Star TYC Research Articles

Results of Observation of the Occultation of the Star TYC 5254-00839-1 by Triton in 2022 at the Sanglokh Observatory

Results of Observation of the Occultation of the Star TYC 5254-00839-1 by Triton in 2022 at the Sanglokh Observatory

Lessons from the apparent peculiar nature of the star TYC 6544‐3483‐1

AbstractWe report a radio and optical study of the star TYC 6544‐3483‐1 originally selected as a follow‐up target in the course of our efforts to cross‐identify Galactic high‐energy sources. The star by itself finally turned out to be a very ordinary main‐sequence star despite the initial expectations that apparently pointed to the contrary. We found that its, at first glance, exotic properties arise as a combined consequence of the limited angular resolution of the radio and optical databases being used. Our preliminary astrophysical interpretation was strongly hampered by the presence of unexpected optical variables inside both the photometric and background apertures. While such an ill‐posed situation is not a frequent one, we believe that our experience is worth sharing with the community to raise a word of caution and help to avoid similar misleading results, especially when dealing with modern TESS data.

Результаты пулковских базисных наблюдений покрытия звезды TYC 1932-469-1 астероидом 87 Sylvia 29 октября 2019

On 29 October 2019 the Pulkovo Observatory observed the occultations of the the star TYC 1932-469-1 (Gaia DR2 Source id = 679856115656562048) by asteroid 87 Sylvia. The observation was made with the one-meter reflector telescope. Simultaneously, the asteroid 87 Sylvia was surveyed using the MTM-500M telescope located at the GAO RAS Mountain Astronomical Station where a visible close approach was observed. Based on this example, the article discusses the possibility of improving the accuracy of ground based astrometric observations and obtaining «instantaneous» parallaxes to refine the ephemeris by means of baseline observations of the occultations and the apparent close approaches. The paper demonstrates that the method allows to obtain the coordinate accuracy of the order of 0.010 arcsec, which in this case gives a parallax of the asteroid with the accuracy of 0".03 arcsec. Comparison with the existing ephemerides showed a high degree of convergence.

WASP Lightcurves: Red Noise and a Cautionary Tale

A recent RNAAS, analyzing data from the WASP survey, claimed that the star TYC 2623-1439-1 underwent a 1% dimming that lasted for 11 days, and interpreted this as a transit of a wide-orbiting planet. However, WASP survey data is prone to red noise. I show that the same dip is seen on a nearby star, and conclude that it is a pipeline artifact rather than being real.

X-Ray Emission from Candidate Stellar Merger Remnant TYC 2597-735-1 and Its Blue Ring Nebula

Abstract Tight binary or multiple-star systems can interact through mass transfer and follow vastly different evolutionary pathways than single stars. The star TYC 2597-735-1 is a candidate for a recent stellar merger remnant resulting from a coalescence of a low-mass companion with a primary star a few thousand years ago. This violent event is evident in a conical outflow (“Blue Ring Nebula”) emitting in UV light and surrounded by leading shock filaments observed in Hα and UV emission. From Chandra data, we report the detection of X-ray emission from the location of TYC 2597-735-1 with a luminosity log ( L X / L bol ) = − 5.5 . Together with a previously reported period of ~14 days, this indicates ongoing stellar activity and the presence of strong magnetic fields on TYC 2597-735-1. Supported by stellar evolution models of merger remnants, we interpret the inferred stellar magnetic field as dynamo action associated with a newly formed convection zone in the atmosphere of TYC 2597-735-1, though internal shocks at the base of an accretion-powered jet cannot be ruled out. We speculate that this object will evolve into an FK Com–type source, i.e., a class of rapidly spinning magnetically active stars for which a merger origin has been proposed but for which no relic accretion or large-scale nebula remains visible. We also detect likely X-ray emission from two small regions close to the outer shock fronts in the Blue Ring Nebula, which may arise from inhomogeneities either in the circumstellar medium or in the mass and velocity distribution in the merger-driven outflow.

