Low Luminosity Research Articles

EMU/GAMA: A technique for detecting active galactic nuclei in low mass systems

Abstract We propose a new method for identifying active galactic nuclei (AGN) in low mass ( $\mathrm{M}_*\leq10^{10}\mathrm{M}_\odot$ ) galaxies. This method relies on spectral energy distribution (SED) fitting to identify galaxies whose radio flux density has an excess over that expected from star formation alone. Combining data in the Galaxy and Mass Assembly (GAMA) G23 region from GAMA, Evolutionary Map of the Universe (EMU) early science observations, and Wide-field Infrared Survey Explorer (WISE), we compare this technique with a selection of different AGN diagnostics to explore the similarities and differences in AGN classification. We find that diagnostics based on optical and near-infrared criteria (the standard BPT diagram, the WISE colour criterion, and the mass-excitation, or MEx diagram) tend to favour detection of AGN in high mass, high luminosity systems, while the “ProSpect” SED fitting tool can identify AGN efficiently in low mass systems. We investigate an explanation for this result in the context of proportionally lower mass black holes in lower mass galaxies compared to higher mass galaxies and differing proportions of emission from AGN and star formation dominating the light at optical and infrared wavelengths as a function of galaxy stellar mass. We conclude that SED-derived AGN classification is an efficient approach to identify low mass hosts with low radio luminosity AGN.

Clinical case of viability in root canal treatment in an elderly patient with dental attrition

In root canal treatment, attention to atrial canals is crucial for the restructuring of dental health, especially in elderly patients with dental attrition. Atrial canals, characterized by low internal luminosity due to secondary dentin deposition, pose a challenge for the endodontist. This study reviews the literature on the preparation of these canals, focusing on foraminal permeability and glide path through biomechanical preparation. Instrumentation procedures and the importance of achieving patency or glide path, attained with appropriate instruments before canal preparation, are highlighted. A detailed evaluation and the use of TCHC computed tomography are essential for correctly diagnosing anatomical limitations in the root canal system. The application of internal anatomy and pathophysiology knowledge is vital to achieve favorable outcomes in endodontic treatments

O Corona, where art thou? eROSITA’s view of UV-optical-IR variability-selected massive black holes in low-mass galaxies

Finding massive black holes (MBHs, MBH ≈ 104–107 M⊙) in the nuclei of low-mass galaxies $\left( {{M_*}\mathop {\mathop < \limits_ }\limits_ {{10}^{10}}{M_ \odot }} \right)$ is crucial to constrain seeding and growth of black holes over cosmic time, but it is particularly challenging due to their low accretion luminosities. Variability selection via long-term photometric ultraviolet, optical, or infrared (UVOIR) light curves has proved effective and identifies lower-Eddington ratios compared to broad and narrow optical spectral lines searches. In the inefficient accretion regime, X-ray and radio searches are effective, but they have been limited to small samples. Therefore, differences between selection techniques have remained uncertain. Here, we present the first large systematic investigation of the X-ray properties of a sample of known MBH candidates in dwarf galaxies. We extracted X-ray photometry and spectra of a sample of ~200 UVOIR variability-selected MBHs and significantly detected 17 of them in the deepest available SRG/eROSITA image, of which four are newly discovered X-ray sources and two are new secure MBHs. This implies that tens to hundreds of LSST MBHs will have SRG/eROSITA counterparts, depending on the seeding model adopted. Surprisingly, the stacked X-ray images of the many non-detected MBHs are incompatible with standard disk-corona relations, typical of active galactic nuclei, inferred from both the optical and radio fluxes. They are instead compatible with the X-ray emission predicted for normal galaxies. After careful consideration of potential biases, we identified that this X-ray weakness needs a physical origin. A possibility is that a canonical X-ray corona might be lacking in the majority of this population of UVOIR-variability selected low-mass galaxies or that unusual accretion modes and spectral energy distributions are in place for MBHs in dwarf galaxies. This result reveals the potential for severe biases in occupation fractions derived from data from only one waveband combined with SEDs and scaling relations of more massive black holes and galaxies.

