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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. EP 240416a: Xinglong and NOT decaying optical counterpart
  2. GRB 240415A: Swift-BAT refined analysis
  3. EP240416A: MASTER optical observations
  4. GRB 240411A: Glowbug gamma-ray detection
  5. GRB 240414A: Swift-BAT refined analysis
  6. EP240416a: Kinder optical counterpart candidate
  7. EP240416a: EP-WXT detection of a fast X-ray transient
  8. GRB 240414A: AbAO optical upprer limit
  9. GRB 240415A: Swift/UVOT Detection
  10. EP240413a: BOOTES-2/TELMA Optical Upper Limit
  11. GRB 240415A: Fermi GBM Observation
  12. GRB 240414A: GAD Observatory, La Spezia, Italy ,upper limit
  13. GRB 240415A: Earliest optical followup with the Kinder observations
  14. GRB 240414A: GMG observation
  15. EP 240414a: BOOTES-4/MET Optical Upper Limits
  16. EP240414a: EP-FXT follow-up observation
  17. GRB 240415A: Enhanced Swift-XRT position
  18. GRB 240415B: Swift ToO observations
  19. GRB 240415B: Swift/BAT-GUANO Correction
  20. GRB 240415B: Swift/BAT-GUANO arcminute localization of a short burst
  21. GRB 240415A: OHP/T193 optical observations
  22. GRB 240415A: optical afterglow detection from the INAF Asiago Observatory
  23. GRB 240415A: SAO RAS optical observations
  24. GRB 240415A: Mondy optical transient detection (photometry correction in GCN 36118 )
  25. GRB 240414A: Fermi GBM Observation
  26. Fermi GRB 240415A: Global MASTER-Net observations report
  27. GRB 240415A: Mondy optical transient detection
  28. GRB 240414A: Photometric observation from 2.2m CAHA
  29. IceCube-240412A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 240414A: Swift/UVOT Detection
  31. LXT 240402A/GRB 240402B: Swift follow-up observations
  32. GRB 240414A: Mondy optical observations
  33. GRB 240414B: Fermi GBM Final Real-time Localization
  34. GRB 240414A: AKO Optical Upper Limit
  35. X-ray transient EP 240414a - GTC spectroscopic observations
  36. GRB 240415A: Prompt Swift-XRT observations
  37. GRB 240415A: Swift detection of a burst
  38. GRB 240415A: Fermi GBM Final Real-time Localization
  39. EP240413a: Upper limits from GECAM-B Observation
  40. EP 240414a: NOT optical counterpart confirmation
  41. GRB 240414A: Swift-XRT refined Analysis
  42. GRB240414A : J-band upper limits from WINTER
  43. GRB 240414A: Enhanced Swift-XRT position
  44. GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
  45. GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  46. LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
  47. EP240413A: GOTO optical upper limits
  48. GRB 240414A: Skynet Optical Afterglow Observations
  49. Fermi trigger No 734754044: Global MASTER-Net observations report
  50. Swift GRB 240414A: Global MASTER-Net observations report
  51. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  52. IPN triangulation of GRB 240410A
  53. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  54. EP240414a: EP-WXT detection of a fast X-ray transient
  55. IPN triangulation of GRB 240411A
  56. Fermi-LAT gamma-ray observations of IceCube-240412A
  57. GRB 240414A : MITSuME Akeno optical upper limits
  58. GRB 240414A: Redshift confirmation from GTC/OSIRIS+
  59. EP240413a: EP-WXT detection of a fast X-ray transient
  60. GRB 240414A : OHP/T193 redshift determination
  61. GRB 240414A : OHP/T193 optical counterpart detection
  62. GRB 240414A: Swift detection of a burst
  63. LIGO/Virgo/KAGRA S240413p: Updated Sky localization
  64. LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S240413p: Zwicky Transient Facility observations
  66. EP240408a: GSP optical upper limit
  67. GRB 240411B: CrAO/ZTSh optical observations
  68. GRB 240411B: Kinder observations with Lulin observatory
  69. LIGO/Virgo/Kagra S240413p: NED Galaxies in the Localization Volume
  70. LIGO/Virgo/KAGRA S240413p: Identification of a GW compact binary merger candidate
  71. GRB 240411B: HiPERCAM/GTC observation
  72. IceCube Alert 240412.23: Global MASTER-Net observations report
  73. GRB 240411B: Swift-BAT refined analysis
  74. GRB 240411B: Swift-XRT refined Analysis
  75. IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 240411B: 1.3m DFOT Optical observations
  77. GRB 240411A: GRBAlpha detection
  78. GRB 240411B: OHP/T193 optical observations
  79. GRB 240405A: Glowbug gamma-ray detection
  80. GRB 240411B: Enhanced Swift-XRT position
  81. GRB 240411B: LCO optical afterglow detection
  82. GRB 240411B: Swift detection of a burst
  83. GRB 240408B: GRBAlpha detection
  84. GRB 240411A: Fermi GBM Final Real-time Localization
  85. EP240408A: MASTER optical observations
  86. EP240408a: GROND detection of a candidate counterpart
  87. EP240408a: Upper limits from GECAM-B Observation
  88. EP240408a: Swift follow-up observation
  89. EP240408a: BOOTES-6/DPRT optical upper limit
  90. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  91. GRB 240405A: GRBAlpha detection
  92. EP240408a: EP-WXT detection of a fast X-ray transient
  93. Swift Trigger 1220736: detection of 4U 1543-62.
  94. GRB 240408B: AstroSat CZTI detection
  95. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  96. Fermi GRB 240408A: Global MASTER-Net observations report
  97. GRB 240408A: Fermi GBM Final Real-time Localization
  98. GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
  99. GRB 240402C: CALET Gamma-Ray Burst Monitor detection
  100. Fermi GRB 240407A: Global MASTER-Net observations report

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