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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. EP240918a: Swift-XRT observation
  2. Fermi GRB 240918A: Global MASTER-Net observations report
  3. GRB 240918A: Fermi GBM Final Real-time Localization
  4. EP EP240918a: Global MASTER-Net observations report
  5. EP240918a: JinShan optical upper limits
  6. EP240918a: YAHPT Optical Upper Limit
  7. EP240918a: Optical upper limits with Kinder observations
  8. EP240918a: GMG Optical Upper Limit
  9. GRB 240916A: GRBAlpha detection
  10. GRB 240914B: GRBAlpha detection
  11. EP240918a: an X-ray transient detected by Einstein Probe
  12. GRB 240916A: NOT optical observation
  13. GRB 240912A: Swift-BAT refined analysis
  14. IPN triangulation of GRB 240913C / EP 240913a
  15. GRB 240825A: INTEGRAL SPI ACS LIGHT CURVE
  16. GRB 240825A: The nature of the afterglow motivates the search of the associated supernova
  17. GRB 240916A: Fermi GBM Observation
  18. LIGO/Virgo/KAGRA S240917cb: Identification of a GW compact binary merger candidate
  19. GRB 240821A: radio observation with the VLA
  20. GRB 240916A (AT 2024vlp / GOTO24fzn): VLT/X-shooter redshift
  21. GRB 240916A: Swift-XRT afterglow detection
  22. LIGO/Virgo/KAGRA S240916ar: Identification of a GW compact binary merger candidate
  23. GRB 240916A: Swift ToO observations
  24. LIGO/Virgo/KAGRA S240915b: NED Galaxies in the Localization Volume
  25. LIGO/Virgo S240915b: Swift XRT observations, 8 X-ray sources
  26. GRB 240916A: JinShan optical decay in one of the two GOTO candidates
  27. GRB 240916B: Fermi GBM Final Real-time Localization
  28. GRB 240914B: Fermi GBM Final Localization
  29. The EP-WXT triggers 01709047257 and 01709047278 are not real sources
  30. GRB 240916A: GOTO identification of two new optical sources within the GBM localisation region
  31. EP EP240913a: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations
  33. GRB 240916A INTEGRAL SPI ACS LIGHT CURVE
  34. GRB 240916A: Fermi GBM Final Real-time Localization
  35. Fermi Gamma-ray Burst Monitor trigger 748124309/240915846 is not a GRB
  36. LIGO/Virgo/KAGRA S240915bd: Updated Sky localization
  37. EP240913a: VLT/HAWK-I near-infrared upper limits
  38. LIGO/Virgo/KAGRA S240915bd: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S240915b: Updated Sky localization and EM Bright Classification
  40. LIGO/Virgo/KAGRA S240915b: Identification of a GW compact binary merger candidate
  41. EP240913a/GRB 240913C: KAIT optical upper limit
  42. EP240913a / GRB 240913C INTEGRAL SPI ACS LIGHT CURVE
  43. GRB 240913C: Fermi GBM detection
  44. GRB 240914A: Swift-XRT observations
  45. GRB 240913C: Joint location by ETJASMIN
  46. GRB 240914B: AstroSat CZTI detection
  47. EP240913A / GRB 240913C: AstroSat CZTI detection
  48. GRB 240914A: SVOM/GRM observation
  49. GRB 240910A: SVOM/VT optical observations
  50. GRB 240914A: Swift ToO observations
  51. EP240913a: NOT optical upper limits
  52. EP240913a: JinShan optical upper limits
  53. EP240913a: ESO-NTT optical observations
  54. GRB 240914A: ESO-NTT optical observations
  55. EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
  56. GRB 240914B: BALROG localization (Fermi Trigger 747990592 / GRB 240914298)
  57. GRB 240914A : An intermediate duration GRB located on-board by SVOM/ECLAIRs.
  58. GRB 240905E: further NOT optical observations
  59. EP240913a: A GRB Event
  60. EP240913a: EP-WXT detection of a fast X-ray transient
  61. GRB 240913B: Fermi GBM Final Real-time Localization
  62. GRB 240911A: LCO optical observations
  63. GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
  64. Fermi Gamma-ray Burst Monitor trigger 747837485/240912526 is not a GRB
  65. GRB 240912A: Swift/UVOT Detection
  66. GRB 240911A: GOTO optical limits on Swift/XRT candidates
  67. Fermi trigger No 747920561: Global MASTER-Net observations report
  68. GRB 240912A: SVOM/GRM observation
  69. GRB 240911A: Swift-XRT observations
  70. Fermi GRB 240913A: Global MASTER-Net observations report
  71. GRB 240913A: Fermi GBM Final Real-time Localization
  72. GRB 240912A: J-band observations with WINTER
  73. GRB 240912A: Swift-XRT refined Analysis
  74. GRB 240912A: Fermi GBM Observation
  75. Swift GRB 240912A: Global MASTER-Net observations report
  76. GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
  77. GRB 240911A: Tiled Swift observations
  78. Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
  79. GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
  80. GRB 240912B: Fermi GBM Final Real-time Localization
  81. GRB 240912A: NOT optical spectroscopy
  82. GRB 240912A: Enhanced Swift-XRT position
  83. GRB 240912A: Redshift from OSIRIS+/GTC
  84. Fast X-ray Transient EP240801a: GMRT radio observations
  85. GRB 240910A: Redshift from OSIRIS+/GTC
  86. GRB 240912A: Swift detection of a burst with an optical counterpart
  87. GRB 240912A: Fermi GBM Final Real-time Localization
  88. GRB 240910A: Fermi GBM Observation
  89. GRB 240910A: NOT optical observations
  90. GRB 240911A : a likely weak GRB detected by SVOM/ECLAIRs
  91. GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
  92. GRB 240910A: JinShan optical observations
  93. GRB 240910A: GOTO candidate optical counterpart
  94. EP240908a: Optical afterglow confirmation
  95. GRB 240710A: SVOM/GRM observation
  96. GRB 240910A: Swift ToO observations
  97. IPN triangulation of GRB 240905B (short)
  98. GRB 240825A: 7DT Optical Upper Limit
  99. GRB 240905E: SVOM/VT optical observations
  100. GRB 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)

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