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At least 1,063 records · Page 59
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DOE OSTI2015

Statistics of time delay and scattering correlation functions in chaotic systems. II. Semiclassical approximation

We consider S-matrix correlation functions for a chaotic cavity having M open channels, in the absence of time-reversal invariance. Relying on a semiclassical approximation, we compute the average over E of the quantities Tr[S{sup †}(E − ϵ) S(E + ϵ)]{sup n}, for general positive integer n. Our result is an infinite series in ϵ, whose coefficients are rational functions of M. From this, we extract moments of the time delay matrix Q = − iħS{sup †}dS/dE and check that the first 8 of them agree with the random matrix theory prediction from our previous paper [M. Novaes, J. Math. Phys. 56, 062110 (2015)].

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

HUBBLE SPACE TELESCOPE AND OPTICAL DATA ON SDSSJ0804+5103 (EZ Lyn) ONE YEAR AFTER OUTBURST

We present an ultraviolet (UV) spectrum and light curve of the short orbital period cataclysmic variable EZ Lyn obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope 14 months after its dwarf nova outburst, along with ground-based optical photometry. The UV spectrum can be fit with a 13,100 K, log g = 8 white dwarf using 0.5 solar composition, while fits to the individual lines are consistent with solar abundance for Si and Al, but only 0.3 solar for C. The Discrete Fourier Transforms of the UV and optical light curves at 14 months following outburst show a prominent period at 256 s. This is the same period reported by Pavlenko in optical data obtained seven months and one year after outburst, indicating its long-term stability over several months, but this period is not evident in the pre-outburst data and is much shorter than the 12.6 minute period that was seen in observations obtained during an interval from 8 months to 2.5 yr after the 2006 outburst. In some respects, the long and short periods are similar to the behavior seen in GW Lib after its outburst but the detailed explanation for the appearance and disappearance of these periods and their relation to non-radial pulsation modes remain to be explored with theoretical models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A NEW SUB-PERIOD-MINIMUM CATACLYSMIC VARIABLE WITH PARTIAL HYDROGEN DEPLETION AND EVIDENCE OF SPIRAL DISK STRUCTURE

We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (CV) period minimum of {approx}78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long-period CVs-but still at least 10 times higher than that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the H{alpha} line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Herschel observations of Circinus X-1 during outburst and quiescence

We have used the Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging REceiver instruments on the Herschel Space Observatory to observe Cir X-1 both in and out of outburst. We detected Cir X-1 during outburst at 70 μm. Unfortunately, a cold background source dominates Cir X-1 at longer wavelengths. We have assembled optical and infrared (IR) data for Cir X-1 to model its spectral energy distribution (SED) in both quiescence and outburst and find that in both states it is consistent with a heavily reddened, 10,000 K blackbody. We believe this behavior is completely consistent with previous suggestions that these outbursts are due to accretion disk events, not unlike those of dwarf novae. To explore the behavior of other low-mass X-ray binaries with reported synchrotron jets, we have extracted and/or compiled optical and near- and mid-IR data sets for five such systems to construct their SEDs. The Z-source GX 349+2 and the black hole system GRS 1915+105 have strong and variable mid-IR excesses that suggest synchrotron emission. The other Z-sources have rather weak (or no) IR excesses that can be explained as reddened blackbody spectra with the addition of either synchrotron or bremsstrahlung components.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Follow up observations of SDSS and CRTS candidate cataclysmic variables

We present photometry and spectroscopy of 11 and 35 potential cataclysmic variables, respectively, from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey, and vsnet alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76 ± 2 minutes, and possible eclipses in SDSS J2158+09 at an orbital period near 100 minutes. Time-resolved spectra reveal short orbital periods near 80 minutes for SDSS J0206+20, 85 minutes for SDSS J1502+33, and near 100 minutes for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15, and SDSS J2158+09. The prominent He II line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the absence of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Cataclysmic variables in the SUPERBLINK proper motion survey

