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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"
  1. GRB 240821A: further radio observations with the VLA
  2. Fermi GRB 241104A: Global MASTER-Net observations report
  3. GRB 241104A: Fermi GBM Final Real-time Localization
  4. GRB 241030A: GRBAlpha detection
  5. EP241101a: EP-FXT observations update
  6. EP241103a: GIT optical upper limit
  7. EP241021a: OHP/T193 further optical observations
  8. LIGO/Virgo/KAGRA S241104a: Retraction of GW compact binary merger candidate
  9. Fermi trigger No 752365806: Global MASTER-Net observations report
  10. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  11. LIGO/Virgo/KAGRA S241102cy: Updated Sky localization
  12. EP241103a: GOTO optical upper limit
  13. LIGO/Virgo/KAGRA S241102br: Updated Sky localization
  14. EP241101a: Possible detection of an optical counterpart with FTW
  15. EP241103a: Swift XRT detection and improved X-ray position
  16. EP241021a: continued SOAR observations
  17. EP241101a: Optical upper limits with Kinder observations
  18. EP241101a: OHP/T193 optical observations
  19. EP241103a: Gemini optical limits
  20. EP241103a: EP observation update
  21. LIGO/Virgo/KAGRA S241102br: MASTER observations and OT detection
  22. LIGO/Virgo/KAGRA S241102br: EP-WXT X-ray follow-up and flux limits
  23. GRB 241030A: Swift-UVOT observations of the optical prompt flare
  24. EP241103a: GSP optical upper limit
  25. EP241103A: LCO optical observations
  26. EP241103a: Global MASTER-Net observations report
  27. EP241103a: an X-ray transient detected by Einstein Probe
  28. GRB 241030A: Rapid release of TESS data.
  29. EP241101a: Global MASTER-Net observations report
  30. GRB 241029A: GRBAlpha detection
  31. EP241101a: BOOTES-7 optical upper limit
  32. LIGO/Virgo/KAGRA S241101ee: Updated Sky localization
  33. S241102cy: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S241102br: NED Galaxies in the Localization Volume
  35. LIGO/Virgo/KAGRA S241102br: Identification of a GW compact binary merger candidate
  36. Kinder optical follow-up observations of EP241021a, EP241026b, and EP241030a/GRB241030A
  37. GRB241030A: OHP/T193 optical observations
  38. EP241030a: Futher EP-FXT observation of the X-ray Afterglow of GRB 241030A
  39. EP241101a: EP-WXT detection of a fast X-ray transient
  40. Swift GRB 241101A: Global MASTER-Net observations report
  41. GRB 241101A: FRAM-ORM optical limit
  42. LIGO/Virgo/KAGRA S241101ee: Identification of a GW compact binary merger candidate
  43. GRB 241030A/EP241030a: TNOT observations of the optical counterpart
  44. EP241021a: Upper limit from Konus-Wind observations
  45. GRB 241101A: Swift-BAT refined analysis
  46. GRB 241030A: further SAO RAS optical observations
  47. GRB 241030A: Optical Observations via Virtual Telescope Project
  48. EP241021a: Liverpool Telescope optical follow-up observations
  49. GRB 241030B: Swift-XRT refined Analysis
  50. GRB 241026A: SAO RAS optical observations
  51. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  52. EP241030a: EP/FXT observation of GRB 241030A X-ray Afterglow
  53. GRB 241101A: Swift detection of a burst
  54. GRB 241030B: NUTTelA-TAO / BSTI Optical Limits (duplicate submission of 38023)
  55. GRB 241030B: NUTTelA-TAO / BSTI Optical Limits
  56. EP241021a: OHP/T193 optical observations
  57. GRB 241030A: Palomar 1-m telescope COSMOS optical observations
  58. GRB 241030B: Montarrenti Observatory optical upper limit
  59. GRB 241030A / EP241030a: FTW Optical and NIR observations of the optical counterpart
  60. EP241026b: Liverpool Telescope optical follow-up
  61. Fermi trigger No 752083996: Global MASTER-Net observations report
  62. GRB 241030A: SAO RAS optical observations
  63. GRB 241030A: Fermi GBM Observation
  64. EP241021a: AMI-LA radio detection
  65. GRB 241030B : GIT optical upper limits
  66. GRB 241030B: LCOGT Optical Upper Limits
  67. GRB 241030B: Swift-BAT refined analysis
  68. GRB 241030A: Swift-BAT refined analysis
  69. GRB 241029A: COLIBRI Detection of the Optical Counterpart
  70. GRB 241030B: Swift/UVOT Detection
  71. EP EP241030a: Global MASTER-Net observations report
  72. GRB 241029A: LCO optical detection
  73. Fermi trigger No 752006065: Global MASTER-Net observations report
  74. GRB 241030B: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.82
  75. Swift GRB241030.77: Global MASTER-Net observations report
  76. GRB 241030B: SVOM/GRM observation
  77. GRB 241030B : MITSuME Akeno optical upper limits
  78. GRB 241030A: COLIBRI Continuing Detection of the Afterglow
  79. GRB 241030B: SVOM/VT optical afterglow observations
  80. GRB 241030B: COLIBRÍ Upper Limits on the Optical Counterpart
  81. EP241030a: EP detection of GRB 241030A X-ray Afterglow
  82. GRB241030B: Fermi GBM Observation
  83. GRB 241030B: BTA observations
  84. GRB 241029A: SVOM/VT optical afterglow observations
  85. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  86. GRB 241030B: Enhanced Swift-XRT position
  87. GRB 241030B: optical observations from the INAF Asiago Observatory
  88. EP241021a: Swift-UVOT detection
  89. GRB241030B: GRANDMA/TAROT Upper Limit
  90. GRB 241030A: Swift-XRT refined Analysis
  91. GRB 241030B: SAO RAS optical observations
  92. GRB 241030B: AKO Optical Afterglow Detection
  93. GRB 241030B: Nanshan/HMT optical afterglow detection
  94. GRB 241030B: SVOM/ECLAIRs detection of a burst
  95. GRB 241030B: Prompt enhanced Swift-XRT position
  96. Konus-Wind detection of GRB 241030A
  97. GRB 241030B: Swift detection of a burst
  98. GRB 241030B: Fermi GBM Final Real-time Localization
  99. GRB 241030A: Fermi-LAT detection
  100. GRB 240912A: radio detection with the VLA

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