Post-asymptotic Giant Branch Stars Research Articles

Modelling of the post-asymptotic giant branch phase as a tool to understand asymptotic giant branch evolution and nucleosynthesis

ABSTRACT We study a sample of single Galactic post-asymptotic giant branch (post-AGB) stars with known surface chemical composition. Gaia EDR3 and Gaia DR3 parallaxes have enabled accurate determinations of the luminosities of these objects, thus making it possible to characterize them in terms of their initial masses, chemical compositions, and progenitor ages. We used extant evolutionary sequences of asymptotic giant branch (AGB) stars produced using the ATON stellar evolutionary code extended to the post-AGB phase, specifically for this study. The luminosity and surface carbon abundance together prove to be the most valuable indicator of the previous evolution and nucleosynthetic history of the star, particularly regarding the efficiency of mixing mechanisms and the growth of the core. This analysis allows us to place the post-AGB sample into classes based on their evolutionary history on the AGB. This includes low-mass objects that evolved as M-type stars without third dredge-up, carbon stars, and intermediate-mass AGB stars with hot bottom burning (HBB). Additionally, our analysis reveals that AGB nucleosynthesis is not homogeneous, even for stars with similar initial masses and metallicities. The approach of using observations of post-AGB stars to constrain AGB and post-AGB models shed new light on still debated issues related to the AGB evolution, such as the threshold mass required to become a C-star, the minimum mass for HBB and the amount of carbon that can be accumulated in the surface regions of the star during the AGB lifetime, as well as deep mixing experienced during the red giant branch phase.

Understanding dust production and mass loss in the AGB phase using post-AGB stars in the Magellanic Clouds

Context. The asymptotic giant branch (AGB) phase of evolution in low- and intermediate-mass stars is governed by poorly understood physical mechanisms, such as convection, mixing, dust production and mass loss, which play a crucial role in determining the internal structure and the evolution of these stars. The spectra of post-asymptotic giant branch (post-AGB) stars hold critical chemical fingerprints that serve as exquisite tracers of the evolution, nucleosynthesis, and dust production during the AGB phase. Aims. We aim to understand the variation in the surface chemistry that occurs during the AGB phase by analysing results from observations of single post-AGB stars in the Magellanic Clouds. We also aim to reconstruct dust-formation processes, which are active in the circumstellar envelope of AGB stars, occurring towards the end of the AGB phase and during the subsequent course of evolution when contraction to the post-AGB has begun. Methods. We study likely single post-AGB sources in the Magellanic Clouds that exhibit a double-peaked (shell-type) spectral energy distribution (SED). We interpret their SED by comparing with results from radiative transfer calculations to derive the luminosity and the dust content of the individual sources. Additionally, we compare the observationally derived stellar parameters and the photospheric chemical abundances of the target sample with results from stellar evolution modelling of AGB and post-AGB stars. This allows for the characterization of the individual sources in terms of the initial mass and formation epoch of the progenitors. The theoretically derived dust mineralogy and optical depth is used to assess when dust formation ceases and to determine the propagation velocity of the dust-gas system during post-AGB evolution. Results. We find that amongst our target sample of 13 likely single post-AGB stars with shell-type SED, eight objects are carbon stars descending from ∼1−2.5 M⊙ progenitors. Five of the 13 objects are of lower mass, descending from M < 1 M⊙ stars. Based on the dust mineralogy, we find that these five stars are surrounded by silicate dust, and thus failed to become carbon stars. The dust optical depth and the luminosity of the stars are correlated, owing to the faster evolutionary timescale of brighter stars, which makes the dusty layer closer to the central object. From our detailed analysis of the SEDs, we deduce that the dust currently observed around post-AGB stars was released after the onset of the central star contraction and an increase in the effective temperature to ∼3500−4000 K.

The 3.3 μm Infrared Emission Feature Profile in HD 44179

HD 44179 is a postasymptotic giant branch star with a biconical nebula known as the Red Rectangle. It shows the 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 μm infrared emission features (commonly known as the polycyclic aromatic hydrocarbon (PAH) emission bands and the Aromatic Infrared Bands). Previous observations of HD 44179 showed that the width of the 3.3 μm emission feature was narrower within 2″ of HD 44179 and wider further away from the star. This was interpreted as an indication that the 3.3 μm emission feature arises from two types of PAHs with spatially varying relative abundances. With new observations of HD 44179 taken with the NASA Infrared Telescope Facility we find that the width of the 3.3 μm emission feature profile is not narrower on HD 44179 and conclude that there is no evidence for two spatially varying components.

