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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/KAGRA S230706ah: Updated Sky localization
  2. Integral GRB230706.70: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S230704f: Updated Sky localization
  4. LIGO/Virgo/KAGRA S230630bq: Updated Sky localization
  5. IBAS trigger number 10311: not a real GRB
  6. LIGO/Virgo/KAGRA S230702an: Updated Sky localization
  7. GRB 230625A: Detection by GRID
  8. LIGO/Virgo/KAGRA S230529ay: Updated Sky localization and EM Bright Classification
  9. LIGO/Virgo/KAGRA S230706ah: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S230627c: GECKO optical follow-up observations of host galaxy candidates and ZTF23aaptsuy/AT2023lxu
  11. ZTF23aaoohpy/AT2023lcr: AMI-LA radio detection
  12. Fermi trigger No 710117592: Global MASTER-Net observations report
  13. GRB 230626A: VZLUSAT-2 detection
  14. LVK S230619bd/GBM-230619: Upper limits from a two-week IceCube neutrino search
  15. GRB 230328B: LBT detection of the likely host galaxy
  16. LIGO/Virgo/KAGRA S230704f: Identification of a GW compact binary merger candidate
  17. Konus-Wind detection of GRB 220623A
  18. GRB 230701B: AstroSat CZTI detection
  19. LIGO/Virgo/KAGRA S230627c: observations of ZTF23aaptsuy/AT2023lx in AbAO observatory
  20. LIGO/Virgo/KAGRA S230702an: Identification of a GW compact binary merger candidate
  21. GRB 230628E: Swift/UVOT Detection
  22. GRB 230628E: Swift-BAT refined analysis
  23. GRB 230702A: Fermi GBM Final Real-time Localization
  24. GRB 230628E: ATCA rapid radio follow-up
  25. GRB 230701A: Fermi GBM Final Real-time Localization
  26. LIGO/Virgo/KAGRA S230627c: GRANDMA observations of galaxies and ZTF counterpart candidates
  27. LIGO/Virgo/KAGRA low-significance gravitational wave candidate S230701z: one counterpart neutrino candidate from IceCube neutrino searches
  28. LIGO/Virgo/KAGRA S230627c: Upper limits from Swift/BAT-GUANO
  29. LIGO/Virgo/KAGRA S230630bq: Identification of a GW compact binary merger candidate
  30. IPN triangulation of GRB 230625B (ultra-long)
  31. AT2023lcr (ATLAS23msn/ZTF23aaoohpy): ALMA 100 GHz Detection
  32. LIGO/Virgo/KAGRA S230630am: Identification of a GW compact binary merger candidate
  33. GRB 230625B: CALET Gamma-Ray Burst Monitor detection
  34. GRB 230628E - VLT spectroscopic observations
  35. ZTF23aaoohpy/AT2023lcr: LBT observations
  36. Fermi GRB 230628C: Global MASTER-Net observations report
  37. GRB 230625B: AstroSat CZTI detection
  38. GRB230628E: VLT optical identification of afterglow candidate
  39. GRB 230628E: Swift-XRT refined Analysis
  40. GRB 230628E: Enhanced Swift-XRT position (Correction to name in GCN 34115)
  41. GRB 230628A: Enhanced Swift-XRT position
  42. Fermi GRB 230628D: Global MASTER-Net observations report
  43. LIGO/Virgo/KAGRA S230628ax: Identification of a GW compact binary merger candidate
  44. GRB 230628E: LCOGT Optical Upper Limit
  45. Swift GRB230628.93: Global MASTER-Net observations report
  46. GRB 230628E: Swift detection of a burst
  47. GRB 230628D: BALROG localization (Fermi Trigger 709676556 / GRB 230628849)
  48. GRB 230628D: Fermi GBM Final Real-time Localization
  49. LIGO/Virgo/KAGRA low-significance gravitational wave candidate S230628aj: one counterpart neutrino candidate from IceCube neutrino searches
