Archival Plates Research Articles

GB6 J1058+5628: A NEW QUASI-PERIODIC BL LAC OBJECT FROM THE ASIAGO PLATE ARCHIVE

We present the historic photographic light curves of three little known Blazars (two BL Lacs and one FSRQ), BZB J1058+5628, BZQ J1148+5254 and BZB J1209+4119 spanning a time interval of about 50 years, mostly built using the Asiago plate archive. All objects show evident long-term variability, over which short-term variations are superposed. One source, BZB J1058+5628, showed a marked quasi-periodic variability of 1 mag on time scale of about 6.3 years, making it one of the few BL Lac objects with a quasi-periodic behavior.

COMPREHENSIVE PHOTOMETRIC HISTORIES OF ALL KNOWN GALACTIC RECURRENT NOVAE

I collect virtually all photometry of the ten known galactic recurrent novae (RNe) and their 37 known eruptions. This consists of my modern measures of nearly all archival plates (providing the only data for half of 37 known eruptions), my own 10,000 CCD magnitudes from 1987 to present (providing virtually all of the magnitudes in quiescence for seven RNe), over 140,000 visual magnitude estimates recorded by amateur astronomers (who discovered half the known eruptions), and the small scattering of magnitudes from all the literature. From this, I produce various uniform products; (1) BVRIJHK comparison star magnitudes and BV comparison star sequences to cover the entire range of eruption, (2) complete light curves for all eruptions, (3) best fit B and V light curve templates, (4) orbital periods for all-but-one RN, (5) exhaustive searches for all missed eruptions, (6) measured discovery efficiencies since 1890, (7) true recurrence time scales, (8) predicted next eruption dates, (9) variations on time scales of minutes, hours, days, months, years, decades, and century, (10) uniform distances and extinctions to all RNe, (11) BV colors at peak and UBVRIJHK colors at minimum all with extinction corrections, and (12) the spectral energy distributions over UBVRIJHK. Highlights of this work include the discoveries of one new RN, six previously-undiscovered eruptions, and the discovery of the orbital periods for half the RNe. The goal of this work is to provide uniform demographics for answering questions like the `What is the death rate of RNe in our galaxy?' and `Are the white dwarfs gaining or losing mass over each eruption cycle?'. An important use of this work is for the question of whether RNe can be the progenitors of Type Ia supernovae.

LONG-TERM LIGHT CURVE OF HIGHLY VARIABLE PROTOSTELLAR STAR GM CEP

We present data from the archival plates at Harvard College Observatory and Sonneberg Observatory showing the field of the solar type pre-main sequence star GM Cep. A total of 186 magnitudes of GM Cep have been measured on these archival plates, with 176 in blue sensitivity, 6 in visible, and 4 in red. We combine our data with data from the literature and from the American Association of Variable Star Observers to depict the long-term light curves of GM Cep in both B and V wavelengths. The light curves span from 1895 until now, with two densely sampled regions (1935 to 1945 in B band, and 2006 until now in V band). The long-term light curves do not show any fast rise behavior as predicted by an accretion mechanism. Both the light curves and the magnitude histograms confirm the conclusion that the light curves are dominated by dips (possibly from extinction) superposed on some quiescence state, instead of outbursts caused by accretion flares.Our result excludes the possibility of GM Cep being a FUor, EXor, or McNeil's Nebula type star. Several special cases of T Tauri stars were checked, but none of these light curves are compatible with that of GM Cep. The lack of periodicity in the light curve excludes the possibility of GM Cep being a KH 15D system.

Identification and Analyses in Optical Light of Gamma‐Ray Sources with Astronomical Archival Plates

The ESA INTEGRAL satellite (International Gamma Ray Laboratory) launched in October 2002 continues to deliver valuable data about the gamma‐ray sky. Nearly 450 gamma‐ray sources have been detected so far mainly by the IBIS onboard instrument, and others are expected in the future. The first 3.5 years of INTEGRAL public and Core Program data have revealed more than 400 sources and this number is expected to increase to more than 500 in the future (Bird et al. 2007). Alternative method to identify and to analyze INTEGRAL gamma‐ray sources using optical light and astronomical archival plates is described, together with additional results from analyses of high‐energy sources in these databases.

