//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28715 SUBJECT: IceCube-201021A: IceCube observation of a high-energy neutrino candidate event DATE: 20/10/21 09:18:00 GMT FROM: Cristina Lagunas Gualda at DESY The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 20/10/21 at 06:37:47.48 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.987 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/134621_31008065.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 20/10/21 Time: 06:37:47.48 UT RA: 260.82 (+ 1.73 - 1.68 deg 90% PSF containment) J2000 Dec: 14.55 (+ 1.35 - 0.74 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. There are no Fermi-LAT 4FGL or 3FHL sources inside the 90% localization region. The closest source is 4FGL J1728.0+1216 located at RA 262.02 deg and Dec 12.28 deg (J2000), at a distance of 2.56 degrees from the best-fit location. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28722 SUBJECT: IceCube Alert 201021.28: Global MASTER-Net observations report DATE: 20/10/21 16:13:09 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the IceCube Alert 201021.28 (trigger No 31008065,17h 22m 45.36s , +14d 39m 10.8s, R=0.51) errorbox 32837 sec after notice time and 32892 sec after trigger time at 2020-10-21 15:45:59 UT, with upper limit up to 17.5 mag. Observations started at twilight. The observations began at zenith distance = 45 deg. The sun altitude is -10.9 deg. The galactic latitude b = 26 deg., longitude l = 37 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1466141 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 32982 | 2020-10-21 15:45:59 | MASTER-Tavrida | (17h 20m 39.25s , +14d 38m 17.4s) | C | 180 | 16.7 | 33384 | 2020-10-21 15:52:41 | MASTER-Tavrida | (17h 20m 35.68s , +14d 38m 01.9s) | C | 180 | 17.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28724 SUBJECT: Swift-XRT observations of IceCube 201021A DATE: 20/10/21 17:02:45 GMT FROM: Timothee Gregoire at Penn State H. A. Ayala Solares (PSU), D.F. Cowen (PSU), J. DeLaunay (PSU), D. B. Fox (PSU), A. Keivani (Columbia U.), J.P. Osborne (U. Leicester), F. Krauss (PSU), T. Gregoire (PSU), P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report: Swift observed the field of IceCube 201021A (GCN Circ. 28715) between 08:56:50 2020 October 21 and 12:05:31 on 2020 October 21, collecting a total of 3.4 ks of cleaned photon counting (PC) mode data. The observations used a 4-point tiling pattern with a radius of ~0.3 degrees. We found 4 X-ray sources, as detailed below. All of these are either known X-ray sources, consistent with catalogued fluxes, or are unknown but with count rate consistent with the previous non-detections. We therefore do not claim any of them as the likely counterpart to IceCube 201021A. The 3-sigma upper limit in the field was in the range 5-8 x 10^-3 ct/sec. The detected sources were: Source no: 1 RA (J2000): 260.80883 [degrees] = 17h 23m 14.12s Dec (J2000): +14.3492 [degrees] = +14d 20' 57.2" Error: +4.5 [arcsec, 90% conf. radius] Count rate (0.3-10 keV): 1.2 (+0.7, -0.5) x 10-2 ct s-1 Flux (0.3-10 keV): 5.3 (+3.2, -2.3) x 10-13 erg cm-2 s-1 Notes: This source is consistent with 1RXS J172314.4+142103 Source no: 2 RA (J2000): 261.04703 [degrees] = 17h 24m 11.29s Dec (J2000): +14.7320 [degrees] = +14d 43' 55.3" Error: +5.2 [arcsec, 90% conf. radius] Count rate (0.3-10 keV): 7 (+4, -3) x 10-3 ct s-1 Flux (0.3-10 keV): 3.1 (+1.9, -1.3) x 10-13 erg cm-2 s-1 Source no: 3 RA (J2000): 260.59538 [degrees] = 17h 22m 22.89s Dec (J2000): +14.7598 [degrees] = +14d 45' 35.3" Error: +6.3 [arcsec, 90% conf. radius] Count rate (0.3-10 keV): 7.2 (+2.9, -2.3) x 10-3 ct s-1 Flux (0.3-10 keV): 3.10 (+1.27, -1.00) x 10-13 erg cm-2 s-1 Source no: 4 RA (J2000): 260.84848 [degrees] = 17h 23m 23.63s Dec (J2000): +14.7720 [degrees] = +14d 46' 19.3" Error: +5.0 [arcsec, 90% conf. radius] Count rate (0.3-10 keV): 7.4 (+3.6, -2.7) x 10-3 ct s-1 Flux (0.3-10 keV): 3.2 (+1.5, -1.2) x 10-13 erg cm-2 s-1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28732 SUBJECT: IceCube-201021A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation DATE: 20/10/21 20:46:16 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using combination of INTEGRAL all-sky detectors (following [1]): SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt gamma-ray counterpart of IceCube-201021A (GCN 28715). At the time of the event (2020-10-21 06:37:47 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 107 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (5.3% of optimal) response of ISGRI, strongly suppressed (36% of optimal) response of IBIS/Veto, and somewhat suppressed (66% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was very stable (excess variance 1.1). