///////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22416 SUBJECT: Swift Trigger 810300 is a probable new Galactic source: Swift J1658.2-4242 DATE: 18/02/16 06:28:49 GMT FROM: David Palmer at LANL S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB), A. Deich (PSU), C. Gronwall (PSU), A. Melandri (INAF-OAB), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 05:37:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located a source in the Galactic plane (trigger=810300). Swift could not immediately slew to the location due to an observing constraint. The BAT on-board calculated location is RA, Dec 254.545, -42.709 which is RA(J2000) = 16h 58m 11s Dec(J2000) = -42d 42' 31" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to the duration of the image that led to the alert (27 minutes), no lightcurve is immediately available. Due to an observing constraint, Swift will not slew until T0+46.4 minutes. There will be no XRT or UVOT data until this time. Based on the duration of the discovery image (27 minutes) and the source's location on the Galactic plane (lat = 0.05, lon = 343.24) we believe that this is a previously-unknown Galactic transient, which we name Swift J1658.2-4242 . ///////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22417 SUBJECT: Swift J1658.2-4242 (trigger 810300): Swift-XRT position DATE: 18/02/16 07:47:24 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D’Avanzo, A. Melandri (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed observations of the probable new Galactic source Swift J1658.2-4242 (trigger=810300; Barthelmy et al. GCN Circ. 22416), collecting 137 s of Photon Counting (PC) mode data between T0+5.9 ks and T0+6.1 ks. Using promptly downlinked data we find an uncatalogued X-ray source located at RA,Dec = 254.5524, -42.6988 which is equivalent to: RA (J2000.0) = 16 58 12.58 DEC (J2000.0) = -42 41 55.7 with an uncertainty of 3.83 arcsec (radius, 90% containment). This location is 41.6 arcsec from the BAT position, inside the BAT error circle. This circular is an official product of the Swift-XRT team ///////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22418 SUBJECT: Swift trigger 810300: MASTER-OAFA robotic report DATE: 18/02/16 09:46:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, O.Ershova, N.Tyurina, V.Kornilov, D.Zimnukhov, A.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.Chazov, D. Kuvshinov (Lomonosov Moscow State University, SAI), V.Yurkov, A.Gabovich, Yu.Sergienko (Blagoveschensk Educational State University, Blagoveschensk), R.Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar (OAFA),National University of San Juan, Argentina), H. Levato, C. Saffe (Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina), D.Buckley, S. Potter (South African Astronomical Observatory), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), O.Gres, N.M.Budnev, Yu.Ishmuhametova (Irkutsk State University), A. Tlatov, V.Senik, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Argentina was pointed to the Swift trigger 810300 (Barthelmy et al. GCN #22416) 23 sec after notice time and 1742 sec after trigger time (18/02/16 05:37:23.51UT) at 2018-02-16 06:06:26 UT with unfiltered mlim=19.1 (5-sigma) on single images, 19.9m on sum(1800s). There is marginally seen optical source, possibly known 2MASS source in 1.3" (with known J-K=1) from SWIFT XRT (D'Avanzo et al. GCN #22417) center RA (J2000.0) = 16 58 12.58 DEC (J2000.0) = -42 41 55.7 inside 3.83 arcsec error-box (radius, 90% containment). The message may be cited. ==================================================================== The observations were made on zenit distance = 66 degrees, galaxy latitude b = -1 degree. The Moon altitude is -44 degree . The Sun altitude is -42.2 degree. The object can be observed till sunrise at 2018-02-16 10:15:34 ///////////////////////////////////////////////////////////////////// ATEL #11307 ATEL #11307 Title: Improved position and possible optical counterpart for the new X-ray transient Swift J1658.2-4242 Author: I. A. Mereminskiy, S. A. Grebenev (Space Research Institute, Moscow) Queries: i.a.mereminskiy@gmail.com Posted: 16 Feb 2018; 16:33 UT Subjects:X-ray, Transient A follow-up pointing observation (ObsId:00810300991, 2.8 ks) of the recently discovered X-ray transient Swift J1658.2-4242 (GCN #22416, #22417) has been performed by Swift-XRT on MJD 58165.3 in PC mode. It allowed us to improve the source position using UVOT data to reduce the systematic errors in telescope pointing (see Goad et al. A&A, 476, 1401, 2007; Evans et al. MNRAS, 397, 1177, 2009): R.A. = 254.55268, Dec. = -42.69847 (=16h 58m 12.64s, -42o 41' 54.5'', epoch 2000.0). The error radius is 1.6'' at 90% confidence. There is a known infrared source VVV J165812.62-424154.78 with Ks magnitude of 15.25 located only 0.4'' off this position. The spectrum measured with XRT can be described by a strongly absorbed power-law with a photon index of 1.2+/-0.3 and NH = 1.5 x 10^{23} cm^{-2}. The source flux was about 7.2 (+/-0.6) x 10^{-10} erg s^{-1} cm^{-2} in the 0.3-10 keV band that corresponds to the unabsorbed luminosity 1.8 x 10^{37} erg/s at an assumed distance of 10 kpc. The hardness of the spectrum is consistent with that based on INTEGRAL data (ATEL #11306). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. /////////////////////////////////////////////////////////////////////