Highly Structured Inner Planetary System Debris around the Intermediate Age Sun-like Star TYC 8830 410 1

Abstract We present a detailed characterization of the extremely dusty main-sequence star TYC 8830 410 1. This system hosts inner planetary system dust (T dust ≈ 300 K) with a fractional infrared luminosity of ∼1%. Mid-infrared spectroscopy reveals a strong, mildly crystalline solid-state emission feature. TYC 8830 410 1 (spectral type G9 V) has a 49.5″ separation M4-type companion comoving and co-distant with it, and we estimate a system age of ∼600 Myr. TYC 8830 410 1 also experiences “dipper”-like dimming events as detected by the All-Sky Automated Survey for Supernovae, Transiting Exoplanet Survey Satellite, and characterized in more detail with the Las Cumbres Observatory Global Telescope. These recurring eclipses suggest at least one roughly star-sized cloud of dust orbits the star in addition to assorted smaller dust structures. The extreme properties of the material orbiting TYC 8830 410 1 point to dramatic dust-production mechanisms that likely included something similar to the giant impact event thought to have formed the Earth–Moon system, although hundreds of millions of years after such processes are thought to have concluded in the solar system. TYC 8830 410 1 holds promise to deliver significant advances in our understanding of the origin, structure, and evolution of extremely dusty inner planetary systems.

A joint occultation and speckle investigation of the binary star TYC 1947-290-1 and of the asteroid (87) Sylvia

ABSTRACT We report on the occultation of the star TYC 1947-290-1 by the asteroid (87) Sylvia. While asteroidal occultations occurring at fixed professional-level locations are relatively rare and are only recently starting to be observed with sufficiently high time resolution and sensitivity, they have the capability to measure sub-milliarcsecond angular diameters. The event described here was especially outstanding because the star was revealed to be a small-separation binary (≈10 mas at discovery), while at the same time the asteroid is not only one of the largest in size but it also has two satellite moons. The observations were carried out at the Russian 6-m telescope in 2019 December, and initially consisted of both a fast photometric series of the occultation itself, as well as of extensive speckle interferometry of the star and asteroid in the time immediately before and after the occultation. Subsequently, we obtained speckle data of TYC 1947-290-1 over a period of 1 yr after the event. We are able to present a detailed study of the binary star including measurements of the angular diameter of the stellar components, their geometry, and relative fluxes over several bandpasses, and to provide an accurate determination of the size of (87) Sylvia. We emphasize that we have been able to obtain the smallest ever directly measured stellar diameter, below the 100 micro-arcsecond level. Our data are also suitable for imaging of the asteroid by speckle holography, a task which we intend to carry out in a separate work.

Observation of the grazing occultation of the star TYC 1280-832-1 by the asteroid (486) Cremona

Observation of the grazing occultation of the star TYC 1280-832-1 by the asteroid (486) Cremona

Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1*

Abstract Even though tens of directly imaged companions have been discovered in the past decades, the number of directly confirmed multiplanet systems is still small. Dynamical analysis of these systems imposes important constraints on formation mechanisms of these wide-orbit companions. As part of the Young Suns Exoplanet Survey we report the detection of a second planetary-mass companion around the 17 Myr-old, solar-type star TYC 8998-760-1 that is located in the Lower Centaurus Crux subgroup of the Scorpius–Centaurus association. The companion has a projected physical separation of 320 au and several individual photometric measurements from 1.1 to 3.8 microns constrain a companion mass of 6 ± 1 M Jup, which is equivalent to a mass ratio of q = 0.57 ± 0.10% with respect to the primary. With the previously detected 14 ± 3 M Jup companion that is orbiting the primary at 160 au, TYC 8998-760-1 is the first directly imaged multiplanet system that is detected around a young, solar analog. We show that circular orbits are stable, but that mildly eccentric orbits for either/both components (e > 0.1) are chaotic on gigayear timescales, implying in situ formation or a very specific ejection by an unseen third companion. Due to the wide separations of the companions TYC 8998-760-1 is an excellent system for spectroscopic and photometric follow-up with space-based observatories such as the James Webb Space Telescope.

The Young Suns Exoplanet Survey: Detection of a wide-orbit planetary-mass companion to a solar-type Sco-Cen member

ABSTRACT The Young Suns Exoplanet Survey consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15 ± 3 Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211–6456207) that is located at a distance of 94.6 ± 0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to $1.00\pm 0.02\, \mathrm{M}_{\odot }$ and an age of $16.7\pm 1.4\,$ Myr. The companion TYC 8998-760-1 b is detected at a projected separation of 1.71″, which implies a projected physical separation of 162 au. Photometric measurements ranging from Y to M band provide a mass estimate of $14\pm 3\, M_\mathrm{jup}$ by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than $12\, M_\mathrm{jup}$ and farther than 12 au away from the host. Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this ‘young Sun’.