Common Envelope Mass Ejection in Evolved Stars: Modeling the Dust Emission from Post-RGB Stars in the LMC

Common envelope (CE) systems are the result of Roche lobe overflow in interacting binaries. The subsequent evolution of the CE, its ejection, and the formation of dust in its ejecta while the primary is on the red giant branch (RGB) gives rise to a recently identified evolutionary class—dusty post-RGB stars. Their spectral energy distributions (SEDs) suggest that their mass-ejecta are similar to dusty post-asymptotic giant branch (post-AGB) stars. We have modeled the SEDs of a select sample of post-RGB and post-AGB stars in the Large Magellanic Cloud, quantified the total dust mass (and gas mass assuming gas-to-dust ratio) in the disks and shells and set constraints on the dust grain compositions and sizes. We find that the shell masses in the post-RGBs are generally less than those in post-AGBs, with the caveat that substantial amount of mass in both types of objects may lie in cold, extended shells. Our models suggest that circumstellar disks, when present, are geometrically thick structures with a substantial opening angle, consistent with numerical simulations of CE evolution (CEE). Comparison of our model dust masses with the predictions of dust production during CEE on the RGB suggest that CEE occurred near or at the tip of the RGB for our post-RGB sources. A surprising result is that some post-RGB stars harbor carbon-rich dust, believed to form when C/O > 1, e.g., following triple-alpha nucleosynthesis and third dredge-up events in AGB stars. This anomaly strengthens the hypothesis that dusty post-RGBs are born in binary systems.

Zwicky Transient Facility and Globular Clusters: Calibration of the gr-band Absolute Magnitudes for the Yellow Post-asymptotic-giant-branch Stars

We present the first absolute calibration for the yellow post-asymptotic-giant-branch (PAGB) stars in the g and r band based on time-series observations from the Zwicky Transient Facility. These absolute magnitudes were calibrated using four yellow PAGB stars (one nonvarying star and three Type II Cepheids) located in the globular clusters. We provide two calibrations of the gr-band absolute magnitudes for the yellow PAGB stars, by using an arithmetic mean and a linear regression. We demonstrate that the linear regression provides a better fit to the g-band absolute magnitudes for the yellow PAGB stars. These calibrated gr-band absolute magnitudes have a potential to be used as Population II distance indicators in the era of time-domain synoptic sky surveys.

Spatially resolved properties of early-type group-dominant galaxies with MUSE: gas content, ionization mechanisms, and metallicity gradients

ABSTRACT With the goal of a thorough investigation of the ionized gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). These data allowed us to study the spatially resolved warm gas properties, including the morphology of the ionized gas, EW(H α), and kinematics as well as the gas-phase metallicity (12 + log(O/H)) of these systems. In order to distinguish between different ionization mechanisms, we used the emission-line ratios [O iii]/H β and [N ii]/H α in the BPT diagrams and EW(H α). We find that the ionization sources in our sample have variable impacts at different radii; central regions are more influenced by low-luminosity active galactic nuclei, while extended regions of low-ionization nuclear emission-line region-like emission are ionized by other mechanisms with post-asymptotic giant branch stars photoionization likely contributing significantly. We classified our sample into three H α +[N ii] emission morphology types. We calculate the gas-phase metallicity assuming several methods and ionization sources. In general, 12 + log(O/H) decreases with radius from the centre for all galaxies, independently of nebular morphology type, indicating a metallicity gradient in the abundance profiles. Interestingly, the more extended filamentary structures and all extranuclear star-forming regions present shallow metallicity gradients. Within the uncertainties these extended structures can be considered chemically homogeneous. We suggest that group-dominant galaxies in our sample likely acquired their cold gas in the past as a consequence of one or more mechanisms, e.g. gas-clouds or satellite mergers/accretion and/or cooling flows that contribute to the growth of the ionized gas structures.

