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Ian Miller

Publications and source records attributed to Ian Miller.

54 records · Page 3Linked to original sources
arXiv2011

The orbital and superhump periods of the SU UMa-type dwarf nova V1212 Tauri

We report CCD photometry of the superoutburst of the dwarf nova V1212 Tau obtained during 2011 January and February. The outburst amplitude was at least 6 magnitudes and it lasted at least 12 days. Three distinct superhump regimes were observed. Initially low amplitude superhumps (0.03 to 0.05 magnitude peak-to-peak) with Psh = 0.0782(52) d were present. The superhumps reached a maximum amplitude of 0.31 magnitudes at the beginning of the plateau phase, with Psh = 0.07031(96) d. Subsequently the star began to fade slowly. During the first part of the decline, the period increased with dPsh/dt = +1.62(9) x 10-3 and the amplitude of the superhumps also declined. Mid way through the slow decline, the superhumps partially regrew and this point coincided with a change to a new superhump regime during which the period decreased with dPsh/dt = -1.50(39) x 10-3. We determined the orbital period as Porb = 0.06818(64) d and the superhump period excess as epsilon = 0.034(15)

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arXiv2011

Superhumps and grazing eclipses in the dwarf nova BG Arietis

We report unfiltered photometry of BG Arietis (= SDSS J015151.87+140047.2) in 2009 and 2010 which shows the presence of superhumps with peak-to-peak amplitude of up to 0.36 magnitudes showing this to be an SU UMa type dwarf nova. The outburst amplitude was 5.1 magnitudes above a mean quiescence magnitude of 19.9. The 2010 event lasted at least 20 days during which we observed a precursor outburst which was immediately followed by a superoutburst. Modulations were observed during the rise to superoutburst with a period approximately half Porb. The mean superhump period during the plateau phase was Psh = 0.0849(6) d, representing a superhump period excess epsilon = 0.030(7). We also observed small eclipses of depth 0.06 to 0.13 magnitude and FWHM duration of ~12 mins (ΔΦ1/2 = 0.10), which we interpret as grazing eclipses of the accretion disc. The 2009 superoutburst was less well observed, especially in the early stages, so we cannot tell whether there was a precursor outburst. The mean superhump period during the plateau was Psh = 0.0851(4) d, but towards the end of the plateau it suddenly decreased to Psh = 0.0845(11) d. Small eclipses were also observed.

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arXiv2011

The orbital period of the eclipsing dwarf nova SDSS J081610.84+453010.2

We present time resolved photometry of the cataclysmic variable SDSS J081610.84+453010.2 and have established for the first time that it is an eclipsing dwarf nova. We observed an outburst of the system which lasted about 11 days and had an amplitude of 3.4 magnitudes above mean quiescence. From an analysis of the eclipse times of minimum during the outburst, we determined the orbital period as Porb = 0.2096(4) d or 5.030(10) h. The orbital period places it above the period gap in the distribution of orbital periods of dwarf novae. The eclipses are of short duration (average FWHM = 10.7 min or 0.036 of the orbital period) and shallow (average 0.4 mag during outburst and 0.6 magnitude in quiescence), suggesting a grazing eclipse.

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arXiv2010

The outburst of V713 Cephei in August 2009

During the outburst of V713 Cephei in August 2009 the times of 8 eclipses were measured and these, together with 5 eclipse timings obtained during quiescence in August 2007, provide an improved orbital period of 0.085418432(4)d. No superhumps were observed in the light curve indicating this was a normal UG-type dwarf nova outburst. We found the eclipse depth decreased linearly with rising system excitation level, falling from ~3 magnitudes in quiescence to ~2 magnitudes during outburst. The depth and totality of eclipses in quiescence suggests a high orbital inclination. We saw no variation in the FWHM of eclipses between quiescence and outburst despite a significant change in shape of the eclipse profile.