TYC 8606-2025-1: a mild barium star surrounded by the ejecta of a very late thermal pulse

ABSTRACT We report the discovery of a spiral-like nebula with the Wide-field Infrared Survey Explorer and the results of optical spectroscopy of its associated star TYC 8606-2025-1 with the Southern African Large Telescope. We find that TYC 8606-2025-1 is a G8 III star of $\approx 3 \, \rm \, M_{\odot }$, showing a carbon depletion by a factor of 2 and a nitrogen enhancement by a factor of 3. We also derived an excess of s-process elements, most strongly for barium, which is a factor of 3 overabundant, indicating that TYC 8606-2025-1 is a mild barium star. We thereby add a new member to the small group of barium stars with circumstellar nebulae. Our radial velocity measurements indicate that TYC 8606-2025-1 has an unseen binary companion. The advanced evolutionary stage of TYC 8606-2025-1, together with the presence of a circumstellar nebula, implies an initial mass of the companion of also about $3 \, \rm \, M_{\odot }$. We conclude that the infrared nebula, due to its spiral shape, and because it has no optical counterpart, was ejected by the companion as a consequence of a very late thermal pulse, during about one orbital rotation.

KELT-22Ab: A Massive, Short-Period Hot Jupiter Transiting a Near-solar Twin

We present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright ($V\sim 11.1$) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period of $P = 1.3866529 \pm 0.0000027 $ days, a radius of $R_{P} = 1.285_{-0.071}^{+0.12}~R_{J}$, and a relatively large mass of $M_{P} = 3.47_{-0.14}^{+0.15}~ M_{J}$. The star has $R_{\star} = 1.099_{-0.046}^{+0.079}~ R_{\odot}$, $M_{\star} = 1.092_{-0.041}^{+0.045}~ M_{\odot}$, ${T_{\rm eff}\,} = 5767_{-49}^{+50}~$ K, ${\log{g_\star}} = 4.393_{-0.060}^{+0.039}~$ (cgs), and [m/H] = $+0.259_{-0.083}^{+0.085}~$, and thus, other than its slightly super-solar metallicity, appears to be a near solar twin. Surprisingly, KELT-22A exhibits kinematics and a Galactic orbit that are somewhat atypical for thin disk stars. Nevertheless, the star is rotating quite rapidly for its estimated age, shows evidence of chromospheric activity, and is somewhat metal rich. Imaging reveals a slightly fainter companion to KELT-22A that is likely bound, with a projected separation of 6\arcsec ($\sim$1400 AU). In addition to the orbital motion caused by the transiting planet, we detect a possible linear trend in the radial velocity of KELT-22A suggesting the presence of another relatively nearby body that is perhaps non-stellar. KELT-22Ab is highly irradiated (as a consequence of the small semi-major axis of $a/R_{\star} = 4.97$), and is mildly inflated. At such small separations, tidal forces become significant. The configuration of this system is optimal for measuring the rate of tidal dissipation within the host star. Our models predict that, due to tidal forces, the semi-major axis of KELT-22Ab is decreasing rapidly, and is thus predicted to spiral into the star within the next Gyr.

TYC 3637-1152-1 – A high amplitude δ Scuti star with peculiar pulsational properties

In some δ Scuti stars, only one or two radial modes are excited (usually the fundamental mode and/or first overtone mode) and the observed peak-to-peak amplitudes exceed 0.3 mag (V). These stars are known as High Amplitude Delta Scuti (HADS) variables.We here present a detailed photometric and spectroscopic analysis of the HADS star TYC 3637-1152-1. We have derived a metallicity close to solar, a spectral type of F4 V and an age of logt=9.1. Employing archival time series data from different sources, two frequencies f0 = 10.034 c/d and f1 = 12.681 c/d and their harmonics and linear combinations were identified. The period ratio of f0/f1=0.791 puts this star into a peculiar position in the Petersen diagram, from which we conclude that TYC 3637-1152-1 is a unique object with peculiar pulsational properties that indicate a transitional state between HADS stars pulsating in the fundamental and first overtone modes and stars pulsating in higher overtones.

