arXiv subjects

H. E. Jermak

Publications and source records attributed to H. E. Jermak.

4 recordsLinked to original sources

arXiv2026

New Robotic Telescope: The big eye to observe the transient Universe

NRT is an international project to build and operate the world's largest robotic telescope. The telescope will have a segmented primary mirror with an equivalent diameter of 4 m, a set of simultaneously mounted optical and near-infrared instruments, and a response time of less than 30 seconds. The project builds on the experience gained with the successful twenty-year operation of the Liverpool telescope, and with the GTC optics and control system. All of the above together with the excellent conditions for astronomical observation of La Palma, represents a solid base and guarantees that NRT will be one of the leading facilities in the field of time domain astronomy. This contribution will analyze the current status of the project with special emphasis on the development of its optics, and the plans for its construction and operation.

astro-ph.IM↗

arXiv2017

Optical Polarimetry of KIC 8462852 in May-August 2017

We present optical polarimetry in the period May-August 2017 of the enigmatic "dipping" star KIC 8462852. During that period three ~1% photometric dips were reported by other observers. We measured the average absolute polarization of the source, and find no excess or unusual polarization compared to a nearby comparison star. We place tight upper limits on any change in the degree of polarization of the source between epochs in- and out-of-dip of <0.1% (8500-Ang.) and <0.2% (7050-Ang. and 5300-Ang.). How our limits are interpreted depends on the specific model being considered. If the whole stellar disk were covered by material with an optical depth of ~0.01 then the fractional polarisation introduced by this material must be less than 10-20%. While our non-detection does not constrain the comet scenario, it predicts that even modest amounts of dust that have properties similar to Solar System comets may be detectable. We note that the sensitivity of our method scales with the depth of the dip. Should a future ~20% photometric dip be observed (as was previously detected by Kepler) our method would constrain any induced polarization associated with any occulting material to 0.5-1.0%.

astro-ph.SR↗

arXiv2017

Polarimetry and Photometry of Gamma-Ray Bursts with RINGO2

We present a catalog of early-time (~10^2-10^4s) photometry and polarimetry of all Gamma-Ray Burst (GRB) optical afterglows observed with RINGO2 imaging polarimeter on the Liverpool Telescope. For the 19 optical afterglows observed, the following 9 were bright enough to perform photometry and attempt polarimetry: GRB 100805A, GRB 101112A, GRB 110205A, GRB 110726A, GRB 120119A, GRB 120308A, GRB 120311A, GRB 120326A and GRB 120327A. We present multi-wavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough investigation of detection probabilities, instrumental properties and systematics. Using two independent methods, we confirm previous reports of significant polarization in GRB 110205A and 120308A, and report new detection of $P=6^{+3}_{-2}\%$ in GRB101112A. We discuss the results for the sample in the context of the reverse and forward shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields and highlights the importance of rapid-response polarimetry.

astro-ph.HE↗

arXiv2016

LOTUS: A low cost, ultraviolet spectrograph

We describe the design, construction and commissioning of LOTUS; a simple, low-cost long-slit spectrograph for the Liverpool Telescope. The design is optimized for near-UV and visible wavelengths and uses all transmitting optics. It exploits the instrument focal plane field curvature to partially correct axial chromatic aberration. A stepped slit provides narrow (2.5x95 arcsec) and wide (5x25 arcsec) options that are optimized for spectral resolution and flux calibration respectively. On sky testing shows a wavelength range of 3200-6300 Angstroms with a peak system throughput (including detector quantum efficiency) of 15 per cent and wavelength dependant spectral resolution of R=225-430. By repeated observations of the symbiotic emission line star AG Peg we demonstrate the wavelength stability of the system is less than 2 Angstroms rms and is limited by the positioning of the object in the slit. The spectrograph is now in routine operation monitoring the activity of comet 67P/Churyumov-Gerasimenko during its current post-perihelion apparition.

astro-ph.IM↗