Nature of UV Variability in NGC 4151 from IUE’s Intensive Monitoring Spectroscopic Data

The International Ultraviolet Explorer (IUE) satellite, launched in 1978 by NASA and ESA, has conducted highly successful long-term monitoring spectroscopic observations of many nearby (low-redshift) bright active galaxies, including NGC 1068, NGC 5548, NGC 7469, Fairall 9,MRK 335 and NGC 4151. Notably, IUE has monitored NGC 4151 more intensively than any other active galaxy, obtaining 414 spectra during its campaign from December 1 to 15, 1993. Here, we present results of our recent studies on the emission line and continuum variabilities characterised by the Rmax and Fvar parameters. From the analysis of the short timescale, intense monitoring data, we obtained Rmax values ranging between 2.14±0.02 and 1.62±0.01 corresponding to the UV continua 1270 Å, and 2705 Å, respectively. The corresponding Fvar values varied from 9.62±0.04% to 5.19±0.04 %. Furthermore, the Rmax values for the UV emission lines Lyα, C IV, He II, O III], C III] and Mg II have been found to be 4.09±0.06, 4.55±0.05, 13.65±0.68, 4.78±0.17, 2.76±0.02, respectively. The corresponding Fvar values obtained are 2.85±0.01 %, 26.51±0.06 %, 15.59±0.02 %, 48.93±1.79 %, 20.30±0.06% and 18.68±0.02 %, respectively. These results provide constraints on the amplitude of UV variability and the size of the broad-line region (BLR) in low luminosity Seyfert galaxies. The decreasing Fvar amplitudes of the UV continuum with respect to increasing wavelengths are significant results of the present study.

Spectroscopic and Photometric Study of the Low-luminous AGN NGC 4395

The study of intermediate mass black holes (IMBHs) and estimating the black hole mass could potentially elucidate the origin of supermassive black hole (SMBH) seeds present at high redshifts and how they co-evolve with their host galaxy. The difficulty in detecting these IMBHs and the requirement of high spatial resolution to measure BHs mass makes this task challenging. In this work, we have performed photometric and spectroscopic analyses of an extremely low luminosity Seyfert 1 galaxy NGC4395. Our observations revealed strong emission lines in the spectra, and we observed a fractional variability in the V-band of 12%. Utilizing the broad-line region (BLR) size-luminosity relation for active galactic nuclei (AGNs), we estimated the size of the BLR to be 74±14 light minutes, based on a continuum luminosity of 1038 erg s−1 at 5100 Å. Additionally, the gas clouds are found to be revolving with a velocity dispersion of 384 km s−1 around the central engine, leading to a black hole mass estimation of ∼3.87−1.1+1.1 ×105 M⊙.

Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XVII. Black Hole Mass Distribution at z ∼ 6 Estimated via Spectral Comparison with Low-z Quasars

We report the distribution of black hole (BH) masses and Eddingont ratios estimated for a sample of 131 low luminosity quasars in the early cosmic epoch (5.6 < z < 7.0). Our work is based on the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which has constructed a low luminosity quasar sample down to M 1450 ∼ − 21 mag, exploiting the survey data of Hyper Suprime-Cam installed on Subaru Telescope. The discovery spectra of these quasars are limited to the rest-frame wavelengths of ∼1200–1400 Å, which contain no emission lines that can be used as BH mass estimators. In order to overcome this problem, we made use of low-z counterpart spectra from the Sloan Digital Sky Survey, which are spectrally matched to the high-z spectra in overlapping wavelengths. We then combined the C iv emission line widths of the counterparts with the continuum luminosity from the SHELLQs data to estimate BH masses. The resulting BH mass distribution has a range of ∼107–10 M ⊙, with most of the quasars having BH masses ∼108 M ⊙ with sub-Eddington accretion. The present study provides not only a new insight into normal quasars in the reionization epoch, but also a new promising way to estimate BH masses of high-z quasars without near-infrared spectroscopy.

