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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').
Advanced Search

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.

Advanced Search Examples (click to copy):

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

19803 results found.

  1. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  2. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  3. GRB 250713A: Mephisto optical upper limits
  4. GRB 250713A: SVOM/VT optical upper limit
  5. GRB 250713A: NOT optical upper limits
  6. GRB 250713A: OHP/T193 upper limit
  7. GRB 250713A: SVOM/C-GFT upper limit
  8. GRB 250706B/C: 7DT Follow-up Observations
  9. GRB 250713A: EP-FXT counterpart detection
  10. EP250711a: COLIBRÍ continuous optical observations
  11. GRB 250713A: JinShan optical upper limits
  12. GRB 250713A: SVOM detection of a long burst
  13. GRB 250711A: DDOTI Optical Upper Limit
  14. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  15. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  16. GRB 250711A: SVOM/GRM observation
  17. EP250711a: NOT optical counterpart candidate
  18. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  19. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  20. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  21. GRB 250704A: GRANDMA observations
  22. GRB 250704A: SVOM/ECLAIRs refined analysis
  23. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  24. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  25. IceCube-250708A: No Candidates from WINTER
  26. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  27. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  28. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  29. EP250704a/GRB 250704B: 10 GHz VLA detection
  30. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  31. IceCube-250706A: No Candidates from WINTER
  32. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  33. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  34. EP250704a/GRB250704B : HCT optical and NIR upper limits
  35. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  36. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  37. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  38. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  39. GRB 250702F: radio detection with the VLA
  40. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  41. GRB 250706B/C: Fermi-LAT detection
  42. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  43. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  44. GRB 250706B: Swift/UVOT Detection
  45. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 250702F: GRANDMA observations
  47. GRB 250706A: Swift/UVOT Upper Limits
  48. GRB 250706B: REM optical observations
  49. GRB 250706A: REM optical/NIR observations
  50. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  51. IceCube-250416A: DDOTI Optical Upper Limit
  52. IceCube-250706A: COLIBRÍ optical upper limits
  53. GRB 250706A: JinShan optical upper limits
  54. GRB 250706A: SAO RAS optical observations
  55. EP250704A: NOWT Detection
  56. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  57. GRB 250706B: iTelescope optical observations
  58. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  59. GRB 250706B: SVOM/VT optical observation
  60. GRB 250706B: TRT bright optical counterpart detection
  61. GRB 250706A: GROWTH-India Telescope optical upper limit
  62. GRB 250706B: SVOM detection of a long burst
  63. GRB 250706A: Swift detection of a burst
  64. GRB 250704B: Swift-XRT refined Analysis
  65. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  66. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  67. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  68. GRB 250704B: Swift/UVOT Upper Limits
  69. GRB 250704A: Swift/UVOT Detection
  70. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  71. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  72. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  73. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  74. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  75. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  76. GRB 250702F: Kilonova-Catcher optical afterglow detection
  77. GRB 250702F: Monte Agliale Observatory optical observations
  78. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  79. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  80. EP250704a / GRB 250704B: JinShan optical observations
  81. EP250704a / GRB 250704B: SAO RAS optical observations
  82. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  83. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  84. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  85. EP 250704a: BOOTES-5 optical detection
  86. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  87. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  88. GRB 250704A: Swift-XRT afterglow detection
  89. EP250704a / GRB 250704B - REM observations
  90. GRB 250702F: GROWTH-India Telescope optical observations
  91. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  92. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  93. EP250702a: WFST optical observations
  94. EP250704a: COLIBRÍ optical counterpart candidate
  95. EP250704a: Einstein Probe detection of an X-ray transient
  96. GRB 250704A: REM detection of the optical afterglow
  97. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  98. GRB 250704A: SVOM detection of a burst
  99. GRB 250702F: Swift/UVOT Detection
  100. GRB 250702F: Leavitt Observatory optical observations

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