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Register a new userExtensive Photometry of V1838 Aql during the 2013 Superoutburst
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We present an in-depth photometric study of the 2013 superoutburst of the recently discovered cataclysmic variable V1838 Aql and subsequent photometry near its quiescent state. A careful examination of the development of the superhumps is presented. Our best determination of the orbital period is Porb = 0.05698(9) days, based on the periodicity of early superhumps. Comparing the superhump periods at stages A and B with the early superhump value we derive a period excess of {epsilon} = 0.024(2) and a mass ratio of q = 0.10(1). We suggest that V1838 Aql is approaching the orbital period minimum and thus has a low-mass star as a donor instead of a sub-stellar object.
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The results of time-resolved observations of SU UMa and U Gem obtained over two-years are presented. Both stars are prototypes of different classes of dwarf novae. We studied brightness variations on different time scales: orbital, QPO and flickering. The multicolor BVRI photometry allows to distinguisch the geometrical and physical sources of these variations.
We report on the multi-wavelength photometry of the 2018 superoutburst in EG Cnc. We have detected stage A superhumps and long-lasting late-stage superhumps via the optical photometry and have constrained the binary mass ratio and its possible range. The median value of the mass ratio is 0.048 and the upper limit is 0.057, which still implies that EG Cnc is one of the possible candidates for the period bouncer. This object also showed multiple rebrightenings in this superoutburst, which are the same as those in its previous superoutburst in 1996--1997 despite the difference in the main superoutburst. This would represent that the rebrightening type is inherent to each object and is independent of the initial disk mass at the beginning of superoutbursts. We also found that $B-I$ and $J-K_{rm S}$ colors were unusually red just before the rebrightening phase and became bluer during the quiescence between rebrightenings, which would mean that the low-temperature mass reservoir at the outermost disk accreted with time after the main superoutburst. Also, the ultraviolet flux was sensitive to rebrightenings as well as the optical flux, and the $U-B$ color became redder during the rebrightening phase, which would indicate that the inner disk became cooler when this object repeated rebrightenings. Our results thus basically support the idea that the cool mass reservoir in the outermost disk is responsible for rebrightenings.
We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent state. An extended emission around the source was observed up to 30 days after the peak of the superoutburst, interpreted it as a bow--shock formed by a quasi-continuous outflow from the source in quiescence. The head of the bow--shock is coincident with the high--proper motion vector of the source ($v_{perp}=123pm5$ km s$^{-1}$) at a distance of $d=202pm7$ pc. The object was detected as a weak X-ray source ($0.015pm0.002$ counts s$^{-1}$) in the plateau of the superoutburst, and its flux lowered by two times in quiescence (0.007$pm$0.002 counts s$^{-1}$). Spectroscopic observations in quiescence we confirmed the orbital period value $P_{rm{orb}}=0.0545pm 0.0026$ days, consistent with early-superhump estimates, and the following orbital parameters: $gamma= -21pm3$ km s$^{-1}$ and $K_1 = 53pm3$ km s$^{-1}$. The white dwarf is revealed as the system approaches quiescence, which enables us to infer the effective temperature of the primary $T_{eff}=11,600pm400$K. The donor temperature is estimated $lesssim 2200$K and suggestive of a system approaching the period minimum. Doppler maps in quiescence show the presence of the hot spot in HeI line at the expected accretion disc-stream shock position and an unusual structure of the accretion disc in H$alpha$.
BVRI photometry and low-, medium- and high-resolution Echelle fluxed spectroscopy is presented and discussed for three faint, heavily reddened novae of the FeII-type which erupted in 2013. V1830 Aql reached a peak V=15.2 mag on 2013 Oct 30.3 UT and suffered from a huge E(B-V)~2.6 mag reddening. After a rapid decline, when the nova was Delta(V)=1.7 mag below maximum, it entered a flat plateau where it remained for a month until Solar conjunction prevented further observations. Similar values were observed for V556 Ser, that peaked near Rc=12.3 around 2013 Nov 25 and soon went lost in the glare of sunset sky. V809 Cep peaked at V=11.18 on 2013 Feb 3.6. The reddening is E(B-V)~1.7 and the nova is located within or immediately behind the spiral Outer Arm, at a distance of ~6.5 kpc as constrained by the velocity of interstellar atomic lines and the rate of decline from maximum. While passing at t_3, the nova begun to form a thick dust layer that caused a peak extinction of Delta(V)>5 mag, and took 125 days to completely dissolve. The dust extinction turned from neutral to selective around 6000 Ang. Monitoring the time evolution of the integrated flux of emission lines allowed to constrain the region of dust formation in the ejecta to be above the region of formation of OI 7774 Ang and below that of CaII triplet. Along the decline from maximum and before the dust obscuration, the emission line profiles of Nova Cep 2013 developed a narrow component (FWHM=210 km/sec) superimposed onto the much larger normal profile, making it a member of the so far exclusive but growing club of novae displaying this peculiar feature. Constrains based on the optical thickness of the innermost part of the ejecta and on the radiated flux, place the origin of the narrow feature within highly structured internal ejecta and well away from the central binary.
We present extensive optical ($UBVRI$, $griz$, and open CCD) and near-infrared ($ZYJH$) photometry for the very nearby Type IIP SN ~2013ej extending from +1 to +461 days after shock breakout, estimated to be MJD $56496.9pm0.3$. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive $UBVRIJHK$ bolometric calibrations from $UBVRI$ and unfiltered measurements that potentially reach 2% precision with a $B-V$ color-dependent correction. We observe moderately strong Si II $lambda6355$ as early as +8 days. The photospheric velocity ($v_{rm ph}$) is determined by modeling the spectra in the vicinity of Fe II $lambda5169$ whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives $v_{rm ph} = 4500pm500$ km s$^{-1}$ at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10--12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be $9.0_{-0.6}^{+0.4}$ Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be $94pm7$ days long, yields an explosion energy of $0.9pm0.3times10^{51}$ ergs, a final pre-explosion progenitor mass of $15.2pm4.2$~M$_odot$ and a radius of $250pm70$~R$_odot$. We observe a broken exponential profile beyond +120 days, with a break point at +$183pm16$ days. Measurements beyond this break time yield a $^{56}$Ni mass of $0.013pm0.001$~M$_odot$.
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