We have discovered a new high proper motion cataclysmic variable (CV) in the SUPERBLINK proper motion survey, which is sensitive to stars with proper motions greater than 40 mas yr{sup −1}. This CV was selected for follow-up observations as part of a larger search for CVs selected based on proper motions and their near-UV−V and V−K{sub s} colors. We present spectroscopic observations from the 2.4 m Hiltner Telescope at MDM Observatory. The new CV's orbital period is near 96 minutes, its spectrum shows the double-peaked Balmer emission lines characteristic of quiescent dwarf novae, and its V magnitude is near 18.2. Additionally, we present a full list of known CVs in the SUPERBLINK catalog.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SPECTROSCOPIC ORBITAL PERIODS FOR 29 CATACLYSMIC VARIABLES FROM THE SLOAN DIGITAL SKY SURVEY

We report follow-up spectroscopy of 29 cataclysmic variables from the Sloan Digital Sky Survey (SDSS), 22 of which were discovered by SDSS and seven of which are previously known systems that were recovered in SDSS. The periods for 16 of these objects were included in the tabulation by Gänsicke et al. While most of the systems have periods less than 2 hr, only one has a period in the 80–86 minutes “spike” found by Gänsicke et al., and 11 have periods longer than 3 hr, indicating that the present sample is skewed toward longer-period, higher-luminosity objects. Seven of the objects have spectra resembling dwarf novae, but have apparently never been observed in outburst, suggesting that many cataclysmics with relatively low variability amplitude remain to be discovered. Some of the objects are notable. SDSS J07568+0858 and SDSS J08129+1911 were previously known to have deep eclipses; in addition to spectroscopy, we use archival data from the Catalina Real Time Transient Survey to refine their periods. We give a parallax-based distance of 195 (+54, −39) pc for LV Cnc (SDSS J09197+0857), which at P{sub orb} = 81 m has the shortest orbital period in our sample. SDSS J08091+3814 shows both the spectroscopic phase offset and phase-dependent absorption found in SW Sextantis stars. The average spectra of SDSS J08055+0720 and SDSS J16191+1351 show contributions from K-type secondaries, and SDSS J080440+0239 shows a contribution from an early M star. We use these to constrain the distances. SDSS J09459+2922 has characteristics typical of a magnetic system. SDSS11324+6249 may be a novalike variable, and if so, its orbital period (99 minutes) is unusually short for that subclass.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

TIME SERIES MODELS OF THREE SETS OF RXTE OBSERVATIONS OF 4U 1543-47

The X-ray nova 4U 1543-47 was in a different physical state (low/hard, high/soft, and very high) during the acquisition of each of the three time series analyzed in this paper. Standard time series models of the autoregressive moving average (ARMA) family are fitted to these series. The low/hard data can be adequately modeled by a simple low-order model with fixed coefficients, once the slowly varying mean count rate has been accounted for. The high/soft series requires a higher order model, or an ARMA model with variable coefficients. The very high state is characterized by a succession of 'dips', with roughly equal depths. These seem to appear independently of one another. The underlying stochastic series can again be modeled by an ARMA form, or roughly as the sum of an ARMA series and white noise. The structuring of each model in terms of short-lived aperiodic and 'quasi-periodic' components is discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

STARDUST INVESTIGATION INTO THE CR CHONDRITE GROVE MOUNTAIN 021710

We report the presolar grain inventory of the CR chondrite Grove Mountain 021710. A total of 35 C-anomalous grains ({approx}236 ppm) and 112 O-anomalous grains ({approx}189 ppm) were identified in situ using NanoSIMS ion imaging. Of 35 C-anomalous grains, 28 were determined to be SiC grains by Auger spectroscopy. Seven of the SiC grains were subsequently measured for N and Si isotopes, allowing classification as one nova grain, one Y grain, one Z grain, and four mainstream grains. Eighty-nine out of 112 O-anomalous grains belong to Group 1, indicating origins in low-to-intermediate-mass red giant and asymptotic giant branch stars. Twenty-one are Group 4 grains and have origins in supernovae. Auger spectroscopic elemental measurements of 35 O-anomalous grains show that 33 of them are ferromagnesian silicates. They have higher Mg/(Mg+Fe) ratios than those reported in other meteorites, suggesting a lower degree of alteration in the nebula and/or asteroid parent bodies. Only two oxide grains were identified, with stoichiometric compositions of MgAl{sub 2}O{sub 4} and SiO{sub 2}, respectively. The presolar silicate/oxide ratio of GRV 021710 is comparable with those of the CR3 chondrites (QUE 99177 and MET 00426) and primitive interplanetary dust particles. In order to search for presolar sulfides, the meteorite was also mapped for S isotopes. However, no presolar sulfides were found, suggesting a maximum abundance of 2 ppm. The scarcity of presolar sulfides may be due to their much faster sputtering rate by cosmic rays compared to silicates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Very low energy supernovae from neutrino mass loss