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2.7e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~2.3e-07 (6.1e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. We report for completeness and in order of FAP, all excesses identified in the search region. We find: 7 likely background excesses: T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP 145 | 1.5 | 5 | 3.74 +/- 0.804 +/- 1.5 | 0.145 42 | 1.1 | 3.7 | 3.22 +/- 0.938 +/- 1.29 | 0.182 -46.5 | 3 | 3 | 1.5 +/- 0.567 +/- 0.6 | 0.329 46.7 | 0.6 | 3.5 | 0.412 +/- 0.127 +/- 0.165 | 0.564 10.9 | 0.15 | 3.4 | 0.802 +/- 0.256 +/- 0.322 | 0.669 9.12 | 0.15 | 3.2 | 0.779 +/- 0.256 +/- 0.312 | 0.818 -30.1 | 0.2 | 3.6 | 0.75 +/- 0.221 +/- 0.301 | 0.82 Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S -- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28735 SUBJECT: IceCube-201021A: Upper limits from Fermi-GBM Observations DATE: 20/10/21 22:07:13 GMT FROM: Stephen Lesage at Fermi-GBM Team S. Lesage (UAH) reports on behalf of the Fermi-GBM team: For the IceCube high-energy neutrino candidate event IceCube-201021A (GCN 28715), at the event time Fermi-GBM was observing the reported neutrino location at: RA: 260.82 (+1.73 -1.68 deg 90% PSF containment) J2000 Dec: 14.55 (+1.35 -0.74 deg 90% PSF containment) J2000 There was no Fermi-GBM onboard trigger around the event time of the neutrino candidate. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around the neutrino candidate time. From this search, no significant signal was found related to IceCube-201021A. We set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------------- 0.128 s: 5.2 8.1 16.0 1.024 s: 2.5 3.5 5.9 8.192 s: 0.6 0.8 1.7 These results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28738 SUBJECT: IceCube-201021A: No neutrino counterpart candidates in ANTARES search DATE: 20/10/22 07:02:53 GMT FROM: Antoine Kouchner at ANTARES Collaboration Alexis Coleiro (APC/Universite de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single track-like event IceCube-201021A (GCN 28715 ). The reconstructed origin was -14 degrees below the horizon for ANTARES. No up-going muon neutrino candidate events were recorded within 90% error box of the IceCube event during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible all time. This leads to a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 19 GeV.cm^-2 over the energy range 5 TeV - 5 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 48 GeV.cm^-2 (850 GeV - 430 TeV) for an E^-2.5 spectrum. A search over an extended time window of +/- 1 day has also yielded no detection (42% visibility). ANTARES is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28746 SUBJECT: IceCube-201021A: Upper limits from a search for additional neutrino events in IceCube DATE: 20/10/22 14:36:54 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for additional track-like muon neutrino events arriving from the direction of IceCube-201021A (https://gcn.gsfc.nasa.gov/gcn3/28715.gcn3) in a time range of 2 days centered on the alert event time (2020-10-20 06:37:47.48 UTC to 2020-10-22 06:37:47.48 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, three additional track-like events are found in spatial coincidence with the 90% containment region of IceCube-201021A. We find that these data are consistent with atmospheric background expectations, with a p-value of 1.0. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/dE = 3.8 x 10^-5 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are approximately between 1 TeV and 1 PeV. A subsequent search was performed to include the month of data prior to the alert event (2020-09-21 06:37:47.48 UTC to 2020-10-22 06:37:47.48 UTC). In this case, we report a p-value of 0.08, consistent with no significant excess of track-like events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) of 6.4 x 10^-5 TeV cm^-2 at the 90% CL. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28749 SUBJECT: Swift-XRT observations of IceCube 201021A (2) DATE: 20/10/22 15:46:10 GMT FROM: Timothee Gregoire at Penn State H. A. Ayala Solares (PSU), D.F. Cowen (PSU), J. DeLaunay (PSU), D. B. Fox (PSU), A. Keivani (Columbia U.), J.P. Osborne (U. Leicester), F. Krauss (PSU), T. Gregoire (PSU), P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report: The Swift observation of the field of IceCube 201021A (GCN Circ. 28715) reported in GCN Circ. 28724 (https://gcn.gsfc.nasa.gov/gcn3/28724.gcn3) had not finished, there has been 300s more observation time and a fifth source has been detected. We report it here for completeness. A fifth X-ray source has been found, which is unknown but with count rate consistent with the previous non-detections. We therefore do not claim it as the likely counterpart to IceCube 201021A. The fifth detected source was: Source no: 5 RA (J2000): 260.56090 [degrees] = 17h 22m 14.62s Dec (J2000): +14.5899 [degrees] = +14d 35' 23.6" Error: +6.5 [arcsec, 90% conf. radius] Count rate (0.3-10 keV): 4.3 (+2.3, -1.7) x 10-3 ct s-1 Flux (0.3-10 keV): 1.8 (+1.0, -0.7) x 10-13 erg cm-2 s-1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28751 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312 DATE: 20/10/22 19:14:08 GMT FROM: Simone Garrappa at DESY S. Buson (Univ. of Wuerzburg), S. Garrappa (DESY-Zeuthen), C. C. Cheung (Naval Research Laboratory) and M. Ajello (Clemson Univ.) