We report on a coordinated campaign by amateur astronomers using a combination of high and low resolution spectroscopy to observe the 2025 eclipse of the symbiotic binary V1413 Aql shortly after a probable Z And-type symbiotic outburst. We measured the eclipse time of minimum and computed an updated eclipse ephemeris. Our spectra were calibrated in absolute flux and multi-Gaussian fits were used to resolve and quantify components of the Hα emission line. We measured the radial velocity curve of the white dwarf and determined the semi-amplitude as 25.7 km/s and the systemic radial velocity as 95.1 km/s. We found the spectral continuum was consistent with that of a late F or early G type giant star.

Mira stars are popular with amateur astronomers because they are generally bright and their pulsations produce large changes in brightness. This also means they are eminently suitable to study using spectroscopy. We report here on spectroscopic observations of five Mira stars: RY Cep, SU Cam, T Cep, V667 Cas and OR Cep. We describe the lifecycle of a Mira star and explain how the carbon-oxygen balance in its atmosphere determines its spectral classification. Atmospheric pulsations in these stars produce shocks which generate Balmer emission. We present graphically their different spectral behaviours and development of emission lines.

OJ287 is a blazar exhibiting high-amplitude variability in all the bands in which it has been studied, from x-ray to radio, over time scales ranging from minutes to decades. It has been particularly well studied in visible light, revealing no clear tendency to show bluer colours when brighter – an interesting anomaly compared to other blazars. It is also one of the active galactic nuclei in which it has proven most difficult to detect the host galaxy: either directly, by resolving it in images, or indirectly, by the change of colour at magnitudes sufficiently faint for the galaxy to be expected to make an important contribution to the total light from the system. Here, we investigate the colour variations of OJ287, finding a slow component of variation with an amplitude of ~0.2 magnitudes on a timescale of years, in both the B – V and V – R colour indices. We identify this tentatively with the effects of the major outbursts that occur every ~12 years. We also find that, contrary to previous findings, OJ287 does show a tendency to bluer colour when brighter, but that these trends are only visible in short segments of data covering a few months to a few years. We interpret this behaviour as due to multiple, overlapping components of emission coexisting, each with its own colour-magnitude correlation. Finally, we show that the colour changes OJ287 exhibits at faint magnitudes are consistent with the host being a giant elliptical galaxy with a magnitude of V = 18.0 and R = 17.1, and that this object can be detected unequivocally, if indirectly, with a backyard telescope.

HD 5501, a hitherto little-studied eclipsing binary with an early A-type primary, has been caught in a short-lived, astrophysically interesting phase of its binary evolution. Recent photometric and spectroscopic observations, including photometric data from TESS, show it has a highly variable light curve as well as complex spectral variability, particularly in both the absorption and emission components at H alpha. Our current campaign, including both professional and amateur observers, has determined that the primary is evolving rapidly across the Hertzsprung gap and that, unusually in the case of mass transfer, the orbital period is declining with a characteristic time-scale P/P-center dot approximate to 170 000 yr. Significantly, the orbit is eccentric and it appears that mass transfer from the primary to the secondary occurs only near periastron. Modelling indicates the presumed B7 V secondary to be surrounded by an accretion torus, which likely has dynamically chaotic variations in size and shape. Our analysis further implies the presence of a circumbinary disc or shell supplied by mass loss through the Lagrange L-3 point. That mass loss appears to account for most of the emission at H alpha. We describe how this astrophysically interesting system may yield valuable information about binary star evolution at the onset of Roche lobe overflow, as well as insights into eccentricity-modifying mechanisms such as the Soker mechanism.

We report our photometric and spectroscopic observations and analysis of the 2024 eclipse of the symbiotic binary V1413 Aquilae. We found the system in a visually bright state and the eclipse time of minimum consistent with the published ephemeris. The eclipse profile showed that the hot component was an extended object rather than an isolated white dwarf. By analyzing the eclipse profile we estimated the orbital inclination to be 67.9, the radius of the extended hot component surrounding the white dwarf to be 39.3 Rsun, and that the red giant star was probably filling its Roche Lobe. From our flux calibrated spectra, we determined the brightest component of the system to be the hot component whose continuum and emission lines together are responsible for 83 contribute over 14 spectra revealed a rich harvest of low ionization emission lines. By measuring how flux in these emission lines varied through the eclipse, we have provided information which should prove useful for future modelling of this symbiotic system.