A census of post-AGB stars in Gaia DR3: evidence for a substantial population of Galactic post-RGB stars

ABSTRACT This paper presents the first census of Galactic post-asymptotic giant branch (post-AGB) stars in the Hertzsprung–Russell (HR) diagram. We combined Gaia DR3 parallax-based distances with extinction corrected integrated fluxes and derived luminosities for a sample of 185 stars that had been proposed to be post-AGB stars in the literature. The luminosities allow us to create an HR diagram containing the largest number of post-AGB candidate objects to date. A significant fraction of the objects fall outside the typical luminosity range as covered by theoretical evolutionary post-AGB tracks as well as observed for planetary nebula central stars. These include massive evolved supergiants and lower luminosity objects. Here, we highlight the fact that one-third of the post-AGB candidates are underluminous and we identify these with the recently recognized class of post-red giant branch objects thought to be the result of binary evolution.

Chemical abundance of LINER galaxies – metallicity calibrations based on SDSS-IV MaNGA

ABSTRACT The ionizing source of low-ionization nuclear emission-line regions (LINERs) is uncertain. Because of this, an empirical relation to determine the chemical abundances of these objects has not been proposed. In this work, for the first time, we derived two semi-empirical calibrations based on photoionization models to estimate the oxygen abundance of LINERS as a function of the N2 and O3N2 emission-line intensity ratios. These relations were calibrated using oxygen abundance estimations obtained by comparing the observational emission-line ratios of 43 LINER galaxies (taken from the MaNGA survey) and grids of photoionization models built with the cloudy code assuming post-asymptotic giant branch stars with different temperatures. We found that the oxygen abundance of LINERs in our sample is in the $\rm 8.48 \: \lesssim \: 12+log(O/H) \: \lesssim 8.84$ range, with a mean value of $\rm 12+\log (O/H)=8.65$. We recommend the use of the N2 index to estimate the oxygen abundances of LINERs, since the calibration with this index presented a much smaller dispersion than the O3N2 index. In addition, the estimated metallicities are in good agreement with those derived by extrapolating the disc oxygen abundance gradients to the centre of the galaxies showing that the assumptions of the models are suitable for LINERs. We also obtained a calibration between the logarithm of the ionization parameter and the [O iii]/[O ii] emission-line ratio.

Post-AGB Stars as Tracers of AGB Nucleosynthesis: An Update

The chemical evolution of galaxies is governed by the chemical yields from stars, and here we focus on the important contributions from asymptotic giant branch (AGB) stars. AGB nucleosynthesis is, however, still riddled with complexities. Observations from post-asymptotic giant branch (post-AGB) stars serve as exquisite tools to quantify and understand AGB nucleosynthesis. In this contribution, we review the invaluable constraints provided by post-AGB stars with which to study AGB nucleosynthesis, especially the slow neutron capture nucleosynthesis (i.e., the s-process).

Sakurai’s Object revisited: new laboratory data for carbonates and melilites suggest the carrier of 6.9-μm excess absorption is a carbonate

ABSTRACTWe present new room-temperature 1100–1800-cm−1 spectra of melilite silicates and 600–2000-cm−1 spectra of three randomly orientated fine-grained carbonates to determine the possible carrier(s) of a 6.9-μm absorption feature observed in a variety of dense astronomical environments, including young stellar objects and molecular clouds. We focus on the low-mass post-asymptotic giant branch star Sakurai’s Object, which has been forming substantial quantities of carbonaceous dust since an eruptive event in the 1990s. Large melilite grains cannot be responsible for the 6.9-μm absorption feature because the similarly shaped feature in the laboratory spectrum was produced by very low (0.1 per cent by mass) carbonate contamination, which was not detected at other wavelengths. Due to the high band strength of the 6.9-μm feature in carbonates, we conclude that carbonates carry the astronomical 6.9-μm feature. Replacement of melilite with carbonates in models of Sakurai’s Object improves fits to the 6–7-μm Spitzer spectra without significantly altering other conclusions of Bowey’s previous models except that there is no link between the feature and the abundance of melilite in meteorites. With magnesite (MgCO3), the abundance of 25-μm-sized SiC grains is increased by 10–50 per cent and better constrained. The mass of carbonate dust is similar to the mass of polycyclic aromatic hydrocarbon dust. Existing experiments suggest that carbonates are stable below 700 K; however, it is difficult to ascertain the applicability of these experiments to astronomical environments, and more studies are required.

