Astreaks: Astrometry of NEOs with trailed background stars

The detection and accurate astrometry of fast-moving near-Earth objects (NEOs) has been a challenge for the follow-up community. Their fast apparent motion results in streaks in sidereal images, thus affecting the telescope's limiting magnitude and astrometric accuracy. A widely adopted technique to mitigate trailing losses is non-sidereal tracking, which transfers the streaking to background reference stars. However, no existing publicly available astrometry software is configured to detect such elongated stars. We present Astreaks, a streaking source detection algorithm, to obtain accurate astrometry of NEOs in non-sidereal data. We validate the astrometric accuracy of Astreaks on 371 non-sidereally tracked images for 115 NEOs with two instrument set-ups of the GROWTH-India Telescope. The observed NEOs had V-band magnitude in the range [15, 22] with proper motion up to 140$^{\prime\prime}$/min, thus resulting in stellar streaks as high as 6.5$^\prime$ (582 pixels) in our data. Our method obtained astrometric solutions for all images with 100% success rate. The standard deviation in Observed-minus-Computed (O-C) residuals is 0.52$^{\prime\prime}$, with O-C residuals <2$^{\prime\prime}$(<1$^{\prime\prime}$) for 98.4% (84.4%) of our measurements. These are appreciable, given the pixel scale of $\sim$0.3$^{\prime\prime}$ and $\sim$0.7$^{\prime\prime}$ of our two instrument set-ups. This demonstrates that our modular and fully-automated algorithm helps improve the telescope system's limiting magnitude without compromising astrometric accuracy by enabling non-sidereal tracking on the target. This will help the NEO follow-up community cope with the accelerated discovery rates and improved sensitivity of the next-generation NEO surveys. Astreaks has been made available to the community under an open-source license.Comment: 10 pages, 7 figure

Fast-transient Searches in Real Time with ZTFReST: Identification of Three Optically Discovered Gamma-Ray Burst Afterglows and New Constraints on the Kilonova Rate

The most common way to discover extragalactic fast transients, which fade within a few nights in the optical, is via follow-up of gamma-ray burst and gravitational-wave triggers. However, wide-field surveys have the potential to identify rapidly fading transients independently of such external triggers. The volumetric survey speed of the Zwicky Transient Facility (ZTF) makes it sensitive to objects as faint and fast fading as kilonovae, the optical counterparts to binary neutron star mergers, out to almost 200 Mpc. We introduce an open-source software infrastructure, the ZTF REaltime Search and Triggering, ZTFReST, designed to identify kilonovae and fast transients in ZTF data. Using the ZTF alert stream combined with forced point-spread-function photometry, we have implemented automated candidate ranking based on their photometric evolution and fitting to kilonova models. Automated triggering, with a human in the loop for monitoring, of follow-up systems has also been implemented. In 13 months of science validation, we found several extragalactic fast transients independently of any external trigger, including two supernovae with post-shock cooling emission, two known afterglows with an associated gamma-ray burst (ZTF20abbiixp, ZTF20abwysqy), two known afterglows without any known gamma-ray counterpart (ZTF20aajnksq, ZTF21aaeyldq), and three new fast-declining sources (ZTF20abtxwfx, ZTF20acozryr, ZTF21aagwbjr) that are likely associated with GRB200817A, GRB201103B, and GRB210204A. However, we have not found any objects that appear to be kilonovae. We constrain the rate of GW170817-like kilonovae to R &lt; 900 Gpc-3 yr-1 (95% confidence). A framework such as ZTFReST could become a prime tool for kilonova and fast-transient discovery with the Vera Rubin Observatory

Association between Serum Sialic Acid Levels and Disease Severity in Psoriasis: A Case-control Study

Introduction: Psoriasis is a chronic inflammatory disease distributed worldwide with varying prevalence among different geographical areas and ethnic groups. It has been recently found that oxidative stress is one of the important factors in the pathogenesis of psoriasis. The varied effects of oxidative stress include changes in cellular uptake, altered enzymatic activity of proteins, increased predisposition to aggregation and proteolysis, which subsequently alter their immunogenicity. Sialic Acid (SA) is an acetylated derivative of neuramic acid. It is a marker for acute phase inflammatory response, with increased levels observed in inflammatory diseases. Aim: To estimate the levels of SA in psoriasis patients and to correlate with the severity of the disease. Materials and Methods: This case-control study was conducted among 50 patients, diagnosed with psoriasis, and 50 age and sex-matched subjects without psoriasis. General, systemic and dermatological examination was carried out. The severity of psoriasis was assessed according to Psoriasis Area Severity Index (PASI). The serum was treated with ethanol and centrifugation to precipitate proteins. The SA of both the precipitate and supernatant was estimated based on the reaction of SA with the ninhydrin reagent. Calculation of sialic acid was done by the formula: OD of test/OD of standard×concentration of the standard. To establish a correlation student’s t-test was used. Results: There were 39 males and 11 females in each case and control group. The mean±SD age of cases and controls was 44.04±10.9 years and 44.10±9.996, respectively. The mean PASI value was 23.1666±18.47. Mean SA in cases and controls were 35.792±2.124 and 28.556±3.854 (p-values <0.001). A positive correlation was observed between the free SA and psoriasis severity (p-value <0.001, r=0.460). Conclusion: Higher levels of free serum SA were significantly associated with more severe forms of psoriasis

India's First Robotic Eye for Time-domain Astrophysics: The GROWTH-India Telescope

We present the design and performance of the GROWTH-India telescope, a 0.7 m robotic telescope dedicated to time-domain astronomy. The telescope is equipped with a 4k back-illuminated camera that gives a 0.degrees 82 field of view and a sensitivity of m (g ') similar to 20.5 in 5 minute exposures. Custom software handles observatory operations: attaining high on-sky observing efficiencies (greater than or similar to 80%) and allowing rapid response to targets of opportunity. The data processing pipelines are capable of performing point-spread function photometry as well as image subtraction for transient searches. We also present an overview of the GROWTH-India telescope's contributions to the studies of gamma-ray bursts, the electromagnetic counterparts to gravitational wave sources, supernovae, novae, and solar system objects