Wide-field plate archives stored in the Ukrainian observatories

The latest version of the Wide-Field Plate Database Catalogue of Wide-Field Plate Archives (April 2008) contains 43 archives stored at some Ukrainian observatories, namely, at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine (Golosiiv, Kyiv), at the Crimean Astrophysical Observatory (Nauchnyi and Simeiz), at the Kyiv, L’viv, and Odesa University Observatories, and at the Mykolaiv Observatory. About 126000 plates were obtained from 1898 to 2005 in the framework of the following observing programmes: Solar System Bodies Observations, Observations of Variable Stars, Investigations of the Emission Nebulae and Connected Stars, Spectral Classification of the Stars and Determination of the Stellar Absorption in the Direction of the Emission Nebulae, Photographic Survey of the Northern Sky (FON), Investigation of the Kinematics and Structure of the Main Meridian Section of our Galaxy (MEGA), Observation of Selected Reference Stars, Artificial Satellites Observations and other. At the moment the basic information on 12609 plates from 13 plate archives of the Main Astronomical Observatory and Crimean Astrophysical Observatory is included into the Wide-Field Plate Database Catalogue of Wide-Field Plate Indexes (Sofia, Bulgaria). The plate digitization is just started with flatbed scanners. Some illustrations of the potential of the Ukrainian plate archives for future reusage are given and some compiled plate catalogues are presented on the basis of data from the Wide-Field Plate Database.

DISCOVERY OF A SECOND NOVA ERUPTION OF V2487 OPHIUCHI

A directed search for previously-undiscovered nova eruptions was conducted in the astronomical plate archives at Harvard College Observatory and Sonneberg Observatory. We found that an eruption of V2487 Oph (Nova Oph 1998) occurred on 1900 June 20. V2487 Oph was previously classified as a classical nova, which we identified as a probable recurrent nova based on its large expansion velocities and the presence of high excitation lines in the outburst spectrum. The event was recorded on Harvard plate AM 505, at a B magnitude of 10.27 +/- 0.11, which is near peak. The outburst can only be seen on one plate, but the image has a characteristic dumbbell shape (caused by a double exposure) that is identical to the other star images on the plate, and thus is not a plate defect. We conclude that this is in fact a previously-undiscovered nova outburst of V2487 Oph, confirming our prediction that it is a recurrent nova. We also examine the discovery efficiency for eruptions of the system and conclude that a randomly-timed outburst has, on average, a 30% chance of being discovered in the past century. Using this, we deduce a recurrence time for V2487 Oph of approximately 18 years, which implies that the next eruption is expected around 2016.

Photometric study of the FUor star V 1735 Cyg (Elias 1-12)

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1⋅m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0⋅m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1⋅m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.

ORBITAL PERIODS FOR THREE RECURRENT NOVAE

I report on the discovery of the orbital periods of three recurrent novae in our galaxy. V745 Sco has an orbital period of 510+-20 days with ellipsoidal modulations, based on SMARTS photometry from 2004-2008. V3890 Sgr has an orbital period of 519.7+-0.3 days with ellipsoidal modulations and a shallow eclipse, based primarily on SMARTS and AAVSO photometry from 1995-2008, but also extending back to 1899 with archival plates. In addition, a sinusoidal modulation of amplitude 0.2 mag and period 103.8+-0.4 days is seen mainly in the red, with this attributed to ordinary pulsations in the giant companion star. V394 CrA has an orbital period equal to twice its primary photometric period (P_orb=1.515682+-0.000008 days), as based on photometry extending from 1989-2008. I use all available information (including the UBVRIJHK spectral energy distributions) to get distances to the four RNe with red giant companions as 800+-140 pc for T CrB, 4300+-700 pc for RS Oph, 7300+-1200 pc for V745 Sco, and 6000+-1000 pc for V3890 Sgr. Further, the red giant in the RS Oph system has a mass loss rate of close to 3.7x10^-8 M_sun/yr as based on many confident measures, and this is too weak (by a factor of 100,000) to supply the white dwarf with mass at the known rate of 3.9x10^-6 M_sun/yr. Thus, the only way to get matter onto the white dwarf fast enough is through Roche lobe overflow, and this confidently demonstrates that the distance to RS Oph is >~3000 pc.