It now seems likely that some percentage of more massive supernova progenitors do not explode by any of the currently discussed explosion mechanisms. This has led to speculation concerning the observable transients that might be produced if such a supernova fails. Even if a prompt outgoing shock fails to form in a collapsing presupernova star, one must still consider the hydrodynamic response of the star to the abrupt loss of mass via neutrinos as the core forms a protoneutron star. Following a suggestion by Nadezhin, we calculate the hydrodynamical responses of typical supernova progenitor stars to the rapid loss of approximately 0.2-0.5 M {sub ☉} of gravitational mass from their centers. In a red supergiant star, a very weak supernova with total kinetic energy ∼10{sup 47} erg results. The binding energy of a large fraction of the hydrogen envelope before the explosion is of the same order and, depending upon assumptions regarding the maximum mass of a neutron star, most of it is ejected. Ejection speeds are ∼100 km s{sup –1} and luminosities ∼10{sup 39} erg s{sup –1} are maintained for about a year. A significant part of the energy comes from the recombination of hydrogen. The color of the explosion is extremely red and the events bear some similarity to 'luminous red novae', but have much lower speeds.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Identification of five interacting binaries in the galactic bulge survey

We present optical light curves, spectroscopy, and classification of five X-ray sources in the Chandra Galactic Bulge Survey (CXOGBS J174009.1–284725 (CX5), CXOGBS J173935.7–272935 (CX18), CXOGBS J173946.9–271809 (CX28), CXOGBS J173729.1–292804 (CX37), CXOGBS J174607.6–261547 (CX561)). These objects were selected based on bright optical counterparts which were quickly found to have emission lines in their optical spectra. This paper presents an illustration of GBS optical follow-up, targeting emission line objects. Of these five objects, four exhibit photometric variability in the Sloan r' band. CX5 shows a tentative period of 2.1 hr and is clearly an intermediate polar (IP). CX28 and CX37 both exhibit flickering with no clear period. Both are also suggested to be IPs. CX18 was observed to undergo two dwarf nova outbursts. Finally, CX561 shows no detectable variability, although its characteristics would be consistent with either a quiescent low-mass X-ray binary or cataclysmic variable.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission

We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R {sub peak} = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic outbursts lacking associated high-energy emission. If so, such sources will be uncovered in large numbers by future wide-field optical and radio transient surveys.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A SEARCH FOR RAPIDLY ACCRETING WHITE DWARFS IN THE SMALL MAGELLANIC CLOUD

The nature of the progenitors of Type Ia supernovae (SNe Ia) is still a mystery. While plausible candidates are known for both the single-degenerate and double-degenerate models, the observed numbers fall significantly short of what is required to reproduce the SNe Ia rate. Some of the most promising single-degenerate Type Ia progenitors are recurrent novae and super-soft sources (SSS). White dwarfs (WDs) with higher mass transfer rates can also be SN Ia progenitors. For these rapidly accreting white dwarfs (RAWDs), more material than is needed for steady burning accretes on the WD, and extends the WD's photosphere. Unlike SSS, such objects will likely not be detectable at soft X-ray energies, but will be bright at longer wavelengths, such as the far-ultraviolet (UV). Possible examples include LMC N66 and the V Sagittae stars. We present a survey using multi-object spectrographs looking for RAWDs in the central core of the Small Magellanic Cloud (SMC), from objects selected to be bright in the far-UV and with blue far UV - V colors. While we find some unusual objects, and recover known planetary nebula and Wolf-Rayet (WR) stars, we detect no candidate RAWD. The upper limits from this non-detection depend on our expectations of what an RAWD should look like, as well assumptions about the internal extinction of the SMC. Assuming they resemble LMC N66 or fainter versions of WR stars we set an upper limit of 10-14 RAWDs in the SMC. However, our survey is unlikely to detect objects like V Sge, and hence we cannot set meaningful upper limits if RAWDs generally resemble V Sge.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

