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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"

32512 results found.

  1. GRB 250327A: SVOM/VT optical candidate
  2. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  3. GRB 250327A: Fermi GBM observation
  4. Fermi GRB 250327A: Global MASTER-Net observations report
  5. Swift GRB 250327A: Global MASTER-Net observations report
  6. GRB 250327A: DDOTI Optical Observations
  7. GRB 250327A: COLIBRÍ optical upper limit
  8. GRB 250327A: Swift detection of a burst
  9. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  10. Konus-Wind detection of GRB 250322A (short)
  11. IPN triangulation of GRB 250322B
  12. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  13. EP250321a: Mondy AZT-33IK Continued Optical Observations
  14. GRB 250322A: third epoch of NOT optical observations
  15. GRB 250322A: Swift-BAT refined analysis
  16. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  17. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  18. GRB 250322A: further NOT optical observations
  19. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  20. GRB 250322A: Swift/UVOT Upper Limits
  21. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  22. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  23. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  24. EP250321a: TNOT Observation of Optical Counterpart
  25. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  26. GRB 250322A: Gemini-North redshift of candidate host galaxy
  27. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  28. GRB 250322A: AstroSat CZTI detection of a short burst
  29. GRB250322A: STEP/T80S optical limits
  30. GRB 250322A: Gemini-South optical observations
  31. GRB 250322A: VLT optical observations
  32. GRB 250322A: VLT near-infrared observations
  33. FRB 250316A: DDOTI Continued Optical Observations
  34. GRB 250322A: NOT optical upper limits
  35. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  36. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  37. GRB 250322A: MASTER optical observation
  38. EP250321a: Liverpool Telescope optical follow-up
  39. EP250321a: Mondy AZT-33IK Optical Observations
  40. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP250321a: KAIT optical observations
  42. EP250321A: COLIBRÍ Continuing Optical Observations
  43. GRB 250225B: GECAM-A detection
  44. GRB 250312A: GECAM-A detection
  45. GRB 250321B: Swift ToO observations
  46. EP250321a: WFST optical observations
  47. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  48. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  49. GRB 250320B: Fermi GBM Observation
  50. EP250321a: Xinglong 216 decaying optical observations
  51. GRB 250321A: Swift-BAT refined analysis
  52. GRB 250320B: Fermi-LAT detection
  53. EP250321a: SVOM/VT optical observation
  54. EP 250321A: Optical counterpart detection by LCO.
  55. EP250321a: Kinder optical follow-up observations
  56. GRB 250321A: Swift/UVOT Upper Limits
  57. GRB 250320B: SVOM/GRM observation of a long burst
  58. EP250321a: LCO optical counterpart detection
  59. EP250321a: Swift-XRT detection of an X-ray source
  60. EP250321A: COLIBRÍ Optical Observations
  61. EP250321a: VLT/X-shooter redshift z = 4.368
  62. GRB 250320B: AstroSat CZTI detection
  63. EP250321a: REM optical/NIR afterglow detection
  64. Fermi GRB 250320B: Global MASTER-Net observations report
  65. EP250321a: TRT optical counterpart detection
  66. EP250321a: Global MASTER-Net observations report
  67. Swift GRB 250321A: Global MASTER-Net observations report
  68. Fermi GRB 250321A: Global MASTER-Net observations report
  69. GRB 250321A: GOTO optical upper limits
  70. GRB 250321A: Swift-XRT localisation
  71. GRB 250314A: Keck/NIRC2 J-band upper limit
  72. EP250226a/GRB 250226A: KAIT optical observations
  73. GRB 250321A: Fermi GBM Observation
  74. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  75. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  76. Fermi GRB 250319B: Global MASTER-Net observations report
  77. GRB 250313A: GRBAlpha detection
  78. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  79. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  80. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  81. GRB 250314A: ATCA radio upper limits
  82. EP250302a: VLA observations
  83. GRB 250317B: OHP/T193 continued follow-up
  84. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  85. GRB 250317C: SVOM/GRM observation of a long burst
  86. GRB 250317B: Leavitt Observatory optical upper limit
  87. GRB 250309B/AT2025dws: further ATCA observations
  88. GRB 250317B: Mondy AZT-33IK Optical Observations
  89. GRB 250317C: AstroSat CZTI detection
  90. GRB 250317B: NOT optical observations suggest an optical plateau phase
  91. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  92. GRB 250317B: OHP/T193 optical observations
  93. GRB250312A: Swift/UVOT Upper Limits
  94. GRB 250317B: REM optical/NIR observations
  95. GRB 250317B: Swift-XRT observations
  96. GRB 250316A: Swift/UVOT Upper Limits
  97. GRB 250314A: REM optical/NIR upper limits
  98. GRB 250316A: AbAO AS-32 Optical Upper Limit
  99. EP 250317B: Fading optical counterpart detection by LCO
  100. GRB 250317B: LCO detection of the fading optical afterglow

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