Living with a Red Dwarf: X-Ray, UV, and Ca ii Activity–Age Relationships of M Dwarfs

The vast majority of stars in the nearby stellar neighborhood are M dwarfs. Their low masses and luminosities result in slow rates of nuclear evolution and minimal changes to the stars’ observable properties, even along astronomical timescales. However, they possess relatively powerful magnetic dynamos and resulting X-ray to UV (X–UV) activity, compared to their bolometric luminosities. This magnetic activity does undergo an observable decline over time, potentially making it a key age determinant for M dwarfs. Observing this activity is important for studying the outer atmospheres of these stars, but also for comparing the behaviors of different spectral type subsets of M dwarfs; e.g., those with partially versus fully convective interiors. Beyond stellar astrophysics, understanding the X–UV activity of M dwarfs over time is a key component when studying the atmospheres and habitability of any hosted exoplanets. Earth-sized exoplanets, in particular, are more commonly found orbiting M dwarfs than any other stellar type, and thermal escape (driven by the M dwarf X–UV activity) is believed to be the dominant atmospheric loss mechanism for these planets. Utilizing recently calibrated M dwarf age–rotation relationships, also constructed as part of the Living with a Red Dwarf program, we have analyzed the evolution of M dwarf activity over time, in terms of coronal (X-ray), chromospheric (Lyα, and Ca ii), and overall X–UV (5–1700 Å) emissions. The activity–age relationships presented here will be useful for studying exoplanet habitability and atmospheric loss, and also for studying the different dynamo and outer atmospheric heating mechanisms at work in M dwarfs.

Clinical case of viability in root canal treatment in an elderly patient with dental attrition

In root canal treatment, attention to atrial canals is crucial for the restructuring of dental health, especially in elderly patients with dental attrition. Atrial canals, characterized by low internal luminosity due to secondary dentin deposition, pose a challenge for the endodontist. This study reviews the literature on the preparation of these canals, focusing on foraminal permeability and glide path through biomechanical preparation. Instrumentation procedures and the importance of achieving patency or glide path, attained with appropriate instruments before canal preparation, are highlighted. A detailed evaluation and the use of TCHC computed tomography are essential for correctly diagnosing anatomical limitations in the root canal system. The application of internal anatomy and pathophysiology knowledge is vital to achieve favorable outcomes in endodontic treatments

A Centiparsec-scale Compact Radio Core in the Nearby Galaxy M60

M60, an elliptical galaxy located 16.5 Mpc away, has an active nucleus with a very low luminosity and an extremely low accretion rate. Its central supermassive black hole (SMBH) has a mass of M BH ∼ 4.5 × 109 M ⊙ and a Schwarzschild radius corresponding to R S ∼ 5.4 μas. To investigate the nature of its innermost radio nucleus, data from the Very Long Baseline Array (VLBA) at 4.4 and 7.6 GHz were reduced. The VLBA images reveal a compact component with total flux densities of ∼20 mJy at both frequencies, a size of ≤0.27 mas (99.7% confidence level), about 0.022 pc (50 R S) at 7.6 GHz, and a brightness temperature of ≥6 × 109 K. This suggests that the observed centiparsec-scale compact core could be attributed to a nonthermal jet base or an advection-dominated accretion flow (ADAF) with nonthermal electrons. The extremely compact structure also supports the presence of an SMBH in the center. Our results indicate that M60 is a promising target for broadband very long baseline interferometry observations at millimeter wavelengths to probe ADAF scenarios and tightly constrain the potential photon ring (about 28 μas) around its SMBH.

