January 11th, 2016 / Comments Off on Multicolour Optical Photometry of V404 Cyg / by Vitaly
ATel #8531: Vitaly Neustroev (University of Oulu) & George Sjoberg (AAVSO)
The black-hole X-ray binary V404 Cyg spent only few months in quiescence since the previous outburst in the summer of 2015 (ATel #8515). On 2015 December 23, the transient entered a new period of activity (GCN #18716; ATel #8453, #8454, #8455, #8457, #8458, #8462, #8501). In order to study the optical photometric behaviour of V404 Cyg during this outburst, we obtained five sets of multicolour photometric data. These observations were performed on 2015 December 29 and 31 and on 2016 January 4, 6 and 10 with the 0.35-m Celestron C14 robotic telescope, located at New Mexico Skies in Mayhill, New Mexico. We used an SBIG ST-10XME CCD camera with Johnson-Cousins BVRI Astrodon Photometric filters.
The images were taken for approximately 40-60 minutes after sunset, in a sequence B-I-R-V with exposure times of 120-240 s for each filter. In order to improve the confidence of our measurements, we aligned and summed all the nightly images for each filter and then measured the average magnitudes. Fluxes were calibrated using the secondary standards established by A. Henden (see the link to the AAVSO web-site below). The quoted uncertainties of these stars are less than 0.02 mag.
During our observations we were lucky to catch the system in both relatively high and low states. On 2015 December 29 (MJD=57385.104), the observations gave the following magnitudes:
B=17.73+-0.15, V=16.16+-0.05, R_c=14.65+-0.04, I_c=13.39+-0.03
On 2015 December 31 (MJD=57387.106), we found the following magnitudes:
B=18.77+-0.18, V=17.03+-0.07, R_c=15.64+-0.05, I_c=14.51+-0.04
The observations on the following nights gave the following magnitudes:
MJD=57391.091: V=18.04+-0.15, R_c=16.59+-0.06, I_c=15.36+-0.05
MJD=57393.064: V=17.68+-0.07, R_c=16.21+-0.05, I_c=15.15+-0.06
MJD=57397.078: V=18.12+-0.19, R_c=16.49+-0.04, I_c=15.36+-0.04
During the latter nights the source was too faint to be detected in the B band, although on 2016 January 10 (MJD=57397.078) there was a tentative detection with the B magnitude being 19.5+-0.3. V404 Cyg is still about a half magnitude brighter than during the previous quiescent period (ATel #8509).
We note, that despite a 2 mag variation of the source during our observations, we detected no significant changes in colours. The average colour indices are B-V=1.57+-0.17, V-R=1.49+-0.09, R-I=1.16+-0.08. However, these colours are bluer than they were in quiescence (Szkody & Margon, 1989, IAU Circ. No. 4794), and redder than they were during a brighter state of previous outbursts (Jones & Carter, 1989, IAU Circ. No. 4794; Marti et al., 2016, A&A, in press). We will continue our monitoring in the following nights, while the source is still visible.
Posted in: Astronomy, Observations, Publications, Work
Tags: ATel, News
December 9th, 2015 / Comments Off on Voracious vortexes in cataclysmic variables: Multi-epoch tomographic study of HT Cassiopeia / by Vitaly
The paper entitled “Voracious vortexes in cataclysmic variables: Multi-epoch tomographic study of HT Cassiopeia” has been accepted on November 4, 2015 for publication in A&A.
DOI – Preprint
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September 1st, 2015 / Comments Off on Workshop on Relativistic Astrophysics / by Vitaly
I participated in an international workshop on Relativistic Astrophysics in Turku (Finland) and have given the talk “Evolution of accretion discs of dwarf novae and low-mass X-ray binary transients through their whole outburst cycle”.
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Tags: Conferences, News
August 27th, 2015 / Comments Off on The future is already here :) / by Vitaly
Two new MAGIC papers have been published in 2016. Oh wait, it’s still 2015! Anyway, the papers are
Aleksić J., …, Neustroev V., et al. (the MAGIC Collaboration):
The major upgrade of the MAGIC telescopes, Part I: The hardware improvements and the commissioning of the system, 2016, APh, 72, 61 (arXiv:1409.6073)
The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula, 2016, APh, 72, 76 (arXiv:1409.5594)
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July 26th, 2015 / Comments Off on “Survey Of Period Variations Of Superhumps In SU UMa-Type Dwarf Novae. VII” / by Vitaly
The paper “Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. VII: The Seventh Year (2014-2015)” has been accepted for publication in PASJ (preprint).
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May 24th, 2015 / Comments Off on MAGIC observations at the Roque de los Muchachos Observatory / by Vitaly
I’m in La Palma at the Roque de los Muchachos Observatory again, performing observations with MAGIC. Like during the previous visit, there were again some problems with the weather. However, if in 2014 there was an icy storm, this time I was met by a heat wave with calima. Anyway, we survived and now have a very good weather.
Posted in: Astronomy, Blog, MAGIC, Observations, Work
Tags: News
April 24th, 2015 / Comments Off on The MAGIC paper on the high-peaked BL Lac object 1ES 0806+524 / by Vitaly
The MAGIC paper entitled “MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524” has been accepted for publication in MNRAS [ArXiv]
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April 2nd, 2015 / Comments Off on My first paper with MAGIC / by Vitaly
The first paper since I joined the MAGIC collaboration has been published in Astronomy and Astrophysics. This paper entitled “MAGIC observations of MWC 656, the only known Be/BH system″, 2015, A&A, 576, id: A36 (5 pp).
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January 25th, 2015 / Comments Off on The research visit to Instituto de Astronomía (UNAM, Mexico) / by Vitaly
The research visit to Instituto de Astronomía (UNAM) and observations in Observatorio Astronómico Nacional at San Pedro Mártir were very productive.
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October 22nd, 2014 / Comments Off on Fifth International Fermi Symposium / by Vitaly
I’m participating in Fifth International Fermi Symposium at Nagoya (Japan).
Posted in: Astronomy, Conferences, Work
Tags: Conferences, News