Dust and Metal Column Densities in Gamma-Ray Burst Host Galaxies

In this paper we present the results from the analysis of a sample of 28 gamma-ray burst (GRB) afterglow spectral energy distributions, spanning the X-ray through to near-infrared wavelengths. This is the largest sample of GRB afterglow spectral energy distributions thus far studied, providing a strong handle on the optical depth distribution of soft X-ray absorption and dust-extinction systems in GRB host galaxies. We detect an absorption system within the GRB host galaxy in 79% of the sample, and an extinction system in 71% of the sample, and find the Small Magellanic Cloud (SMC) extinction law to provide an acceptable fit to the host galaxy extinction profile for the majority of cases, consistent with previous findings. The range in the soft X-ray absorption to dust-extinction ratio, N_{H,X}/Av, in GRB host galaxies spans almost two orders of magnitude, and the typical ratios are significantly larger than those of the Magellanic Clouds or Milky Way. Although dust destruction could be a cause, at least in part, for the large N_{H,X}/Av ratios, the good fit provided by the SMC extinction law for the majority of our sample suggests that there is an abundance of small dust grains in the GRB environment, which we would expect to have been destroyed if dust destruction were responsible for the large N_{H,X}/Av ratios. Instead, our analysis suggests that the distribution of N_{H,X}/Av in GRB host galaxies may be mostly intrinsic to these galaxies, and this is further substantiated by evidence for a strong negative correlation between N_{H,X}/Av and metallicity for a subsample of GRB hosts with known metallicity. Furthermore, we find the N_{H,X}/Av ratio and metallicity for this subsample of GRBs to be comparable to the relation found in other more metal-rich galaxies.Comment: 23 pages, 10 figures, accepted for publication in MNRA

Taxonomy of GRB optical light-curves: identification of a salient class of early afterglows

The temporal behaviour of the early optical emission from Gamma-Ray Burst afterglows can be divided in four classes: fast-rising with an early peak, slow-rising with a late peak, flat plateaus, and rapid decays since first measurement. The fast-rising optical afterglows display correlations among peak flux, peak epoch, and post-peak power-law decay index that can be explained with a structured outflow seen off-axis, but the shock origin (reverse or forward) of the optical emission cannot be determined. The afterglows with plateaus and slow-rises may be accommodated by the same model, if observer location offsets are larger than for the fast-rising afterglows, or could be due to a long-lived injection of energy and/or ejecta in the blast-wave. If better calibrated with more afterglows, the peak flux-peak epoch relation exhibited by the fast and slow-rising optical light-curves could provide a way to use this type of afterglows as standard candles.Comment: 8 pages, submitted to MNRA

The effects of tolterodine for the treatment of stent-related symptoms

Aim: То evaluate the effects of tolterodine for the treatment of stent-related lower urinary tract symptoms. Patients and methods: Since January 2010 to February 2011 143 patients (69 men and 74 women: age range - 18-76, mean age 49.6 years) who underwent insertion of a Double-J stent after urological surgery were prospectively randomized into 2 groups. Group 1 included 69 patients who received 2 mg of tolterodine (Urotol, Zentiva), twice daily for 37 days and routine anti-inflammatory (pefloxacine) therapy; group 2 included 74 patients who received only anti-inflammatory drugs for the same protocol. All patients completed a validated Ureteral Stent Symptom Questionnaire and Visual Analog Scale (VAS) after the stent placement. Results: The mean urinary symptom index was 13.8 in group 1,18.7 in group 2 (p < 0,05). The mean VAS scores were 59% and 48%, respectively (p< 0,05). There were no cases of drug adverse effects. Conclusions: Tolterodine administration improves quality of life and up to 25% decreases severety of stent-related urinary symptoms.Целью данной работы являлось изучение влияния терапии толтеродином на качество жизни и «стент-зависимые симтомы» у больных с внутренними стентами. Пациенты и методы: С января 2010 г. по февраль 2011 г в ГКУБ №47 г. Москвы и на кафедре урологии с курсом нефрологии Астраханской Государственной Медицинской Академии нами было проспективно отобрано 143 пациента (69 мужчин, 74 женщин, в возрасте от 18 до 76 лет (в среднем 49,6 г), которым по тем или иным причинам было произведено стентирование мочеточника. Случайным образом пациенты были рандомизированы на 2 группы. Первая группа больных (n = 69) принимала после установки стента толтеродин (Уротол, Зентива) в дозе 2 мг два раза в день в сочетании с курсом противовоспалительной терапии, включавшим в себя прием фторхинолона (пефлоксацин 400 мг дважды в день) в течение 7 дней с последующим переходом на уроантисептики, и спазмолитической терапии по потребности. Средняя длительность приема толтеродина на данном зтапе исследования составила 37 дней. Вторая группа пациентов (n = 74) не получала м-холиноблокатора. Терапия симптомов, связанных с наличием стента, заключалась в проведении аналогичной с первой группой противовоспалительной и спазмолитической терапии. Через 31-49 (в среднем 37) дней от момента установки стента всем 143 пациентам проведена цистоскопия и удаление стента. Перед манипуляцией пациенты также заполняли опросник и визуальную аналоговую шкалу симптомов. Результаты: добавление толтеродина к проводимой стандартной противовоспалительной и спазмолитической терапии уже ко второй неделе стентирования привело к снижению суммарной симптоматики на 25% (13,8 против 18,7 баллов) по сравнению с группой больных, получавших только стандартное лечение. Схожие данные, свидетельствующие об объективности оценки пациентами своих жалоб, были получены по данным сравнения визуальной аналоговой шкалы (59% против 48%). Безопасность приема толтеродина подтверждена в нашем исследовании отсутствием побочных эффектов, связанных с его приемом и тем, что ни в одном случае пациенты не выбыли из исследования в связи с отказом от приема препарата. Выводы: Применение толтеродина у больных с наличием внутреннего стента позволяет на 25% снизить выраженность ирритативных симптомов, связанных с наличием стента и улучшить качество жизни больных