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC201021A neutrino event (GCN 28715) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2020-10-21 at 06:37:47.48 UT (T0) with J2000 position RA = 260.82 (+1.73, -1.68) deg, Decl. = 14.55 (+1.35, -0.74) deg (90% PSF containment). No cataloged >100 MeV gamma-ray sources (The Fourth Fermi-LAT catalog, 4FGL; The Fermi-LAT collaboration 2020, ApJS, 247, 33) are located within the 90% IC201021A localization error. We searched for intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC201021A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC201021A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4.2e-10 ph cm^-2 s^-1 for ~12-years (2008-08-04 to 2020-10-21 UTC), and < 1.3e-8 (< 4.3e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Within the 90% confidence localization of the neutrino, 10 arcmin offset from the best-fit IC201021A position, an excess of gamma rays, Fermi J1725.5+1312, was detected in an analysis of the integrated LAT data (0.1 - 300 GeV) between 2008-08-04 and 2020-10-21. This putative new source is detected at a statistical significance >3 sigma (calculated following the prescription adopted in the 4FGL). Assuming a power-law spectrum, the candidate gamma-ray source has best-fit localization of RA = 260.76 deg, Decl. = 14.39 deg (5 arcmin 68% containment, 11 arcmin 99% containment) with best-fit spectral parameters, flux = (1.8 +/- 0.5)e-9 ph cm^-2 s^-1, index = 2.2 +/- 0.2. In a preliminary analysis of the LAT data over one day and one month prior T0, Fermi J1725.5+1312 is not significantly detected in the LAT data. All values include the statistical uncertainty only. The highest-energy photon likely associated to the source is a ~52 GeV event (90% prob), detected on 2009 November 20. A possible counterpart of Fermi J1725.5+1312 is 1RXS J172314.4+142103 (RA = 260.812500 deg, Decl. = 14.350556 deg; Voges et al. 1999, A&A, 349, 389) of unknown redshift. It is located 4 arcmin from the Fermi J1725.5+1312 best-fit position, and within the gamma-ray 68% positional uncertainty. This X-ray source has been previously reported by XMM-Newton, as XMMSL1 J172315.0+142102 (observed on 2006-09-04; Saxton et al. 2008 A&A, 480, 611). A Swift follow up observation of the field of IC201021A was performed on 2020-10-21 and detected 1RXS J172314.4+142103 at a flux consistent with catalogued values (GCN 28724). A possible infrared counterpart of 1RXS J172314.4+142103 is WISEA J172314.13+142101.5 (Cutri et al. 2013 wise.rept, 1). Coincident with this WISE source there is a faint radio source (~1.1 mJy peak at 3 GHz), as seen in the the NRAO VLASS quick-look image (https://science.nrao.edu/vlass/data-access/vlass-epoch-1-quick-look-users-guide) from data obtained on 2019-03-30. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at desy.de ) and S. Buson (sara.buson at uni-wuerzburg.de ). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28756 SUBJECT: IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5 DATE: 20/10/23 08:08:26 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Gregory S. Paek, Gu Lim, Sungyong Hwang (CEOU/SNU) and H.-I. Sung (KASI), on behalf of a larger collaboration Using the LOAO 1m telescope at Mt. Lemmon, Arizona, USA, we observed the field centered on WISEA J172314.13+142101.5, an IR source suggested as a possible counterpart of the gamma ray source Fermi J1725.5+1312 (Buson et al., GCN 28751). Note that Fermi J1725.5+1312 is a new gamma ray source that appeared recently within the 90% localization of the neutrino event, IC201021A (IceCube collaboration, GCN 28715). The observation started at 2020-10-23 01:51:54 (UT). The images were taken in R-band with on-source integration time of 27 min. We find an optical counterpart of WISEA J172314.13+142101.5 near the detection limit of the stacked LOAO image with a tentative magnitude of R=21.0 +- 0.3 AB mag. The PS1 DR2 archive (Chambers, K. C. et al.) shows that this source has a mean magnitude of r=21.22 +- 0.04 AB mag (PSF magnitude). Examination of the PS1 data also shows the variability of this object at the level of a few tenths of magnitude in the past. Our result indicates that the object has not brightened significantly (<0.2 mag) compared to the historic mean. A deeper observation is desirable to better constrain the current optical variability state of this source. We thank the staff of LOAO, Jaehyuk Yoon, for performing the observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28757 