From these maps we have produced catalogs of the H\alpha luminosities and effective radii of 557 HII regions across the disk, and derived the [SII] emission line ratios of 370 of these. The H\alpha observations were used to derive the mean luminosity-weighted electron densities for the regions of the sample, while the [SII] line ratios allowed us to derive values of the in situ electron densities in the denser zones from which the major fraction of the radiation in these lines is emitted, for 58 of the regions. This is by far the largest data set of its kind for a single galaxy. A classical two phase model is used to derive the filling factors of the regions. We find that although the mean electron density decreases with the square root of the radius of the regions, the in situ density is essentially independent of this radius. Thus the filling factor falls systematically, as the radius and the luminosity of the regions increases, with a power law of exponent -2.23 between filling factor and radius. These measurements should enhance the perspectives for more refined physical models of HII regions.

SpIOMM and SITELLE: Wide-field Imaging FTS for the Study of Galaxy Evolution

AbstractSpIOMM, a wide-field Imaging Fourier Transform Spectrometer attached to the Mont Mégantic 1.6-m telescope, is capable of obtaining the visible spectrum of every source of light in a 12 arcminute field of view, with a spectral resolution ranging from R = 1 (wide-band image) to R = 25 000, resulting in 1.7 million spectra with a spatial resolution of one arcsecond. SITELLE will be a similar instrument attached to the Canada-France-Hawaii telescope, and will be in operation in early 2013. We present a short description of these instruments and illustrate their capabilities to study nearby galaxies with the results of a data cube of M51.

Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observations

Photon-dominated regions (PDRs) are expected to show a layered structure in molecular abundances and emerging line emission, which is sensitive to the physical structure of the region as well as the UV radiation illuminating it. We aim to study this layering in the Orion Bar, a prototypical nearby PDR with a favorable edge-on geometry. We present new maps of 2 by 2 arcminute fields at 14-23 arcsecond resolution toward the Orion Bar in the SO 8_8-9_9, H2CO 5_(1,5)-4_(1,4), 13CO 3-2, C2H 4_(9/2)-3_(7/2) and 4_(7/2)-3_(5/2), C18O 2-1 and HCN 3-2 transitions. The data reveal a clear chemical stratification pattern. The C2H emission peaks close to the ionization front, followed by H2CO and SO, while C18O, HCN and 13CO peak deeper into the cloud. A simple PDR model reproduces the observed stratification, although the SO emission is predicted to peak much deeper into the cloud than observed while H2CO is predicted to peak closer to the ionization front than observed. In addition, the predicted SO abundance is higher than observed while the H2CO abundance is lower than observed. The discrepancies between the models and observations indicate that more sophisticated models, including production of H2CO through grain surface chemistry, are needed to quantitatively match the observations of this region.

The Morphological Content of 10 EDisCS Clusters at 0.5 &lt;z&lt; 0.8

We describe Hubble Space Telescope (HST) imaging of 10 of the 20 ESO Distant Cluster Survey (EDisCS) fields. Each ~40 square arcminute field was imaged in the F814W filter with the Advanced Camera for Surveys Wide Field Camera. Based on these data, we present visual morphological classifications for the ~920 sources per field that are brighter than I_auto=23 mag. We use these classifications to quantify the morphological content of 10 intermediate-redshift (0.5 < z < 0.8) galaxy clusters within the HST survey region. The EDisCS results, combined with previously published data from seven higher redshift clusters, show no statistically significant evidence for evolution in the mean fractions of elliptical, S0, and late-type (Sp+Irr) galaxies in clusters over the redshift range 0.5 < z < 1.2. In contrast, existing studies of lower redshift clusters have revealed a factor of ~2 increase in the typical S0 fraction between z=0.4 and z=0, accompanied by a commensurate decrease in the Sp+Irr fraction and no evolution in the elliptical fraction. The EDisCS clusters demonstrate that cluster morphological fractions plateau beyond z ~ 0.4. They also exhibit a mild correlation between morphological content and cluster velocity dispersion, highlighting the importance of careful sample selection in evaluating evolution. We discuss these findings in the context of a recently proposed scenario in which the fractions of passive (E,S0) and star-forming (Sp,Irr) galaxies are determined primarily by the growth history of clusters.

