//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26694 SUBJECT: IceCube Alert 200109.99: Global MASTER-Net observations report DATE: 20/01/09 23:52:30 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), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), 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) started inspect of the IceCube Alert 200109.99 (11h 01m 03.91s , +14d 55m 43.7s, R=1.9429) errorbox 20 sec after notice time and 75 sec after trigger time at 2020-01-09 23:42:55 UT, with upper limit up to 16.1 mag. The observations began at zenith distance = 36 deg. The sun altitude is -58.1 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the IceCube Alert 200109.99 errorbox 50 sec after notice time and 105 sec after trigger time at 2020-01-09 23:43:25 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 71 deg. The sun altitude is -69.6 deg. The galactic latitude b = 62 deg., longitude l = 234 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1255752 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 165 | 2020-01-09 23:42:55 | MASTER-Tavrida | (10h 56m 21.38s , +15d 06m 07.1s) | R | 180 | 16.1 | 116 | 2020-01-09 23:43:25 | MASTER-IAC | (10h 59m 44.66s , +14d 59m 44.6s) | P- | 20 | 13.7 | 116 | 2020-01-09 23:43:25 | MASTER-IAC | (10h 59m 05.97s , +15d 03m 29.4s) | P| | 20 | 16.4 | 204 | 2020-01-09 23:44:48 | MASTER-IAC | (10h 59m 41.41s , +15d 00m 39.1s) | P- | 30 | 14.6 | 204 | 2020-01-09 23:44:48 | MASTER-IAC | (10h 59m 02.65s , +15d 04m 23.9s) | P| | 30 | 16.6 | 301 | 2020-01-09 23:46:15 | MASTER-IAC | (10h 59m 08.75s , +15d 03m 20.4s) | P| | 50 | 17.0 | The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26695 SUBJECT: IceCube Alert 200109.99: Global MASTER-Net observations report DATE: 20/01/09 23:52:38 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), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), 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) started inspect of the IceCube Alert 200109.99 (trigger No 37927131,11h 01m 03.84s , +14d 55m 44.4s, R=1.94) errorbox 22 sec after notice time and 75 sec after trigger time at 2020-01-09 23:42:55 UT, with upper limit up to 16.1 mag. The observations began at zenith distance = 36 deg. The sun altitude is -58.1 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the IceCube Alert 200109.99 errorbox 53 sec after notice time and 105 sec after trigger time at 2020-01-09 23:43:25 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 71 deg. The sun altitude is -69.6 deg. The galactic latitude b = 62 deg., longitude l = 234 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1255748 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 165 | 2020-01-09 23:42:55 | MASTER-Tavrida | (10h 56m 21.38s , +15d 06m 07.1s) | R | 180 | 16.1 | 116 | 2020-01-09 23:43:25 | MASTER-IAC | (10h 59m 44.66s , +14d 59m 44.6s) | P- | 20 | 13.7 | 116 | 2020-01-09 23:43:25 | MASTER-IAC | (10h 59m 05.97s , +15d 03m 29.4s) | P| | 20 | 16.4 | 204 | 2020-01-09 23:44:48 | MASTER-IAC | (10h 59m 41.41s , +15d 00m 39.1s) | P- | 30 | 14.6 | 204 | 2020-01-09 23:44:48 | MASTER-IAC | (10h 59m 02.65s , +15d 04m 23.9s) | P| | 30 | 16.6 | 301 | 2020-01-09 23:46:15 | MASTER-IAC | (10h 59m 08.75s , +15d 03m 20.4s) | P| | 50 | 17.0 | The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26696 SUBJECT: IceCube-200109A: IceCube observation of a high-energy neutrino candidate event DATE: 20/01/10 01:14:56 GMT FROM: Robert Stein at DESY The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 20/01/09 at 23:41:39.94 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Gold alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.64 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/133609_37927131.amon ), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 20/01/09 Time: 23:41:39.94 UT RA: 164.49 (+4.94 -4.19 deg 90% PSF containment) J2000 Dec: 11.87 (+1.16 -1.36 deg 90% PSF containment) J2000 Due to the unique topology of this event, with a partially-contained track in the detector, it was challenging for online algorithms to reconstruct. The initially-reported direction was offset from this updated best-fit position by approximately 3 degrees. We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. There is one Fermi 4FGL source within the 90% localization region, 4FGL J1103.0+1157 at RA: 165.77 deg, Dec: 11.97 deg (1.26 deg away from the best-fit event position). This source, which is associated with the quasar TXS 1100+122 at z=0.91, is also found in the 3FHL catalog. 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: 26697 SUBJECT: IceCube-200109A: Upper limits from Fermi-GBM Observations DATE: 20/01/10 04:44:32 GMT FROM: Joshua Wood at MSFC/Fermi-GBM J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM team: For the IceCube high-energy neutrino candidate event 200109A (GCN 26696), at the event time Fermi-GBM was observing the reported neutrino location at: RA: 164.49 (+4.94 -4.19 deg 90% PSF containment) J2000 Dec: 11.87 (+1.16 -1.36 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-200109A. 