A JWST/NIRSpec First Census of Broad-line AGNs at z = 4–7: Detection of 10 Faint AGNs with M BH ∼ 106–108 M ⊙ and Their Host Galaxy Properties

We present the first statistical sample of faint type 1 AGNs at z > 4 identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at z spec = 3.8–8.9 confirmed with NIRSpec, our systematic search for broad-line emission reveals 10 type 1 AGNs at z = 4.015–6.936 whose broad component is only seen in the permitted Hα line and not in the forbidden [O iii]λ5007 line that is detected with greater significance than Hα. The broad Hα line widths of FWHM ≃ 1000–6000 km s−1 suggest that the AGNs have low-mass black holes with M BH ∼ 106–108 M ⊙, remarkably lower than those of low-luminosity quasars previously identified at z > 4 with ground-based telescopes. JWST and Hubble Space Telescope high-resolution images reveal that the majority of them show extended morphologies indicating significant contribution to the total lights from their host galaxies, except for three compact objects two of which show red spectral energy distributions, probably in a transition phase from faint AGNs to low luminosity quasars. Careful AGN-host decomposition analyses show that their host’s stellar masses are systematically lower than the local relation between the black hole mass and the stellar mass, implying a fast black hole growth consistent with predictions from theoretical simulations. A high fraction of the broad-line AGNs (∼5%), higher than z ∼ 0, indicates that the number density of such faint AGNs is higher than an extrapolation of the quasar luminosity function, implying a large population of AGNs in the early universe. Such faint AGNs contribute to cosmic reionization, while the total contribution is not large, up to ∼50% at z ∼ 6, because of their faint nature.

SN 2022vqz: a peculiar subluminous Type Ia supernova with prominent early excess emission

ABSTRACT We present extensive photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2022vqz. It shares many similarities with the SN 2002es-like SNe Ia, such as low luminosity ($M_{B,\rm max}=-18.11\pm 0.16$ mag) and moderate post-peak decline rate (Δm15,B = 1.33 ± 0.11 mag). The nickel mass synthesized in the explosion is estimated as 0.20 ± 0.04 M⊙ from the bolometric light curve, which is obviously lower than that of normal SNe Ia. SN 2022vqz is also characterized by slowly expanding ejecta, with Si ii velocities persisting around 7000 km s−1 since 16 d before peak brightness, unique among all known SNe Ia. While all of these properties imply a lower energy thermonuclear explosion that should leave a considerable amount of unburnt materials, the absent signature of unburnt carbon in spectra of SN 2022vqz is puzzling. A prominent early peak is clearly detected in the Asteroid Terrestrial-impact Last Alert System c- and o-band light curves and in the Zwicky Transient Facility gr-band data within days after the explosion. Possible mechanisms for the early peak are discussed, including the sub-Chandrasekhar-mass double-detonation model and interaction of SN ejecta with circumstellar material. We find that both models face some difficulties in replicating all aspects of the observed data. As an alternative, we propose a hybrid C–O–Ne white dwarf as the progenitor of SN 2022vqz; it can simultaneously reconcile the tension between low ejecta velocity and the absence of carbon. We further discuss the diversity of SN 2002es-like objects and their origin in the context of different scenarios.

The Structure Function of Mid-infrared Variability in Low-redshift Active Galactic Nuclei

Using the multi-epoch mid-infrared (MIR) photometry from the Wide-field Infrared Survey Explorer spanning a baseline of ∼10 yr, we extensively investigate the MIR variability of nearby active galactic nuclei (AGNs) at 0.15 < z < 0.4. We find that the ensemble structure function in the W1 band (3.4 μm) can be modeled with a broken power law. Type 1 AGNs tend to exhibit larger variability amplitudes than type 2 AGNs, possibly due to the extinction by the torus. The variability amplitude is inversely correlated with the AGN luminosity, consistent with a similar relation known in the optical. Meanwhile, the slope of the power law increases with AGN luminosity. This trend can be attributed to the fact that the inner radius of the torus is proportional to the AGN luminosity, as expected from the size−luminosity relation of the torus. Interestingly, low-luminosity type 2 AGNs, unlike low-luminosity type 1 AGNs, tend to exhibit smaller variability amplitude than do high-luminosity AGNs. We argue that either low-luminosity type 2 AGNs have distinctive central structures due to their low luminosity or their MIR brightness is contaminated by emission from the cold dust in the host galaxy. Our findings suggest that the AGN unification scheme may need to be revised. We find that the variability amplitude of dust-deficient AGNs is systematically larger than that of normal AGNs, supporting the notion that the hot and warm dust in dust-deficient AGNs may be destroyed and reformed according to the strength of the ultraviolet radiation from the accretion disk.