A Study of the Dusty Disks and Shells around Post-RGB Stars in the LMC

A new class of dusty post-Red Giant Branch (post-RGB) stars has recently been identified in the Magellanic Clouds. Their spectral energy distributions (SEDs) suggest that their mass-ejecta are similar to dusty post-Asymptotic Giant Branch (post-AGB) stars. We modeled the SEDs of a select sample of post-RGB and post-AGB stars in the Large Magellanic Cloud (LMC), quantified the total dust mass in the disks and shells and set rough constraints on the dust grain compositions and sizes. The shells were significantly more massive than the disks. Our models suggest that circumstellar disks, when present, are geometrically thick with a substantial opening angle, which is consistent with numerical simulations of CE evolution (CEE). Comparison of our model dust mass values with the predictions of dust production during CEE on the RGB suggest that CEE occurred near or at the tip of the RGB for the post-RGB sources in our sample. Amorphous silicate emission features at 10 and 18 μm are seen in the model spectra of several post-RGBs. A surprising result is that the ejected dust in certain post-RGB sources appears to be carbon-rich, thus, providing independent support for the hypothesis of binary interactions leading to the formation of dusty post-RGB objects.

Chemistry of nebulae around binary post-AGB stars: A molecular survey of mm-wave lines

Context. There is a class of binary post-asymptotic giant branch (post-AGB) stars that exhibit remarkable near-infrared excess. Such stars are surrounded by Keplerian or quasi-Keplerian disks, as well as extended outflows composed of gas escaping from the disk. This class can be subdivided into disk- and outflow-dominated sources, depending on whether it is the disk or the outflow that represents most of the nebular mass, respectively. The chemistry of this type of source has been practically unknown thus far. Aims. Our objective is to study the molecular content of nebulae around binary post-AGB stars that show disks with Keplerian dynamics, including molecular line intensities, chemistry, and abundances. Methods. We focused our observations on the 1.3, 2, 3 mm bands of the 30mIRAM telescope and on the 7 and 13 mm bands of the 40 m Yebes telescope. Our observations add up ~600 h of telescope time. We investigated the integrated intensities of pairs of molecular transitions for CO, other molecular species, and IRAS fluxes at 12, 25, and 60 μm. Additionally, we studied isotopic ratios, in particular 17O/18O, to analyze the initial stellar mass, as well as 12CO/13CO, to study the line and abundance ratios. Results. We present the first single-dish molecular survey of mm-wave lines in nebulae around binary post-AGB stars. We conclude that the molecular content is relatively low in nebulae around binary post-AGB stars, as their molecular lines and abundances are especially weaker compared with AGB stars. This fact is very significant in those sources where the Keplerian disk is the dominant component of the nebula. The study of their chemistry allows us to classify nebulae around AC Her, the Red Rectangle, AI CMi, R Sct, and IRAS 20056+1834 as O-rich, while that of 89 Her is probably C-rich. The calculated abundances of the detected species other than CO are particularly low compared with AGB stars. The initial stellar mass derived from the 17O/18O ratio for the Red Rectangle and 89 Her is compatible with the central total stellar mass derived from previous mm-wave interferometric maps. The very low 12CO/13CO ratios found in binary post-AGB stars reveal a high 13CO abundance compared to AGB and other post-AGB stars.

Luminosities and Masses of Single Galactic Post-asymptotic Giant Branch Stars with Distances from Gaia EDR3: The Revelation of an s-process Diversity