Engineering Hyperthermostability into a GH11 Xylanase Is Mediated by Subtle Changes to Protein Structure

Understanding the structural basis for protein thermostability is of considerable biological and biotechnological importance as exemplified by the industrial use of xylanases at elevated temperatures in the paper pulp and animal feed sectors. Here we have used directed protein evolution to generate hyperthermostable variants of a thermophilic GH11 xylanase, EvXyn11. The Gene Site Saturation Mutagenesis (GSSM) methodology employed assesses the influence on thermostability of all possible amino acid substitutions at each position in the primary structure of the target protein. The 15 most thermostable mutants, which generally clustered in the N-terminal region of the enzyme, had melting temperatures (Tm) 1-8 degrees C higher than the parent protein. Screening of a combinatorial library of the single mutants identified a hyperthermostable variant, EvXyn11TS, containing seven mutations. EvXyn11TS had a Tm approximately 25 degrees C higher than the parent enzyme while displaying catalytic properties that were similar to EvXyn11. The crystal structures of EvXyn11 and EvXyn11TS revealed an absence of substantial changes to identifiable intramolecular interactions. The only explicable mutations are T13F, which increases hydrophobic interactions, and S9P that apparently locks the conformation of a surface loop. This report shows that the molecular basis for the increased thermostability is extraordinarily subtle and points to the requirement for new tools to interrogate protein folding at non-ambient temperatures.

INFRARED SPECTROSCOPY OF SYMBIOTIC STARS. VI. COMBINED ORBITS FOR TWO S-TYPE SYSTEMS: V455 SCORPII AND SS 73-90

We have combined new infrared radial velocities and previously obtained spectropolarimetric observations to compute orbits of the M6 giants in two southern S-type symbiotic systems. The spectropolarimetric data enable the orbital inclinations of the systems to be determined, placing greater constraints on the properties of the components. V455 Sco has a circular orbit with a period of 1398 ± 6 days and an inclination of 94 ◦ ± 1 ◦ . The orbit of SS 73-90 has a period of 898 ± 5 days, a modest eccentricity of 0.16, and an inclination of 97 ◦ ± 7 ◦ . The center of mass velocity of each system is large, −77.9 km s −1 for V455 Sco and 89.5 km s −1 for SS 73-90, making them members of the old disk population. The M giant component of each system is likely on the asymptotic giant branch. From estimates of the M giants’ radii we predict that both systems are eclipsing and provide ephemerides to search for the eclipses. For V455 Sco, the predicted eclipses are found in data from the Harvard College Observatory plate archives. The Heii emission feature near 1.0123 µm is associated with the hot component in both systems. However, the orbits produced from the emission-line radial velocities do not lead to masses that are consistent with other results.

THE PLEASURES OF THE VAULT

Lick Observatory's photographic plate archive is among the world's most extensive. Its value lies both in its scientific potential and in the history it preserves. Its direct and spectrographic plates constitute a hundred years of data, valuable for a variety of investigations, especially those concerned with time-varying phenomena. Its historical importance lies in a wealth of material illuminating the life and work of Lick astronomers. Don Osterbrock, more than any other Lick astronomer, recognized and exploited the Plate Vault's historical potential, however many more treasures await discovery.

