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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"

5402 results found.

  1. GRB 250328A: 1.6m Mephisto optical observations
  2. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  3. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  4. IceCube Alert 250330.35: Global MASTER-Net observations report
  5. Swift GRB250330.26: Global MASTER-Net observations report
  6. GRB 250329B: SVOM/C-GFT optical upper limit
  7. GRB 250327B: VLA detection
  8. GRB 250329B: SVOM/VT optical upper limit
  9. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  10. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  11. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  12. GRB 250329B: GWAC-F50A optical upper limit
  13. GRB 250329B: SVOM detection of a faint transient
  14. GRB 250329A: Fading optical counterpart detection by LCO.
  15. GRB 250328A: SVOM/C-GFT optical upper limit
  16. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  17. GRB 250329A: SVOM detection of a burst
  18. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  19. GRB 250327B: J-band observations with WINTER
  20. GRB 250327B: MASTER detection of OT rebrightening
  21. GRB 250327B: LCO optical counterpart detection
  22. GRB 250328A: GWAC-F50A optical upper limit
  23. GRB 250328A: SVOM detection of a burst
  24. FRB 20250316A: FTW optical observations
  25. GRB 250327B: CrAO and SAO RAS Optical Observations
  26. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  27. GRB 250327B: further optical observations by LCOGT
  28. EP250315a: Pan-STARRS r and i-band imaging and photometry
  29. GRB 250327b: Liverpool Telescope optical observations
  30. GRB 250327A: SVOM/VT upper limits on the XRT position
  31. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  32. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  33. GRB 250327B: Las Cumbres optical counterpart detection
  34. GRB 250327B: 1.6m Mephisto optical observations
  35. GRB 250327B: GOTO optical counterpart detection
  36. GRB 250327B: SVOM detection of a burst
  37. GRB 250327A: J-band observations with WINTER
  38. GRB 250327A: SVOM/VT optical candidate
  39. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  40. Fermi GRB 250327A: Global MASTER-Net observations report
  41. Swift GRB 250327A: Global MASTER-Net observations report
  42. GRB 250327A: DDOTI Optical Observations
  43. GRB 250327A: COLIBRÍ optical upper limit
  44. Fermi trigger No 764700395: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  46. EP250321a: Mondy AZT-33IK Continued Optical Observations
  47. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  48. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  49. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  50. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  51. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  52. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  53. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  54. EP250321a: TNOT Observation of Optical Counterpart
  55. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  56. GRB 250322A: Gemini-North redshift of candidate host galaxy
  57. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  58. SVOM/sb25032302: SVOM detection of a long X-ray transient
  59. GRB 250322A: AstroSat CZTI detection of a short burst
  60. GRB 250322B: AstroSat CZTI detection of a bright long burst
  61. GRB 250322A: Gemini-South optical observations
  62. FRB 250316A: DDOTI Continued Optical Observations
  63. GRB 250322A: NOT optical upper limits
  64. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  65. GRB 250322A: MASTER optical observation
  66. EP250321a: Liverpool Telescope optical follow-up
  67. EP250321a: Mondy AZT-33IK Optical Observations
  68. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  69. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  70. EP250321A: COLIBRÍ Continuing Optical Observations
  71. GRB 250312A: GECAM-A detection
  72. EP250321a: WFST optical observations
  73. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  74. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  75. EP250321a: Xinglong 216 decaying optical observations
  76. GRB 250321A: Swift-BAT refined analysis
  77. GRB 250321B: SVOM detection of a sub-threshold transient event
  78. EP250321a: SVOM/VT optical observation
  79. EP 250321A: Optical counterpart detection by LCO.
  80. GRB 250320B: SVOM/GRM observation of a long burst
  81. EP250321a: LCO optical counterpart detection
  82. EP250321A: COLIBRÍ Optical Observations
  83. GRB 250320B: AstroSat CZTI detection
  84. Fermi GRB 250320B: Global MASTER-Net observations report
  85. EP250321a: BOOTES-5/JGT optical afterglow detection
  86. EP250321a: Global MASTER-Net observations report
  87. Swift GRB 250321A: Global MASTER-Net observations report
  88. Fermi GRB 250321A: Global MASTER-Net observations report
  89. EP250321a: Einstein Probe detection of an X-ray transient
  90. GRB 250321A: GOTO optical upper limits
  91. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  92. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  93. Fermi GRB 250319B: Global MASTER-Net observations report
  94. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  95. GRB 250313A: GRBAlpha detection
  96. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  97. GRB 250317D: EIRSAT-1 GMOD Detection
  98. EP250302a: VLA observations
  99. GRB 250317B: OHP/T193 continued follow-up
  100. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate

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