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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. INTEGRAL detection of a burst from 1E 1841-045
  2. EP241107a: AbAO optical upper limit
  3. LIGO/Virgo/KAGRA S241109bn: Upper limits from Fermi-GBM Observations
  4. GRB 241108A: Further COLIBRÍ Upper Limits on the Optical Counterpart
  5. LIGO/Virgo/KAGRA S241109p: Updated Sky localization and Source Classification
  6. LIGO/Virgo/KAGRA S241109bn: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S241109bn: Identification of a GW compact binary merger candidate
  8. EP241109a: confirmation of a stellar flare by BOOTES-7
  9. EP241109a: EP on-board trigger and autonomous follow-up observation
  10. GRB 241108A: Swift-XRT observations
  11. LIGO/Virgo/KAGRA S241109p: Identification of a GW compact binary merger candidate
  12. EP241107A: MASTER optical observations of xray transient
  13. EP241107a: KAIT optical observations
  14. GRB 241108A: Swift ToO observations
  15. GRB 241030A: TESS observations
  16. GRB 241108A: COLIBRÍ Upper Limits on the Optical Counterpart
  17. GRB 241108A : a likely weak long GRB detected by SVOM/ECLAIRs
  18. EP241107a: Kinder optical follow-up observations
  19. GRB 241025A: radio detection with the VLA
  20. GRB 241104A: CALET Gamma-Ray Burst Monitor detection
  21. EP241107a: AKO Optical Afterglow Follow-Up Observations
  22. EP241107a: GSP detects optical counterpart
  23. EP241107a: Gemini-South spectroscopic confirmation (z = 0.456)
  24. GRB 241107A: SVOM/GRM detection of a short burst
  25. GRB 241105A: EP-FXT follow-up observations
  26. GRB 241105A: SVOM/GRM observation
  27. EP241107a: OHP/T193 photometric and spectroscopic observations
  28. GRB 241105a: PRIME near-infrared upper limits
  29. EP241107a: FTW Optical and NIR observations of the optical counterpart
  30. GRB 241105A: ePESSTO+ NTT optical afterglow detection
  31. EP241107a: GIT optical observations
  32. EP241107a: Global MASTER-Net observations report
  33. EP241107a: SVOM/C-GFT optical observations
  34. EP241107a: AKO Optical Afterglow Detection
  35. GRB 241025A: LBT optical observations
  36. GRB241105A: Gemini-South Optical Afterglow Detection
  37. EP241107a: EP on-board trigger and autonomous follow-up observation
  38. GRB 241105A: VLT/FORS2 optical afterglow rapid fading
  39. GRB 241105A: Swift/UVOT Detection
  40. EP241101a: CrAO ZTSH optical observations
  41. GRB 241105A: Swift/BAT-GUANO refined analysis of short burst with extended emission
  42. GRB 241030A: optical afterglow detection from the INAF Asiago Observatory
  43. GRB 241105A: BOOTES-7 optical detection
  44. GRB 241030A: Mondy optical observations
  45. GRB 241105A: Fermi GBM Observation of a Short Burst with Extended Emission
  46. Konus-Wind detection of GRB 241105A (short with extended emission)
  47. LIGO/Virgo/KAGRA S241106ba: 1 counterpart neutrino candidate event from an IceCube neutrino search
  48. LIGO/Virgo/KAGRA S241102o: 1 counterpart neutrino candidate event from an IceCube neutrino search
  49. Konus-Wind detection of GRB 241021A
  50. GRB 241105A: SVOM/VT optical afterglow observations
  51. GRB 241105A: Swift-XRT afterglow detection
  52. GRB 241105A: VLT/FORS2 spectroscopic redshift z = 2.681
  53. GRB 241104A: Swift-XRT observations
  54. GRB 240511A: LCO upper limits
  55. GRB 241104A: Fermi GBM Observation
  56. GRB 241104A: The SVOM/VT candidate in GCN circular 38086 is not an astrophysical source
  57. GRB 241105A: Swift ToO observations
  58. GRB 241105A: Swift/BAT-GUANO arcminute localization of a short burst
  59. GRB 241104A: Swift ToO observations
  60. GRB 241104A: NOT optical non-detection
  61. GRB 241105A: GOTO tentative optical counterpart candidate
  62. Fermi GRB 241105A: Global MASTER-Net observations report
  63. GRB 241104A: SVOM/VT optical candidate
  64. GRB 241105A: Fermi GBM Final Real-time Localization
  65. GRB 241104A/EP241104a: Optical upper limits with Kinder observations
  66. GRB 241104A: COLIBRÍ Upper Limits on the Optical Counterpart
  67. GRB 241104A: SVOM/GRM observation
  68. EP241104a: EP detection of GRB 241104A X-ray emission
  69. GRB 241010A: host galaxy redshift z = 0.977
  70. EP241101a NUTTelA-TAO / BSTI Measurements 2024-11-02
  71. GRB 241104A : Detection and localization by SVOM/ECLAIRs
  72. GRB 240821A: further radio observations with the VLA
  73. Fermi GRB 241104A: Global MASTER-Net observations report
  74. GRB 241104A: Fermi GBM Final Real-time Localization
  75. GRB 241030A: GRBAlpha detection
  76. EP241101a: EP-FXT observations update
  77. EP241103a: GIT optical upper limit
  78. EP241021a: OHP/T193 further optical observations
  79. LIGO/Virgo/KAGRA S241104a: Retraction of GW compact binary merger candidate
  80. Fermi trigger No 752365806: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  82. LIGO/Virgo/KAGRA S241102cy: Updated Sky localization
  83. EP241103a: GOTO optical upper limit
  84. LIGO/Virgo/KAGRA S241102br: Updated Sky localization
  85. EP241101a: Possible detection of an optical counterpart with FTW
  86. EP241103a: Swift XRT detection and improved X-ray position
  87. EP241021a: continued SOAR observations
  88. EP241101a: Optical upper limits with Kinder observations
  89. EP241101a: OHP/T193 optical observations
  90. EP241103a: Gemini optical limits
  91. EP241103a: EP observation update
  92. LIGO/Virgo/KAGRA S241102br: MASTER observations and OT detection
  93. LIGO/Virgo/KAGRA S241102br: EP-WXT X-ray follow-up and flux limits
  94. GRB 241030A: Swift-UVOT observations of the optical prompt flare
  95. EP241103a: GSP optical upper limit
  96. EP241103A: LCO optical observations
  97. EP241103a: Global MASTER-Net observations report
  98. EP241103a: an X-ray transient detected by Einstein Probe
  99. GRB 241030A: Rapid release of TESS data.
  100. EP241101a: Global MASTER-Net observations report

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