Hubble-type outflows of the high-excitation poly-polar planetary nebula NGC 6302 - from expansion proper motions

The outflowing proper motions of 15 knots in the dominant northwestern lobe of the high-excitation poly-polar planetary nebula NGC 6302 have been determined by comparing their positions relative to those of faint stars in an image taken at the San Pedro Martir Observatory in 2007 to those in a South African Astronomical Observatory archival plate obtained by Evans in 1956. The Hubble-type expansion of this lobe is now directly confirmed in a model-independent way from these measurements. Furthermore, an unambigous distance to NGC 6302 of 1.17 ± 0.14 kpc is now determined. Also, all the velocity vectors of the 15 knots (and two others) point back to the central source. An eruptive event from within the central torus ≈2200 yr previously must have created the high-speed lobes of NGC 6302.

A systematic search for novae in M 31 on a large set of digitized archival Schmidt plates

This paper reports on the detection of optical novae in our neighbour galaxy M31 based on digitized historical Tautenburg Schmidt plates. The accurate positions of the detected novae lead to a much larger database when searching for recurrent novae in M31. We conducted a systematic search for novae on 306 digitized Tautenburg Schmidt plates covering a time span of 36 years from 1960 to 1996. From the database of both ~ 300 000 light curves and about one million detections on only one plate per colour band, nova candidates were efficiently selected by automated algorithms and subsequently individually inspected by eye. We report the detection of 84 nova candidates. We found 55 nova candidates from the automated analysis of the light curves. Among these, 22 were previously unknown, 12 were known but not identified on Tautenburg Schmidt plates before, and 21 novae had been previously discovered on Tautenburg plates. An additional 29 known novae could be confirmed by the detailed investigation of single detections. One of our newly discovered nova candidates shows a high position coincidence with a nova detected about 30 years earlier. Therefore, this object is likely to be a recurrent nova. Furthermore, we re-investigated all 41 nova candidates previously found on Tautenburg plates and confirm all but two. Positions are given for all nova candidates with a typical accuracy of ~ 0.4 arcsec. We present light curves and finding charts as online material. The analysis of the plates has shown the wealth of information still buried in old plate archives. Extrapolating from this survey, digitization of other historical M31 plate archives (e.g. from the Mount Wilson or Asiago observatories) for a systematic nova search looks very promising.

Optical Variability of the Strong-lined and X-Ray-bright Source 1WGA J0447.9-0322

We present the historic light curve of 1WGA J0447.9-0322, spanning the time interval from 1962 to 1991, built using the Asiago archive plates. The source shows small fluctuations of about 0.3 mag around B=16 until 1986 and a fast dimming of its average level by about 0.5 mag after that date, again with small short term variations. The variability pattern is within the values shown by other QSOs with long term monitoring, notwithstanding its high X-ray/optical ratio. We present also its overall SED using literature data and recent UV-optical SWIFT observations.

Searches for Supermassive Back Hole Binaries

The digitisation of astronomical plate archives, novel software and powerful computers allow data mining in extended plate databases for the first time. We refer on the project of searches for and analysis of supermassive binary black holes (binary blazars) requiring very long time intervals (50 years and more) which cannot be provided by other data sources.

Solar system bodies ‘Observations in the Past’ with the plate archive of the Main Astronomical Observatory of the Ukrainian National Academy of Sciences

The improvement of the dynamical models of solar system bodies’ motions will be very useful for the future space astrometry mission Gaia for a fast identification of objects, to discriminate between the well-known objects and the new ones. ‘Observations in the Past’ with plate archives allow realising it.

Photometric and spectroscopic variability of the pre-main sequence star V1184 Tauri (CB 34V)

We present recent results from optical photometric and spectroscopic observations of the pre-main sequence star V1184 Tau (CB 34V). The star is associated with the Bok globule CB 34 and was considered as a FUOR candidate in previous studies. Our photometric data obtained from October 2000 to April 2003 show that the stellar brightness varies with an amplitude of about 0.m 5 (I ), but from August 2003 the photometric behavior of the star has changed dramatically. Three deep brightness minima (ΔI ∼ 4m.2) were observed during the past two years. The analysis of available photometric data suggests that V1184 Tau shows two types of variability produced (1) by rotation of large cool spotted surface and (2) by occultation from circumstellar clouds of dust or from features of a circumstellar disk. The behavior of the V – I index indicates that the star becomes redder towards minimum light, but from a certain turning point (V ∼ 18m.2) it gets bluer and is fading further. Five medium dispersion optical spectra of V1184 Tau were obtained in the period 2001–2004. Signi.cant changes in the profile and strength of the emission lines in the spectrum of V1184 Tau were found. During minimum light the equivalent width of the Hα emission line increases from 4 A to 9 A. The [O I] lines (λλ 6003, 6363 A) are also seen in emission while the sodium doublet keeps its absorption strength and equivalent width. The possibility to reconstruct the historical light curve of V1184 Tau using photographical plate archives is brie.y discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Long-Term Optical Variability of the BL Lacertae Object S5 0716+714: Evidence for a Precessing Jet