A unifying view of Gamma Ray Burst Afterglows

We selected a sample of 33 Gamma Ray Bursts (GRBs) detected by Swift, with known redshift and optical extinction at the host frame. For these, we constructed the de-absorbed and K-corrected X-ray and optical rest frame light curves. These are modelled as the sum of two components: emission from the forward shock due to the interaction of a fireball with the circum-burst medium and an additional component, treated in a completely phenomenological way. The latter can be identified, among other possibilities, as "late prompt" emission produced by a long lived central engine with mechanisms similar to those responsible for the production of the "standard" early prompt radiation. Apart from flares or re-brightenings, that we do not model, we find a good agreement with the data, despite of their complexity and diversity. Although based in part on a phenomenological model with a relatively large number of free parameters, we believe that our findings are a first step towards the construction of a more physical scenario. Our approach allows us to interpret the behaviour of the optical and X-ray afterglows in a coherent way, by a relatively simple scenario. Within this context it is possible to explain why sometimes no jet break is observed; why, even if a jet break is observed, it is often chromatic; why the steepening after the jet break time is often shallower than predicted. Finally, the decay slope of the late prompt emission after the shallow phase is found to be remarkably similar to the time profile expected by the accretion rate of fall-back material (i.e. proportional to t^{-5/3}), suggesting that this can be the reason why the central engine can be active for a long time.Comment: 20 pages, 17 figures, Accepted for publication in MNRA

The optically unbiased gamma-ray burst host (TOUGH) survey. I. survey design and catalogs

Long-duration gamma-ray bursts (GRBs) are powerful tracers of star-forming galaxies. We have defined a homogeneous subsample of 69 Swift GRB-selected galaxies spanning a very wide redshift range. Special attention has been devoted to making the sample optically unbiased through simple and well-defined selection criteria based on the high-energy properties of the bursts and their positions on the sky. Thanks to our extensive follow-up observations, this sample has now achieved a comparatively high degree of redshift completeness, and thus provides a legacy sample, useful for statistical studies of GRBs and their host galaxies. In this paper, we present the survey design and summarize the results of our observing program conducted at the ESO Very Large Telescope (VLT) aimed at obtaining the most basic properties of galaxies in this sample, including a catalog of R and K-s magnitudes and redshifts. We detect the host galaxies for 80% of the GRBs in the sample, although only 42% have K-s-band detections, which confirms that GRB-selected host galaxies are generally blue. The sample is not uniformly blue, however, with two extremely red objects detected. Moreover, galaxies hosting GRBs with no optical/NIR afterglows, whose identification therefore relies on X-ray localizations, are significantly brighter and redder than those with an optical/NIR afterglow. This supports a scenario where GRBs occurring in more massive and dusty galaxies frequently suffer high optical obscuration. Our spectroscopic campaign has resulted in 77% now having redshift measurements, with a median redshift of 2.14 +/- 0.18. TOUGH alone includes 17 detected z > 2 Swift GRB host galaxies suitable for individual and statistical studies-a substantial increase over previous samples. Seven hosts have detections of the Ly alpha emission line and we can exclude an early indication that Ly alpha emission is ubiquitous among GRB hosts, but confirm that Ly alpha is stronger in GRB-selected galaxies than in flux-limited samples of Lyman break galaxies