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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. LIGO/Virgo S200225q: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  2. LIGO/Virgo S200225q: Coverage and upper limits from MAXI/GSC observations
  3. LIGO/Virgo S200219ac: No counterpart candidates from Nanshan/NEXT observations
  4. LIGO/Virgo S200224ca: upper limits from AGILE/GRID observations
  5. GRB 200224A: Swift-BAT refined analysis
  6. LIGO/Virgo S200225q: Identification of a GW compact binary merger candidate The LIGO Scientific Collaboration and the Virgo Collaboration
  7. LIGO/Virgo S200224ca: not observable by Fermi-GBM
  8. GRB 200224A: LCO Upper Limits
  9. LIGO/Virgo S200224ca: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  10. GRB 200224A: RATIR Optical Observations and Confirmation of the Afterglow
  11. LIGO/Virgo S200224ca: Coverage and upper limits from MAXI/GSC observations
  12. LIGO/Virgo S200224ca: upper limits from AGILE/MCAL observations
  13. LIGO/Virgo S200224ca: Global MASTER-Net observations report
  14. LIGO/Virgo S200224ca: Upper limits from IceCube neutrino searches
  15. LIGO/Virgo S200224ca: Identification of a GW compact binary merger candidate The LIGO Scientific Collaboration and the Virgo Collaboration
  16. IPN triangulation of GRB 200224C
  17. GRB 200224A: Swift/UVOT Detection
  18. Correction in name: GRB 200224B and GRB 200224C (not GRB 200224A)
  19. GRB 200219C: Swift-XRT afterglow confirmation
  20. GRB 200224A: Swift-XRT refined Analysis
  21. GRB 200224C: Fermi GBM Final Real-time Localization
  22. GRB 200224A: Tautenburg observations
  23. GRB 200224A: BOOTES-1 and 1.5m OSN optical observations
  24. Fermi trigger No 604213554: Global MASTER-Net observations report
  25. GRB 200224B: Fermi GBM Final Real-time Localization
  26. GRB 200224A: Swift detection of a burst
  27. Swift GRB200224.14: Global MASTER-Net observations report
  28. GRB 200223A: Fermi GBM Final Real-time Localization
  29. LIGO/Virgo S200219ac: no counterpart candidate in SVOM/GWAC-F30 observations
  30. LIGO/Virgo S200219ac: no counterpart candidate in SVOM/GWAC observations
  31. LIGO/Virgo S200219ac : No significant candidates in TAROT - FRAM - GRANDMA observations.
  32. IPN triangulation of GRB 200219B (inconsistent with the LIGO/Virgo S200219ac)
  33. GRB 200219C: OAJ afterglow confirmation
  34. GRB 200219A: UVOT Upper Limits
  35. GRB 200219A: FRAM-Auger optical limit
  36. GRB 200219C: CALET Gamma-Ray Burst Monitor detection
  37. GRB 200219C: Mondy and TSHAO optical observations
  38. GRB 200219C: Nanshan/NEXT optical upper limit and possible host galaxy from PanSTARRS
  39. LIGO/Virgo S200219ac: No counterpart candidates in KAIT observations
  40. GRB 200221A: Fermi GBM Final Real-time Localization
  41. Fermi trigger No 603949983: Global MASTER-Net observations report
  42. GRB 200219C: Swift-XRT afterglow detection
  43. GRB 200219C: DDOTI Observations
  44. GRB 200219C: Fermi GBM detection
  45. LIGO/Virgo S200213t: AT2020clw/ZTF20aanaoyz, AT2020crd/ZTF20aanakge and AT2020cly/ZTF20aanakes 10.4m GTC spectroscopy
  46. LIGO/Virgo S200213t: Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
  47. GRB 200219C: Tiled Swift observations
  48. GRB 200219C: Fermi-LAT detection
  49. GRB 200215A: LCO Optical Upper Limits
  50. LIGO/Virgo S200219ac: No transient candidates in CALET observations
  51. GRB 200219A, Swift-BAT refined analysis
  52. LIGO/Virgo S200219ac: no counterpart candidates in the Swift/BAT observations
  53. Fermi trigger No 603849435: Global MASTER-Net observations report
  54. GRB 200219C: Fermi GBM Final Real-time Localization
  55. LIGO/Virgo S200219ac: Fermi GBM transient event not confidently associated with GW signal
  56. LIGO/Virgo S200219ac: No counterpart candidates in Fermi-LAT observations
  57. GRB 200219A: Swift-XRT refined Analysis correction
  58. LIGO/Virgo S200219ac: upper limits from AGILE/GRID observations
  59. LIGO/Virgo S200213t: Keck/LRIS spectroscopy of counterpart candidates from the Zwicky Transient Facility
  60. GRB 200219A: Swift-XRT refined Analysis
  61. GRB 200219A: Enhanced Swift-XRT position
  62. GRB 200219A: Fermi GBM observation
  63. LIGO/Virgo S200219ac: upper limits from AGILE/MCAL observations
  64. LIGO/Virgo S200219ac : no neutrino counterpart candidate in ANTARES search
  65. LIGO/Virgo S200219ac: Upper limits from IceCube neutrino searches
  66. LIGO/Virgo S200219ac: No counterpart candidates in HAWC observations
  67. LIGO/Virgo S200219ac: Coverage and upper limits from MAXI/GSC observations
  68. LIGO/Virgo S200219ac: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  69. LIGO/Virgo S200219ac: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo S200219ac: Global MASTER-Net observations report
  71. GRB 200216B: second epoch optical upper limit at Mondy observatory
  72. GRB 200219B: Fermi GBM Final Real-time Localization
  73. GRB 200219A: MASTER catalog automatic possible Host Galaxy candidate
  74. GRB 200219A: Swift detection of a short burst
  75. Swift GRB200219.32: Global MASTER-Net observations report
  76. GRB 200219A: Fermi GBM Final Real-time Localization
  77. GRB 200216B: Mondy and AbAO optical upper limits
  78. LIGO/Virgo (S200213t/IceCube neutrino candidate: No counterpart candidates in the Swift-XRT Observations
  79. GRB 200216B: Swift-XRT refined Analysis
  80. LIGO/Virgo S200213t: No EM counterparts found from continued GECKO observation of host galaxy candidates
  81. LIGO/Virgo S200213t: APO Upper Limits for ZTF20aanakes/AT2020cly
  82. GRB 200216B: Swift-BAT refined analysis
  83. LIGO/Virgo S200213t : No significant candidates in FRAM - OAJ - TAROT - GRANDMA observations
  84. Further Swift-XRT observations of Swift J0840.7-3516
  85. GRB 200216B - possible IR counterpart from VLT
  86. GRB 200215A: CALET Gamma-Ray Burst Monitor detection
  87. GRB 200216A: Fermi GBM detection
  88. LIGO/Virgo S200213t: AstroSat CZTI upper limits
  89. GRB 200216B: z-band limit from NOT
  90. GRB 200216B: Fermi GBM observation
  91. GRB 200216B: Swift/UVOT Upper Limits
  92. GRB 200216A: Swift/BAT detection and arcminute localization from GUANO
  93. GRB 200216B: Enhanced Swift-XRT position
  94. GRB 200215A: RATIR Optical Observations
  95. GRB 200216B: Nanshan/NEXT early optical upper limit and possible host galaxy
  96. GRB 200216B: GMG upper limit
  97. GRB 200216B: Swift detection of a burst
  98. GRB 200216B: Fermi GBM Final Real-time Localization
  99. Swift GRB200216.56: Global MASTER-Net observations report
  100. GRB 200215A: UKIRT H-band observations

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