HUBBLE SPACE TELESCOPE AND GROUND-BASED OBSERVATIONS OF V455 ANDROMEDAE POST-OUTBURST

Hubble Space Telescope spectra obtained in 2010 and 2011, 3 and 4 yr after the large amplitude dwarf nova outburst of V455 And, were combined with optical photometry and spectra to study the cooling of the white dwarf, its spin, and possible pulsation periods after the outburst. The modeling of the ultraviolet (UV) spectra shows that the white dwarf temperature remains ∼600 K hotter than its quiescent value at 3 yr post-outburst, and still a few hundred degrees hotter at 4 yr post-outburst. The white dwarf spin at 67.6 s and its second harmonic at 33.8 s are visible in the optical within a month of outburst and are obvious in the later UV observations in the shortest wavelength continuum and the UV emission lines, indicating an origin in high-temperature regions near the accretion curtains. The UV light curves folded on the spin period show a double-humped modulation consistent with two-pole accretion. The optical photometry 2 yr after outburst shows a group of frequencies present at shorter periods (250-263 s) than the periods ascribed to pulsation at quiescence, and these gradually shift toward the quiescent frequencies (300-360 s) as time progresses past outburst. The most surprising result is that the frequencies near this period in the UV data are only prominent in the emission lines, not the UV continuum, implying an origin away from the white dwarf photosphere. Thus, the connection of this group of periods with non-radial pulsations of the white dwarf remains elusive.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A search for fast optical transients in the Pan-STARRS1 medium-deep survey: M-dwarf flares, asteroids, limits on extragalactic rates, and implications for LSST

We present a search for fast optical transients (τ ∼ 0.5 hr-1 day) using repeated observations of the Pan-STARRS1 Medium-Deep Survey (PS1/MDS) fields. Our search takes advantage of the consecutive g {sub P1} r {sub P1} observations (16.5 minutes in each filter), by requiring detections in both bands, with non-detections on preceding and subsequent nights. We identify 19 transients brighter than 22.5 AB mag (S/N ≳ 10). Of these, 11 events exhibit quiescent counterparts in the deep PS1/MDS templates that we identify as M4-M9 dwarfs at d ≈ 0.2-1.2 kpc. The remaining eight transients lack quiescent counterparts, exhibit mild but significant astrometric shifts between the g {sub P1} and r {sub P1} images, colors of (g – r){sub P1} ≈ 0.5-0.8 mag, non-varying light curves, and locations near the ecliptic plane with solar elongations of about 130°, which are all indicative of main-belt asteroids near the stationary point of their orbits. With identifications for all 19 transients, we place an upper limit of R {sub FOT}(τ ∼ 0.5 hr) ≲ 0.12 deg{sup –2} day{sup –1} (95% confidence level) on the sky-projected rate of extragalactic fast transients at ≲ 22.5 mag, a factor of 30-50 times lower than previous limits; the limit for a timescale of ∼1 day is R {sub FOT} ≲ 2.4 × 10{sup –3} deg{sup –2} day{sup –1}. To convert these sky-projected rates to volumetric rates, we explore the expected peak luminosities of fast optical transients powered by various mechanisms, and find that non-relativistic events are limited to M ≈ –10 to ≈ – 14 mag for a timescale of ∼0.5 hr to ∼1 day, while relativistic sources (e.g., gamma-ray bursts, magnetar-powered transients) can reach much larger luminosities. The resulting volumetric rates are ≲ 13 Mpc{sup –3} yr{sup –1} (M ≈ –10 mag), ≲ 0.05 Mpc{sup –3} yr{sup –1} (M ≈ –14 mag), and ≲ 10{sup –6} Mpc{sup –3} yr{sup –1} (M ≈ –24 mag), significantly above the nova, supernova, and gamma-ray burst rates, respectively, indicating that much larger surveys are required to provide meaningful constraints. Motivated by the results of our search, we discuss strategies for identifying fast optical transients in the Large Synoptic Survey Telescope main survey, and reach the optimistic conclusion that the veil of foreground contaminants can be lifted with the survey data, without the need for expensive follow-up observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Convection causes enhanced magnetic turbulence in accretion disks in outburst

