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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').
  1. EP250321a: Mondy AZT-33IK Continued Optical Observations
  2. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  3. GRB 250322A: third epoch of NOT optical observations
  4. GRB 250322A: Swift-BAT refined analysis
  5. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  6. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  7. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  8. GRB 250322A: further NOT optical observations
  9. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  10. GRB 250322A: Swift/UVOT Upper Limits
  11. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  12. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  13. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  14. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  15. GRB 250321B: Swift-XRT observations
  16. GRB 250322A: Swift-XRT refined Analysis
  17. EP250321a: TNOT Observation of Optical Counterpart
  18. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  19. GRB 250322A: Gemini-North redshift of candidate host galaxy
  20. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  21. SVOM/sb25032302: SVOM detection of a long X-ray transient
  22. GRB 250322A: AstroSat CZTI detection of a short burst
  23. GRB 250322B: AstroSat CZTI detection of a bright long burst
  24. GRB250322A: STEP/T80S optical limits
  25. GRB 250322A: Gemini-South optical observations
  26. GRB 250322A: VLT optical observations
  27. GRB 250322A: VLT near-infrared observations
  28. FRB 250316A: DDOTI Continued Optical Observations
  29. GRB 250322A: NOT optical upper limits
  30. GRB 250322A: Enhanced Swift-XRT position
  31. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  32. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  33. GRB 250322A: MASTER optical observation
  34. EP250321a: Liverpool Telescope optical follow-up
  35. EP250321a: Mondy AZT-33IK Optical Observations
  36. GRB 250322A: Swift detection of a short burst
  37. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  38. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  39. EP250321a: KAIT optical observations
  40. EP250321A: COLIBRÍ Continuing Optical Observations
  41. GRB 250225B: GECAM-A detection
  42. GRB 250312A: GECAM-A detection
  43. GRB 250321B: Swift ToO observations
  44. EP250321a: WFST optical observations
  45. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  46. GRB 250321C: Fermi GBM Final Real-time Localization
  47. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  48. GRB 250320B: Fermi GBM Observation
  49. EP250321a: Xinglong 216 decaying optical observations
  50. GRB 250321A: Swift-BAT refined analysis
  51. GRB 250321A: Swift-XRT refined Analysis
  52. GRB 250320B: Fermi-LAT detection
  53. GRB 250321B: SVOM detection of a sub-threshold transient event
  54. EP250321a: SVOM/VT optical observation
  55. EP 250321A: Optical counterpart detection by LCO.
  56. EP250321a: Kinder optical follow-up observations
  57. GRB 250321A: Swift/UVOT Upper Limits
  58. GRB 250320B: SVOM/GRM observation of a long burst
  59. EP250321a: LCO optical counterpart detection
  60. EP250321a: Swift-XRT detection of an X-ray source
  61. EP250321A: COLIBRÍ Optical Observations
  62. EP250321a: VLT/X-shooter redshift z = 4.368
  63. GRB 250320B: AstroSat CZTI detection
  64. EP250321a: REM optical/NIR afterglow detection
  65. Fermi GRB 250320B: Global MASTER-Net observations report
  66. EP250321a: BOOTES-5/JGT optical afterglow detection
  67. EP250321a: TRT optical counterpart detection
  68. EP250321a: Global MASTER-Net observations report
  69. Swift GRB 250321A: Global MASTER-Net observations report
  70. Fermi GRB 250321A: Global MASTER-Net observations report
  71. EP250321a: Einstein Probe detection of an X-ray transient
  72. GRB 250321A: GOTO optical upper limits
  73. GRB 250321A: Swift-XRT localisation
  74. GRB 250314A: Keck/NIRC2 J-band upper limit
  75. EP250226a/GRB 250226A: KAIT optical observations
  76. GRB 250321A: Fermi GBM Observation
  77. GRB 250321A: Swift detection of a burst
  78. GRB 250321A: Fermi GBM Final Real-time Localization
  79. GRB 250320B: Fermi GBM Final Real-time Localization
  80. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  81. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  82. GRB 250320A: Fermi GBM Final Real-time Localization
  83. Fermi GRB 250319B: Global MASTER-Net observations report
  84. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  85. GRB 250313A: GRBAlpha detection
  86. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  87. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  88. GRB 250319B: Fermi GBM Final Localization
  89. GRB 250319A: Fermi GBM Final Localization
  90. GRB 250317D: EIRSAT-1 GMOD Detection
  91. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  92. GRB 250314A: ATCA radio upper limits
  93. EP250302a: VLA observations
  94. GRB 250317B: OHP/T193 continued follow-up
  95. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  96. GRB 250317C: SVOM/GRM observation of a long burst
  97. GRB 250317B: Leavitt Observatory optical upper limit
  98. GRB 250309B/AT2025dws: further ATCA observations
  99. GRB 250317B: Mondy AZT-33IK Optical Observations
  100. GRB 250317C: AstroSat CZTI detection

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