AT 2023prq: A Classical Nova in the Halo of the Andromeda Galaxy

The classical nova, AT 2023prq, was discovered on 2023 August 15 and is located at a distance of 46 kpc from the Andromeda galaxy (M31). Here we report photometry and spectroscopy of the nova. The “very fast” ( days) and low luminosity () nature of the transient along with the helium in its spectra would indicate that AT 2023prq is a “faint-and-fast” He/N nova. Additionally, at such a large distance from the center of M31, AT 2023prq is a member of the halo nova population.

CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with Keck/NIRES

Y dwarfs, the coolest known spectral class of brown dwarfs, overlap in mass and temperature with giant exoplanets, providing unique laboratories for studying low-temperature atmospheres. However, only a fraction of Y dwarf candidates have been spectroscopically confirmed. We present Keck/NIRES near-infrared spectroscopy of the nearby (d ≈ 6–8 pc) brown dwarf CWISE J105512.11+544328.3. Although its near-infrared spectrum aligns best with the Y0 standard in the J band, no standard matches well across the full YJHK wavelength range. The CWISE J105512.11+544328.3 NH3-H = 0.427 ± 0.0012 and CH4-J = 0.0385 ± 0.0007 absorption indices and absolute Spitzer [4.5] magnitude of 15.18 ± 0.22 are also indicative of an early-Y dwarf rather than a late-T dwarf. CWISE J105512.11+544328.3 additionally exhibits the bluest Spitzer [3.6]−[4.5] color among all spectroscopically confirmed Y dwarfs. Despite this anomalously blue Spitzer color given its low luminosity, CWISE J105512.11+544328.3 does not show other clear kinematic or spectral indications of low metallicity. Atmospheric model comparisons yield a log(g) ≤ 4.5 and T eff ≈ 500 ± 150 K for this source. We classify CWISE J105512.11+544328.3 as a Y0 (pec) dwarf, adding to the remarkable diversity of the Y-type population. JWST spectroscopy would be crucial to understanding the origin of this Y dwarf’s unusual preference for low-gravity models and blue 3–5 μm color.

The distribution, kinematics, and luminosities of extreme helium stars as probes of their origin and evolution

ABSTRACT Hydrogen-deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces rich in helium, nitrogen, and carbon, their origins have been identified with the merger of two white dwarfs. Using Gaia to focus on the EHes, we aim to identify progenitor populations and test the evolution models. Gaia DR3 measurements and ground-based radial velocities have been used to compute Galactic orbits using galpy. Each orbit has been classified by population; EHe stars are found in all of the thin disc, thick disc, halo, and bulge, as are RCB, HdC, and He-sdO stars. Spectral energy distributions were constructed for all EHes, to provide angular diameters, and hence radii and luminosities. The EHes fall into two luminosity groups divided at $L \approx 2500 \, {\rm L_{\odot }}$. This supports theory for the origin of EHes, and is the strongest confirmation so far in terms of luminosity. The lower luminosity EHes correspond well with the post-merger evolution of a double helium white dwarf binary. Likewise, the higher luminosity EHes match the post-merger evolution of a carbon/oxygen plus helium white dwarf binary. In terms of parent populations, current models predict that double white dwarf mergers should occur in all Galactic populations, but favour mergers arising from recent star formation (i.e. thin disc), whereas the statistics favour an older epoch (i.e. thick disc).

