American Association of Variable Star Observers

ABSTRACT We present a comprehensive analysis of BRITE photometry for 85 chemically peculiar stars, aimed at refining or determining their rotational periods. Utilizing a uniform Lomb–Scargle-based pipeline, we derived significant periods for 47 targets. A comparison with existing literature periods reveals generally good agreement, although several stars exhibit discrepant or previously unrecognized behaviour. Notably, six targets display clear multiperiodicity, which, when combined with archival TESS data, suggests that these six candidates are likely misclassified, for example, as a magnetic CP2 or a CP4 star and instead exhibit characteristics consistent with a Be/shell star. Furthermore, eleven stars show no detectable periodic variations within the precision limits of BRITE. Our analysis demonstrates the effectiveness of long-term nanosatellite photometry, particularly when complemented by TESS data, in verifying catalogue periods, identifying multiperiodic behaviour, and detecting potential misclassifications among bright CP stars.

Abstract In this article, we present the study for the reclassification of the variability of the star CzeV961 by SSV-UAI-GRAV, classified by Variable Star Index as an EW eclipsing binary. In the same field of observation, there were two variable stars already discovered by Gaia but of an undefined type. In examining the comparison stars for our study, we then discovered a new variable star that had not yet been classified. The star CzeV961 turned out to be a Gamma Doradus variable star, like the two Gaia stars, while the newly discovered variable turned out to be an RS Canum Venaticorum type star.

Recurrent nova U Scorpii (U Sco) is one of the prototypes for a Type Ia supernova progenitor. The logic is that the white dwarf is near the Chandrasekhar mass and gas is accumulating onto its surface at a near-maximal accretion rate, so it will soon increase its mass to the supernova trigger. But the white dwarf loses mass every nova eruption, so the issue is balancing the mass ejected ($M_{\rm ejecta}$) against the mass accreted between eruptions ($M_{\rm accreted}$). Measuring $M_{\rm accreted}$ can be done in several ways to useable accuracy. But the old methods for measuring $M_{\rm ejecta}$ (involving the flux in hydrogen emission lines) are all with real error bars of 2--3 orders of magnitude. The only solution is to measure the change of the orbital period across the nova eruption ($\Delta P$). But this solution requires a vast photometric program of eclipse timings stretching decades. For U Sco, a program started in 1989, now reaches its culmination with measures of $\Delta P$ for the eruptions of 1999, 2010, 2016, and 2022. This paper reports on 52 new eclipse times (for a total of 218 eclipses 1945--2025), plus a new theory result allowing for the confident calculation of $M_{\rm ejecta}$ from $\Delta P$. The four eruptions ejected a total of (103$\pm$14)$\times$$10^{-6}$ $M_{\odot}$, while the white dwarf accreted 4$\times$$10^{-6}$ $M_{\odot}$ over the four previous eruption cycles. With M$_{\rm ejecta}$=26$\times$M$_{\rm accreted}$, the U Sco white dwarf is losing large masses each eruption cycle, so U Sco can never produce a Type Ia supernova.

Abstract We present the discovery of 30 transiting giant planets that were initially detected using data from NASA’s Transiting Exoplanet Survey Satellite mission. These new planets orbit relatively bright ( G ≤ 12.5) FGK host stars with orbital periods between 1.6 and 8.2 days, and have radii between 0.9 and 1.7 Jupiter radii. We performed follow-up ground-based photometry, high angular resolution imaging, high-resolution spectroscopy, and radial velocity monitoring for each of these objects to confirm that they are planets and determine their masses and other system parameters. The planets’ masses span more than an order of magnitude (0.17 M J &lt; M p &lt; 3.3 M J ). For two planets, TOI-3593 b and TOI-4961 b, we measured significant nonzero eccentricities of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.1</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.1</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.04</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , respectively, while for the other planets, the data typically provide a 1 σ upper bound of 0.15 on the eccentricity. These discoveries represent a major step toward assembling a complete, magnitude-limited sample of transiting hot Jupiters around FGK stars.