We present the results of a multi-wavelength Pro-Am campaign to study the behaviour of flares from the active M1.5V star binary CR Draconis. CR Dra was observed with TESS 20-s photometry, Swift near-UV (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 characterise 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.

We report analysis of photometry and spectroscopy of a deep Algol-like minimum of the pre-main-sequence star WW Vul in July and August 2016. This revealed substantial reddening due to absorption by circumstellar material. After dereddening, our spectra of WW Vul were consistent with spectral type A3V throughout the event. Hα is normally in emission in WW Vul. During the minimum, Hα emission dropped by 30 reduced by 15

We report on spectroscopic and photometric observations of the S-type Mira V667 Cas and the carbon star Mira OR Cep recorded during one pulsation cycle of each star in 2022. Spectra are calibrated in absolute flux using concurrent photometry. We present measurements of V and Ic magnitudes and V-Ic colour index, classify spectra in the revised MK system and investigate how absolute flux in the H-alpha to H-delta emission lines varies with pulsation phase for each star.

V503 Her was previously proposed as an eclipsing symbiotic candidate based on photometric behavior and spectroscopic appearance indicating the composite optical spectrum. To investigate its nature, we analyzed long-term photometric observations covering 100 yr of its photometric history and new low-resolution optical spectroscopic data, supplemented with the multifrequency measurements collected from several surveys and satellites. Based on the analysis presented in this paper, we claim that V503 Her is not an eclipsing binary star. The optical and infrared wavelengths are dominated by a K-type bright giant with an effective temperature of 4500 K, luminosity of 1900 L _⊙ , and subsolar metallicity on the asymptotic giant branch showing semiregular complex multiperiodic pulsation behavior. V503 Her does not show the characteristics of strongly interacting symbiotic variables, but some pieces of evidence suggest that it could still be one of the “hidden” accreting-only symbiotic systems. However, the currently available data do not allow us to fully confirm or constrain the parameters of a possible companion.

We report results of an observing campaign to study the dwarf M flare star EV Lacertae. Between October 2021 and January 2022 we obtained concurrent B band photometry and low resolution spectroscopy of EV Lac on 39 occasions during 10 of which we observed flares with amplitude greater than 0.1 magnitude. Spectra were calibrated in absolute flux using concurrent photometry and flare-only spectra obtained by subtracting mean quiescent spectra. We measured B band flare energies between Log E = 30.8 and 32.6 erg. In the brightest flares we measured temporal development of flare flux in H I and He I emission lines and in the adjacent continuum and found that flux in the continuum subsided more rapidly than in the emission lines. Although our time resolution was limited, in our brightest flare we saw flux in the continuum clearly peaking before flux in the emission lines. We observed a progressive decrease in flare energy from H\b{eta} to H{\delta}. On average we found 37% of B band flare energy appeared in the H\b{eta} to H{\epsilon} emission lines with the remainder contributing to a rise in continuum flux. We measured black-body temperatures for the brightest flares between 10,500 +- 700 K and 19,500 +- 500 K and found a linear relationship between flare temperature and continuum flux at 4170 {\AA}. Balmer lines in flare-only spectra were well fitted by Gaussian profiles with some evidence of additional short-lived blue-shifted emission at the flare peak.

TU Tau (=HD 38218 = HIP 27135) is a binary system consisting of a C-N carbon star primary and an A-type secondary. We report on new photometry and spectroscopy which tracked the recent disappearance of the A-star secondary. The dimming of the A star was gradual and irregular, with one or more brief brightenings, implying the presence of nonhomogeneities in the carbon star outflow. We also present evidence that the A star is actively accreting s -process enriched material from the carbon star and suggest that it will therefore eventually evolve into a Barium giant. This is an important system as well because the A-type star can serve as a probe of the outer atmosphere of the carbon star.