Abstract Post-asymptotic giant branch (AGB) stars are exquisite probes of AGB nucleosynthesis. However, the previous lack of accurate distances jeopardized comparison with theoretical AGB models. The Gaia Early Data Release 3 (Gaia EDR3) has now allowed for a breakthrough in this research landscape. In this study, we focus on a sample of single Galactic post-AGBs for which chemical abundance studies were completed. We combined photometry with geometric distances to carry out a spectral energy distribution (SED) analysis and derive accurate luminosities. We subsequently determined their positions on the Hertzsprung-Russell (HR) diagram and compared this with theoretical post-AGB evolutionary tracks. While most objects are in the post-AGB phase of evolution, we found a subset of low-luminosity objects that are likely to be in the post-horizontal branch phase of evolution, similar to AGB-manqué objects found in globular clusters. Additionally, we also investigated the observed bimodality in the s-process enrichment of Galactic post-AGB single stars of similar T eff and metallicities. This bimodality was expected to be a direct consequence of luminosity with the s-process rich objects having evolved further on the AGB. However, we find that the two populations, the s-process enriched and non-enriched, have similar luminosities (and hence initial masses), revealing an intriguing chemical diversity. For a given initial mass and metallicity, AGB nucleosynthesis appears inhomogeneous and sensitive to other factors, which could be mass loss, along with convective and non-convective mixing mechanisms. Modeling individual objects in detail will be needed to investigate which parameters and processes dominate the photospheric chemical enrichment in these stars.

The Missing Lead: Developments in the Lead (Pb) Discrepancy in Intrinsically s-Process Enriched Single Post-AGB Stars

Lead (Pb) is predicted to have large over-abundances with respect to other s-process elements in Asymptotic Giant Branch (AGB) stars, especially of low metallicities. However, our previous abundance studies of s-process enriched post-Asymptotic Giant Branch (post-AGB) stars in the Galaxy and the Magellanic Clouds show a discrepancy between observed and predicted Pb abundances. For the subset of post-AGB stars with low metallicities the determined upper limits based on detailed chemical abundance studies are much lower than what is predicted. Recent theoretical studies have pointed to the occurrence of the i-process to explain the observed chemical patterns, especially of Pb. A major development, in the observational context, is the release of the GAIA EDR3 parallaxes of the post-AGBs in the Galaxy, which has opened the gateway to systematically studying the sample of stars as a function of current luminosities (which can be linked to their initial masses). In this paper, we succinctly review the Pb discrepancy in post-AGB stars and present the latest observational and theoretical developments in this research landscape.

Laboratory Observation of C and O Emission Lines of the White Dwarf H1504+65-like Atmosphere Model

Abstract White dwarfs play important roles in stellar evolution and help us gauge the age of our galaxy. The white dwarf H1504+65, the hottest known post-asymptotic giant branch star, is peculiar due to its C- and O-rich but He- and H- deficient atmosphere whose composition cannot be well predicted by current stellar evolution models. The analysis of the elemental abundance and the benchmark of stellar atmospheric models depends heavily on spectral data under cosmic conditions, which are currently extremely scarce. We created a well-defined, uniform, relatively large-scale ∼millimeter plasma sample in the laboratory with a temperature and a C/O ratio similar to those of H1504+65’s atmosphere. The emission spectra with high precision in the range of 10–80 nm were obtained and identified according to databases such as NIST and Kelly. A detailed comparison between our emission lines and the Chandra-observed white dwarf H1504+65 atmosphere’s absorption lines was performed. The stongly isolated O VI lines in the range of 10–13 nm are observed in both cases. We observed a wealth of O V lines in the range of 13–14 nm that cannot be well identified or predicted by models due to the weak flux and also probably due to the blending effect of Fe group elements in the Chandra spectrum. Long-wavelength lines ranging from 14 to 80 nm, which are not observed in the Chandra spectrum because of the high interstellar neutral hydrogen column density, show abundant O IV-V, C IV lines, and strong O VI lines. Moreover, the intensities of the lines at 62.973 and 17.216 nm are analyzed to characterize the plasma temperature.

Observations of the Bright Star in the Globular Cluster 47 Tucanae (NGC 104)

Abstract The Bright Star in the globular cluster 47 Tucanae (NGC 104) is a post-asymptotic giant branch (post-AGB) star of spectral type B8 III. The ultraviolet spectra of late-B stars exhibit myriad absorption features, many due to species unobservable from the ground. The Bright Star thus represents a unique window into the chemistry of 47 Tuc. We have analyzed observations obtained with the Far Ultraviolet Spectroscopic Explorer, the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, and the Magellan Inamori Kyocera Echelle Spectrograph on the Magellan Telescope. By fitting these data with synthetic spectra, we determine various stellar parameters (T eff = 10,850 ± 250 K, log g = 2.20 ± 0.13 ) and the photospheric abundances of 26 elements, including Ne, P, Cl, Ga, Pd, In, Sn, Hg, and Pb, which have not previously been published for this cluster. Abundances of intermediate-mass elements (Mg through Ga) generally scale with Fe, while the heaviest elements (Pd through Pb) have roughly solar abundances. Its low C/O ratio indicates that the star did not undergo third dredge-up and suggests that its heavy elements were made by a previous generation of stars. If so, this pattern should be present throughout the cluster, not just in this star. Stellar-evolution models suggest that the Bright Star is powered by a He-burning shell, having left the AGB during or immediately after a thermal pulse. Its mass (0.54 ± 0.16M ⊙) implies that single stars in 47 Tuc lose 0.1–0.2 M ⊙ on the AGB, only slightly less than they lose on the red giant branch.