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: 7.3 11. 16. 1.024 s: 2.1 2.8 3.6 8.192 s: 0.4 0.6 1.2 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26698 SUBJECT: IceCube-200109A: INTEGRAL was inactive at the time of the event DATE: 20/01/10 08:48:10 GMT FROM: Carlo Ferrigno at IAAT/ISDC Alexis Coleiro (APC, France), Carlo Ferrigno, V. Savchenko (ISDC/UniGE, Switzerland), S. Mereghetti (INAF IASF-Milano, Italy), J. Rodi (IAPS-Roma, Italy), on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration The INTEGRAL spacecraft has a highly elliptical orbit and the instruments are not acquiring science data during perigee passage, every 2.6 days to prevent radiation-induced damages. Unfortunately, at the time of IceCube-200109A (2020-01-09 23:41:39) the spacecraft was preparing to the start the observations after the perigee passage between the orbits number 2181 and 2182. Therefore, no scientific data are available between 2020-01-09 16:27 and 2020-01-10 01:48. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26700 SUBJECT: IceCube-200109A: Swift-XRT and UVoT Follow-up Observations DATE: 20/01/10 22:39:51 GMT FROM: Azadeh Keivani at Columbia U IceCube-200109A: Swift-XRT and UVoT Follow-up Observations P. A. Evans (U. Leicester), A. Keivani (Columbia U.), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), and D. B. Fox (PSU), report: The Neil Gehrels Swift Observatory observed the field of the IceCube Astrotrack Gold astrophysical neutrino candidate event IceCube-200109A (revision 1, https://gcn.gsfc.nasa.gov/gcn3/26696.gcn3) beginning Jan 10, 05:55:10 UT (~6 hours after the neutrino arrival time). Swift utilized a 35-point tiling pattern to cover a region centered on R.A., Dec. (J2000) = 164.49d, 11.87d, with a radius of approximately 66 arcmin; estimated 90%-containment error region for this event is rather large with asymmetric (+4.94d, -4.19d) on RA and (+1.16, -1.36) on Dec. Swift-XRT collected ~230 s per field of PC-mode data per tile (except for one tile which only 8 s were obtained). The X-ray data have been reduced using the analysis approach and software routines of Evans et al. 2014 (ApJS, 210, 8). Only one X-ray source (RA = 165.34231 deg, Dec = 12.58648 deg) is detected in the field of observation, which is consistent with a double or multiple star (HEI 155; 1.5 arcsec away) which is also 18.8 arcsec away from a known X-ray source 1RXS J110123.1+123524 from ROSAT/RASSFSC. This is not considered as a source of interest. Excluding the identified source, the 3-sigma upper limit on the count rate of any point-like counterpart over the rest of the tiled region is 0.03 ct s^-1, which corresponds to a 0.3-10 keV flux of 1.2e-12 erg cm^-2 s^-1 for a typical AGN spectrum (nH=3e20 cm^-2, Gamma=1.7). Swift/UVOT co-observed with XRT (with a slightly smaller field-of-view) using the U filter. The exposures are ~219 s except for one tile (target ID 00013102), for which only 8 s were obtained. No uncatalogued sources were found with a limiting magnitude of about 18.9 for the typical field and 17.5 for target ID 00013102. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26707 SUBJECT: IceCube-200109A: Upper limits from a search for additional neutrino events in IceCube DATE: 20/01/11 16:09:51 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-200109A (https://gcn.gsfc.nasa.gov/gcn3/26696.gcn3) in a time range of 2 days centered on the alert event time (2020-01-08 23:41:39.94 UTC to 2020-01-10 23:41:39.94 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero additional track-like events are found in spatial coincidence with the 90% containment region of IceCube-200109A. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/ dE = 4.12 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 (2019-12-10 23:41:39.94 UTC to 2020-01-10 23:41:39.94 UTC). In this case, we report a p-value of 1.0, 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 9.39 x 10^-4 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: 26709 SUBJECT: IceCube 200109A: No significant detection in HAWC DATE: 20/01/11 17:53:53 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 2020/01/09 23:41:39 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-200109A. Location is at RA: 164.49 (+4.94/-41.9 90% PSF containment) J2000 Dec: 11.87 (+1.16/-1.36 deg 90% PSF containment) J2000 https://gcn.gsfc.nasa.gov/gcn3/26696.gcn3 (GCN circular 26696). 