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arXiv2010

Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. II: The Second Year (2009-2010)

As an extension of the project in Kato et al. (2009, arXiv:0905.1757), we collected times of superhump maxima for 61 SU UMa-type dwarf novae mainly observed during the 2009-2010 season. The newly obtained data confirmed the basic findings reported in Kato et al. (2009): the presence of stages A-C, as well as the predominance of positive period derivatives during stage B in systems with superhump periods shorter than 0.07 d. There was a systematic difference in period derivatives for systems with superhump periods longer than 0.075 d between this study and Kato et al. (2009). We suggest that this difference is possibly caused by the relative lack of frequently outbursting SU UMa-type dwarf novae in this period regime in the present study. We recorded a strong beat phenomenon during the 2009 superoutburst of IY UMa. The close correlation between the beat period and superhump period suggests that the changing angular velocity of the apsidal motion of the elliptical disk is responsible for the variation of superhump periods. We also described three new WZ Sge-type objects with established early superhumps and one with likely early superhumps. We also suggest that two systems, VX For and EL UMa, are WZ Sge-type dwarf novae with multiple rebrightenings. The O-C variation in OT J213806.6+261957 suggests that the frequent absence of rebrightenings in very short-Porb objects can be a result of sustained superoutburst plateau at the epoch when usual SU UMa-type dwarf novae return to quiescence preceding a rebrightening. We also present a formulation for a variety of Bayesian extension to traditional period analyses.

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arXiv2010

Precursor outbursts and superoutbursts in the SU UMa-type dwarf nova NN Camelopardalis

We report photometry of three outbursts of NN Cam in 2007, 2008 and 2009. The 2007 event started with a normal outburst, lasting about 4 days, which was a precursor to a superoutburst lasting at least 13 days. Both the precursor and the superoutburst had an amplitude of 4.9 mag above mean quiescence. Superhumps with a maximum peak-to-peak amplitude of 0.22 mag were detected during the superoutburst with a mean superhump period Psh = 0.07385(56) d. Psh decreased continuously with dPsh /dt = -1.72(23) x 10-3. We used our measurement to confirm that the shorter of two possible values of Porb reported by another researcher is the correct one, Porb = 0.0717 d. The 2008 outburst was rather poorly observed, although we present evidence that this too may have been a superoutburst. The 2009 event was also a superoutburst, with Psh = 0.07414(44) d, but we could find no evidence for a precursor. From the 2007 and 2009 data, we report a superhump period excess of epsilon = 0.030(8) to 0.034(6), which is typical for SU UMa dwarf novae of similar orbital period, and estimate the binary mass ratio q = Mwd/Msec $\simeq$ 0.11 to 0.17

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arXiv2010

The orbital and superhump periods of the deeply eclipsing dwarf nova SDSS J150240.98+333423.9

During July 2009 we observed the first confirmed superoutburst of the eclipsing dwarf nova SDSS J150240.98+333423.9 using CCD photometry. The outburst amplitude was at least 3.9 magnitudes and it lasted at least 16 days. Superhumps having up to 0.35 peak-to-peak amplitude were present during the outburst, thereby establishing it to be a member of the SU UMa family. The mean superhump period during the first 4 days of the outburst was Psh = 0.06028(19) d, although it increased during the outburst with dPsh/dt = + 2.8(1.0) x 10-4. The orbital period was measured as Porb = 0.05890946(5) d from times of eclipses measured during outburst and quiescence. Based on the mean superhump period, the superhump period excess was 0.023(3). The FWHM eclipse duration declined from a maximum of 10.5 min at the peak of the outburst to 3.5 min later in the outburst. The eclipse depth increased from ~0.9 mag to 2.1 mag over the same period. Eclipses in quiescence were 2.7 min in duration and 2.8 mag deep.