A radio and infrared exploration around Cygnus X-3

To confirm, or rule out, the possible hot spot nature of two previously detected radio sources in the vicinity of the Cygnus X-3 microquasar. We present the results of a radio and near infrared exploration of the several arc-minute field around the well known galactic relativistic jet source Cygnus X-3 using the Very Large Array and the Calar Alto 3.5~m telescope. The data this paper is based on do not presently support the hot spot hypothesis. Instead, our new observations suggest that these sources are most likely background or foreground objects. Actually, none of them appears to be even barely extended as would be expected if they were part of a bow shock structure. Our near infrared observations also include a search for extended emission in the Bracket $\gamma$ (2.166 $\mu$m) and $H_{2}$ (2.122 $\mu$m) lines as possible tracers of shocked gas in the Cygnus X-3 surroundings. The results were similarly negative and the corresponding upper limits are reported.

The Space Density of Redshift 5.7 Lyα Emitters: First Constraints from a Multislit Windows Search

We present results from a blind, spectroscopic search for redshift 5.7 LyA emission-line galaxies at Keck I. Using a band-limiting filter and custom slitmask, the LRIS detector was covered with low resolution spectra in the 8100 - 8250 A atmospheric window which contains no bright night sky emission lines. Nine objects with line fluxes greater than our flux limit of 6e-18 erg/s/cm2 were found in the ~5.1 square arcminute field. Follow up observations indicate none of these are z=5.7 LyA emitters -- a result which places strong limits on evolution scenarios for LyA emitters between redshift 3 and redshift 5.7. In particular, the paucity of z=5.7 LyA emitters raises the question of whether the LyA -selected population plays a significant role in maintaining the ionization of the intergalactic medium at z = 5.7. We argue that if the escape fraction of LyA from galaxies is less than $0.4 f_{LyC}$, where $f_{LyC}$ is the escape fraction of Lyman continuum photons, then the star formation rate in the \lya emitting population is high enough in the no-evolution model (our upper limit) to maintain the ionization of the IGM at z=5.7.

Two Thousand X-ray Stars in the Central 20 pc of the Galaxy

We present a catalog of 2357 point sources detected during 620 ks of Chandra observations of the 17 × 17 arcminutes field around Sgr A*. This field encompasses a physical area of 40 × 40 parsecs at 8 kpc. The completeness limit of the sample at the Galactic Center is ≈1031 erg s−1 (2–8 keV), while the detection limit is an order of magnitude lower. We estimate that 20–100 of the observed sources are background AGN. The spectra of the majority of the Galactic Center sources are very hard and are best described by a power law (E−Γ) with photon index Γ < 1. Such hard spectra are only seen from magnetically accreting white dwarfs (polars and intermediate polars) and neutron stars (pulsars). The spatial density of the Galactic Center X-ray sources falls off as R−2, similar to that of the infrared stars in the field. This highlights the possibility that these X-ray sources can be used to study the history of star formation at the Galactic Center. The log(N) − log(S) distribution of the Galactic Center sources is extremely steep, such that point sources could account for all of the previously reported diffuse emission if the number counts extend down to 1029 erg s−1 with the same slope. However, there are numerous fllamentary structures in the field that also contribute to the total flux, which implies that the luminosity distribution between 2–8 keV must turn over below our completeness limit.

A DeepChandraCatalog of X‐Ray Point Sources toward the Galactic Center

(abridged) We present a catalog of 2357 point sources detected during 590 ks of Chandra observations of the 17-by-17 arcminute field around Sgr A*. This field encompasses a physical area of 40 by 40 pc at a distance of 8 kpc. The completeness limit of the sample at the Galactic center is 10^{31} erg s^{-1} (2.0--8.0 keV), while the detection limit is an order of magnitude lower. The 281 sources detected below 1.5 keV are mainly in the foreground of the Galactic center, while comparisons to the Chandra deep fields at high Galactic latitudes suggest that only about 100 of the observed sources are background AGN. The surface density of absorbed sources (not detected below 1.5 keV) falls off as 1/theta away from Sgr A*, in agreement with the distribution of stars in infrared surveys. Point sources brighter than our completeness limit produce 10% of the flux previously attributed to diffuse emission. The log(N)-log(S) distribution of the Galactic center sources is extremely steep (power-law slope alpha = 1.7). If this distribution extends down to a flux of 10^{-17} erg cm^{-1} s^{-1} (10^{29} erg s^{-1} at 8 kpc, 2.0--8.0 keV) with the same slope, then point sources would account for all of the previously reported diffuse emission. Therefore, the 2.0--8.0 keV luminosity distribution must flatten between 10^{29} - 10^{31} erg s^{-1}. Finally, the spectra of more than half of the Galactic center sources are very hard, and can be described by a power law ($E^{-Gamma}) with photon index Gamma < 1. Such hard spectra have been seen previously only from magnetically accreting white dwarfs and wind-accreting neutron stars, suggesting that there are large numbers of these systems in our field.