  50. GRB 230628C: Fermi GBM Final Real-time Localization
  51. GRB 230628B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  52. GRB 230623B: CALET Gamma-Ray Burst Monitor detection
  53. LIGO/Virgo/KAGRA S230516az: GOTO candidate counterpart GOTO23hu ruled out by Zwicky Transient Facility observations
  54. ZTF23aaoohpy /AT2023lcr: TNG NIR detection
  55. GRB 230628A: Fermi GBM Final Localization
  56. LIGO/Virgo/KAGRA S230627c: Additional observations from the Zwicky Transient Facility
  57. GRB 230626A: GRBAlpha detection
  58. AT2023lcr: JCMT SCUBA-2 sub-mm observations
  59. LIGO/Virgo/KAGRA S230527c: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  60. LIGO/Virgo/KAGRA S230627c: ATLAS information on the ZTF candidates
  61. LIGO/Virgo/KAGRA S230627c: Upper limits from Fermi-GBM Observations
  62. GRB230626A: Fermi GBM Detection
  63. LIGO/Virgo/KAGRA S230627c: Global MASTER-Net observations report
  64. LIGO/Virgo/Kagra S230627c: NED Galaxies in the Localization Volume
  65. Konus-Wind detection of GRB 230616A
  66. LIGO/Virgo/KAGRA S230627c: Correction to HasMassGap probability
  67. LIGO/Virgo/KAGRA S230627c: Zwicky Transient Facility observations and candidates
  68. LIGO/Virgo/KAGRA S230627c: Coverage and upper limits from MAXI/GSC observations
  69. LIGO/Virgo/KAGRA S230627c: Updated Sky localization and EM Bright Classification
  70. LIGO/Virgo/KAGRA S230627c: Identification of a GW compact binary merger candidate
  71. GRB 230618A: Swift-BAT refined analysis
  72. GRB 230625B: Swift/BAT-GUANO detection of a long burst
  73. LIGO/Virgo/KAGRA S230624av: Updated Sky localization
  74. GRB 230622A: Swift-BAT refined analysis
  75. GRB 230623A: Swift-XRT observations
  76. GRB 230625A: Fermi GBM Final Real-time Localization
  77. INTEGRAL upper limit on any GRB associated with ZTF23aaoohpy/AT2023lcr
  78. ZTF23aaoohpy/AT2023lcr: further SAO RAS observations
  79. ATLAS23msn/ZTF23aaoohpy/AT2023lcr: Zeiss-1000 of Koshka observatory optical observations
  80. GRB 230623B: Swift/BAT-GUANO detection of a long burst outside the coded FOV 
  81. LIGO/Virgo/KAGRA S230624av: Identification of a GW compact binary merger candidate
  82. IceCube-Cascade 230622A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 230623A: Tiled Swift observations
  84. MAXI GRB 230623A: MASTER optical observations
  85. GRB 230623A: Tiled Swift observations
  86. GRB 230622A: ATCA rapid radio follow-up
  87. GRB 230622A: Swift-XRT refined Analysis
  88. GRB 230623A: MAXI/GSC detection
  89. Swift GRB 230622A: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S230615az: LBT spectroscopic classification of GOTO23hn
  91. LIGO/Virgo/KAGRA S230622ba: Retraction of GW compact binary merger candidate
  92. LIGO/Virgo S230622e: Global MASTER-Net observations report
  93. LIGO/Virgo S230621bq: Global MASTER-Net observations report
  94. LIGO/Virgo S230621ad: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S230615az: LBT spectroscopic redshift of the host galaxy of GOTO23hn
  96. ZTF23aaoohpy/AT2023lcr: SAO RAS observations
  97. Fermi GBM-230619: AstroSat CZTI non-detection and upper limits for the sub-threshold candidate
  98. GRB 230622A: Swift detection of a burst
  99. IceCube-Cascade 230621A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 230621A: Fermi GBM Final Localization Correction

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