We present the results of local, vertically stratified, radiation magnetohydrodynamic (MHD) shearing box simulations of magneto-rotational instability (MRI) turbulence appropriate for the hydrogen ionizing regime of dwarf nova and soft X-ray transient outbursts. We incorporate the frequency-integrated opacities and equation of state for this regime, but neglect non-ideal MHD effects and surface irradiation, and do not impose net vertical magnetic flux. We find two stable thermal equilibrium tracks in the effective temperature versus surface mass density plane, in qualitative agreement with the S-curve picture of the standard disk instability model. We find that the large opacity at temperatures near 10{sup 4} K, a corollary of the hydrogen ionization transition, triggers strong, intermittent thermal convection on the upper stable branch. This convection strengthens the magnetic turbulent dynamo and greatly enhances the time-averaged value of the stress to thermal pressure ratio α, possibly by generating vertical magnetic field that may seed the axisymmetric MRI, and by increasing cooling so that the pressure does not rise in proportion to the turbulent dissipation. These enhanced stress to pressure ratios may alleviate the order of magnitude discrepancy between the α-values observationally inferred in the outburst state and those that have been measured from previous local numerical simulations of magnetorotational turbulence that lack net vertical magnetic flux.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Constraints on the progenitor system of the type Ia supernova 2014J from pre-explosion Hubble space telescope imaging

We constrain the properties of the progenitor system of the highly reddened Type Ia supernova (SN Ia) 2014J in Messier 82 (M82; d ≈ 3.5 Mpc). We determine the supernova (SN) location using Keck-II K-band adaptive optics images, and we find no evidence for flux from a progenitor system in pre-explosion near-ultraviolet through near-infrared Hubble Space Telescope (HST) images. Our upper limits exclude systems having a bright red giant companion, including symbiotic novae with luminosities comparable to that of RS Ophiuchi. While the flux constraints are also inconsistent with predictions for comparatively cool He-donor systems (T ≲ 35,000 K), we cannot preclude a system similar to V445 Puppis. The progenitor constraints are robust across a wide range of R{sub V} and A{sub V} values, but significantly greater values than those inferred from the SN light curve and spectrum would yield proportionally brighter luminosity limits. The comparatively faint flux expected from a binary progenitor system consisting of white dwarf stars would not have been detected in the pre-explosion HST imaging. Infrared HST exposures yield more stringent constraints on the luminosities of very cool (T < 3000 K) companion stars than was possible in the case of SN Ia 2011fe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

First detection of the white dwarf cooling sequence of the galactic bulge

We present Hubble Space Telescope data of the low-reddening Sagittarius window in the Galactic bulge. The Sagittarius Window Eclipsing Extrasolar Planet Search field (∼3'× 3'), together with three more Advanced Camera for Surveys and eight Wide-Field Camera 3 fields, were observed in the F606W and F814W filters, approximately every two weeks for 2 yr, with the principal aim of detecting a hidden population of isolated black holes and neutron stars through astrometric microlensing. Proper motions were measured with an accuracy of ≈0.1 mas yr{sup –1} (≈4 km s{sup –1}) at F606W ≈ 25.5 mag, and better than ≈0.5 mas yr{sup –1} (≈20 km s{sup –1}) at F606W ≈ 28 mag, in both axes. Proper-motion measurements allowed us to separate disk and bulge stars and obtain a clean bulge color-magnitude diagram. We then identified for the first time a white dwarf (WD) cooling sequence in the Galactic bulge, together with a dozen candidate extreme horizontal branch stars. The comparison between theory and observations shows that a substantial fraction of the WDs (≈30%) are systematically redder than the cooling tracks for CO-core H-rich and He-rich envelope WDs. This evidence would suggest the presence of a significant number of low-mass WDs and WD-main-sequence binaries in the bulge. This hypothesis is further supported by the finding of two dwarf novae in outburst, two short-period (P ≲ 1 day) ellipsoidal variables, and a few candidate cataclysmic variables in the same field.

79 ASTRONOMY AND ASTROPHYSICS↗