The most luminous AGN do not produce the majority of the detected stellar-mass black hole binary mergers in the local Universe

ABSTRACT Despite the increasing number of gravitational wave (GW) detections, the astrophysical origin of binary black hole (BBH) mergers remains elusive. A promising formation channel for BBHs is inside accretion discs around supermassive black holes, that power active galactic nuclei (AGN). In this paper, we test for the first time the spatial correlation between observed GW events and AGN. To this end, we assemble all sky catalogues with 1,412 (242) AGN with a bolometric luminosity greater than 1045.5erg s−1 ($10^{46}\, {\rm erg\, s}^{-1}$) with spectroscopic redshift of z ≤ 0.3 from the Milliquas catalogue, version 7.7b. These AGN are cross-matched with localization volumes of BBH mergers observed in the same redshift range by the LIGO and Virgo interferometers during their first three observing runs. We find that the fraction of the detected mergers originated in AGN brighter than $10^{45.5}\, {\rm erg\, s}^{-1}$ ($10^{46}\, {\rm erg\, s}^{-1}$) cannot be higher than 0.49 (0.17) at a 95 per cent credibility level. Our upper limits imply a limited BBH merger production efficiency of the brightest AGN, while most or all GW events may still come from lower luminosity ones. Alternatively, the AGN formation path for merging stellar-mass BBHs may be actually overall subdominant in the local Universe. To our knowledge, ours are the first observational constraints on the fractional contribution of the AGN channel to the observed BBH mergers.

Early Results from GLASS-JWST. XXIII. The Transmission of Lyα from UV-faint z ∼ 3–6 Galaxies

Lyα emission from galaxies can be used to trace neutral hydrogen in the epoch of reionization, however, there is a degeneracy between the attenuation of Lyα in the intergalactic medium (IGM) and the line profile emitted by the galaxy. Large shifts of Lyα redward of systemic due to scattering in the interstellar medium can boost Lyα transmission in the IGM during reionization. The relationship between the Lyα velocity offset from systemic and other galaxy properties is not well established at high redshift or low luminosities, due to the difficulty of observing emission lines which trace the systemic redshift. Rest-frame optical spectroscopy with JWST/NIRSpec has opened a new window into understanding Lyα at z > 3. We present a sample of 12 UV-faint galaxies (−20 ≲ M UV ≲ −16) at 3 ≲ z ≲ 6, with Lyα velocity offsets, Δv Lyα , measured from the Very Large Telescope/MUSE and JWST/NIRSpec from the GLASS-JWST Early Release Program. We find a median Δv Lyα of 205 km s−1 and standard deviation of 75 km s−1, compared to 320 and 170 km s−1, respectively, for M UV < −20 galaxies in the literature. Our new sample demonstrates the previously observed trend of decreasing Lyα velocity offset with decreasing UV luminosity and optical line velocity dispersion, which extends to M UV ≳ −20, consistent with a picture where the Lyα profile is shaped by gas close to the systemic redshift. Our results imply that during reionization Lyα from UV-faint galaxies will be preferentially attenuated, but that detecting Lyα with low Δv Lyα can be an indicator of large ionized bubbles.

Characterization and post-harvest management of Cucurbita moschata Duchesne exhibiting a novel yellow color and grown as a “baby” summer squash

Although immature fruit of the domesticated species of Cucurbita (pumpkin and squash) are edible, it is usually fruit of C. pepo L. that are harvested as summer (immature) squash. Cucurbita pepo is not widely cultivated in Puerto Rico because of its susceptibility to a variety of diseases. By contrast, C. moschata Duchesne (tropical pumpkin) is well adapted and widely grown on the island but is used almost exclusively as a winter squash, harvested at maturity. We conducted physicochemical, nutritional, and sensory analyses of fresh and stored immature fruits of recently developed tropical pumpkin lines with a novel yellow color to determine their potential use as miniature (“baby”) summer squash. Two-d-old fruits were stored at 5º C for 14 d or at 10º C for 16 d. The nutritional composition of fresh 2-d-old fruits was like that of C. pepo summer squash. Changes in O2 and CO2 composition within sealed bags, and physical and chemical characteristics were measured before and after storage. The effect of fruit age (1- to 5-d-old fruit) on weight and color was evaluated. A sensory panel evaluated the general appearance and flavor of immature tropical pumpkin fruits. Over the storage period, O2 decreased, and CO2 increased within sealed bags. The increase in CO2 was greater at 10º C. Weight loss during storage ranged from 2.22% to 3.11%. There were decreases in luminosity and hue angle, but not chroma; fruits became more difficult to penetrate after storage. Fruits exhibited a decrease in pH, acidity, vitamin C, beta-carotene and antioxidant activity, and an increase in soluble solids and phenolics during storage. The effect of storage temperature on chemical characteristics was significant only for acidity, beta-carotene, and antioxidant activity; there were minimal changes in fruits stored at 10º C. Among 1- to 5-d-old fruit, older fruits tended to have a lower luminosity, with a somewhat more saturated orange color (increased chroma and decreased hue angle), compared to younger fruits. Panelists’ reaction to the appearance of whole, uncooked fruit ranged from “slightly like” to “extremely like”. The evaluation of the flavor of cooked pieces of fruit ranged from “moderately dislike” to “extremely like”, with 82% of participants rating cooked fruit as “slightly like” or better. Tropical pumpkin in its immature state is a fruit with nutritional value, an attractive appearance and a flavor likely to be accepted by consumers. Two-day-old fruit stored at 10° C maintained better quality than did fruit stored at 5° C. The immature fruit of these uniquely colored tropical pumpkin lines are a potentially high-value product for Puerto Rico or other areas where C. pepo cannot be grown.