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arXiv2010

Discovery and outburst characteristics of the dwarf nova ASAS J224349+0809.5

We report the discovery of a new dwarf nova and our observations of its first confirmed superoutburst during 2009 October. The outburst amplitude was 6 magnitudes. The main outburst lasted 17 days and was followed 4 days later by a remarkable rebrightening. Superhumps were present during the main outburst, which confirms that it belongs to the SU UMa family. Initially the mean superhump period was Psh = 0.06965(17) d, but analysis of the O-C residuals showed a dramatic evolution in Psh during the outburst. During the first two-thirds of the plateau phase the period increased with dPsh/dt = +1.24(5) x 10-3. There was then an abrupt change following which the period decreased with dPsh/dt = -1.01(9) x 10-3. The amplitude of the superhumps also varied, with a maximum amplitude near the beginning of the outburst and a second maximum corresponding to the discontinuity in Psh. Analysis of archival data showed outbursts also occurred in October 2005, June 2006 and June 2007. Assuming that the superoutbursts are periodic, we estimate that the outburst period is around 450 days.

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arXiv2010

Superoutbursts of the SU UMa-type dwarf nova CP Draconis

Analysis of observations of the SU UMa-type dwarf nova, CP Dra, between February 2001 and April 2009 has revealed 15 outbursts, at least eight of which were superoutbursts. The supercycle length is 230+/-56 d. We report photometry of the 2001 and 2009 superoutbursts which shows that they were remarkably similar to each other in terms of the profile of the outburst light curve and the evolution of the superhumps. The outburst amplitude was 5.5 magnitudes and the Psh during the plateau phase was measured at 0.08335(31) and 0.08343(21) d, respectively. In both cases, Psh decreased during the course of the outburst and there is some evidence that there was an abrupt change corresponding to the point in the plateau where a slow fade begins. The 2001 superoutburst was caught during the rise to maximum and during this period we found that the Psh was significantly longer than during the subsequent stages. Superhumps of 0.3 magnitude peak-to-peak amplitude were present at the height of each outburst and these gradually diminished during the outburst. We also report photometry from the 2002 superoutburst, although coverage was not so extensive, which revealed Psh = 0.08348(32) d consistent with the other two superoutbursts. Analysis of time resolved photometry from the 2009 outburst revealed evidence for an orbital period of 0.08084(86) d, giving a fractional superhump period excess epsilon = 0.032(3) d.

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arXiv2009

CSS090530:144011+494734: a new SU UMa-type dwarf nova in Bootes

We report photometry and analysis of a previously unknown SU UMa-type dwarf nova in Bootes detected in outburst by the Catalina Real-time Transient Survey on 2009 May 30 with the discovery identifier CSS090530:144011+494734. This apparently stellar object had previously been catalogued by the Sloan Digital Sky survey as SDSS J144011.01+494733.4. We measured its mean superhump period over the first 3 days following detection as 0.06500(4) d at which point this changed to 0.06438(3) d. We detected a possible orbital period of 0.06322(8) d implying a mean superhump period excess of 0.020(2). After detection, the dwarf nova maintained steady brightness for 5 days before starting to fade. The outburst amplitude was 5.5 magnitudes above its quiescent level.

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arXiv2009

Measuring the superhump period of the dwarf nova RX J1715.6+6856

We report unfiltered CCD observations of the first confirmed superoutburst of the dwarf nova RX J1715.6+6856 in August 2009. At quiescence the star was magnitude 18.3 (CCD, clear). The outburst amplitude was at least 2.4 magnitudes and it lasted at least 6 days, although the first part of the outburst was probably missed. Analysis of the light curve revealed superhumps with peak-to-peak amplitude of 0.1 magnitude, thereby showing it to be a member of the SU UMa family. The mean superhump period was Psh = 0.07086(78) d with a superhump period excess of epsilon = 0.038 and an estimated mass ratio q = 0.167. In the final stages of the outburst, as the star approached quiescence, the superhumps disappeared to be replaced by a modulation corresponding to the orbital period. The star was regularly monitored between August 2007 and September 2009 revealing a total of 12 outbursts, with an outburst frequency of approximately once per month.