The mass of the Pleiades

A membership catalogue for the Pleiades is divided into four mass bins, and a tidally truncated King profile is fitted to each bin with good agreement with the data. The tidal radius of the cluster is found to be 13.1 pc, and the total mass of the cluster down to the stellar limit is calculated to be 735 M. The spread of stars in each bin, as well as the relaxation and crossing times, shows the Pleiades to be an approximately relaxed cluster with equilibrium between the density and velocity distributions. The cluster kinetic energy and binding energy are consistent with the virial theorem, indicating no large unseen population of brown dwarfs. However, the 1 σ errors in the cluster parameters provide an upper limit to the mass of any brown dwarf population of 131 M, which would show up in deep CCD surveys as ≤ 5.5 brown dwarfs per 10 × 10 arcminute field in the cluster centre.

CN and CH band strengths of 283 47 tucanae giants.

view Abstract Citations (51) References (60) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CN and CH band strengths of 283 47 tucanae giants. Briley, Michael M. Abstract To characterize further the star-to-star CN and CH band strength variations observed among 47 Tucanae giants, CCD B, V and DDO photometry has been obtained for a 14 x 12 arcminute field centered 8.5 arcminutes NE of the cluster center. From this sample, C(4142) and C(4245) colors have been used to characterize the CN and CH bands of 283 cluster giants down to V = 16 (M_v ~ +2.5). The analysis examines four aspects of the present data: 1) Observed C(4142) and C(4245) colors are compared against model DDO colors as a function of luminosity (evolutionary state). As opposed to the more metal-poor clusters, little change in the range and distribution of C and N is seen with evolutionary state on the 47 Tuc red giant branch (RGB) over the 4 magnitudes observed. 2) The ratio of CN-weak to CN-strong stars appears to remain the same both before and after the luminosity function ''bump'' believed to signal the onset of RGB mixing. 3) The spatial distribution of CN-strong and CN-weak stars is determined for 294 red giants exterior to 4 arc minutes from the cluster center. The distribution of CN among stars exterior to 13 - 20 arc minutes is clearly biased toward CN-weak stars. The DDO colors are also consistent with the suggestion that CN-strong stars dominate the central 0 - 5 arc minutes. This result confirms earlier studies which suggest a radial trend in the CN distribution of 47 Tuc. 4) An examination of the positions of horizontal branch (HB) stars on the color-magnitude diagram reveals that the CN-strong HB stars are on average, about 0.05 mags more luminous in V and tend to be bluer than their CN-weak counterparts. This result appears consistent with the idea that the CN-strong stars of 47 Tuc have mixed small amounts of additional He into their envelopes during RGB ascent, as outlined by \cite{alan97}. It is therefore suggested that the bulk C and N abundance differences observed among 47 Tuc giants are not likely the result of a progressive deep mixing of CN-cycle material to the stellar surface during the later phases of RGB ascent, but are rather the signature of an earlier process. That some deep dredge-up may have occurred among the evolved giants cannot be ruled out, and is consistent with the HB morphology described below as well as with previously observed (12}C/({13)) C ratios, but the extent of such mixing is clearly less than that believed to occur in stars of more metal-poor clusters. Publication: The Astronomical Journal Pub Date: September 1997 DOI: 10.1086/118535 Bibcode: 1997AJ....114.1051B Keywords: STARS: HORIZONTAL-BRANCH; GLOBULAR CLUSTERS: INDIVIDUAL 47 TUCANAE; GALAXY: EVOLUTION full text sources ADS | data products SIMBAD (5)

A catalogue of stars in the field of the X-ray transient source KS 1947+300

Abstract A catlogue of astrometric coordinates and photographic magnitudes of 188 stars in the 6 arcminute field around the X-ray source KS 1947+300 (a = 19 h 49 m 34 s , δ = +30°12'22″, FK5, J2000) is given. Two charts with radii 40' and 6' showing stars around KS 1947+300 are presented. Some stars from this catalogue could be of interest for astrophysical investigation with large telescopes and CCD-detectors in order to identify and to study this X-ray source.