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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24665 results found.

  1. GRB 250215A: Swift/UVOT Upper Limits
  2. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  3. GRB 250215A: Fermi GBM Observation
  4. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  5. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  6. GRB 250215A: Swift-XRT refined Analysis
  7. GRB 250215A: SVOM/GRM observation
  8. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  9. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  10. EP250207b: Xinglong optical upper limit
  11. EP250212a: Xinglong optical upper limit
  12. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  13. EP250212a: Global MASTER-Net observations report
  14. GRB 250205A: VIRT Optical Upper Limit
  15. GRB 250205A: Leavitt Observatory optical upper limit
  16. EP250207B: Chandra localization of the X-ray counterpart
  17. EP250212a: Liverpool Telescope optical upper limits
  18. GRB250101A: Radio upper limits from GMRT observations
  19. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  20. EP250207B: GTC z-band Observations
  21. Fermi GRB 250212A: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  23. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. Fermi trigger No 760945500: Global MASTER-Net observations report
  25. EP250207b: NOT optical counterpart candidate
  26. GRB 250211B: A long GRB detected by INTEGRAL
  27. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  28. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  29. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  30. GRB 250207A: Fermi GBM Observation
  31. GRB 250206A: Fermi GBM Observation
  32. GRB 250205A / EP250205A: radio detection with the VLA
  33. EP250207b: Tentative z-band brightening source
  34. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  35. Konus-Wind detection of GRB 250206A
  36. GRB 250210A: SVOM/GRM observation of a long burst
  37. EP250207b: Liverpool Telescope possible optical counterpart
  38. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  40. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  41. GRB 250207A: Skynet optical afterglow observations
  42. GRB 241128A: VIRT Optical Upper Limit
  43. EP250207b: Gemini GMOS-N z-band observations
  44. EP250207A: Upper limits from Fermi-GBM Observations
  45. EP250207b: a new X-ray transient detected by Einstein Probe
  46. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  47. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  48. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  49. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  51. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  52. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  53. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  54. GRB 250207A: 1.3m DFOT Optical observations
  55. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  56. GRB 250206A: Swift-XRT observations
  57. GRB 250129A: GRANDMA Continued Afterglow Detection
  58. GRB 250207A: Swift-BAT refined analysis
  59. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  60. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  61. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  62. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  63. GRB 250205A: 1.3m DFOT optical upper limit
  64. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  65. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  66. GRB 250206A: EIRSAT-1 GMOD Detection
  67. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  68. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  69. GRB 250207B: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  71. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  72. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  74. GRB 250207A: Swift-XRT refined Analysis
  75. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  76. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  77. GRB 250207A: Enhanced Swift-XRT position
  78. CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
  79. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  80. GRB 250207A: REM IR afterglow detection
  81. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  82. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  83. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  84. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  85. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  86. GRB 250207A: REM optical afterglow detection
  87. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  88. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  89. GRB 250207A: Swift/UVOT Detection
  90. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  91. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  92. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  93. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  94. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  95. GRB 250129A: Continued AbAO and Mondy optical observations
  96. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  97. GRB 250207B: MAXI/GSC detection
  98. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  99. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  100. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification

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