Papers by Evgeny Gorbikov
The Astrophysical Journal
We report the first unambiguous detection and mass measurement of an isolated stellar-mass black ... more We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star’s apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth’s motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or...
VizieR Online Data Catalog, Apr 1, 2011
The astronomer's telegram, Sep 1, 2013
The astronomer's telegram, 2014
On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We ... more On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra, and the prompt appearance of low-ionization spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in
We describe the final product of the North Celestial Cap Survey (NCC Survey, NCCS)-the optical-UV... more We describe the final product of the North Celestial Cap Survey (NCC Survey, NCCS)-the optical-UV-IR merged catalogue for the region within 10 • of the North Celestial Pole. The NCC region at δ ≥ 80 • is poorly covered by modern CCD-based surveys. The optical part of the survey was observed in V, R and I with the Wise Observatory telescopes and was merged with GALEX UV and WISE IR data, producing the catalogue. More than four million objects were observed in at least one optical band. The final catalogue contains ∼1.6 million sources observed in all three optical bands, of which some 1.4 million have WISE counterparts and ∼300,000 have GALEX counterparts. The astrometric accuracy of the optical NCCS data, derived from a comparison with the UCAC3 catalogue, is better than 0.2 arcsec and the photometry, when compared with SDSS, is good to ∼0.15 mag for sources brighter than V = 20.3, R = 21.0 and I = 19.2 mag. The SDSS point-extended source separation is reproduced with >92% efficiency.
Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, st... more Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN 2011dh/PTF 11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (ǫ e /ǫ B ∼ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R −2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000±1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early (∼ 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio ǫ e /ǫ B .
The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn,... more The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn, in the nearby galaxy, NGC 5806 (22.5 Mpc). Our spectral sequence in the optical and infrared suggests a Type Ib classification. We identify
The Astronomical Journal, 2016
With every new discovery of an extra-solar planet, the absence of planets in globular clusters (G... more With every new discovery of an extra-solar planet, the absence of planets in globular clusters (GCs) becomes more and more conspicuous. Null detection of transiting hot Jupiters in globular clusters 47 Tuc, omega Cen and NGC6397 presents an important puzzle, raising questions about the role played by cluster metallicity and environment on formation and survival of planetary systems in densely populated stellar clusters. GCs were postulated to have many free-floating planets, for which the microlensing (ML) is an established tool for detection. Dense environment, well-constrained distances and kinematics of lenses and sources, and photometry of thousands of stars simultaneously make GCs the ideal targets to search for the microlensing. We present first results of a multi-site, 69-nights long campaign to search for ML signatures of low-mass objects in the globular cluster M4, which was chosen due to its proximity, location and an actual existence of a planet. M4 was observed in R and I bands by two telescopes, 1-m T40 and 18-inch C18, of WISE Observatory, Tel Aviv, Israel, from April to July 2011. Observations on 1-m telescope were carried out in service mode, gathering 6 to 18 20-sec exposures a night for a total of 69 nights. C18 observations were done for about 4 hrs a night for 7 nights in May 2011. We employ the semi-automated pipeline to calibrate and reduce the images to the light curves that our group is developing for this purpose which includes the differential photometry package DIAPL, written by Wozniak and modified by W. Pych. Several different diagnostics are employed for search of variability/transients. While no high-significance ML event was found in this observational run, we have detected more than twenty new variables and variable candidates in M4 field, which we present here.
The iPTF (ATel #4807) reports the discovery and classification of the following core-collapse sup... more The iPTF (ATel #4807) reports the discovery and classification of the following core-collapse supernovae:
The Astrophysical Journal, 2012
Because of the development of large-format, wide-field cameras, microlensing surveys are now able... more Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will span the full range of significance levels including planetary signals too small to be distinguished from the noise. At present, we do not understand where the threshold is for detecting planets. MOA-2011-BLG-293Lb is the first planet to be published from the new surveys, and it also has substantial followup observations. This planet is robustly detected in survey+followup data (∆χ 2 ∼ 5400). The planet/host mass ratio is q = 5.3 ± 0.2 × 10 −3. The best fit projected separation is s = 0.548 ± 0.005 Einstein radii. However, due to the s ↔ s −1 degeneracy, projected separations of s −1 are only marginally disfavored at ∆χ 2 = 3. A Bayesian estimate of the host mass gives M L = 0.43 +0.27 −0.17 M ⊙ , with a sharp upper limit of M L < 1.2 M ⊙ from upper limits on the lens flux. Hence, the planet mass is m p = 2.4 +1.5 −0.9 M Jup , and the physical projected separation is either r ⊥ ≃ 1.0 AU or r ⊥ ≃ 3.4 AU. We show that survey data alone predict this solution and are able to characterize the planet, but the ∆χ 2 is much smaller (∆χ 2 ∼ 500) than with the followup data. The ∆χ 2 for the survey data alone is smaller than for any other securely detected planet. This event suggests a means to probe the detection threshold, by analyzing a large sample of events like MOA-2011-BLG-293, which have both followup data and high cadence survey data, to provide a guide for the interpretation of pure survey microlensing data.
The Astrophysical Journal, 2013
We analyze MOA-2010-BLG-311, a high magnification (A max > 600) microlensing event with complete ... more We analyze MOA-2010-BLG-311, a high magnification (A max > 600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a 2-body lens model and find that the 2-body lens model is a better fit but with only ∆χ 2 ∼ 140. The preferred mass ratio between the lens star and its companion is q = 10 −3.7±0.1 , placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question.
Monthly Notices of the Royal Astronomical Society, 2013
Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, st... more Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN 2011dh/PTF 11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (ǫ e /ǫ B ∼ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R −2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000±1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early (∼ 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio ǫ e /ǫ B .
Monthly Notices of the Royal Astronomical Society, 2010
We report results concerning the distribution and properties of galactic extinction at high galac... more We report results concerning the distribution and properties of galactic extinction at high galactic latitudes derived from stellar statistics using the Sloan Digital Sky Survey (SDSS). We use the classical Wolf diagram method to identify regions with extinction, and derive the extinction and the extinction law of the dust using all five SDSS spectral bands. We estimate the distance to the extinguishing medium using simple assumptions about the stellar populations in the line of sight. We report the identification of three extinguishing clouds, each a few tens of pc wide, producing 0.2-0.4 mag of g-band extinction, located 1-2 kpc away or 0.5-1 kpc above the Galactic plane. All clouds exhibit grey extinction, i.e. almost wavelength independent in the limited spectral range of the SDSS. We discuss the implication of this finding on general astrophysical questions.
The Astrophysical Journal, 2011
On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We ... more On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra, and the prompt appearance of low-ionization spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in
The Astrophysical Journal, 2013
The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn,... more The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn, in the nearby galaxy, NGC 5806 (22.5 Mpc). Our spectral sequence in the optical and infrared suggests a Type Ib classification. We identify
Astrophysics and Space Science, 2011
We present preliminary results of an optical-UV survey of the North Celestial Cap (NCCS) based on... more We present preliminary results of an optical-UV survey of the North Celestial Cap (NCCS) based on ∼5% areal coverage. The NCCS will provide good photometric and astrometric data for the North Celestial Cap region (80 • ≤ δ ≤ 90 •). This region, at galactic latitudes from 17 • b 37 • , is poorly covered by modern CCD-based surveys. The expected number of detected objects in NCCS is ∼1,500,000. We discuss issues of galactic structure, extinction, and the galaxy clustering in the colour-colour diagrams.
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Papers by Evgeny Gorbikov