SW Sex stars are an informal sub-class of eclipsing nova-like cataclysmic variables. We report 934 new eclipse times measured over the past 17 years for HS 0728+6738 (V482 Cam), SW Sex, DW UMa, HS 0129+2933 (TT Tri), V1315 Aql, PX And, HS 0455+8315, HS 0220+0603, BP Lyn, BH Lyn, LX Ser, UU Aqr, V1776 Cyg, RW Tri, 1RXS J064434.5+334451, AC Cnc, V363 Aur, and BT Mon. When combined with published eclipse times going back in some cases many decades, we show that these binary systems exhibit a range of behaviors, including increasing, decreasing, and possibly oscillating orbital periods. Nevertheless, the duration of these observations is still not long enough to be able to make reliable quantitative statements about their long term behaviors. In addition to these long term trends, we also observed rapid and unusual decreases in the orbital periods of SW Sex and RW Tri during 2017 and 2018, respectively.

Spectroscopy and photometry of the Asymptotic Giant Branch star T Cephei were recorded concurrently on 36 nights during its 387 day pulsation cycle in 2022. Photometry was used to calibrate all spectra in absolute flux. We report on the variation of B and V magnitudes, B-V colour index, spectral type, effective temperature and Balmer emission line flux during one complete pulsation cycle.

Lightcurves of many classical novae deviate from the canonical "fast rise - smooth decline" pattern and display complex variability behavior. We present the first TESS-space-photometry-based investigation of this phenomenon. We use Sector 41 full-frame images to extract a lightcurve of the slow Galactic nova V606 Vul that erupted nine days prior to the start of the TESS observations. The lightcurve covers the first of two major peaks of V606 Vul that was reached 19 days after the start of the eruption. The nova reached its brightest visual magnitude V=9.9 in its second peak 64 days after the eruption onset, following the completion of Sector 41 observations. To increase the confidence level of the extracted lightcurve, we performed the analysis using four different codes implementing the aperture photometry (Lightkurve, VaST) and image subtraction (TESSreduce, tequila_shots) and find good agreement between them. We performed ground-based photometric and spectroscopic monitoring to complement the TESS data. The TESS lightcurve reveals two features: periodic variations (0.12771 d, 0.01 mag average peak-to-peak amplitude) that disappeared when the source was within 1 mag of peak optical brightness and a series of isolated mini-flares (with peak-to-peak amplitudes of up to 0.5 mag) appearing at seemingly random times. We interpret the periodic variations as the result of azimuthal asymmetry of the photosphere engulfing the nova-hosting binary that was distorted by and rotating with the binary. Whereas we use spectra to associate the two major peaks in the nova lightcurve with distinct episodes of mass ejection, the origin of mini-flares remains elusive.

ABSTRACT Despite being bright (V ≃ 11.8) and nearby (d = 212 pc) ASAS J071404+7004.3 has only recently been identified as a nova-like cataclysmic variable. We present time-resolved optical spectroscopy obtained at the Isaac Newton and the Hiltner and McGraw-Hill Telescopes, together with Swift X-ray and ultraviolet observations. We combined these with TESS photometry and find a period of 3.28 h and a mass transfer rate of $4\!-\!9\times 10^{-9}\, {\mathrm{M_{\odot }\, yr}^{-1}}$. Historical photometry shows at least one low state establishing the system as a VY Scl star. Our high-cadence spectroscopy also revealed rapidly changing winds emanating from the accretion disc. We have modelled these using the Monte Carlo python code and shown that all the emission lines could emanate from the wind – which would explain the lack of double-peaked lines in such systems. In passing, we discuss the effect of variability on the position of cataclysmic variables in the Gaia Hertzsprung–Russell diagram.