Abstract Sub-Neptunes—volatile-rich exoplanets smaller than Neptune—are intrinsically the most common type of planet known. However, the formation and nature of these objects, as well as the distinctions between subclasses (if any), remain unclear. Two powerful tools to tease out the secrets of these worlds are measurements of (i) atmospheric composition and structure revealed by transit and/or eclipse spectroscopy, and (ii) mass, radius, and density revealed by transit photometry and Doppler spectroscopy. Here, we present OrCAS, a survey to better elucidate the origins, compositions, and atmospheres of sub-Neptunes. This radial velocity survey uses a repeatable, quantifiable metric to select targets suitable for subsequent transmission spectroscopy and address key science themes about the atmospheric and internal compositions and architectures of these systems. Our survey targets 26 systems with transiting sub-Neptune planet candidates, with the overarching goal of increasing the sample of such planets suitable for subsequent atmospheric characterization. This paper lays out our survey's science goals, defines our target prioritization metric, and performs light-curve fits and statistical validation using existing TESS photometry and ground-based follow-up observations. Our survey serves to continue expanding the sample of small exoplanets with well-measured properties orbiting nearby bright stars, ensuring fruitful studies of these systems for many years to come.

In the original version of article [Publ. Astron. Soc. Japan (2024) 76(2); https://doi.org/10.1093/pasj/psae010], the email address was incorrectly typed during the production process. The PDF and HTML versions of the original article are updated with the correct email address upon the publication of this erratum.

ABSTRACT We present the results of a multiwavelength Professional–Amateur campaign to study the behaviour of flares from the active M1.5V star binary CR Draconis. CR Dra was observed with Transiting Exoplanet Survey Satellite (TESS) 20-s photometry, Swift near-ultraviolet (NUV) grism spectroscopy and with ground-based optical photometry and spectroscopy from a global collaboration of amateur astronomers. We detected 14 flares with TESS and Swift simultaneously, one of which also had simultaneous ground-based photometry and spectroscopy. We used the simultaneous two-colour optical and NUV observations to characterize the temperature evolution of the flare and test the accuracy of using optical data to predict NUV emission. We measured a peak temperature of $7100^{+150}_{-130}$ K for this flare, cooler than the typically assumed 9000 K blackbody model used by flare studies. We also found that the 9000 K blackbody overestimated the NUV flux for other flares in our sample, which we attributed to our Swift observations occurring during flare decays, highlighting the phase-dependence for the accuracy of flare models.

ABSTRACT We catalogue the 443 bright supernovae (SNe) discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in 2018−2020 along with the 519 SNe recovered by ASAS-SN and 516 additional mpeak ≤ 18 mag SNe missed by ASAS-SN. Our statistical analysis focuses primarily on the 984 SNe discovered or recovered in ASAS-SN g-band observations. The complete sample of 2427 ASAS-SN SNe includes earlier V-band samples and unrecovered SNe. For each SN, we identify the host galaxy, its UV to mid-IR photometry, and the SN’s offset from the centre of the host. Updated peak magnitudes, redshifts, spectral classifications, and host galaxy identifications supersede earlier results. With the increase of the limiting magnitude to g ≤ 18 mag, the ASAS-SN sample is nearly complete up to mpeak = 16.7 mag and is 90 per cent complete for mpeak ≤ 17.0 mag. This is an increase from the V-band sample, where it was roughly complete up to mpeak = 16.2 mag and 70 per cent complete for mpeak ≤ 17.0 mag.

ABSTRACT We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius of planet b. TOI-1288 b has a period of $2.699835^{+0.000004}_{-0.000003}$ d, a radius of 5.24 ± 0.09 R⊕, and a mass of 42 ± 3 M⊕, making this planet a hot transiting super-Neptune situated right in the Neptunian desert. This desert refers to a paucity of Neptune-sized planets on short period orbits. Our 2.4-yr-long Doppler monitoring of TOI-1288 revealed the presence of a Saturn–mass planet on a moderately eccentric orbit ($0.13^{+0.07}_{-0.09}$) with a minimum mass of 84 ± 7 M⊕ and a period of $443^{+11}_{-13}$ d. The five sectors worth of TESS data do not cover our expected mid-transit time for TOI-1288 c, and we do not detect a transit for this planet in these sectors.