A Surprising Periodicity Detected during a Super-outburst of V844 Herculis by TESS

We identify a previously undetected periodicity at a frequency of 49.08 ± 0.01 days−1 (period of 29.34 ± 0.01 minutes) during a super-outburst of V844 Her observed by TESS. V844 Her is an SU UMa type cataclysmic variable with an orbital period of 78.69 minutes, near the period minimum. The frequency of this new signal is constant in contrast to the superhump oscillations commonly seen in SU UMa outbursts. We searched without success for oscillations during quiescence using MDM, TESS, and XMM-Newton data. The lack of a periodic signal in the XMM light curve and the relatively low X-ray luminosity of V844 Her suggest that it is not a typical IP. We consider the possibility that the 29-minute signal is the result of super-Nyquist sampling of a dwarf nova oscillation with a period near the 2-minute cadence of the TESS data. Our analysis of archival AAVSO photometry from a 2006 super-outburst supports the existence of a 29-minute oscillation, although a published study of an earlier super-outburst did not detect the signal. We compare the X-ray properties of V844 Her with short orbital period intermediate polars (IP), V1025 Cen and DW Cnc. We conclude that the new signal is a real photometric oscillation coming from the V844 Her system and that it is unlikely to be an aliased high-frequency oscillation. The steady frequency of the new signal suggests that its origin is related to an asynchronously rotating white dwarf in V844 Her, although the precise mechanism producing the flux variations remains unclear.

Timing properties of the X-ray accreting pulsar RX J0440.9+4431 studied with Insight-HXMT and NICER

ABSTRACT RX J0440.9+4431, a Be/X-ray binary, had its brightest outburst in 2022 since its discovery, with a peak X-ray flux of 2.25 Crab (as recorded by Swift/BAT, 15–50 keV). We analyze the timing properties of this giant outburst using data from Insight-Hard X-ray Modulation Telescope and Neutron Star Interior Composition Exlporer, focusing on the evolution of the pulse profile and pulse fraction. We observe that when the luminosity reached around ~$3\times 10^{37}\ {\rm erg\ \rm s^{-1}}$, a transition from double-peaked to single-peaked pulse profiles occurred across the energy range, with the peak of the low-energy profile aligning gradually with the peak of the high-energy profile. This change indicates a transition from subcritical to supercritical accretion. Additionally, we found a concave in the pulse fraction as a function of energy around 20–30 keV throughout the entire outburst period. Compared to the low luminosity, the concave becomes weaker in high luminosities, and overall, the pulse fraction is higher. We propose that this concave could be caused by the scattering of high-energy photons by the atmosphere of a neutron star, leading to a dilution of the pulse fraction. As the accretion reaches the supercritical state, the accretion column height increases, resulting in a larger direct component of strongly beamed X-ray flux, and an elevated pulse fraction.