ABSTRACTOJ 287 is a BL Lacertae type quasar in which the active galactic nucleus (AGN) outshines the host galaxy by an order of magnitude. The only exception to this may be at minimum light when the AGN activity is so low that the host galaxy may make quite a considerable contribution to the photometric intensity of the source. Such a dip or a fade in the intensity of OJ 287 occurred in 2017 November, when its brightness was about 1.75 mag lower than the recent mean level. We compare the observations of this fade with similar fades in OJ 287 observed earlier in 1989, 1999, and 2010. It appears that there is a relatively strong reddening of the B− V colours of OJ 287 when its V-band brightness drops below magnitude 17. Similar changes are also seen in V− R, V− I, and R− I colours during these deep fades. These data support the conclusion that the total magnitude of the host galaxy is V = 18.0 ± 0.3, corresponding to MK = −26.5 ± 0.3 in the K-band. This is in agreement with the results, obtained using the integrated surface brightness method, from recent surface photometry of the host. These results should encourage us to use the colour separation method also in other host galaxies with strongly variable AGN. In the case of OJ 287, both the host galaxy and its central black hole are among the biggest known, and its position in the black hole mass–galaxy mass diagram lies close to the mean correlation.

We present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr, and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the flux decreases, indicating a change in the sources’ accretion properties as they transition to the low state. For V1223 Sgr, we find that the variability is almost completely quenched at the lowest flux, but we do not find evidence for a changing accretion geometry. For RX J2133.7+5107, the temporal properties do not change in the low state, but we do see a period of enhanced accretion that is coincident with increased variability on the beat frequency, which we do not associate with a change in the accretion mechanisms in the system.

ABSTRACT V392 Persei is a known dwarf nova (DN) that underwent a classical nova eruption in 2018. Here we report ground-based optical, Swift UV and X-ray, and Fermi-LAT γ-ray observations following the eruption for almost three years. V392 Per is one of the fastest evolving novae yet observed, with a t2 decline time of 2 d. Early spectra present evidence for multiple and interacting mass ejections, with the associated shocks driving both the γ-ray and early optical luminosity. V392 Per entered Sun-constraint within days of eruption. Upon exit, the nova had evolved to the nebular phase, and we saw the tail of the supersoft X-ray phase. Subsequent optical emission captured the fading ejecta alongside a persistent narrow line emission spectrum from the accretion disc. Ongoing hard X-ray emission is characteristic of a standing accretion shock in an intermediate polar. Analysis of the optical data reveals an orbital period of 3.230 ± 0.003 d, but we see no evidence for a white dwarf (WD) spin period. The optical and X-ray data suggest a high mass WD, the pre-nova spectral energy distribution (SED) indicates an evolved donor, and the post-nova SED points to a high mass accretion rate. Following eruption, the system has remained in a nova-like high mass transfer state, rather than returning to the pre-nova DN low mass transfer configuration. We suggest that this high state is driven by irradiation of the donor by the nova eruption. In many ways, V392 Per shows similarity to the well-studied nova and DN GK Persei.

We report evidence from eclipse timing that two otherwise apparently normal cataclysmic variables have experienced abrupt changes in their orbital periods. The orbital period of HS 2325+8205 increased by 22.15 msec (1.3 x 10-6 of the orbital period) around 1 February 2011 and the orbital period of EP Dra increased by 4.51 msec (7.2 x 10-7 of the orbital period) around 7 December 2001. In neither case was there any apparent change in the subsequent behaviour of the system. These changes are currently unexplained.

The first radial velocity curves for V404 And have been obtained. Combined with new light curve data, simultaneous Roche-based light curve analyses have been carried out using the 2003 version of the Wilson-Devinney code. New values for the masses, radii, and luminosities have been obtained: M-1 = 0.870 (11) M p, M-2 = 0.706 (9) M-?, R-1 = 1.10 (13) Rp, R-2 = 1.37 (13) R-?, L-1 = 0.75 (7) L-?, and L-2 = 0.87 (8) L-?. Reference to the sample of close binary stars from Yakut and Eggleton (2005) and the ZAMS indicates that both stars are evolved. Further, the system may have been a classical Algol in the past but with the secondary then contracting, yielding the near semi-contact binary that we have today.