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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. EP240919a is likely a GRB event (duplicate submission of 37563)
  2. EP240919a is likely a GRB event
  3. LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
  4. EP240919a: EP-WXT detection of a fast X-ray transient
  5. GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE
  6. LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
  7. GRB 240918B: Fermi GBM Detection
  8. LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
  9. LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
  10. EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients
  11. EP240918a: EP observation update
  12. GRB 240910A: further Swift observations and confirmation of afterglow
  13. LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate
  14. EP240918a: Swift-XRT observation
  15. Fermi GRB 240918A: Global MASTER-Net observations report
  16. GRB 240918A: Fermi GBM Final Real-time Localization
  17. EP EP240918a: Global MASTER-Net observations report
  18. EP240918a: JinShan optical upper limits
  19. EP240918a: YAHPT Optical Upper Limit
  20. EP240918a: Optical upper limits with Kinder observations
  21. EP240918a: GMG Optical Upper Limit
  22. GRB 240916A: GRBAlpha detection
  23. GRB 240914B: GRBAlpha detection
  24. EP240918a: an X-ray transient detected by Einstein Probe
  25. GRB 240916A: NOT optical observation
  26. GRB 240912A: Swift-BAT refined analysis
  27. IPN triangulation of GRB 240913C / EP 240913a
  28. GRB 240825A: INTEGRAL SPI ACS LIGHT CURVE
  29. GRB 240825A: The nature of the afterglow motivates the search of the associated supernova
  30. GRB 240916A: Fermi GBM Observation
  31. LIGO/Virgo/KAGRA S240917cb: Identification of a GW compact binary merger candidate
  32. GRB 240821A: radio observation with the VLA
  33. GRB 240916A (AT 2024vlp / GOTO24fzn): VLT/X-shooter redshift
  34. GRB 240916A: Swift-XRT afterglow detection
  35. LIGO/Virgo/KAGRA S240916ar: Identification of a GW compact binary merger candidate
  36. GRB 240916A: Swift ToO observations
  37. LIGO/Virgo/KAGRA S240915b: NED Galaxies in the Localization Volume
  38. LIGO/Virgo S240915b: Swift XRT observations, 8 X-ray sources
  39. GRB 240916A: JinShan optical decay in one of the two GOTO candidates
  40. GRB 240916B: Fermi GBM Final Real-time Localization
  41. GRB 240914B: Fermi GBM Final Localization
  42. The EP-WXT triggers 01709047257 and 01709047278 are not real sources
  43. GRB 240916A: GOTO identification of two new optical sources within the GBM localisation region
  44. EP EP240913a: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations
  46. GRB 240916A INTEGRAL SPI ACS LIGHT CURVE
  47. GRB 240916A: Fermi GBM Final Real-time Localization
  48. Fermi Gamma-ray Burst Monitor trigger 748124309/240915846 is not a GRB
  49. LIGO/Virgo/KAGRA S240915bd: Updated Sky localization
  50. EP240913a: VLT/HAWK-I near-infrared upper limits
  51. LIGO/Virgo/KAGRA S240915bd: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S240915b: Updated Sky localization and EM Bright Classification
  53. LIGO/Virgo/KAGRA S240915b: Identification of a GW compact binary merger candidate
  54. EP240913a/GRB 240913C: KAIT optical upper limit
  55. EP240913a / GRB 240913C INTEGRAL SPI ACS LIGHT CURVE
  56. GRB 240913C: Fermi GBM detection
  57. GRB 240914A: Swift-XRT observations
  58. GRB 240913C: Joint location by ETJASMIN
  59. GRB 240914B: AstroSat CZTI detection
  60. EP240913A / GRB 240913C: AstroSat CZTI detection
  61. GRB 240914A: SVOM/GRM observation
  62. GRB 240910A: SVOM/VT optical observations
  63. GRB 240914A: Swift ToO observations
  64. EP240913a: NOT optical upper limits
  65. EP240913a: JinShan optical upper limits
  66. EP240913a: ESO-NTT optical observations
  67. GRB 240914A: ESO-NTT optical observations
  68. EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
  69. GRB 240914B: BALROG localization (Fermi Trigger 747990592 / GRB 240914298)
  70. GRB 240914A : An intermediate duration GRB located on-board by SVOM/ECLAIRs.
  71. GRB 240905E: further NOT optical observations
  72. EP240913a: A GRB Event
  73. EP240913a: EP-WXT detection of a fast X-ray transient
  74. GRB 240913B: Fermi GBM Final Real-time Localization
  75. GRB 240911A: LCO optical observations
  76. GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
  77. Fermi Gamma-ray Burst Monitor trigger 747837485/240912526 is not a GRB
  78. GRB 240912A: Swift/UVOT Detection
  79. GRB 240911A: GOTO optical limits on Swift/XRT candidates
  80. Fermi trigger No 747920561: Global MASTER-Net observations report
  81. GRB 240912A: SVOM/GRM observation
  82. GRB 240911A: Swift-XRT observations
  83. Fermi GRB 240913A: Global MASTER-Net observations report
  84. GRB 240913A: Fermi GBM Final Real-time Localization
  85. GRB 240912A: J-band observations with WINTER
  86. GRB 240912A: Swift-XRT refined Analysis
  87. GRB 240912A: Fermi GBM Observation
  88. Swift GRB 240912A: Global MASTER-Net observations report
  89. GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
  90. GRB 240911A: Tiled Swift observations
  91. Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
  92. GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
  93. GRB 240912B: Fermi GBM Final Real-time Localization
  94. GRB 240912A: NOT optical spectroscopy
  95. GRB 240912A: Enhanced Swift-XRT position
  96. GRB 240912A: Redshift from OSIRIS+/GTC
  97. Fast X-ray Transient EP240801a: GMRT radio observations
  98. GRB 240910A: Redshift from OSIRIS+/GTC
  99. GRB 240912A: Swift detection of a burst with an optical counterpart
  100. GRB 240912A: Fermi GBM Final Real-time Localization

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