SUBJECT: IceCube-201021A: One candidate counterpart from the Zwicky Transient Facility DATE: 20/10/23 16:28:36 GMT FROM: Robert Stein at DESY Robert Stein (DESY), Simeon Reusch (DESY), Sven Weimann (Ruhr University Bochum) and Michael Coughlin (University of Minnesota) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We observed the localization region of the neutrino event IceCube-201021A (Lagunas et. al, GCN 28715) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2020-10-23 02:21 UTC, approximately 43.7 hours after event time. We covered 6.3 sq deg at least twice, corresponding to 95.7% of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2020) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with one high-significance transient candidate by our pipeline, lying within the 90.0% localization of the skymap. +---------------------------------------------------------------------------------+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | +---------------------------------------------------------------------------------+ | ZTF20acmxnpa | AT2020ybb | 260.4617133 | +14.7743083 | g | 20.94 | 0.17 | +---------------------------------------------------------------------------------+ ZTF20acmxnpa/AT2020ybb was first detected on 2020-10-13 02:37 UTC, and is a candidate supernova around peak. This would be consistent with a CSM-interaction supernova neutrino production model. We encourage spectroscopic follow-up of this object to confirm its nature. We were unable to retrieve the optical source reported by Im et al. (GCN 28756) with forced photometry of the ZTF science images (at SNR=3). However, our limiting magnitude is comparable to the reported flux level. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the AMPEL Follow-up Pipeline (Stein et al. 2020). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28758 SUBJECT: IceCube-201021A: No significant detection in HAWC DATE: 20/10/23 20:00:34 GMT FROM: Hugo Ayala at Pennsylvania State University Hugo Ayala (PSU) reports on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration): On 2020/10/21 06:37:47 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-201021A. Location is at RA: 260.82 (+ 1.73 - 1.68 deg 90% PSF containment) J2000 Dec: 14.55 (+ 1.35 - 0.74 deg 90% PSF containment) J2000 (GCN circular 28715). We performed two types of analyses for the follow-up. The first is for a steady source in archival data and the second is a search for a transient source. We assume a power-law spectrum with an index of -2.3 for both analyses. Search for a steady source in archival data: The archival data spans from November 2014 to June 2019. We searched inside the reported IceCube error region. The most significant location, with p-value 5.54e-03 (1.83e-01 post-trials), is at RA 259.41deg, Dec +15.79 deg (±0.21 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit on gamma rays at the maximum position of: E^2 dN/dE = 2.18e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1 Search for a transient source. Since the event was not in our field of view at the time reported, we report the combined result for the transits before and after the IceCube event. Data acquisition started on 2020/10/20 00:44:12 UTC and ended 2020/10/22 01:01:46 UTC. The most significant location, with p-value 2.33e-03 (8.11e-02 post-trials), is at RA 259.41 deg, Dec +14.71 deg (±0.17 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 8.99e-12 (E/TeV)^-0.3 TeV.cm^-2.s^-1 HAWC is a very-high-energy gamma-ray observatory operating in Central Mexico at latitude 19 deg. north. Operating day and night with over 95% duty cycle, HAWC has an instantaneous field of view of 2 sr and surveys 2/3 of the sky every day. It is sensitive to gamma rays from 300 GeV to 100 TeV. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28812 SUBJECT: IceCube 201021A: Swift follow-up of Fermi J1725.5+1312 DATE: 20/10/30 20:44:01 GMT FROM: Timothee Gregoire at Penn State D.F. Cowen (PSU), J. DeLaunay (PSU), D. B. Fox (PSU), A. Keivani (Columbia U.), J.P. Osborne (U. Leicester), F. Krauss (PSU), T. Gregoire (PSU), P.A. Evans (U. Leicester), J.A. Kennea (PSU) and H. A. Ayala Solares (PSU) report: We have analysed 2.7 ks of XRT data for Fermi J1725.51312 (Buson et al. GCN Circ. 28751). The data were taken in Photon Counting (PC) mode. XRT observations establish a refined position for the source: R.A. 17:23:14.09, Dec. +14:20:59.1, with a 90% containment radius r_90 = 2.9". The best-fit power-law spectrum has a photon index alpha = 1.5 (+0.8, -0.4) and observed flux f_X = 6.5 (+3.1, -2.5) x 10-13 erg cm-2 s-1 (0.3-10 keV) The observed flux is lower by a factor of 4 to 10 by comparison to its XMM slew observation on 2006-09-04 (XMMSL2 J172313.9+142100, OsID:9123400002) We do not claim this source as a counterpart to IceCube 201021A from these observations.