KELT-19Ab: A P ∼ 4.6-day Hot Jupiter Transiting a Likely Am Star with a Distant Stellar Companion

Abstract We present the discovery of the giant planet KELT-19Ab, which transits the moderately bright ( ) A8V star TYC 764-1494-1 with an orbital period of 4.61 days. We confirm the planetary nature of the companion via a combination of radial velocities, which limit the mass to ( ), and a clear Doppler tomography signal, which indicates a retrograde projected spin–orbit misalignment of degrees. Global modeling indicates that the K host star has and . The planet has a radius of and receives a stellar insolation flux of , leading to an inferred equilibrium temperature of K assuming zero albedo and complete heat redistribution. With a , the host is relatively slowly rotating compared to other stars with similar effective temperatures, and it appears to be enhanced in metallic elements but deficient in calcium, suggesting that it is likely an Am star. KELT-19A would be the first detection of an Am host of a transiting planet of which we are aware. Adaptive optics observations of the system reveal the existence of a companion with late-G9V/early-K1V spectral type at a projected separation of . Radial velocity measurements indicate that this companion is bound. Most Am stars are known to have stellar companions, which are often invoked to explain the relatively slow rotation of the primary. In this case, the stellar companion is unlikely to have caused the tidal braking of the primary. However, it may have emplaced the transiting planetary companion via the Kozai–Lidov mechanism.

The GAPS Programme with HARPS-N at TNG

Context. Identification of planetary companions of giant stars is made difficult because of the astrophysical noise, that may produce radial velocity (RV) variations similar to those induced by a companion. On the other hand any stellar signal is wavelength dependent, while signals due to a companion are achromatic. Aims. Our goal is to determine the origin of the Doppler periodic variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the presence of a substellar companion. Methods. Several methods have been used to exclude the stellar origin of the observed signal including detailed analysis of activity indicators and bisector and the analysis of the photometric light curve. Finally we have conducted an observational campaign to monitor the near infrared (NIR) RV with GIANO at the TNG in order to verify whether the NIR amplitude variations are comparable with those observed in the visible. Results. Both optical and NIR RVs show consistent variations with a period at 101 days and similar amplitude, pointing to the presence of a companion orbiting the target. The main orbital properties obtained for our giant star with a derived mass of M=0.97+-0.03M_sun are M_Psini=10.78+-0.12MJ;P=101.54+-0.05days;e=0.28+-0.01 and a=0.422+-0.009AU. The chemical analysis shows a significant enrichment in the abundance of Nai, Mgi, Ali and S i while the rest of analyzed elements are consistent with the solar value demonstrating that the chemical composition corresponds with an old K giant (age = 10.1 Gyr) belonging to local thick disk. Conclusions. We conclude that the substellar companion hypothesis for this K giant is the best explanation for the observed periodic RV variation. This study also shows the high potential of multi-wavelength RV observations for the validation of planet candidates.

KELT-12b: A P ∼ 5 day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star

Abstract We announce the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting the mildly evolved, V = 10.64 host star TYC 2619-1057-1. We followed up the initial transit signal in the KELT-North survey data with precise ground-based photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the host star has = 6279 ± 51 K, = 3.89 ± 0.05, [Fe/H] = , = , and = 2.37 ± 0.17 . The planetary companion has = 0.95 ± 0.14 , = , = , and density = g cm−3, making it one of the most inflated giant planets known. Furthermore, for future follow-up, we report a high-precision time of inferior conjunction in of 2,457,083.660459 ± 0.000894 and period of days. Despite the relatively large separation of ∼0.07 au implied by its ∼5.03-day orbital period, KELT-12b receives significant flux of erg s−1 cm−2 from its host. We compare the radii and insolations of transiting gas giant planets around hot ( K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite to search for inflated gas giants in longer-period orbits.

KELT-16b: A Highly Irradiated, Ultra-short Period Hot Jupiter Nearing Tidal Disruption

Abstract We announce the discovery of KELT-16b, a highly irradiated, ultra-short period hot Jupiter transiting the relatively bright (V = 11.7) star TYC 2688-1839-1/KELT-16. A global analysis of the system shows KELT-16 to be an F7V star with K, , , , and . The planet is a relatively high-mass inflated gas giant with , , density g cm−3, surface gravity , and K. The best-fitting linear ephemeris is and day. KELT-16b joins WASP-18b, −19b, −43b, −103b, and HATS-18b as the only giant transiting planets with P < 1 day. Its ultra-short period and high irradiation make it a benchmark target for atmospheric studies by the Hubble Space Telescope, Spitzer, and eventually the James Webb Space Telescope. For example, as a hotter, higher-mass analog of WASP-43b, KELT-16b may feature an atmospheric temperature–pressure inversion and day-to-night temperature swing extreme enough for TiO to rain out at the terminator. KELT-16b could also join WASP-43b in extending tests of the observed mass–metallicity relation of the solar system gas giants to higher masses. KELT-16b currently orbits at a mere ∼1.7 Roche radii from its host star, and could be tidally disrupted in as little as a few ×105 years (for a stellar tidal quality factor of ). Finally, the likely existence of a widely separated bound stellar companion in the KELT-16 system makes it possible that Kozai–Lidov (KL) oscillations played a role in driving KELT-16b inward to its current precarious orbit.