Signatures of wind formation in optical spectra of precursors of planetary nebulae

AbstractGenerally it is thought that shaping of planetary nebula from initially spherical envelope of asymptotic giant branch stars into non-spherical morphologies is a consequence of binary interactions. However, post asymptotic giant branch stars HD 235858 and HD 161796 seem to be at odds with this idea and perhaps the non-spherical nebulae surrounding them arose from intrinsic change in the nature of the stellar wind which is poorly understood for this evolutionary phase. Spectroscopic monitoring of these two stars has revealed signatures in the spectra that point to variable outflow. This indicates the prospect of spectroscopic monitoring to advance the knowledge of wind launching mechanism in post asymptotic giant branch stars and other dynamical processes in their extended atmospheres.

Chemical abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA

ABSTRACT Chemical abundance determinations in Low-Ionization Nuclear Emission-line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC 4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies survey was employed to derive the O/H abundance of the UGC 4805 nucleus based on the extrapolation of the disc abundance gradient, on calibrations between O/H abundance and strong emission-lines for active galactic nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-asymptotic giant branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN, and p-AGB photoionization models produce similar O/H values for the UGC 4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC 4805 nucleus probably has a stellar origin rather than an AGN.

Deciphering the origin of ionized gas in IC 1459 with VLT/MUSE

ABSTRACT IC 1459 is an early-type galaxy (ETG) with a rapidly counter-rotating stellar core, and is the central galaxy in a gas-rich group of spirals. In this work, we investigate the abundant ionized gas in IC 1459 and present new stellar orbital models to connect its complex array of observed properties and build a more complete picture of its evolution. Using the Multi-Unit Spectroscopic Explorer (MUSE), the optical integral field unit (IFU) on the Very Large Telescope (VLT), we examine the gas and stellar properties of IC 1459 to decipher the origin and powering mechanism of the galaxy’s ionized gas. We detect ionized gas in a non-disc-like structure rotating in the opposite sense to the central stars. Using emission-line flux ratios and velocity dispersion from full-spectral fitting, we find two kinematically distinct regions of shocked emission-line gas in IC 1459, which we distinguished using narrow (σ ≤ 155 km s−1) and broad (σ > 155 km s−1) profiles. Our results imply that the emission-line gas in IC 1459 has a different origin than that of its counter-rotating stellar component. We propose that the ionized gas is from late-stage accretion of gas from the group environment, which occurred long after the formation of the central stellar component. We find that shock heating and AGN activity are both ionizing mechanisms in IC 1459 but that the dominant excitation mechanism is by post-asymptotic giant branch stars from its old stellar population.

These are not the Stars You are Looking for: On the Detection of X-Ray Emission from HD 143352

Abstract As part of a search for X-ray emission from RV Tau variable stars, we discovered a serendipitous X-ray detection of the closest RV Tau variable star, HD 143352. X-rays were detected in the 0.2–2.0 keV energy band, with most counts detected in the 0.5–1.0 keV band. The emission is consistent with a 106 K plasma and L X ∼ 2 × 1028 erg s−1. This would be the second RV Tau star detected in X-ray emission. However, after estimating the temperature (T eff ∼ 6000 K) and bolometric luminosity (L bol ∼ 4L ⊙) from the spectral energy distribution, we place HD 143352 on the main sequence. These stellar parameters suggest HD 143352 is neither an RV Tau variable nor a post-asymptotic giant branch star nor a super giant, but rather an early F-type main sequence star. The X-ray emission detected from HD 143352 is consistent with coronal-like emission with L X/L bol ∼ 10−6.