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arXiv2009

The 2008 outburst of the cataclysmic variable V358 Lyrae

We report photometry of V358 Lyr during its 2008 November outburst, the first confirmed outburst since 1965. At its brightest the star was V=15.9 and the outburst amplitude was at least 7.3 magnitudes and lasted at least 23 days. The first 4 days of the outburst corresponded to the plateau phase and the star then faded at 0.13 mag/d over the next 7 days. There was then a drop in brightness to a temporary minimum at mag 19.5, which lasted less than 4 days, after which the star recovered to its previous brightness. The final stages of the outburst were poorly covered. Time resolved photometry during the outburst revealed no obvious large-scale modulations such as superhumps. Although some small apparently periodic signals were detected, their significance is uncertain. Our observations, and those of previous researchers, support V358 Lyr being a dwarf nova and are consistent with it being a member of the WZ Sge family.

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arXiv2009

GSC2.3 N152008120 - a new SU UMa-type dwarf nova in Draco

We report observations during 2008 October of the first recorded superoutburst of a previously unknown SU UMa-type dwarf nova in Draco located at 19h 14m 43.52s +60d 52m 14.1s (J2000). Simbad lists a 21st magnitude star at this position with identifiers GSC2.3 N152008120 and USNO-B1.0 1508-0249096. The outburst reached magnitude 14.9, its amplitude was approximately 6 magnitudes and its duration at least 11 days. About 11 days after the end of the main outburst there was a short-lived rebrightening by more than 2 magnitudes. Superhumps were observed with a mean period of 0.07117(1) d and amplitude 0.12 mag. There was a distinct shortening in the superhump period around cycle 80 with Psh = 0.07137(2) d before and Psh = 0.07091(2) d after. We saw weak evidence of an increasing Psh before cycle 80 with dPsh/dt = 3.4(2.0) * 10-5.

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arXiv2008

Observations of the cataclysmic variable SDSS J081321.91+452809.4

Our observations of the first reported outburst of SDSS J081321.91+452809.4 during 2008 April show that this cataclysmic variable is a dwarf nova. The outburst amplitude was at least 3.1 magnitudes and the outburst appears to have been rather short-lived at around 3 days with a rapid decline to quiescence of 0.73 mag/day.

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arXiv2008

SDSS J162718.39+120435.0 - a dwarf nova in the period gap

SDSS J162718.39+120435.0 was suspected of being a dwarf nova from spectroscopic observations made available by the Sloan Digital Sky Survey. Photometry conducted during the 2008 outburst, the first ever outburst of this object detected and followed up in real time, shows that the outburst reached magnitude 14.6 at maximum, had an amplitude of 4.6 magnitudes and lasted for at least 18 days. Common superhumps were detected with an amplitude of up to 0.4 magnitudes, confirming it to be a member of the SU UMa family. Initially the superhump period, Psh, was 0.10993(7) days (2.638 hours), but it subsequently reduced to Psh = 0.10890(9) days (2.614 hours) later in the outburst. The period change corresponds to the end of the plateau period of the outburst. The orbital period, Porb, was estimated from the two Psh values as between 0.1026 d and 0.1016 d, which places SDSS1627 near the centre of the period gap in the orbital period distribution of cataclysmic variables.

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arXiv2008

The 2008 February superoutburst of V452 Cas

Observations of the 2008 February outburst of V452 Cas show that the profile, duration and magnitude at maximum were very similar to the previous superoutburst in 2007 September. Low-amplitude variations consistent with previously observed superhumps were also seen.

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arXiv2008

Outburst characteristics of the dwarf nova V452 Cassiopeiae

V452 Cas was thought to have rare outbursts, but monitoring from 2005 to 2008 has shown that the outburst interval is about one month and is weakly periodic. Observations of seven superoutbursts over the same period shows a very repeatable superoutburst period of 146 +/-16 days. Time series photometry of the 2007 September superoutburst shows that the outburst reached magnitude 15.3 at maximum and had an amplitude of 3.2 magnitudes. The outburst lasted for 12 days. Early superhumps with an amplitude of 0.3 magnitudes and period of Psh = 0.08943(7) days gave way to superhumps with decreasing amplitude and Psh = 0.08870(2) days later in the outburst, corresponding to a continuous period change Pdot/P = -9(2)x10-4 d-1 . V452 Cas has one of the smallest outburst amplitudes and shortest superoutburst periods of typical UGSU systems.

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