We present the historic light curve of the BL Lac object S5 0716+714, spanning the time interval from 1953 to 2003, built using Asiago archive plates and our recent CCD observations, together with literature data. The source shows an evident long term variability, over which well known short term variations are superposed. In particular, in the period from 1961 to 1983 the mean brightness of S5 0716+714 remained significantly fainter than that observed after 1994. Assuming a constant variation rate of the mean magnitude we can estimate a value of about 0.11 magnitude/year. The simultaneous occurrence of decreasing ejection velocities of superluminal moving components in the jet reported by Bach et al. (2005) suggests that both phenomena are related to the change of the direction of the jet to the line of sight from about 5 to 0.7 degrees for an approximately constant bulk Lorentz factor of about 12. A simple explanation is that of a precessing relativistic jet, which should presently be close to the smallest orientation angle. One can therefore expect in the next ten years a decrease of the mean brightness of about 1 magnitude.

A Test of Nova Trigger Theory

The theory of nova eruptions is robust, and its predictions for the expanding shell are well confirmed by observations. However, the aspect of the triggering of novae has not been experimentally tested. One prediction of theory is that the total mass accumulated by the white dwarf between eruptions should be a constant for a particular system. That is, the average accretion rate times the intereruption interval should be constant for successive eruptions by a given system. For systems where the blue light is dominated by the light from the accretion disk, the average accretion rate will be proportional to the blue flux raised to power from 1.5 to 2 (as a bolometric correction). This prediction can be tested for two recurrent novae (T Pyx and U Sco) that have complete eruption records involving three or more eruptions. I have collected archival plates, brightnesses from the literature, and a large collection of my CCD magnitudes since 1987. This provides reasonable coverage for four intereruption intervals for T Pyx and three intereruption intervals for U Sco. My results are that the product of the intereruption time interval times the average bolometrically corrected flux is indeed a constant for both T Pyx and U Sco, despite large variations in the time intervals. I take this as a good confirmation of the theory of nova triggers. This result also provides a physical basis for predicting when the next eruptions will occur, with T Pyx next erupting in the year 2052 ± 3 and U Sco next erupting in the year 2009.3 ± 1.0.

A photometric pilot study on Sonneberg archival patrol plates

The light curves of 216 arbitrarly chosen field stars and of 23 known variables in the Aur/Tau/Ori region were derived (7. m 8 ≤ B ≤ 12. m 2) from scanned, blue-sensitive archival patrol plates, covering a total of 34 years (1961−1995). We achieved a photometric accuracy of 0.07 ... 0.12 mag in spite of rather unfavourable locations of most stars near the plate borders. 17 field stars turned out to be variables, most of them with time scales of 1000−8000 days in the form of slow waves with amplitudes between 0.1 and 0.3 mag, i.e. below the threshold of traditional variable searches on photographic plates. About 50% of these new long-term variables exhibit drifts indicating periodic or erratic variability at much longer time scales than covered here. For the 23 known variables we achieved improvements in their periods and amplitudes and detected long- term variations (drifts, waves) in about 50% of them. The above fraction of low-amplitude long-term variables among field stars implies that a total of about 45 000 new variables should be detectable in the Sonneberg patrol plate archive. They will represent a new, hitherto not investigated population of variable stars with a possibly significant impact on our understanding of the stellar interior and evolution.