Does the chemical signature of TYC 8442–1036–1 originate from a rotating massive star that died in a faint explosion?

Context. We have recently investigated the origin of chemical signatures observed in Galactic halo stars by means of a stochastic chemical evolution model. We have found that rotating massive stars are a promising way to explain several signatures observed in these fossil stars. Aims. In the present paper we discuss how the extremely metal-poor halo star TYC 8442-1036-1, for which we have now obtained detailed abundances from VLT-UVES spectra, fits into the framework of our previous work. Methods. We apply a standard 1D LTE analysis to the spectrum of this star. We measure the abundances of 14 chemical elements; for Na, Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni and Zn we compute the abundances using equivalent widths; for C, Sr and Ba we obtain the abundances by means of synthetic spectra generated by MOOG. Results. We find an abundance of [Fe/H]= $-$3.5 $\pm$0.13 dex based on our high resolution spectrum; this points to an iron content lower by a factor of three (0.5 dex) compared to the one obtained by a low resolution spectrum. The star has a [C/Fe] = 0.4 dex, and it is not carbon enhanced like most of the stars at this metallicity. Moreover, this star lies in the plane [Ba/Fe] vs. [Fe/H] in a relatively unusual position, shared by a few others galactic halo stars that is only marginally explained by our past results. Conclusions. The comparison of the model results with the chemical abundance characteristics of this group of stars can be improved if we consider in our model the presence of faint supernovae coupled with rotating massive stars. These results seem to imply that rotating massive stars and faint supernovae scenarios are complementary to each other, and are both required in order to match the observed chemistry of the earliest phases of the chemical enrichment of the Universe.

Discovery of an unusual bright eclipsing binary with the longest known period: TYC 2505-672-1/MASTER OT J095310.04+335352.8

We report on the MASTER Global Robotic Net discovery of an eclipsing binary, MASTER OT J095310.04+335352.8, previously known as unremarkable star TYC 2505-672-1, which displays extreme orbital parameters. The orbital period P=69.1 yr is more than 2.5 times longer than that of epsilon-Aurigae, which is the previous record holder. The light curve is characterized by an extremely deep total eclipse with a depth of more than 4.5 mag, which is symmetrically shaped and has a total duration of 3.5 yrs. The eclipse is essentially gray. The spectra acquired with the Russian 6 m BTA telescope both at minimum and maximum light mainly correspond to an M0-1III--type red giant, but the spectra taken at the bottom of eclipse show small traces of a sufficiently hot source. The observed properties of this system can be better explained as the red giant eclipsed by a large cloud (the disk) of small particles surrounding the invisible secondary companion.

Tracking Advanced Planetary Systems (TAPAS) with HARPS-N

Context. Stars that have evolved-off the Main Sequence are crucial in expanding the frontiers of knowledge on exoplanets toward higher stellar masses, and to constrain star-planet interaction mechanisms. These stars, however suffer from intrinsic activity that complicates the interpretation of precise radial velocity measurement and are often avoided in planet searches. We have, over the last 10 years, monitored about 1000 evolved stars for radial velocity variations in search for low-mass companions under the Penn State - Toru\'n Centre for Astronomy Planet Search with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision meassurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo. Aims. To detect planetary systems around evolved stars, to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidences of star-planet interaction processes. Methods. We have obtained for TYC 1422-614-1 69 epochs of precise radial velocity measurements collected over 3651 days with the Hobby-Eberly Telescope, and 17 epochs of ultra precise HARPS-N data collected over 408 days. We have complemented these RV data with photometric time-series from the All Sky Automatic Survey archive. Results. We report the discovery of a multiple planetary system around the evolved K2 giant star TYC 1422-614-1. The system orbiting the 1.15 M$_\odot$ star is composed of a planet with mass m$sin i$=2.5 M$_J$ in a 0.69 AU orbit, and a planet/brown dwarf with m$sin i$=10 M$_J$ in a 1.37 AU orbit. The multiple planetary system orbiting TYC 1422-614-1 is the first finding of the TAPAS project, a HARPS-N monitoring of evolved planetary systems identified with the Hobby-Eberly Telescope.