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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"

5054 results found.

  1. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  2. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  3. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  4. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  5. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  6. EP250321a: TNOT Observation of Optical Counterpart
  7. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  8. GRB 250322A: Gemini-North redshift of candidate host galaxy
  9. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  10. SVOM/sb25032302: SVOM detection of a long X-ray transient
  11. GRB 250322A: AstroSat CZTI detection of a short burst
  12. GRB 250322B: AstroSat CZTI detection of a bright long burst
  13. GRB 250322A: Gemini-South optical observations
  14. FRB 250316A: DDOTI Continued Optical Observations
  15. GRB 250322A: NOT optical upper limits
  16. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  17. GRB 250322A: MASTER optical observation
  18. EP250321a: Liverpool Telescope optical follow-up
  19. EP250321a: Mondy AZT-33IK Optical Observations
  20. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  21. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250321A: COLIBRÍ Continuing Optical Observations
  23. GRB 250312A: GECAM-A detection
  24. EP250321a: WFST optical observations
  25. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  26. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  27. EP250321a: Xinglong 216 decaying optical observations
  28. GRB 250321A: Swift-BAT refined analysis
  29. GRB 250321B: SVOM detection of a sub-threshold transient event
  30. EP250321a: SVOM/VT optical observation
  31. EP 250321A: Optical counterpart detection by LCO.
  32. GRB 250320B: SVOM/GRM observation of a long burst
  33. EP250321a: LCO optical counterpart detection
  34. EP250321A: COLIBRÍ Optical Observations
  35. GRB 250320B: AstroSat CZTI detection
  36. Fermi GRB 250320B: Global MASTER-Net observations report
  37. EP250321a: BOOTES-5/JGT optical afterglow detection
  38. EP250321a: Global MASTER-Net observations report
  39. Swift GRB 250321A: Global MASTER-Net observations report
  40. Fermi GRB 250321A: Global MASTER-Net observations report
  41. EP250321a: Einstein Probe detection of an X-ray transient
  42. GRB 250321A: GOTO optical upper limits
  43. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  44. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  45. Fermi GRB 250319B: Global MASTER-Net observations report
  46. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  47. GRB 250313A: GRBAlpha detection
  48. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  49. GRB 250317D: EIRSAT-1 GMOD Detection
  50. EP250302a: VLA observations
  51. GRB 250317B: OHP/T193 continued follow-up
  52. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  53. GRB 250317C: SVOM/GRM observation of a long burst
  54. GRB 250317B: Leavitt Observatory optical upper limit
  55. GRB 250309B/AT2025dws: further ATCA observations
  56. GRB 250317B: Mondy AZT-33IK Optical Observations
  57. GRB 250317C: AstroSat CZTI detection
  58. GRB 250317B: NOT optical observations suggest an optical plateau phase
  59. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  60. GRB 250317C: GECAM-B detection
  61. GRB 250317B: OHP/T193 optical observations
  62. Fermi trigger No 763933627: Global MASTER-Net observations report
  63. GRB 250317B: REM optical/NIR observations
  64. GRB 250316A: AbAO AS-32 Optical Upper Limit
  65. EP 250317B: Fading optical counterpart detection by LCO
  66. GRB 250317B: LCO detection of the fading optical afterglow
  67. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  68. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  69. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  70. GRB 250317B: SVOM detection of a burst
  71. Fermi trigger No 763862734: Global MASTER-Net observations report
  72. Fermi GRB 250316A: Global MASTER-Net observations report
  73. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  74. The EP-WXT trigger 01709132801 is likely a flaring star
  75. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  76. GRB 250314A: EP-FXT afterglow detection
  77. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250312B: GRBAlpha detection
  79. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  80. EP250315a: Einstein Probe detection of an X-ray transient
  81. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  82. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  83. GRB 250314A: SVOM detection of a burst
  84. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  85. GRB 250313B: SVOM/GRM observation of a soft bright short burst
  86. GRB 250313A: SVOM/GRM observation of a bright long burst
  87. GRB 250313A: AstroSat CZTI detection of a bright long burst
  88. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  89. Fermi trigger No 763581136: Global MASTER-Net observations report
  90. EP250304a: Pan-STARRS r and i-band imaging and photometry
  91. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  92. Fermi GRB 250313A: Global MASTER-Net observations report
  93. The EP-WXT trigger 01709132551 is not a real source
  94. EP250304a: SVOM/VT optical observation
  95. EP250311a/GRB 250311A: EP-FXT follow-up observation
  96. EP250302a: Chandra X-ray Detection
  97. Fermi trigger No 763509110: Global MASTER-Net observations report
  98. Fermi GRB 250312B: Global MASTER-Net observations report
  99. Swift GRB 250312A: Global MASTER-Net observations report
  100. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation

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