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 November 2019. We searched inside the IceCube error region from the circular. The highest significance, 2.77 sigma (0.89 post-trials), is at RA 167.39 deg, Dec 11.03 deg (+-1.78 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 = 3.02e-13 (E/TeV)^-0.3 TeV cm^-2 s^-1 Search for a transient source. Since the IceCube event fall inside the HAWC field of view, we report on the result for the current transit of the IceCube position.Data acquisition started on Data Start: 2020/01/08 13:01:36 UTC and ended 2020/01/10 13:29:43 UTC. The most significant location, with 2.40 sigma (-1.76 post-trials), is at RA 164.0 deg, Dec 11.15 deg (+-1.8 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 1.12e-11 (E/1TeV)^-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: 26728 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-200109A and detection of a possible new gamma-ray source, Fermi J1055.8+1034 DATE: 20/01/13 09:54:53 GMT FROM: Simone Garrappa at DESY S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and V. Paliya (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC200109A neutrino event (GCN 26696) 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 2020-01-09 at 23:41:39.94 UT (T0) with J2000 position RA = 164.49 (+4.94, -4.19) deg, Decl. = 11.87 (+1.16, -1.36) deg 90% PSF containment. Two cataloged >100 MeV gamma-ray sources (The Fermi-LAT Collaboration 2019, arXiv:1902.10045) are located within the 90% IC200109A localization error. These are the objects 4FGL J1103.0+1157 and 4FGL J1114.6+1225. Based on a preliminary analysis of the LAT data over the timescales of 1-day and 1-month prior to T0, these objects are not significantly detected at gamma-rays. We searched for the existence of intermediate (months 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 IC200109A 90% best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2020-01-09 UTC), < 8e-9 (< 7e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Within the error circle for the direction of the neutrino, ~1.2deg offset from the best-fit IC200109A position, a ~4 sigma excess of gamma rays, Fermi J1055.8+1034 was detected in an analysis of the integrated LAT data (> 100 MeV) between 2008-08-04 and  2020-01-09. Assuming a power-law spectrum, the best-fit localization is (J2000) RA:  163.97, Dec: 10.58 (0.19 deg 99% containment, 0.09 deg 68% containment), with best-fit spectral parameters flux = (1.6 +/- 0.8)e-9 ph cm^-2 s^-1 and index = 2.06 +/- 0.18. In a preliminary analysis of the LAT data over one day and one month prior T0, Fermi J1055.8+1034  is not significantly detected in the LAT data. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For these sources 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: 26747 SUBJECT: IceCube-200109A: Candidate Counterparts from the Zwicky Transient Facility DATE: 20/01/14 15:44:12 GMT FROM: Simeon Reusch at DESY * Simeon Reusch and Robert Stein (DESY) 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-200109A (Stein et. al, GCN 26696) 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-band and r-band beginning at 2020-01-11T08:03:45.800 UTC, approximately 32.4 hours after event time due to bad weather. We covered 22.4 sq deg, corresponding to the entire localisation region. This estimate accounts does not account 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) 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 the following high-significance transient candidates by our pipeline, all lying within the 90.0% localization of the neutrino.  +--------------------------------------------------------------------------------+ | ZTF Name     | IAU Name | RA (deg)   | DEC (deg) | Filter | Mag   | MagErr | +--------------------------------------------------------------------------------+ | ZTF19acmwlds | AT 2019yfm | 163.8379011| +11.0507782 | r      | 20.74 | 0.13 |  | ZTF20aaeuufe | AT 2019yii | 161.616044 | +10.8570761 | r      | 20.80 | 0.18 |   | ZTF20aaevfwa | AT 2019zxa | 162.7251345| +12.9120284 | r      | 21.13 | 0.21 |  | ZTF20aaevgvt | AT 2020uw  | 162.25426 | +10.6885268 | r      | 20.54 | 0.16 |  +--------------------------------------------------------------------------------+ AT 2019yfm was reported to the TNS by the Pan-STARRS1 survey (Chambers, et al. 2019), who first detected it on 2019-11-02. This object was first detected by ZTF on 2019-10-29, and has since faded by 1 mag. AT 2019yii was also first reported by Pan-STARRS1 to the TNS, with a discovery on 2019-12-24. ZTF first detected it on 2019-12-29.ZTF20aaevfwa (AT 2019zxy) was first detected on 2019-12-29. It has a hostspectroscopic redshift of z=0.13, which gives it an absolute magnitude of -17.91. These three objects have lightcurves consistent with supernovae that are now post-peak. ZTF20aaevgvt (AT 2020uw) was first detected on 2020-01-07. There is no apparent host galaxy. This candidate is consistent with being young SNe.  The arrival of a neutrino from any of these four objects would be consistent with a supernova CSM-interaction model for neutrino production. We encourage spectroscopic and photometric observations to discern the nature of the four unclassified objects listed above. Additional observations of the localisation region of IceCube 200109A will continue as part of the regular survey operations. 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; IIT-B, 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 and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). *